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INDEX TO FINANCIAL STATEMENTS

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As filed with the Securities and Exchange Commission on April 19, 2011

Registration No. 333-172007

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, DC 20549

AMENDMENT NO. 4
TO
FORM S-1
REGISTRATION STATEMENT
UNDER THE
SECURITIES ACT OF 1933

THERMON GROUP HOLDINGS, INC.
(Exact name of registrant as specified in its charter)

100 Thermon Drive, San Marcos, Texas 78666, (512) 396-5801
(Address, including zip code, and telephone number, including area code, of registrant's principal executive offices)

Rodney Bingham
President and Chief Executive Officer
Thermon Group Holdings, Inc.
100 Thermon Drive
San Marcos, Texas 78666
(512) 396-5801
(Name, address, including zip code, and telephone number, including area code, of agent for service)

Approximate date of commencement of proposed sale of the securities to the public:
As soon as practicable after this registration statement becomes effective.

          If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box: o

          If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: o

          If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: o

          If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: o

          Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of "large accelerated filer," "accelerated filer" and "smaller reporting company" in Rule 12b-2 of the Exchange Act. (Check one):

          The registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Securities and Exchange Commission acting pursuant to said Section 8(a), may determine.

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The information in this preliminary prospectus is not complete and may be changed. We and the selling stockholders may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities and neither we nor the selling stockholders are soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

Subject to Completion, dated April 19, 2011

PROSPECTUS

10,000,000 Shares

Thermon Group Holdings, Inc.

Common Stock

This is the initial public offering of the common stock of Thermon Group Holdings, Inc. We are offering 4,000,000 shares of the common stock and the selling stockholders identified in this prospectus are offering 6,000,000 shares. We will not receive any proceeds from sale of shares held by the selling stockholders. No public market currently exists for our common stock.

Our common stock has been approved for listing on the New York Stock Exchange under the symbol "THR."

We anticipate that the initial public offering price will be between $12.00 and $14.00 per share.

Investing in our common stock involves risks. See "Risk Factors" beginning on page 17 of this prospectus.

We and certain of the selling stockholders have granted the underwriters the option to purchase up to 1,500,000 additional shares of common stock on the same terms and conditions as set forth above if the underwriters sell more than 10,000,000 shares of common stock in this offering.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed on the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares on or about                           , 2011.

Prospectus dated                                        , 2011

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        You should rely only on information contained in this prospectus, any amendment or supplement to this prospectus or any free writing prospectus prepared by or on behalf of us, or to which we have referred you. Neither we nor any of the selling stockholders has authorized anyone to provide you with information that is different. If anyone provides you with different or inconsistent information, you should not rely on it. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. This prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any of the shares of common stock offered hereby by any person in any jurisdiction in which it is unlawful for such person to make such an offering or solicitation. The information contained in this prospectus is accurate only as of the date of this prospectus, regardless of the time of delivery of this prospectus or of any sale of the common stock.

        Unless otherwise indicated, all information contained in this prospectus concerning the industry in general, including information regarding our market position and market share within our industry and expectations regarding future growth of sales in our industry, is based on management's estimates using internal data, data from industry related publications, consumer research and marketing studies and other externally obtained data. Industry and market data involve risks and uncertainties and are subject to change based on various factors, including those discussed under the caption "Risk Factors" in this prospectus.

        Through and including                        , 2011 (the 25th day after the date of this prospectus), all dealers that effect transactions in these securities, whether or not participating in this offering, may be required to deliver a prospectus. This requirement is in addition to the dealers' obligation to deliver a prospectus when acting as underwriters and with respect to their unsold allotments or subscriptions.

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PROSPECTUS SUMMARY

        The following summary highlights selected information contained in this prospectus and may not contain all the information that may be important to you. You should read this entire prospectus, including the section entitled "Risk Factors," before making an investment decision. Unless otherwise specified or the context otherwise requires, references to "$" or "dollars" in this prospectus are to United States dollars, and the terms "we," "our," "us" and the "Company," as used in this prospectus, refer to Thermon Group Holdings, Inc. and its directly and indirectly owned subsidiaries as a combined entity.

Our Business

        We are one of the largest providers of highly engineered thermal solutions for process industries. For over 50 years, we have served a diverse base of thousands of customers around the world in attractive and growing markets, including energy, chemical processing and power generation. We are a global leader and one of the few thermal solutions providers with a global footprint and a full suite of products (heating cables, tubing bundles and control systems) and services (design optimization, engineering, installation and maintenance services) required to deliver comprehensive solutions to complex projects. We serve our customers locally through a global network of sales and service professionals and distributors in more than 30 countries and through our four manufacturing facilities on three continents. These capabilities and longstanding relationships with some of the largest multinational energy, chemical processing, power and engineering, procurement and construction, or EPC, companies in the world have enabled us to diversify our revenue streams and opportunistically access high growth markets worldwide.

        Our thermal solutions, also referred to as heat tracing, provide an external heat source to pipes, vessels and instruments for the purposes of freeze protection, temperature and flow maintenance and environmental monitoring. Customers typically purchase our products when constructing a new facility, which we refer to as Greenfield projects, or when performing maintenance, repair and operations on a facility's existing heat-traced pipes or upgrading or expanding a current facility, which we refer to collectively as MRO/UE. Our products are low in cost relative to the total cost of a typical processing facility, but critical to the safe and profitable operation of the facility.

        Our customers' need for MRO/UE solutions provides us with an attractive recurring revenue stream. Customers typically use the incumbent heat tracing provider for MRO/UE projects to avoid complications and compatibility problems associated with switching providers. We typically begin to realize meaningful MRO/UE revenue from new Greenfield installations one to three years after completion of the project as customers begin to remove and replace our products during routine and preventative maintenance on in-line mechanical equipment, such as pipes and valves. As a result, our growth has been driven by new facility construction, as well as by servicing our continually growing base of solutions installed around the world, which we refer to as our installed base.

        Our revenues have grown in 17 of the past 21 fiscal years, and our gross margins have averaged 44% over that period. In addition, we have generated significant growth in both revenue and profitability in recent years. Our revenue grew by 59% to $192.7 million for fiscal 2010 from $121.4 million for fiscal 2007, and gross profit grew by 65% to $91.3 million from $55.3 million over the same period. For the nine months ended December 31, 2010, we achieved revenue of $179.0 million, gross profit of $73.7 million, a net loss of $11.2 million and Adjusted EBITDA of $43.8 million and 71% of our revenues were generated outside of the United States. See note 9 to the "—Summary Historical and Pro Forma Consolidated Financial and Operating Data" table.

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Our Industry

        Alvarez & Marsal Private Equity Performance Improvement Group, LLC, or A&M, estimates that the market for industrial electric heat tracing is approximately $1 billion in annual revenues and estimates that it is growing its share of the overall heat tracing market as end users appear to continue to favor electric heat tracing solutions over steam heat tracing solutions for new installations. When revenues for steam heat tracing parts are included, A&M estimates the overall addressable market for heat tracing is approximately $2 billion in annual revenues. The industrial electric heat tracing industry is fragmented and consists of approximately 40 companies that typically only serve discrete local markets with manufactured products and provide a limited service offering. Large multinational companies drive the majority of spending for the types of major industrial facilities that require heat tracing, and we believe that they prefer providers who have a global footprint and a comprehensive suite of products and services.

        The major end markets that drive demand for heat tracing include energy, petrochemical and power generation. We believe that there are attractive near- to medium-term trends in each of these end markets.

•

Energy.  Heat tracing is used to facilitate the processing, transportation and freeze protection of energy products in both upstream and downstream oil and gas applications. In order to meet growing demand and offset natural declines in existing oil and gas production, a significant increase in capital expenditures in upstream infrastructure will be required, with a particular focus on reservoirs that are in harsher climates, are deeper or have other complex characteristics that magnify the need for heat tracing. According to Wood Mackenzie, a leading independent energy research and consulting firm, as of October 2010, global upstream development expenditures are expected to increase 11% to approximately $420 billion in 2013 from approximately $380 billion in 2010. An increase in upstream production coupled with increased demand for refined products will require a corresponding increase in downstream refining capacity.



•

Chemical Processing.  Heat tracing is required for temperature maintenance and freeze protection in a variety of chemical processing applications. Factors that may impact heat tracing demand in chemicals end markets include the rapid industrialization of the developing world, a shift in base chemical processing operations to low-cost feedstock regions, a transition of Western chemical processing activities from commodity products to specialty products and environmental compliance. According to the American Institute of Chemical Engineers, global capital spending by the chemical processing industry is estimated to increase to $418.4 billion, representing a compound annual growth rate of 11.1% from 2010 to 2015.



•

Power Generation.  Heat tracing is required in high-temperature processes, freeze protection and environmental regulation compliance in coal and gas facilities and for safety injection systems in nuclear facilities. An important driver of demand for heat tracing solutions for power generation is increasing demand for electricity worldwide. According to the EIA, global net electricity generation is projected to increase 87% between 2007 and 2035. We believe capital spending on new and existing power generation infrastructure will be required to meet this demand.



•

Continuing selection of electric-based heat tracing solutions over steam-based solutions. Beginning in the 1960s, electric heat tracing products entered the market as an alternative to steam heat tracing products. While steam-based products are still used today for heavy oil, chemical and processing applications, electric-based products generally offer greater cost savings and operating efficiencies. As a consequence, Greenfield projects commissioned in recent years are increasingly designed to incorporate electric heat tracing.

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Our Competitive Strengths

        We believe that the following strengths differentiate us from our competitors:

        We have access to attractive high growth sectors of our global addressable market.    We have a network of sales and service professionals and distributors in more than 30 countries and a manufacturing footprint that includes four facilities on three continents. This footprint allows us to diversify our revenue streams and opportunistically access the most attractive regions and sub-sectors of our markets. For example, growing demand for energy is pushing the search for resources to increasingly harsh cold weather countries, including Canada and Russia, where demand for our products is magnified, and strong petrochemical demand in China and India has led to a shift in chemical production to the Asia-Pacific region. We have a strong, established local presence in each of these markets.

        We are a global market leader.    We believe that we are the second largest industrial electric heat tracing company in the world, significantly larger than our next largest competitor and one of only a few solutions providers with a comprehensive suite of products and services, global capabilities and local on-site presence. Over our 56-year history, we have developed an installed base operated by thousands of customers and long-standing relationships with some of the largest companies in the world that drive the spending decisions for the major facilities that require our products. We believe these multinational companies prefer providers with our scale, global presence and comprehensive product and service offering.

        Our highly engineered solutions are "mission critical" to our customers.    Reliable thermal solutions are critical to the safe and profitable operation of our customers' facilities. These facilities are often complex, with numerous classified areas that are inherently hazardous and where product safety concerns are paramount. Therefore, we believe that our customers consider safety, reliability and customer service to be the most important purchase criteria for our products. We are a leader in the national and international standards setting process for the heat tracing industry and hold leadership positions on numerous industry standards development organizations.

        Our favorable business model positions us to achieve attractive financial results.    The following features of our business model contribute to our attractive financial results:

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Existing installed base generates significant recurring revenue.  On average, annual MRO/UE expenditures generated from an installed heat tracing system are approximately 5 to 10% of the initial cost of the system and expansions may require approximately 10 to 20% of the initial cost of the system. We estimate that approximately 60% of our revenues in fiscal 2010 were generated from MRO/UE sales. We believe that we have the second largest installed base in the industrial electric heat tracing industry and, as we continue to complete new Greenfield installations, we believe that, subject to customers' continuing capital and maintenance expenditures, our growing global installed base of heat tracing solutions will drive increased MRO/UE business.



•

Diversified, global customer base and end markets.  Over the past five decades, we have sold our solutions to thousands of customers in more than 90 countries, serving a broad range of end-market applications. The diversity of our customer base and end-markets limits our exposure to any individual industry sector or geographic region and provides us with an opportunity to access the most attractive high growth sectors of our end markets.



•

Strong revenue visibility.  We believe that we have strong visibility into our future revenue as a result of recurring demand that we expect will be generated from our global installed base, a growing backlog of signed purchase orders and a robust pipeline of planned projects. Our visibility into the timing of our recognition of revenue out of backlog is not always certain, particularly with larger projects; however, our solutions are ordered and installed toward the end

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of Greenfield project construction, and therefore, historically, purchase orders have rarely been cancelled.

•

Consistent gross margins and cash flow generation.  We have a long history of stable gross margins and positive operating cash flow through a variety of economic cycles. We have consistently had positive income from operations, and gross margins have averaged 44% over the past 21 fiscal years, which we believe reflect our customers' recognition of the value and reliability of our heat tracing solutions, our highly variable cost structure and the limited capital expenditures required to maintain our business.

        Our management team has a proven track record.    Our senior management team averages approximately 22 years of experience with us and is responsible for growing Thermon through a variety of business cycles, building our global platform and developing our reputation for quality and reliability in the heat tracing industry. Our senior management and key employees will continue to have a significant equity stake in Thermon following this offering.

Our Growth Strategy

        Our business strategy is designed to capitalize on our competitive strengths. Key elements of our strategy include:

        Capitalize on our leading market position to continue pursuing organic growth opportunities.    Our primary growth engine has traditionally been organic expansion. We will continue to focus on strategically building the necessary global sales infrastructure to expand our footprint in high growth markets. We believe that this footprint and our local presence are attractive to our customers and differentiate us from other industry participants. We expect to continue to pursue growth opportunities in emerging markets and across industry sectors in the future.

        Leverage our installed base to expand our recurring revenue stream.    Once the MRO/UE cycle begins, we typically realize MRO/UE revenues, which are typically higher margin than Greenfield revenues, over the life of each installation. As we continue to grow our large, global installed base with new Greenfield projects, we expect to generate incremental MRO/UE revenues related to these new projects. Since the beginning of fiscal 2008 through December 31, 2010, we estimate that we have realized approximately $290 million in revenues from Greenfield projects, which represents a meaningful opportunity for us to create MRO/UE revenues in the future.

        Drive growth through alliances with major customers and suppliers.    We have developed strategic alliances with other industry participants in order to enhance our growth opportunities, and we are a "pre-qualified" heat tracing provider for several of our key customers. These relationships provide us with an advantage in identifying and bidding for new Greenfield and MRO/UE projects, and we intend to target additional opportunities with suppliers of complementary products that will allow us to take mutual advantage of our customer relationships and enhance our cross-selling opportunities.

        Continue to offer solutions that support evolving environmental applications.    A portion of our recent growth has been driven by the use of our products in alternative energy initiatives, including carbon capture, thermal solar and coal gasification facilities. In addition, our products help our customers monitor their facilities' environmental or other regulatory compliance. We intend to continue to focus on driving growth by providing solutions that address our customers' evolving environmental application needs.

        Selectively pursue investment opportunities.    

•

Given the fragmented nature of the heat tracing industry, we believe that there will be opportunities to pursue value-added acquisitions at attractive valuations in the future, including

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by augmenting our geographic footprint, broadening our product offerings, expanding our technological capabilities and capitalizing on potential operating synergies.

•

We plan to pursue strategic investment opportunities, including the expansion of our principal manufacturing facility in San Marcos, Texas.

Risk Factors

        There are a number of risks related to our business, this offering and our common stock that you should consider before you decide to participate in this offering. You should carefully consider all the information presented in the section entitled "Risk Factors" in this prospectus. Some of the principal risks related to our business include the following:

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The markets we serve are subject to general economic conditions and cyclical demand, which could harm our business and lead to significant shifts in our results of operations from quarter to quarter that make it difficult to project long-term performance.



•

A sustained downturn in the energy industry, due to oil and gas prices decreasing or otherwise, could decrease demand for some of our products and services, which could materially and adversely affect our business, financial condition and results of operations.



•

As a global business, we are exposed to economic, political and other risks in a number of countries, which could materially reduce our revenues, profitability or cash flows or materially increase our liabilities. If we are unable to continue operating successfully in one or more foreign countries, it may have a material adverse effect on our business and financial condition.



•

A failure to deliver our backlog on time could affect our future sales and profitability and our relationships with our customers, and if we were to experience a material amount of modifications or cancellations of orders, our sales could be negatively impacted.



•

Our future revenue depends in part on our ability to bid and win new contracts. Our failure to effectively obtain future contracts could adversely affect our profitability.



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We may be unable to compete successfully in the highly competitive markets in which we operate.



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Volatility in currency exchange rates may adversely affect our financial condition, results of operations or cash flows.



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Our business strategy includes acquiring smaller, value-added companies and making investments that complement our existing business. These acquisitions and investments could be unsuccessful or consume significant resources, which could adversely affect our operating results.



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On a pro forma basis after giving effect to this offering and the redemption of a portion of our senior secured notes scheduled to occur on April 29, 2011, as of December 31, 2010, we would have had outstanding indebtedness of $168.0 million. Our debt agreements impose certain operating and financial restrictions, with which failure to comply could result in an event of default that could adversely affect our results of operations.

        These and other risks are more fully described in the section entitled "Risk Factors" in this prospectus. If any of these risks actually occur, they could materially harm our business, prospects, financial condition and results of operations. In this event, you could lose part or all of your investment in our common stock offered hereby.

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Recent Developments

        While we have not finalized our results of operations for the fourth quarter of fiscal 2011 or full fiscal year 2011, the following preliminary and unaudited information reflects our estimates with respect to such results based on currently available information.

        We currently expect sales of between $58 million and $60 million for the fourth quarter of fiscal 2011 and between $237 million and $239 million for full fiscal year 2011, compared to sales of $49.8 million and $192.7 million for the fourth quarter of fiscal 2010 and full fiscal year 2010, respectively. The estimated increase in sales for the fourth quarter of fiscal 2011 was primarily the result of increased demand for our core thermal products and services. We currently expect income before provision for income taxes of between $1.1 million and $3.1 million for the fourth quarter of fiscal 2011 and a loss before provision for income taxes between $(26.7) million and $(24.7) million for full fiscal year 2011, compared to income before provision for income taxes of $5.9 million and $32.9 million for the fourth quarter of fiscal 2010 and full fiscal year 2010, respectively. Income before provision for income taxes for the fourth quarter of fiscal 2011 was positively affected by the estimated increase in sales on comparable operating expenses that reflect some efficiency from fixed costs when compared to the fourth quarter of fiscal 2010, but those effects were largely offset by the factors discussed below.

        Our estimated results of operations for the fourth quarter of fiscal 2011 and full fiscal year 2011 were significantly impacted by the effects of the Acquisition referred to below. See "—Our Principal Stockholder." We estimate that amortization of intangible assets, including cost of sales adjustment will be $2.9 million in the fourth quarter of fiscal 2011 and $25.9 million for the full fiscal year 2011, compared to $0.6 million and $2.4 million for the fourth quarter of fiscal 2010 and full fiscal year 2010, respectively. The increase in intangible amortization expense over prior periods is due to purchase price accounting expense related to the Acquisition. We recognized transaction expenses related to the Acquisition of $0.5 million and $22.1 million in the fourth quarter of fiscal 2011 and full fiscal year 2011, respectively; similar expenses in fiscal 2010 totaled $1.0 million, $0.7 million of which was recognized in the fourth quarter of fiscal 2010. As a result of the issuance of $210.0 million aggregate principal amount of our senior secured notes used to partially finance the Acquisition, our interest expense also increased substantially. We estimate interest expense of $5.7 million and $29.0 million in the fourth quarter of 2011 and full fiscal year 2011, respectively. In fiscal 2010, interest expense totaled $1.8 million and $7.4 million for the fourth quarter and full fiscal year 2010, respectively. Our management fees also increased as a result of the Acquisition to an estimated $0.5 million and $2.0 million for the fourth quarter of 2011 and full fiscal year 2011, respectively, from $0.2 million and $0.9 million for the fourth quarter of 2010 and full fiscal year 2010, respectively. Excluding these items that were significantly affected by the Acquisition, we estimate that our income before provision for income taxes for the fourth quarter of fiscal 2011 would be between $10.7 million and $12.7 million and for full fiscal year 2011 would be between $52.3 million and $54.3 million. For additional discussion regarding factors impacting fiscal year 2011 results of operations prior to the fourth quarter, see "Management's Discussion and Analysis of Financial Condition and Results of Operations—Nine Months Ended December 31, 2010 (Combined) Compared to the Nine Months Ended December 31, 2009 (Non-GAAP)."

        Because we have not completed our closing processes, including our analysis of the potential impact of additional taxes arising from our receipt on March 31, 2011 of dividends from certain of our foreign subsidiaries in an aggregate amount of $34.3 million to be used to fund the redemption of $21.0 million aggregate principal amount of our senior secured notes scheduled to occur on April 29, 2011 and to pay certain transaction costs incurred in connection with this offering, we are not currently able to estimate our income tax benefit (expense) or net income (loss) for the fourth quarter of fiscal 2011. See "Management's Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources—Repatriation considerations." Although we are not able to estimate

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those items at this time, we have not identified any unusual or unique events or trends that occurred during the fourth quarter of fiscal 2011 that might materially affect our results of operations for that quarter, other than those discussed above. We believe that the foregoing information about our sales and income before provision for income taxes, even when unaccompanied by information regarding our net income (loss) that is not yet available, is helpful to an investor's understanding of our performance and is a meaningful indicator for assessing our operating performance because it demonstrates our continued ability to capture organic growth opportunities and achieve attractive operating results.

        We are currently in the process of preparing our audited consolidated financial statements as of and for the year ended March 31, 2011. These financial statements are not currently available and are not expected to be available and filed with the Securities and Exchange Commission until after the consummation of this offering. Estimates of financial results and position are inherently uncertain and subject to change, and adjustments may arise and actual results may differ materially from these estimates. Accordingly, you are cautioned not to place undue reliance on the estimates. This information is a summary of estimated financial data and should be read in conjunction with the "Risk Factors," "Selected Historical and Pro Forma Consolidated Financial and Operating Data," "Management's Discussion and Analysis of Financial Condition and Results of Operations," and our unaudited and audited consolidated financial statements and the accompanying notes appearing elsewhere in this prospectus.

Our Principal Stockholder

        Our principal stockholder, CHS Capital LLC, or CHS, acquired its interest in us on April 30, 2010, which we refer to as the Acquisition. CHS beneficially owns 50% of our outstanding shares of common stock on a fully-diluted basis. Two other private equity firms also acquired stakes in us at the time of the Acquisition. We refer to CHS and such other firms collectively in this prospectus as our sponsors.

        CHS is a Chicago-based private equity firm with 23 years of experience investing in the middle market. Targeting well-managed companies with enterprise values between $75 and $500 million, CHS partners with management teams to focus on accelerating growth, enhancing capabilities and resources and positioning companies for attractive exits. CHS has specialized expertise in the consumer and business services; distribution; and industrial, infrastructure and energy sectors and has completed 74 platform investments and 237 add-on investments. Founded in 1988, CHS has formed five private equity funds and has $2.3 billion of committed capital in active investment funds. CHS currently manages 16 portfolio investments with combined annual revenues in excess of $4.5 billion.

Our Corporate Information

        We are incorporated in Delaware and our corporate offices are located at 100 Thermon Drive, San Marcos, TX 78666. Our telephone number is (512) 396-5801. Our website address is www.thermon.com. None of the information on our website or any other website identified herein is part of this prospectus or the registration statement of which it forms a part.

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Our Organizational Chart

        The following chart summarizes our corporate structure:

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THE OFFERING

        The number of shares of our common stock to be outstanding following this offering is based on 24,933,407 shares of our common stock outstanding as of the date of this prospectus, but excludes 5,660,488 shares of common stock reserved for issuance under our equity incentive plans, of which options to purchase 2,757,524 shares have been granted at a weighted average exercise price of $5.38 per share, all of which will vest and become exercisable upon the consummation of this offering.

        Concurrently with the pricing of this offering, we intend to grant to our executive officers and certain other employees options to purchase 122,000 shares with an exercise price equal to the initial public offering price from the number of shares of common stock reserved for issuance under our equity incentive plans.

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        Unless otherwise expressly stated or the context otherwise requires, all information in this prospectus gives effect to and assumes the following:

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the acceleration and vesting immediately prior to the consummation of this offering of options to purchase 2,757,524 shares of common stock pursuant to the terms of our existing restricted stock and stock option plan;



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no exercise by the underwriters of their option to purchase up to 1,500,000 additional shares of our common stock from us and certain selling stockholders to cover over-allotments, if any;



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the effectiveness of a 192.458681-for-one split of our common stock, which occurred on March 31, 2011;



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the automatic conversion of our common stock into one class of voting common stock, which will occur immediately prior to the consummation of this offering;



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the adoption of our second amended and restated certificate of incorporation, which will occur immediately prior to the consummation of this offering; and



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an initial public offering price of $13.00 per share, the midpoint of the estimated initial public offering price range set forth on the cover of this prospectus.

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SUMMARY HISTORICAL AND PRO FORMA CONSOLIDATED FINANCIAL AND OPERATING DATA

        The following tables set forth certain summary historical and pro forma consolidated financial and operating data for the fiscal years ended March 31, 2008, March 31, 2009 and March 31, 2010, for the nine months ended December 31, 2009 and December 31, 2010, and as of December 31, 2010, and certain pro forma financial information for the fiscal year ended March 31, 2010 and for the nine months ended December 31, 2009 and December 31, 2010. The data set forth below should be read in conjunction with the sections entitled "Management's Discussion and Analysis of Financial Condition and Results of Operations," "Capitalization," "Unaudited Pro Forma Condensed Consolidated Financial Statements," and "Selected Historical and Pro Forma Consolidated Financial and Operating Data," each of which is contained elsewhere in this prospectus, and our consolidated financial statements and the notes thereto for the fiscal years ended March 31, 2008, March 31, 2009 and March 31, 2010 and for the nine months ended December 31, 2009 and December 31, 2010, each of which is contained elsewhere in this prospectus.

        In this prospectus, we have included the condensed consolidated financial statements of Thermon Group Holdings, Inc. as of December 31, 2010 and for the period from May 1, 2010 through December 31, 2010 ("successor") and the condensed consolidated financial statements of Thermon Holdings, LLC for the fiscal years ended March 31, 2010 and March 31, 2009, for the period from August 30, 2007 through March 31, 2008, for the nine months ended December 31, 2009 ("predecessor"), and for the period from April 1, 2007 through August 29, 2007 ("pre-predecessor"). Concurrent with the consummation of the Acquisition on April 30, 2010, Thermon Holdings, LLC no longer owned any interest in us, and, beginning with the period from May 1, 2010 through December 31, 2010, we reported the consolidated financial statements of Thermon Group Holdings, Inc. We do not anticipate that there would have been any material difference in our consolidated financial statements and notes thereto for the fiscal years ended March 31, 2008, March 31, 2009 and March 31, 2010 and for the nine months ended December 31, 2009 had such statements been prepared for Thermon Group Holdings, Inc., except as it relates to purchase accounting in connection with the Acquisition.

        The presentation of fiscal 2008 includes the combined results of the pre-predecessor and predecessor owners for fiscal 2008 and the predecessor and successor owners for the nine months ended December 31, 2010, respectively. We have presented the combination of these respective periods because it provides an easier-to-read discussion of the results of operations and provides the investor with information from which to analyze our financial results in a manner that is consistent with the way management reviews and analyzes our results of operations. In addition, the combined results provide investors with the most meaningful comparison between our results for prior and future periods. Please refer to notes 1 and 2 to the "Selected Historical and Pro Forma Consolidated Financial and Operating Data" table and our historical consolidated financial statements and notes thereto for the year ended March 31, 2008 and the nine months ended December 31, 2010 included elsewhere in this prospectus for a separate presentation of the results for the pre-predecessor and predecessor and predecessor and successor periods.

        The summary unaudited pro forma data have been prepared to give effect to the CHS Transactions (as defined below), this offering and the application of the net proceeds therefrom as if they had occurred on April 1, 2009. Assumptions underlying the pro forma adjustments are described in the section entitled "Unaudited Pro Forma Condensed Consolidated Financial Statements—Notes to the Unaudited Pro Forma Condensed Consolidated Financial Statements" contained elsewhere in this prospectus. The pro forma adjustments are based upon available information and certain assumptions that we believe are reasonable. Please see "Unaudited Pro Forma Condensed Consolidated Financial Statements—Notes to the Unaudited Pro Forma Condensed Consolidated Financial Statements" for a more detailed discussion of how pro forma adjustments are presented in our unaudited pro forma

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condensed consolidated financial statements. The unaudited pro forma condensed consolidated data is provided for informational purposes only. The summary unaudited pro forma data do not purport to represent what our results of operations actually would have been if the CHS Transactions, this offering and the application of the net proceeds therefrom had occurred at any date, nor do such data purport to project the results of operations for any future period.

        As used in this prospectus, the CHS Transactions refer collectively to the equity investment in us by CHS, our other sponsors and certain members of our management team, the entry into our revolving credit facility, the repayment of amounts owed under, and the termination of, certain then-existing revolving credit and term loan facilities, the issuance of our senior secured notes and the application of the gross proceeds from the offering of our senior secured notes and the equity investment to complete the Acquisition and to pay related fees and expenses of these transactions.

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RISK FACTORS

        Investing in our common stock involves substantial risks. In addition to the other information in this prospectus, you should carefully consider the following risk factors before investing in our common stock. Additional risks and uncertainties not presently known to us, or that we currently deem immaterial, may also materially adversely affect our business, financial condition or results of operations. We cannot assure you that any of the events discussed in the risk factors below, or other risks, will not occur. If they do, our business, financial condition and results of operations could be materially adversely affected. In such case, the trading price of our common stock could decline, and you may lose all or part of your investment. Certain statements in "Risk Factors" are forward-looking statements. See "Forward-Looking Statements" elsewhere in this prospectus.

Risks Related to Our Business and Industry

The markets we serve are subject to general economic conditions and cyclical demand, which could harm our business and lead to significant shifts in our results of operations from quarter to quarter that make it difficult to project long-term performance.

        Our operating results have been and may in the future be adversely affected by general economic conditions and the cyclical pattern of certain industries in which our customers and end users operate. Demand for our products and services depends in large part upon the level of capital and maintenance expenditures by many of our customers and end users, in particular those in the energy, chemical processing and power generation industries, and firms that design and construct facilities for these industries. These customers' expenditures historically have been cyclical in nature and vulnerable to economic downturns. Prolonged periods of little or no economic growth could decrease demand for oil and gas which, in turn, could result in lower demand for our products and a negative impact on our results of operations and cash flows. In addition, this historically cyclical demand may lead to significant shifts in our results of operations from quarter to quarter, which limits our ability to make accurate long-term predictions about our future performance.

A sustained downturn in the energy industry, due to oil and gas prices decreasing or otherwise, could decrease demand for some of our products and services, which could materially and adversely affect our business, financial condition and results of operations.

        A significant portion of our revenue historically has been generated by end-users in the upstream oil and gas markets. The businesses of most of our customers in the energy industry are, to varying degrees, cyclical and historically have experienced periodic downturns. Profitability in the energy industry is highly sensitive to supply and demand cycles and commodity prices, which historically have been volatile, and our customers in this industry historically have tended to delay large capital projects, including expensive maintenance and upgrades, during industry downturns. Customer project delays may limit our ability to realize value from our backlog as expected and cause fluctuations in the timing or the amount of revenue earned and the profitability of our business in a particular period. In addition, such delays may lead to significant fluctuations in results of operations from quarter to quarter, making it difficult to predict our financial performance on a quarterly basis.

        Demand for a significant portion of our products and services depends upon the level of capital expenditure by companies in the energy industry, which depends, in part, on energy prices. Prices of oil and gas have been very volatile over the past three years, with significant increases until achieving historic highs in July 2008, followed immediately by a steep decline through 2009 and a moderate increase throughout 2010. A sustained downturn in the capital expenditures of our customers, whether due to a decrease in the market price of oil and gas or otherwise, may delay projects, decrease demand for our products and services and cause downward pressure on the prices we charge, which, in turn, could have a material adverse effect on our business, financial condition and results of operations. Such

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downturns, including the perception that they might continue, could have a significant negative impact on the market price of our common stock.

As a global business, we are exposed to economic, political and other risks in a number of countries, which could materially reduce our revenues, profitability or cash flows or materially increase our liabilities. If we are unable to continue operating successfully in one or more foreign countries, it may have a material adverse effect on our business and financial condition.

        For fiscal 2010, approximately 66% of our revenues were generated by outside of the United States, and approximately 40% were generated outside North America. In addition, one of our key growth strategies is to continue to expand our global footprint in emerging and high growth markets around the world, although we may not be successful in expanding our international business.

        Conducting business outside the United States is subject to additional risks, including the following:

•

changes in a specific country's or region's political, social or economic conditions, particularly in emerging markets;



•

trade relations between the United States and those foreign countries in which our customers and suppliers have operations, including protectionist measures such as tariffs and import or export licensing requirements;



•

restrictions on our ability to own or operate subsidiaries in, expand in and repatriate cash from, foreign jurisdictions;



•

exchange controls and currency restrictions;



•

the burden of complying with multiple and potentially conflicting laws;



•

potentially negative consequences from changes in U.S. and foreign tax laws;



•

difficulty in staffing and managing (including ensuring compliance with internal policies and controls) geographically widespread operations;



•

different regulatory regimes controlling the protection of our intellectual property;



•

difficulty in the enforcement of contractual obligations in non-U.S. jurisdictions and the collection of accounts receivable from foreign accounts; and



•

transportation delays or interruptions.

        One or more of these factors could prevent us from successfully expanding our presence in international markets, could have a material adverse effect on our revenues, profitability or cash flows or cause an increase in our liabilities. We may not succeed in developing and implementing policies and strategies to counter the foregoing factors effectively in each location where we do business.

A failure to deliver our backlog on time could affect our future sales and profitability and our relationships with our customers, and if we were to experience a material amount of modifications or cancellations of orders, our sales could be negatively impacted.

        Our backlog is comprised of the portion of firm signed purchase orders or other written contractual commitments received from customers that we have not recognized as revenue. The dollar amount of backlog as of December 31, 2010 was $79.7 million. The timing of our recognition of revenue out of our backlog is subject to a variety of factors that may cause delays, many of which, including fluctuations in our customers' delivery schedules, are beyond our control. Such delays may lead to significant fluctuations in results of operations from quarter to quarter, making it difficult to predict our financial performance on a quarterly basis. For example, a delay in the completion of a

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large Greenfield project resulted in approximately several million dollars in revenue attributable to such project being realized in the quarter ended September 30, 2010, which was one quarter later than expected. Further, while we have historically experienced few order cancellations and the amount of order cancellations has not been material compared to our total contract volume, if we were to experience a significant amount of cancellations of or reductions in purchase orders, it would reduce our backlog and, consequently, our future sales and results of operations.

        Our ability to meet customer delivery schedules for our backlog is dependent on a number of factors including, but not limited to, access to raw materials, an adequate and capable workforce, engineering expertise for certain projects, sufficient manufacturing capacity and, in some cases, our reliance on subcontractors. For example, we are currently evaluating the expansion of our principal manufacturing facility in San Marcos, Texas, which we expect will serve our production capacity needs at that location for at least five years based on our current business plan. We cannot, however, provide any assurance that such expansion will be undertaken in a timely fashion, or at all, or that we will realize the gain in capacity we expect. The availability of these factors may in some cases be subject to conditions outside of our control. A failure to deliver in accordance with our performance obligations may result in financial penalties and damage to existing customer relationships, our reputation and a loss of future bidding opportunities, which could cause the loss of future business and could negatively impact our financial performance.

Our future revenue depends in part on our ability to bid and win new contracts. Our failure to effectively obtain future contracts could adversely affect our profitability.

        Our future revenue and overall results of operations require us to successfully bid on new contracts and, in particular, contracts for large Greenfield projects, which are frequently subject to competitive bidding processes. For example, for fiscal 2010, approximately 17% of our revenue consisted of designing, engineering, supplying and/or installing equipment for large Greenfield projects pursuant to competitive bids. Our revenue from major projects depends in part on the level of capital expenditures in our principal end markets, including the energy, chemical processing and power generation industries. The number of such projects we win in any year fluctuates, and is dependent upon the number of projects available and our ability to bid successfully for such projects. Contract proposals and negotiations are complex and frequently involve a lengthy bidding and selection process, which is affected by a number of factors, such as competitive position, market conditions, financing arrangements and required governmental approvals. For example, a client may require us to provide a bond or letter of credit to protect the client should we fail to perform under the terms of the contract. If negative market conditions arise, or if we fail to secure adequate financial arrangements or required governmental approvals, we may not be able to pursue particular projects, which could adversely affect our profitability.

We may be unable to compete successfully in the highly competitive markets in which we operate.

        We operate in competitive domestic and international markets and compete with highly competitive domestic and international manufacturers and service providers. The fragmented nature of the industrial electric heat tracing industry, which consists of approximately 40 companies, makes the market for our products and services highly competitive. A number of our direct and indirect competitors are major multinational corporations, some of which have substantially greater technical, financial and marketing resources than us, and additional competitors may enter these markets. Our competitors may develop products that are superior to our products, develop methods of more efficiently and effectively providing products and services, or adapt more quickly than we do to new technologies or evolving customer requirements. Any increase in competition may cause us to lose market share or compel us to reduce prices to remain competitive, which could result in reduced sales and earnings.

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Volatility in currency exchange rates may adversely affect our financial condition, results of operations or cash flows.

        We may not be able to effectively manage our exchange rate and/or currency transaction risks. Volatility in currency exchange rates may decrease our revenues and profitability, adversely affect our liquidity and impair our financial condition. We have not historically entered into hedging instruments to manage our exchange rate risk.

        Our non-U.S. subsidiaries generally sell their products and services in the local currency, but obtain a significant amount of their products from our facilities located in another country, primarily the United States, Canada or Europe. In particular, significant fluctuations in the Canadian Dollar, the Russian Ruble, the Euro or the Pound Sterling against the U.S. Dollar could adversely affect our results of operations. We also bid for certain foreign projects in U.S. Dollars or Euros. If the U.S. Dollar or Euro strengthens relative to the value of the local currency, we may be less competitive in bidding for those projects. See "Management's Discussion and Analysis of Financial Condition and Results of Operations—Quantitative and Qualitative Disclosures about Market Risk" for additional information regarding our foreign currency exposure relating to operations.

        In order to meet our global cash management needs, we often transfer cash between the United States and foreign operations and sometimes between foreign entities. In addition, our debt service requirements are primarily in U.S. Dollars and a substantial portion of our cash flow is generated in foreign currencies, and we may need to repatriate cash to the United States in order to meet our U.S. debt service obligations, including on our senior secured notes. These transfers of cash expose us to currency exchange rate risks, and significant changes in the value of the foreign currencies relative to the U.S. Dollar could limit our ability to meet our debt obligations, including under our senior secured notes, and impair our financial condition.

        Because our consolidated financial results are reported in U.S. Dollars, and we generate a substantial amount of our sales and earnings in other currencies, the translation of those results into U.S. Dollars can result in a significant decrease in the amount of those sales and earnings. In addition, fluctuations in currencies relative to the U.S. Dollar may make it more difficult to perform period-to-period comparisons of our reported results of operations.

Due to the nature of our business, we may be liable for damages based on product liability claims. We are also exposed to potential indemnity claims from customers for losses due to our work or if our employees are injured performing services.

        We face a risk of exposure to claims in the event that the failure, use or misuse of our products results, or is alleged to result, in death, bodily injury, property damage or economic loss. Although we maintain quality controls and procedures, we cannot be sure that our products will be free from defects. If any of our products prove to be defective, we may be required to replace the product. In addition, we may be required to recall or redesign such products, which could result in significant unexpected costs. Some of our products contain components manufactured by third parties, which may also have defects. In addition, if we are installing our products, we may be subject to claims that our installation caused damage or loss. Our products are often installed in our customers' or end users' complex and capital intensive facilities in inherently hazardous or dangerous industries, including energy, chemical processing and power generation, where the potential liability from risk of loss could be substantial. Although we currently maintain product liability coverage, which we believe is adequate for the continued operation of our business, we cannot be certain that this insurance coverage will continue to be available to us at a reasonable cost or, if available, will be adequate to cover any potential liabilities. With respect to components manufactured by third-party suppliers, the contractual indemnification that we seek from our third-party suppliers may be insufficient to cover claims made against us. In the event that we do not have adequate insurance or contractual indemnification, product

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liabilities could have a material adverse effect on our business, financial condition or results of operations.

        Under our customer contracts, we often indemnify our customers from damages and losses they incur due to our work or services performed by us, as well as for losses our customers incur due to any injury or loss of life suffered by any of our employees or our subcontractor's personnel occurring on our customer's property. Many, but not all, of our customer contracts include provisions designed to limit our potential liability by excluding consequential damages and lost profits from our indemnity obligations. However, substantial indemnity claims may exceed the amount of insurance we maintain and could have a material adverse affect on our reputation, business, financial condition or results of operations.

A material disruption at any of our manufacturing facilities could adversely affect our results of operations.

        If operations at any of our manufacturing facilities were to be disrupted as a result of significant equipment failures, natural disasters, power outages, fires, explosions, terrorism, adverse weather conditions, labor disputes or other reasons, we may be unable to fill customer orders and otherwise meet customer demand for our products, which could adversely affect our financial performance. For example, our marketing and research & development buildings, located on the same campus as our corporate headquarters and primary manufacturing facility in San Marcos, Texas, were destroyed by a tornado in January 2007.

        Interruptions in production, in particular at our manufacturing facilities in San Marcos, Texas, or Calgary, Canada, at which we manufacture the majority of our products, could increase our costs and reduce our sales. Any interruption in production capability could require us to make substantial capital expenditures to fill customer orders, which could negatively affect our profitability and financial condition. We maintain property damage insurance that we believe to be adequate to provide for reconstruction of facilities and equipment, as well as business interruption insurance to mitigate losses resulting from any production interruption or shutdown caused by an insured loss. However, any recovery under our insurance policies may not offset the lost sales or increased costs that may be experienced during the disruption of operations, which could adversely affect our financial performance.

Our international operations and non-U.S. subsidiaries are subject to a variety of complex and continually changing laws and regulations and, in particular, export control regulations.

        Due to the international scope of our operations, we are subject to a complex system of laws and regulations, including regulations issued by the U.S. Department of Justice, or the DOJ, the SEC, the Internal Revenue Service, or the IRS, Customs and Border Protection, or CBP, the Bureau of Industry and Security, or BIS, the Office of Antiboycott Compliance, or OAC, and the Office of Foreign Assets Control, or OFAC, as well as the counterparts of these agencies in foreign countries. While we believe we are in material compliance with these regulations and maintain programs intended to achieve compliance, we may currently or may in the future be in violation of these regulations. In 2009, we entered into settlement agreements with BIS and OFAC, and in 2010, we entered into a settlement agreement with OAC, in each case with respect to matters we voluntarily disclosed to such agencies.

        Any alleged or actual violations may subject us to government scrutiny, investigation and civil and criminal penalties and may limit our ability to export our products or provide services outside the United States. Additionally, we cannot predict the nature, scope or effect of future regulatory requirements to which our international operations might be subject or the manner in which existing laws might be administered or interpreted.

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        In addition, our geographically widespread operations, coupled with our relatively smaller offices in many countries and our reliance on third party subcontractors, suppliers and manufacturers in the completion of our projects, make it more difficult to oversee and ensure that all our offices and employees comply with our internal policies and control procedures. We have in the past experienced employee theft, although the amounts involved have not been material, and we cannot assure you that we can ensure compliance with our internal control policies and procedures.

We operate in many different jurisdictions and we could be adversely affected by violations of the U.S. Foreign Corrupt Practices Act and similar foreign anti-corruption laws.

        The U.S. Foreign Corrupt Practices Act, which we refer to as the FCPA, and similar foreign anti-corruption laws generally prohibit companies and their intermediaries from making improper payments or providing anything of value to influence foreign government officials for the purpose of obtaining or retaining business or obtaining an unfair advantage. Recent years have seen a substantial increase in the global enforcement of anti-corruption laws, with more frequent voluntary self-disclosures by companies, aggressive investigations and enforcement proceedings by both the DOJ and the SEC resulting in record fines and penalties, increased enforcement activity by non-U.S. regulators, and increases in criminal and civil proceedings brought against companies and individuals. Because many of our customers and end users are involved in infrastructure construction and energy production, they are often subject to increased scrutiny by regulators. Our internal policies mandate compliance with these anti-corruption laws. We operate in many parts of the world that are recognized as having governmental corruption problems to some degree and where strict compliance with anti-corruption laws may conflict with local customs and practices. Our continued operation and expansion outside the United States, including in developing countries, could increase the risk of such violations in the future. Despite our training and compliance programs, we cannot assure you that our internal control policies and procedures always will protect us from unauthorized reckless or criminal acts committed by our employees or agents. In the event that we believe or have reason to believe that our employees or agents have or may have violated applicable anti-corruption laws, including the FCPA, we may be required to investigate or have outside counsel investigate the relevant facts and circumstances, which can be expensive and require significant time and attention from senior management. Violations of these laws may result in severe criminal or civil sanctions, which could disrupt our business and result in a material adverse effect on our reputation, business, results of operations or financial condition.

Our dependence on subcontractors could adversely affect our results of operations.

        We often rely on third party subcontractors as well as third party suppliers and manufacturers to complete our projects. To the extent that we cannot engage subcontractors or acquire supplies or materials, our ability to complete a project in a timely fashion or at a profit may be impaired. If the amount we are required to pay for these goods and services exceeds the amount we have estimated in bidding for fixed-price contracts, we could experience losses on these contracts. In addition, if a subcontractor or supplier is unable to deliver its services or materials according to the negotiated contract terms for any reason, including the deterioration of its financial condition or over-commitment of its resources, we may be required to purchase the services or materials from another source at a higher price. This may reduce the profit to be realized or result in a loss on a project for which the services or materials were needed.

We may lose money on fixed-price contracts, and we are exposed to liquidated damages risks in many of our customer contracts.

        We often agree to provide products and services under fixed-price contracts, including our turnkey solutions. Under these contracts, we are typically responsible for all cost overruns, other than the amount of any cost overruns resulting from requested changes in order specifications. Our actual costs

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and any gross profit realized on these fixed-price contracts could vary from the estimated costs on which these contracts were originally based. This may occur for various reasons, including errors in estimates or bidding, changes in availability and cost of labor and raw materials and unforeseen technical and logistical challenges, including with managing our geographically widespread operations and use of third party subcontractors, suppliers and manufacturers in many countries. These variations and the risks inherent in our projects may result in reduced profitability or losses on projects. Depending on the size of a project, variations from estimated contract performance could have a material adverse impact on our operating results. In addition, many of our customer contracts, including fixed-price contracts, contain liquidated damages provisions in the event that we fail to perform our obligations thereunder in a timely manner or in accordance with the agreed terms, conditions and standards.

If we lose our senior management or other key employees, our business may be adversely affected.

        Our ability to successfully operate and grow our global business and implement our strategies is largely dependent on the efforts, abilities and services of our senior management and other key employees. If we lose the services of our senior management or other key employees and are unable to find qualified replacements with comparable experience in the industry, our business could be negatively affected. Our future success will also depend on, among other factors, our ability to attract and retain qualified personnel, such as engineers and other skilled labor, and in particular management and skilled employees for our foreign operations.

Our business strategy includes acquiring smaller, value-added companies and making investments that complement our existing business. These acquisitions and investments could be unsuccessful or consume significant resources, which could adversely affect our operating results.

        Acquisitions and investments may involve cash expenditures, debt incurrence, operating losses and expenses that could have a material adverse effect on our financial condition and operating results. Acquisitions involve numerous other risks, including:

•

diversion of management time and attention from daily operations;



•

difficulties integrating acquired businesses, technologies and personnel into our business;



•

potential loss of key employees, key contractual relationships or key customers of acquired companies or of us; and



•

assumption of the liabilities and exposure to unforeseen liabilities of acquired companies.

        We have limited experience in acquiring or integrating other businesses or making investments or undertaking joint ventures with others. It may be difficult for us to complete transactions quickly and to integrate acquired operations efficiently into our current business operations. Any acquisitions or investments may ultimately harm our business or financial condition, as such acquisitions may not be successful and may ultimately result in impairment charges.

We are subject to numerous environmental and health and safety laws and regulations, as well as potential environmental liabilities, which may require us to make substantial expenditures.

        Our operations and properties are subject to a variety of federal, state, local and foreign environmental laws and regulations, including those governing the discharge of pollutants into the air or water, the management and disposal of hazardous substances or wastes, the cleanup of contaminated sites and workplace health and safety. As an owner or operator of real property, or generator of waste, we could become subject to liability for environmental contamination, regardless of whether we caused such contamination. Certain environmental laws, including the Comprehensive Environmental Response, Compensation, and Liability Act, or CERCLA, impose joint and several liability for cleanup

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costs, without regard to fault, on persons who have disposed of or released hazardous substances into the environment. In addition, we could become liable to third parties for damages resulting from the disposal or release of hazardous substances into the environment. Some of our operations require environmental permits and controls to prevent and reduce air and water pollution, and these permits are subject to modification, renewal and revocation by issuing authorities. From time to time, we could be subject to requests for information, notices of violation, and/or investigations initiated by environmental regulatory agencies relating to our operations and properties. Violations of environmental and health and safety laws can result in substantial penalties, civil and criminal sanctions, permit revocations, and facility shutdowns. Environmental and health and safety laws may change rapidly and have tended to become more stringent over time. As a result, we could incur costs for past, present, or future failure to comply with all environmental and health and safety laws and regulations. In addition, we could become subject to potential regulations concerning the emission of greenhouse gases, and while the effect of such future regulations cannot be determined at this time, they could require us to incur substantial costs in order to achieve and maintain compliance. In the ordinary course of business, we may be held responsible for any environmental damages we may cause to our customers' premises.

Additional liabilities related to taxes or potential tax adjustments could adversely impact our financial results, financial condition and cash flow.

        We are subject to tax and related obligations in the jurisdictions in which we operate or do business, including state, local, federal and foreign taxes. The taxing rules of the various jurisdictions in which we operate or do business often are complex and subject to varying interpretations. Tax authorities may challenge tax positions that we take or historically have taken, and may assess taxes where we have not made tax filings or may audit the tax filings we have made and assess additional taxes, as they have done from time to time in the past. Some of these assessments may be substantial, and also may involve the imposition of substantial penalties and interest. In particular, in the years eligible for future audit, we consummated certain significant business transactions that we treated or intend to treat as not resulting in immediate gain for income tax purposes. Significant judgment is required in evaluating our tax positions and in establishing appropriate reserves. The resolutions of our tax positions are unpredictable. The payment of substantial additional taxes, penalties or interest resulting from any assessments could materially and adversely impact our results of operations, financial condition and cash flow.

        Even though we have increased and may in the future increase our repatriation of cash earned by our non-U.S. subsidiaries to fund one-time redemptions of our outstanding senior secured notes or other extraordinary corporate events in the United States, we will leave a portion of such cash outside the United States as permanently reinvested earnings and profits. Accordingly, our current estimated annual effective tax rate is based on partial, and not full, repatriation of cash earned by our non-U.S. subsidiaries. If we underestimate our need for repatriated cash, or our needs change, significant tax adjustments may result.

        We have anticipated the need for a valuation reserve against deferred tax assets that are expected to arise this year as we repatriate earnings to fund one-time redemptions of our outstanding senior secured notes in the United States. We expect the deferred tax asset to arise from limitations on our ability to recover the foreign taxes paid on repatriated earnings. This calculation is complex and we may have underestimated or overestimated the need for a valuation reserve and significant tax adjustments may result.

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The obligations associated with being a public company will require significant resources and management attention.

        As a public company with listed equity securities, we will need to comply with new laws, regulations and requirements, including the requirements of the Securities Exchange Act of 1934, as amended, which we refer to the Exchange Act, certain corporate governance provisions of the Sarbanes-Oxley Act of 2002, which we refer to as the Sarbanes-Oxley Act, related regulations of the SEC and requirements of the New York Stock Exchange, which we refer to as the NYSE, with which we were not required to comply as a private company. Complying with these statutes, regulations and requirements will occupy a significant amount of time of our board of directors and management and will significantly increase our legal, accounting and other expenses. The Exchange Act requires that we file annual, quarterly and current reports with respect to our business and financial condition. The Sarbanes-Oxley Act requires, among other things, that we establish and maintain effective internal controls and procedures for financial reporting. Furthermore, the need to establish the corporate infrastructure demanded of a public company may divert management's attention from implementing our growth strategy, which could prevent us from improving our business, results of operations and financial condition. We have made, and will continue to make, changes to our internal controls and procedures for financial reporting and accounting systems to meet our reporting obligations as a public company. However, the measures we take may not be sufficient to satisfy our obligations. In addition, we cannot predict or estimate the amount of additional costs we may incur in order to comply with these requirements.

        Section 404 of the Sarbanes-Oxley Act requires annual management assessments and attestation by our independent registered public accounting firm of the effectiveness of our internal control over financial reporting. Starting with the annual report for the fiscal year ending March 31, 2012, we will be required to file an annual management assessment of the effectiveness of our internal control over financial reporting with the SEC. For the fiscal year ending March 31, 2013, in addition to the management assessment, we will have to file an attestation by our independent registered public accounting firm of the effectiveness of our internal control over financial reporting with the SEC. In connection with the implementation of the necessary procedures and practices related to internal control over financial reporting, we or our independent registered public accounting firm may identify deficiencies that we may not be able to remediate in time to meet the deadline imposed by the Sarbanes-Oxley Act for compliance with the requirements of Section 404. If we fail to comply with Section 404, or if we or our independent registered public accounting firm identify and report a material weakness, it may affect the reliability of our internal control over financial reporting, which could adversely affect the market price of our common stock and subject us to sanctions or investigations by the NYSE, the SEC or other regulatory authorities, which would require additional financial and management resources.

Our current or future indebtedness could impair our financial condition and reduce the funds available to us for other purposes. Our debt agreements impose certain operating and financial restrictions, with which failure to comply could result in an event of default that could adversely affect our results of operations.

        We have substantial indebtedness. On a pro forma basis, after giving effect to this offering, the redemption of $21.0 million aggregate principal amount of our senior secured notes scheduled to occur on April 29, 2011 and the prepayment of $21.0 million of our senior secured notes using proceeds from this offering, as of December 31, 2010, we would have had aggregate indebtedness, net of current portion, of $168.0 million, all of which was secured. In the nine months ended December 31, 2010, our consolidated interest expense on our senior secured notes was approximately $13.3 million (which excludes interest expense resulting from debt costs relating to the CHS Transactions, our revolving credit facility and amortization). Following the redemption of our senior secured notes scheduled to

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occur on April 29, 2011 and the consummation of this offering, we expect annual interest expense on our senior secured notes to be reduced by approximately $4.0 million, assuming net proceeds to us in this offering of approximately $45.9 million, based on an assumed initial public offering price of $13.00 per share, the midpoint of the range on the cover of this prospectus. If our cash flows and capital resources are insufficient to fund these and other debt service obligations and keep us in compliance with the covenants under our debt agreements or to fund our other liquidity needs, we may be forced to reduce or delay capital expenditures, sell assets or operations, seek additional capital or restructure or refinance our indebtedness. We cannot ensure that we would be able to take any of these actions, that these actions would permit us to meet our scheduled debt service obligations or that these actions would be permitted under the terms of our existing or future debt agreements, which may impose significant operating and financial restrictions on us and could adversely affect our ability to finance our future operations or capital needs; obtain standby letters of credit, bank guarantees or performance bonds required to bid on or secure certain customer contracts; make strategic acquisitions or investments or enter into alliances; withstand a future downturn in our business or the economy in general; engage in business activities, including future opportunities, that may be in our interest; and plan for or react to market conditions or otherwise execute our business strategies.

        If we cannot make scheduled payments on our debt, or if we breach any of the covenants in debt agreements, we will be in default and, as a result, our debt holders could declare all outstanding principal and interest to be due and payable, the lenders under our revolving credit facility could terminate their commitments to lend us money and foreclose against the assets securing our borrowings, and we could be forced into bankruptcy or liquidation.

        In addition, we and certain of our subsidiaries may incur significant additional indebtedness, including additional secured indebtedness. Although the terms of our debt agreements contain restrictions on the incurrence of additional indebtedness, these restrictions are subject to a number of qualifications and exceptions, and additional indebtedness incurred in compliance with these restrictions could be significant. Incurring additional indebtedness could increase the risks associated with our substantial indebtedness, including our ability to service our indebtedness.

A significant portion of our business is conducted through foreign subsidiaries and our failure to generate sufficient cash flow from these subsidiaries, or otherwise repatriate or receive cash from these subsidiaries, could result in our inability to repay our indebtedness.

        For the nine months ended December 31, 2010, 71% of our revenues were generated outside of the United States. While we have been able to meet the regular interest payment obligations on our senior secured notes to date from cash generated through our U.S. operations, we may not be able to do so in the future or may seek to repatriate cash for other uses, and our ability to withdraw cash from foreign subsidiaries will depend upon the results of operations of these subsidiaries and may be subject to legal, contractual or other restrictions and other business considerations. Our foreign subsidiaries may enter into financing arrangements that limit their ability to make loans or other payments to fund payments of our debt. In particular, to the extent our foreign subsidiaries incur additional indebtedness, the ability of our foreign subsidiaries to provide us with cash may be limited. In addition, dividend and interest payments to us from our foreign subsidiaries may be subject to foreign withholding taxes, which could reduce the amount of funds we receive from our foreign subsidiaries. Dividends and other distributions from our foreign subsidiaries may also be subject to fluctuations in currency exchange rates and legal and other restrictions on repatriation, which could further reduce the amount of funds we receive from our foreign subsidiaries.

        In general, when an entity in a foreign jurisdiction repatriates cash to the United States, the amount of such cash is treated as a dividend taxable at current U.S. tax rates. Accordingly, upon the distribution of cash to us from our foreign subsidiaries, we will be subject to U.S. income taxes. Although foreign tax credits may be available to reduce the amount of the additional tax liability, these

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credits may be limited based on our tax attributes. Therefore, to the extent that we must use cash generated in foreign jurisdictions, there may be a cost associated with repatriating cash to the United States.

We rely heavily on trade secrets to gain a competitive advantage in the market and the unenforceability of our nondisclosure agreements may adversely affect our operations.

        The heat tracing industry is highly competitive and subject to the introduction of innovative techniques and services using new technologies. While we have patented some of our products and processes, we historically have not relied upon patents to protect our design or manufacturing processes or products, and our patents are not material to our operations or business. Instead, we rely significantly on maintaining confidential our trade secrets and other information related to our operations. Accordingly, we require all employees to sign a nondisclosure agreement to protect our trade secrets, business strategy and other proprietary information. If the provisions of these agreements are found unenforceable in any jurisdiction within which we operate, the disclosure of our proprietary information may place us at a competitive disadvantage. Even where the provisions are enforceable, the confidentiality clauses may not provide adequate protection of our trade secrets and proprietary information in every jurisdiction.

        We may be unable to prevent third parties from using our intellectual property rights, including trade secrets and know-how, without our authorization or from independently developing intellectual property that is the same as or similar to ours, particularly in those countries where the laws do not protect our intellectual property rights as fully as in the United States. The unauthorized use of our trade secrets or know-how by third parties could reduce or eliminate any competitive advantage we have developed, cause us to lose sales or otherwise harm our business or increase our expenses as we attempt to enforce our rights.

Our intellectual property rights may not be successfully asserted in the future or may be invalidated, circumvented or challenged.

        We have obtained and applied for some U.S. and, to a lesser extent, foreign trademark registrations and will continue to evaluate the registration of additional trademarks. We cannot guarantee that any of our pending applications will be approved. Moreover, even if the applications are approved, third parties may seek to oppose or otherwise challenge them. In addition, we rely on a number of significant unregistered trademarks, primarily abroad, but also in the United States, in the day-to-day operation of our business. Without the protections afforded by registration, our ability to protect and use our trademarks may be limited and could negatively affect our business.

        In addition, while we have not faced intellectual property infringement claims from others in recent years, in the event successful infringement claims are brought against us, particularly claims (under patents or otherwise) against our product design or manufacturing processes, such claims could have a material adverse affect on our business, financial condition or results of operation.

Risks Related to This Offering and Our Common Stock

There is currently no public market for our common stock and an active trading market for our common stock may never develop following this offering.

        Prior to this offering, there has been no public market for our common stock. Although our common stock has been approved for listing on the NYSE, an active public market for our shares may not develop or be sustained after this offering and there can be no assurance as to they liquidity of any market that may develop for our common stock. If an active market does not develop, the market price and liquidity of our common stock may be adversely affected. The initial public offering price will be determined by negotiations between the underwriters, the selling stockholders and our board of

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directors and may not be representative of the market price at which our shares of common stock will trade after this offering. In particular, we cannot assure you that you will be able to resell our shares at or above the initial public offering price.

The price of our common stock could be volatile.

        The overall market and the price of our common stock may fluctuate greatly. The trading price of our common stock may be significantly affected by various factors, including:

•

quarterly fluctuations in our operating results;



•

changes in investors' and analysts' perception of the business risks and conditions of our business or our competitors;



•

our ability to meet the earnings estimates and other performance expectations of financial analysts or investors;



•

unfavorable commentary or downgrades of our stock by equity research analysts;



•

the emergence of new sales channels in which we are unable to compete effectively;



•

disruption to our operations;



•

termination of lock-up agreements or other restrictions on the ability of our existing stockholders to sell their shares after this offering;



•

fluctuations in the stock prices of our peer companies or in stock markets in general; and



•

general economic or political conditions.

Future sales of our common stock may lower our stock price.

        If our existing stockholders sell a large number of shares of our common stock following this offering, the market price of our common stock could decline significantly. In addition, the perception in the public market that our existing stockholders might sell shares of common stock could depress the market price of our common stock, regardless of the actual plans of our existing stockholders. Immediately after this offering, 28,933,407 shares of our common stock will be outstanding. This includes the 10,000,000 shares of common stock that we and the selling stockholders are selling in this offering, which may be resold in the public market immediately after this offering (unless purchased by an "affiliate," as such term is defined in Rule 144 under the Securities Act of 1933, as amended, which we refer to as the Securities Act, in which case such affiliate will be subject to the restrictions imposed by Rule 144).

        We expect that the remaining 18,933,407 shares, representing 65% of our total outstanding shares of common stock following this offering, will become available for resale in the public market as shown in the chart below. Our directors and executive officers, the holders of all of our outstanding shares and vested options and participants in the directed share program, have signed lock-up agreements for a period of 180 days following the date of this prospectus, subject to extension in the case of an earnings release or material news or a material event relating to us. Barclays Capital Inc. and Jefferies & Company, Inc. may, in their sole discretion and without notice, release all or any portion of the shares of common stock subject to lock-up agreements. As restrictions on resale end, the market price of our shares of common stock could drop significantly if the holders of these restricted shares sell them or are perceived by the market as intending to sell them. These factors could also make it

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more difficult for us to raise additional funds through future offerings of our shares of common stock or other securities.

        In addition, 2,757,524 shares of common stock will be eligible for sale upon exercise of vested options 180 days following the date of this prospectus, subject to extension as described under "Underwriting." Following this offering, we intend to file a registration statement on Form S-8 under the Securities Act to register all of the shares of common stock subject to outstanding options under our existing option plan as well as all shares of our common stock that may be covered by additional options and other awards granted under the our new 2011 Long-Term Incentive Plan. See "Compensation Discussion and Analysis—2011 Long-Term Incentive Plan." Once these shares are registered, they can be sold in the public market upon issuance, subject to restrictions under the securities laws applicable to resales by affiliates.

        In addition, commencing 180 days following this offering, CHS will have the right, subject to certain exceptions and conditions, to require us to register their 9,556,793 shares of common stock under the Securities Act, and holders of an additional 9,376,614 shares of our common stock will have the right to participate in future registrations of securities by us. Registration of any of these outstanding shares of common stock would result in such shares becoming freely tradable without compliance with Rule 144 upon effectiveness of the registration statement. See "Shares Available for Future Sale."

Investors in this offering will suffer immediate and substantial dilution.

        The initial public offering price per share of common stock will be substantially higher than our pro forma net tangible book value per share immediately after this offering. As a result, you will pay a price per share that substantially exceeds the book value of our assets after subtracting our liabilities. At an offering price of $13.00 per share, the midpoint range set forth on the cover of this prospectus, you will incur immediate and substantial dilution in an amount of $17.19 per share of common stock. See "Dilution."

        Moreover, we issued options in the past to acquire common stock at prices significantly below the assumed initial public offering price. As of the date of this prospectus, 2,757,524 shares of common stock were issuable upon exercise of outstanding stock options. To the extent that these outstanding options are ultimately exercised, you will incur further dilution.

An increase in interest rates may cause the market price of our common stock to decline.

        Like all equity investments, an investment in our common stock is subject to certain risks. In exchange for accepting these risks, investors may expect to receive a higher rate of return than would otherwise be obtainable from lower-risk investments. Accordingly, as interest rates rise, the ability of investors to obtain higher risk-adjusted rates of return by purchasing government-backed debt securities

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may cause a corresponding decline in demand for riskier investments generally, including yield-based equity investments. Reduced demand for our common stock resulting from investors seeking other more favorable investment opportunities may cause the trading price of our common stock to decline.

Anti-takeover provisions contained in our amended and restated certificate of incorporation and amended and restated bylaws, as well as provisions of Delaware law, could impair a takeover attempt that our stockholders may find beneficial.

        Our second amended and restated certificate of incorporation, amended and restated bylaws and Delaware law contain provisions that could have the effect of rendering more difficult or discouraging an acquisition deemed undesirable by our board of directors. Our corporate governance documents include provisions:

•

authorizing our board of directors, without further action by the stockholders, to issue blank check preferred stock;



•

limiting the ability of our stockholders to call and bring business before special meetings and to take action by written consent in lieu of a meeting;



•

requiring advance notice of stockholder proposals for business to be conducted at meetings of our stockholders and for nominations of candidates for election to our board of directors;



•

authorizing our board of directors, without stockholder approval, to amend our amended and restated bylaws;



•

limiting the determination of the number of directors on our board of directors and the filling of vacancies or newly created seats on our board of directors to our board of directors then in office; and



•

subject to certain exceptions, limiting our ability to engage in certain business combinations with an "interested stockholder" for a three-year period following the time that the stockholder became an interested stockholder.

        These provisions, alone or together, could delay hostile takeovers and changes in control of our company or changes in our management.

        As a Delaware corporation, we are also subject to provisions of Delaware law, which may impair a takeover attempt that our stockholders may find beneficial. Any provision of our second amended and restated certificate of incorporation or amended and restated bylaws or Delaware law that has the effect of delaying or deterring a change in control could limit the opportunity for our stockholders to receive a premium for their shares of our common stock, and could also affect the price that some investors are willing to pay for our common stock.

Our existing stockholders will exert significant influence over us after the consummation of this offering, and their interests may not coincide with yours.

        After this offering, CHS and its affiliates will own, in the aggregate, 33.0% of our outstanding common stock. CHS and its affiliates, together with the investment funds associated with the other sponsors, will own, in the aggregate, 54.4% of our outstanding common stock. These percentages will decrease to 31.5% and 51.8%, respectively, if the underwriters exercise their over-allotment option in full. As a result, these stockholders, acting individually or together, could control substantially all matters requiring stockholder approval for the foreseeable future, including approval of significant corporate transactions. In addition, following this offering, pursuant to the terms of our Securityholder Agreement (as described below in "Certain Relationships and Related Party Transactions—Securityholder Agreement"), CHS will continue to have the ability to designate one member of our board of directors and to require all other parties to the Securityholder Agreement to sell their respective shares of our common stock, on substantially the same terms and conditions as CHS is

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selling its shares, in the event that CHS approves a sale of us. After giving effect to this offering, the parties to the Securityholder Agreement, other than CHS, will own in the aggregate 32.4% of our outstanding common stock (or 30.6% if the underwriters exercise their over-allotment option in full). The interests of these stockholders may not always coincide with our interests as a company or the interest of other stockholders. In addition, this concentration of ownership may delay or prevent a change in control of our company, even if that change in control would benefit our stockholders. This significant concentration of stock ownership and voting power may adversely affect the trading price of our common stock due to investors' perception that conflicts of interest may exist or arise. See "Principal and Selling Stockholders" and "Certain Relationships and Related Party Transactions" for further information about the equity interests held by our sponsors and their respective affiliates.

        Moreover, our second amended and restated certificate of incorporation contains a provision renouncing our interest and expectancy in, or in being offered an opportunity to participate in, any business opportunity that may be presented to the sponsors or any of their respective affiliates (other than us and our subsidiaries), subsidiaries, officers, directors, agents, stockholders, members, partners and employees and that may be a business opportunity for such sponsor, even if the opportunity is one that we might reasonably have pursued or had the ability or desire to pursue if granted the opportunity to do so. None of the sponsors has any duty to refrain from engaging directly or indirectly in the same or similar business activities or lines of business as us or any of our subsidiaries. See "Description of Capital Stock—Anti-Takeover Effects of Provisions of Our Second Amended and Restated Certificate of Incorporation, Our Amended and Restated Bylaws and Delaware Law—Corporate Opportunity."

We may be eligible to take advantage of the NYSE's "controlled company" exemption from certain NYSE corporate governance requirements, and if we elect to do so, our stockholders will not have the same protections afforded to stockholders of companies that are subject to such requirements.

        Under the NYSE rules, a company of which more than 50% of the voting power is held by another person or group of persons acting together is a "controlled company" and may elect not to comply with certain NYSE corporate governance requirements. We may be eligible to take advantage of the "controlled company" exception in light of the collective voting power of our sponsors and their respective affiliates after giving effect to this offering. We currently do not intend to rely on this exception even if we are so eligible, but may elect to do so in the future. If we were to elect to be treated as a "controlled company" in the future, we would be exempt from certain NYSE corporate governance requirements, including the requirements that our board of directors consist of a majority of independent directors and that we have compensation and nominating and corporate governance committees comprised entirely of independent directors, and our stockholders would not have the same protections afforded to stockholders of companies that are subject to all of the NYSE corporate governance requirements.

If securities or industry analysts do not publish research or reports about our business, if they adversely change their recommendations regarding our common stock or if our operating results do not meet their expectations, our common stock price could decline.

        The market price of our common stock will be influenced by the research and reports that industry or securities analysts publish about us or our business. If one or more of these analysts cease coverage of our company or fail to publish reports on us regularly, we could lose visibility in the financial markets, which in turn could cause the market price of our common stock or its trading volume to decline. Moreover, if one or more of the analysts who cover our company downgrade our common stock or if our operating results or prospects do not meet their expectations, the market price of our common stock could decline.

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FORWARD-LOOKING STATEMENTS

        This prospectus includes forward-looking statements within the meaning of the U.S. federal securities laws in addition to historical information. These forward-looking statements are included throughout this prospectus, including in the sections entitled "Prospectus Summary," "Risk Factors," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and "Business" and include, without limitation, statements regarding our industry, business strategy, plans, goals and expectations concerning our market position, future operations, margins, profitability, capital expenditures, liquidity and capital resources and other financial and operating information. When used in this discussion, the words "anticipate," "assume," "believe," "budget," "continue," "could," "estimate," "expect," "intend," "may," "plan," "potential," "predict," "project," "will," "future" and similar terms and phrases are intended to identify forward-looking statements in this prospectus.

        Forward-looking statements reflect our current expectations regarding future events, results or outcomes. These expectations may or may not be realized. Some of these expectations may be based upon assumptions, data or judgments that prove to be incorrect. In addition, our business and operations involve numerous risks and uncertainties, many of which are beyond our control, which could result in our expectations not being realized or otherwise materially affect our financial condition, results of operations and cash flows. The statements include but are not limited to statements regarding: (i) our plans to strategically pursue emerging growth opportunities in diverse regions and across industry sectors; (ii) our plans to secure more Greenfield project bids; (iii) our ability to generate more MRO/UE revenue from our existing and future installed base; (iv) our ability to timely deliver backlog; (v) our ability to respond to new market developments and technological advances; (vi) our expectations regarding energy consumption and demand in the future and its impact on our future results of operations; (vii) our plans to develop strategic alliances with major customers and suppliers; (viii) our expectations that our revenues will continue to increase; (ix) our belief in the sufficiency of our cash flows to meet our needs for the next year; (x) our expectations regarding our expansion of our principal manufacturing facility in San Marcos, Texas; and (xi) our intended use of proceeds from this offering.

        Actual events, results and outcomes may differ materially from our expectations due to a variety of factors. Although it is not possible to identify all of these factors, they include, among others, (i) general economic conditions and cyclicality in the markets we serve; (ii) future growth of energy and chemical processing capital investments; (iii) changes in relevant currency exchange rates; (iv) our ability to comply with the complex and dynamic system of laws and regulations applicable to international operations; (v) a material disruption at any of our manufacturing facilities; (vi) our dependence on subcontractors and suppliers; (vii) our ability to obtain standby letters of credit, bank guarantees or performance bonds required to bid on or secure certain customer contracts; (viii) competition from various other sources providing similar heat tracing products and services, or other alternative technologies, to customers; (ix) our ability to attract and retain qualified management and employees, particularly in our overseas markets; (x) our ability to continue to generate sufficient cash flow to satisfy our liquidity needs; (xi) the extent to which federal, state, local and foreign governmental regulation of energy, chemical processing and power generation products and services limits or prohibits the operation of our business; and (xii) other factors discussed in more detail under the caption "Risk Factors." Any one of these factors or a combination of these factors could materially affect our future results of operations and could influence whether any forward-looking statements contained in this prospectus ultimately prove to be accurate. See also "Risk Factors" included elsewhere in this prospectus regarding the additional factors that have impacted or may impact our business and operations.

        Our forward-looking statements are not guarantees of future performance, and actual results and future performance may differ materially from those suggested in any forward-looking statements. We do not intend to update these statements unless we are required to do so under applicable securities laws.

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USE OF PROCEEDS

        Based upon an assumed initial public offering price of $13.00 per share, which is the mid-point of the price range set forth on the cover page of this prospectus, we estimate that we will receive net proceeds from this offering of approximately $45.9 million (or approximately $63.1 million if the underwriters exercise their option to purchase additional shares of common stock in full), after deducting the underwriting discounts and commissions in connection with this offering and estimated offering expenses payable by us of $2.5 million. See "Underwriting."

        We intend to use $21.6 million of the net proceeds from this offering received by us to prepay $21.0 million of the $189.0 million principal amount of our 9.500% Senior Secured Notes that will be outstanding immediately prior to the consummation of this offering, which mature on May 1, 2017, reflecting a redemption price of 103% of the principal amount thereof, plus accrued and unpaid interest and additional interest, if any, to the redemption date, and the balance for general corporate purposes. The 9.500% Senior Secured Notes were issued in connection with the Acquisition by our wholly owned subsidiary, Thermon Industries, Inc. The proceeds were used to fund a portion of the purchase price for the Acquisition.

        We will not receive any proceeds from the shares sold by the selling stockholders.

        For additional information regarding our liquidity and outstanding indebtedness, see "Management's Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources."

        A $1.00 increase (decrease) in the assumed initial public offering price per share would increase (decrease) the estimated net proceeds to us by approximately $3.7 million (or approximately $5.0 million if the underwriters exercise their option to purchase additional shares of common stock in full), assuming that the number of shares of common stock sold by us, as set forth on the cover page of this prospectus, remains the same and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us. A 1.0 million share increase (decrease) in the number of shares of common stock sold by us in this offering would increase (decrease) the net proceeds to us from this offering by approximately $12.1 million, assuming an initial public offering price per share equal to the midpoint of the estimated price range set forth on the cover page of this prospectus and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

DIVIDEND POLICY

        Since the consummation of the CHS Transactions on April 30, 2010, we have not declared or paid any cash dividends on our capital stock, and we do not currently intend to pay any cash dividends on our common stock. We currently intend to retain earnings to finance the growth and development of our business and for working capital and general corporate purposes. Any payment of dividends will be at the discretion of our board of directors and will depend upon earnings, financial condition, capital requirements, level of indebtedness, contractual restrictions with respect to payment of dividends, restrictions imposed by applicable law and other factors. In particular, the indenture governing our senior secured notes and our revolving credit facility limit our ability to pay dividends from cash generated from operations. See "Management's Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources."

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CAPITALIZATION

        The following table sets forth our total capitalization as of December 31, 2010:

•

on an actual basis; and



•

on an as adjusted basis to give effect to (i) the adoption of our second amended and restated certificate of incorporation immediately prior to this offering; (ii) the redemption of $21.0 million aggregate principal amount of our senior secured notes at a redemption price of 103% of the principal amount thereof, which is scheduled to occur on April 29, 2011; and (iii) the issuance and sale by us of shares of our common stock in this offering at an assumed initial public offering price of $13.00 per share, the midpoint range set forth on the cover of this prospectus, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us and the application of the net proceeds to us from this offering as described in "Use of Proceeds."

        The table below should be read in conjunction with "Use of Proceeds," "Unaudited Pro Forma Condensed Consolidated Financial Statements," "Selected Historical and Pro Forma Consolidated Financial and Operating Data," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and our consolidated financial statements and accompanying notes included elsewhere in this prospectus.

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DILUTION

        If you invest in our common stock in this offering, your ownership interest will be immediately diluted to the extent of the difference between the initial public offering price per share of our common stock and the net tangible book value per share of our common stock immediately after this offering. Dilution results from the fact that the per share offering price of the common stock is substantially in excess of the book value per share attributable to the existing stockholders for the presently outstanding stock.

        Our net tangible book value at December 31, 2010 was $(167.2) million, and our net tangible book value per share was $(6.70). Net tangible book value per share before the offering has been determined by dividing net tangible book value (total book value of tangible assets less total liabilities) by the number of shares of common stock outstanding after the automatic conversion of our common stock into one class of voting stock.

        After giving effect to the sale of our common stock in this offering at an assumed initial public offering price of $13.00 per share, the midpoint of the price range set forth on the cover page of this prospectus, and after deducting the underwriting discount and estimated offering expenses payable by us, our pro forma net tangible book value at December 31, 2010 would have been $(121.3) million, or $(4.19) per share. This represents an immediate increase in net tangible book value per share of $2.51 to the existing stockholders and dilution in net tangible book value per share of $17.19 to new investors who purchase shares in the offering. The following table illustrates this per share dilution to new investors:

        The dilution information discussed above is illustrative only and will change based on the actual initial public offering price and other terms of this offering. If the underwriters exercise their option to purchase additional shares of common stock in full, the pro forma net tangible book value per share after giving effect to this offering would be $(3.43) per share, and the dilution in pro forma net tangible book value per share to new investors in this offering would be $16.43 per share, in each case calculated as described above.

        The following table summarizes, on the same pro forma basis as of December 31, 2010, the total number of shares of common stock purchased from us, the total consideration paid to us and the average price per share paid by the existing stockholders and by new investors purchasing shares in this offering, before deducting the underwriting discounts and commissions and estimated offering expenses payable by us (amounts in thousands, except percentages and per share data):

        If the underwriters exercise their option to purchase additional shares of common stock in full, our existing stockholders would own 82% and our new investors would own 18% of the total number of shares of our common stock outstanding immediately after this offering, and our existing stockholders

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would have paid $129.5 million, or 65%, of the total consideration and new investors would have paid $70.5 million, or 35% of the total consideration, in each case calculated as described above.

        The information in the preceding table has been calculated using an assumed public offering price of $13.00 per share, which is the midpoint of the price range set forth on the cover page of this prospectus. A $1.00 increase or decrease in the assumed initial public offering price per share would increase or decrease, respectively, the consideration paid to us by new investors and in total by approximately $4.0 million (or by $5.0 million if the underwriters exercise their option to purchase additional shares of common stock in full) and the percentage of total consideration paid by new investors by approximately 1%, and would decrease or increase, respectively, the percentage of total consideration paid by existing stockholders by approximately 1%, in each case calculated as described above and assuming that the number of shares sold by us and the selling stockholders, as set forth on the cover page of this prospectus, remains the same. A 1.0 million share increase or decrease in the number of shares of common stock that we sell in this offering would increase or decrease, respectively, the percentage of shares purchased by new investors by approximately 3%, the amount of consideration paid by new investors and in total by approximately $13.0 million and the percentage of total consideration paid by new investors by approximately 4% and would decrease or increase, respectively, the percentage of shares purchased by existing stockholders by approximately 3% and the percentage of total consideration paid by existing stockholders by approximately 4%, in each case calculated as described above.

        The tables above exclude the following shares:

•

2,757,524 shares of our common stock issuable upon the exercise of options outstanding under our existing restricted stock and stock option plan (2,648,402 of which were outstanding as of December 31, 2010); and



•

2,893,341 shares of our common stock reserved for issuance under our 2011 Long-Term Incentive Plan, which we refer to as our LTIP, 122,000 of which we intend to grant to our executive officers and certain other employees concurrently with the pricing of this offering with an exercise price equal to the initial public offering price. See "Compensation Discussion and Analysis—2011 Long-Term Incentive Plan."

        To the extent that any of these options are exercised, there will be further dilution to new investors participating in this offering. Assuming the exercise in full of the 2,648,402 stock options outstanding as of December 31, 2010, the pro forma net tangible book value per share after giving effect to this offering would be $(3.41) per share, representing an immediate increase in net tangible book value of $3.30 per share to existing stockholders and an immediate dilution to net tangible book value of $16.41 per share to new investors, and our existing stockholders would own 79% and our new investors would own 21% of the total number of shares of our common stock outstanding immediately after this offering, and our existing stockholders would have paid $129.5 million, or 66%, of the total consideration and new investors would have paid $65.8 million, or 34% of the total consideration, in each case calculated as described above.

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UNAUDITED PRO FORMA CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

        The following unaudited pro forma condensed consolidated balance sheet as of December 31, 2010 and unaudited pro forma condensed consolidated statements of operations for the year ended March 31, 2010, the period from April 1, through April 30, 2010 ("predecessor"), the period from May 1, through December 31, 2010 ("successor") and the nine months ended December 31, 2009 ("predecessor") are based on our historical consolidated financial statements and give effect to the CHS Transactions and this offering, including the issuance by us of 4,000,000 shares of our common stock at a price of $13.00 per share, the midpoint of the estimated price range set forth on the cover page of this prospectus, the use of proceeds as set forth under "Use of Proceeds" and the termination of our management fee, as if they had occurred as of April 1, 2009.

        The unaudited pro forma condensed consolidated financial data includes unaudited pro forma adjustments that are directly attributable to the CHS Transactions and this offering. In addition, with respect to the unaudited pro forma condensed consolidated financial statements, the unaudited pro forma adjustments are expected to have a continuing impact on the consolidated results.

        Pro forma adjustments were made to reflect the:

•

increase in amortization expense for changes in the estimated fair values of the acquired intangible assets of the Company;



•

increase in interest expense resulting from additional indebtedness incurred in connection with our senior secured notes and our revolving credit facility, along with the amortization of debt issuance costs on our senior secured notes, net of the reduction in interest expense resulting from the redemption of $21.0 million aggregate principal amount of our senior secured notes scheduled to occur on April 29, 2011 and the repayment of $21.0 million of our outstanding indebtedness using the net proceeds from this offering and assuming an offering price of $13.00 per share, the midpoint of the estimated price range set forth on the cover page of this prospectus;



•

increase in the number of basic shares outstanding by 4,000,000 and the number of diluted shares outstanding by 5,589,041;



•

elimination of the transaction expenses related to the Acquisition;



•

elimination of the management fee which is being terminated in connection with this offering; and



•

the income tax effect of the pro forma adjustments.

        The Acquisition has been accounted for as a purchase in accordance with the applicable Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, guidance. We have allocated the excess of the purchase price over the net assets acquired to intangible assets and goodwill. The preliminary allocation to intangible assets and goodwill is based on management's best estimate of the fair value of the intangible assets (including trademarks, developed technology, customer list, backlog, certifications and non-compete agreements) and is consistent with the methodology applied during 2007 in connection with the Audax Transaction. We have not allocated any of the excess purchase price to the acquired tangible assets or liabilities assumed, except for inventory, but rather utilized their current carrying value as we believe these carrying values approximate fair value, although we have not completed a third party valuation of the acquired assets or liabilities. The pro forma data presented will be revised based upon final calculations and the resolution of purchase price adjustments as additional information becomes available. The final allocation of the purchase price in the Acquisition will be determined at a later date and depends on a number of factors, including the final valuation of the tangible and identifiable intangible assets acquired and liabilities assumed in the Acquisition. An independent third-party appraiser will perform a valuation of these assets as of the

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closing date of the Acquisition, and upon a final valuation the purchase allocation will be adjusted. Such final adjustments, including changes to depreciation and amortization resulting from the allocation of purchase price to amortizable tangible and intangible assets, may be material. This valuation will be based on the net tangible and intangible assets and liabilities as of the closing date of the Acquisition.

        We believe that the assumptions used to derive the unaudited pro forma condensed consolidated financial data are reasonable given the information available; however, such assumptions are subject to change and the effect of any such change could be material. The unaudited pro forma condensed consolidated financial data should be read in conjunction with "Management's Discussion and Analysis of Financial Condition and Results of Operations," and the historical consolidated financial statements and related notes of Thermon Holdings, LLC and Thermon Group Holdings, Inc., as applicable, included elsewhere in this prospectus. The unaudited pro forma condensed consolidated financial data is presented for informational purposes only and is not intended to represent or be indicative of the consolidated results of operations or financial position that we would have reported had the CHS Transactions or this offering been completed as of the dates and for the periods presented, and should not be taken as representative of our consolidated results of operations or financial condition following the completion of the CHS Transactions or this offering.

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Thermon Group Holdings, Inc.

Unaudited Pro Forma Condensed Consolidated Balance Sheet

As of December 31, 2010

See accompanying notes.

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Thermon Holdings, LLC

Unaudited Pro Forma Condensed Consolidated Statement of Operations

Year Ended March 31, 2010

See accompanying notes

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Thermon Group Holdings, Inc.

Unaudited Pro Forma Condensed Consolidated Statement of Operations

Nine Months Ended December 31, 2010