Modular condensing-type boilers are now used for a significant number of commercial applications. Non-condensing boilers have maximum thermal efficiency of 88%. Condensing boilers are available with efficiency up to 98%. Condensing boilers incorporate a heat exchanger to capture energy that would otherwise be lost in flue gas, to avoid condensation within exhaust piping. Designers must use care to size heating coils to lower water temperatures, to maximize condensing potential. Products like the Lochinvar Knight boiler can be used in variable primary pumping applications, with good modulation capabiliy.
Other major competitors include Aerco, Patterson-Kelley, and Fulton.