Williamson-Thermaflo Brand Overview

Williamson-Thermaflo Manufacturer Overview

Williamson-Thermoflo Co. offers a full line of oil and gas furnaces, oil and gas boilers, indirect-fired water heaters, and air conditioning products. Williamson-Thermoflo is an independent business unit of Weil-McLain, which is a subsidiary of SPX Corp. SPX posted revenues of about $1.4 billion in 2017.

Corporate History

Williamson was established in 1890 and Thermoflo was founded in 1946. They partnered in 1999 to become Williamson-Thermoflo and were acquired by Weil-McLain the same year. SPX was founded in Muskegon, Mich., in 1911 as The Piston Ring Co. and acquired Weil-McLain in 2001.

Despite the 1999 partnership of the two manufacturers, the company today sells its furnaces, boilers and air conditioners under two brands: Williamson and Thermoflo. The company promotes the former brand for its easy-to-service design and durable performance, while noting the latter brand’s value and range of heating capacities.

Product Lines

 [ Williamson-Thermoflo Series : Temp-O-Matic ]

The Williamson-Thermoflo range of boilers includes a wall-mounted gas-fired condensing unit and an oil-fired water boiler with tankless heater. The company also manufactures both an oil-fired and a gas-fired steam boiler. The company’s boilers are constructed of cast iron and are available in models with up to 91 percent AFUE except for the wall-mounted stainless steel Freestyle unit, which has an AFUE of above 92 percent.

Williamson-Thermoflo furnaces are available in models with up to 90 percent AFUE, in single- or variable-speed, and for any number of installation profiles.


Williamson-Thermoflo boilers come with a limited lifetime warranty. There is a lifetime warranty against leaking. Williamson-Thermoflo products are serviced through professional heating contractors.

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