Unitherm Furnace, LLC.

We strive to provide strong, consistent customer service and quality furnace products specific to customer needs at competitive prices. We pride ourselves in tailoring our furnace products to each customer while maintaining our established variety of products. Everything is designed to help you save energy, cut costs, and improve quality. Download our line card.

Reputation for Excellence

Since its inception, Unitherm has relied on the quality of its work and word of mouth to drive business. Part of its success can be attributed to Frank’s insightful understanding of Unitherm’s customers.  He knows that buyers might be hesitant to invest in products from a small company and rely on it for specialized spare parts. Unitherm builds everything — even custom furnaces — with standard components, so customers never have to worry about locating the OEM parts they need. Unitherm’s products are used nationwide in a vast array of industries.  Our custom products are at work in military installations, aerospace facilities, charcoal-manufacturing firms, ceramics companies, and metal-forging plants. Our ISO 10725 accreditation allows us to meet the strict AMS2750E Aerospace Specifications, which are the industry’s toughest.


Unitherm Furnace, LLC, headquartered in Wentzville, Mo., is an ISO 9001 and ISO/IEC 17025 accredited manufacturer of custom thermal processing equipment, namely industrial furnaces and ovens. With more than 65 years of industry experience, Unitherm creates unique designs using standard components to ensure ease of maintenance over the life of the equipment. Unitherm Furnace has specialized in solving problems since 1980. The industrial-furnace company was the brainchild of Frank Lim, who already had two decades of experience in the furnace industry when he started considering the possibility of launching his own business. The country was in the midst of a recession, and Lim saw a market opportunity for rebuilt furnaces. Frank approached colleague Ron Kientzy, who also had extensive experience in furnace manufacturing — along with instrumentation and controls — about launching a company together. Despite the economic difficulties at the time, the company they built together thrived. Unitherm started with Frank’s idea of selling rebuilt furnaces for industrial use and then expanded into custom orders.

Frank says, “We build what customers need.” Unitherm’s many innovative custom projects over the years have included a rotary kiln explosive waste incinerator. The kiln’s 6,000,000-BTUh (British Thermal Units per Hour) gas-fired burner heats the machine’s chamber and detonates explosive materials as they move through the kiln. Another Unitherm custom product melts rubber off the steel in steel-belted tires. The machine can move through 400 tires per hour. A Unitherm-built fluorescent penetrant inspection unit, which is a machine that identifies defects that could comprise parts’ integrity, is used today for aerospace and aircraft metal structural parts. The company continues to accept custom orders and to welcome challenges other companies turn away.

Under Frank and Ron’s leadership, Unitherm has developed into a one-stop shop for industrial furnace manufacturing and service. The company handles furnace designs, builds, modifications, re-builds, retrofits and upgrades. Unitherm also takes parts orders, provides heattreating services, and certifies furnaces, all at its Wentzville facility. Unitherm is a key provider for furnace certifications for the US aerospace industry.


Organic growth in Unitherm’s customer base and production capabilities for the near future is promising due to their long-term customer relationships and the recent acquisition of Unitherm by Eberhart Capital, a multimillion dollar private equity firm. They have the capacity to continue tried and true tested practices and products while innovating ways to provide standardized products to the many, technologically advanced industries they support.

Our Team

Frank Lim
Ron Kientzy
Frank LimCo-Founder

Frank Lim's analytical mind has made Unitherm Furnace an innovator in its industry since the company first opened its doors in 1980.

Frank has always enjoyed a good challenge. He was raised in China, until moving with his father to Louisiana at age 12. When he was 14, Frank got his first job — as a projectionist at the local movie theater.

During World War II, Frank served in the Army Air Corps. He trained in air reconnaissance and map making. During the peak of the war, Frank was transferred to the 28th Infantry Division of the Pennsylvania National Guard. He served with that division from the invasion of the Allied Forces at Normandy, France, until the end of the war.

After completing his military service, Frank earned an associate's degree in industrial controls at a college in Missouri. Over the years, he has worked in photography and has been a restaurant owner. He has worked for Dow Chemical and for an aluminum-aircraft forging company.

The remainder of Frank's career has been spent in the furnace industry, in which he developed a keen understanding of the intricacies of furnaces and their controls. At the St. Louis-area furnace-manufacturing company where he worked before launching Unitherm, Frank served as production manager.

Frank, who now has 65+ years of experience in furnace manufacturing and instrumentation, has developed a reputation in his industry as a problem solver. His input and technological know-how have made it possible for countless companies to overcome significant hurdles. For instance, a major charcoal manufacturer turned to Frank to help it put a stop to the fires that were igniting during the briquettes' drying process. Frank recognized the problem — the dryers' temperature-control system — and Unitherm built a new control panel that put an end to the issue.

That client was one of numerous clients — from the U.S. government to General Electric — that turned to Unitherm and Frank to build them unique products that address engineering, instrumentation, sensor, and space-constraint challenges.

Frank says he takes pride in Unitherm's successes over the years and the company's ability to grow and maintain a loyal base of customers based on word of mouth. “If you do things right,” he says, “people remember.”

At age 89, Frank shows no signs of slowing down. In fact, he rarely sleeps more than two hours a night. He plans to continue his role as a problem solver, for both Unitherm and others who would jump at the chance to benefit from his expertise and counsel.

Ron KientzyCo-Founder

Ron Kientzy, one of Unitherm's founding partners, has worn numerous hats at Unitherm, from manager to sales representative to engineer.

A native of the Wentzville, Missouri, area, Ron attended welding school and earned an associate's degree in electronic technology. He has been working in the furnace industry since 1973, when he started working for a local manufacturing company. He learned the business from the ground up and developed expertise in nearly every aspect of the operation. Ron has taken the same hands-on approach at Unitherm, where he consistently holds its staff to the same high standards of hard work and excellence that he expects from himself.

Ron isn't shy about plunging into work projects. Most of the products that come out of Unitherm's doors have been welded, wired, or enhanced in some way by Ron. His devotion to his work is linked with his pride in the company's workmanship and its attentiveness to customers' needs.

What sets Unitherm apart, Ron says, is the custom work it takes on for clients. Unitherm, he says, accepts the projects no one else wants to build and makes them a success.

Ron's colleagues at Unitherm describe him as the company's driving force. President Frank Lim develops Unitherm's ideas, they say, and Ron does whatever it takes to bring them to fruition.