U.S. Boiler Company K2

K2 is a wall-hung gas condensing hot-water boiler, not a steam boiler.

U.S. Boiler describes a stainless exchanger, Sage 2.2 controls, pre-installed loop circulator and up to 95% AFUE. Listed input range: 80–180 MBH input. Venting on file: direct vent. Warranty on file: heat exchanger lifetime limited; parts 5-year.

It is best suited to homes replacing gas hot-water heating with a condensing system. Before ordering, a contractor should complete a room-by-room heat-loss calculation, check the distribution system's water temperatures and confirm venting and clearances against the installation manual.

Pros: Condensing design captures heat from flue gases when return water is cool enough. Modulating burners can match output more closely to mild-weather loads. Multiple sizes (80–180 MBH input) allow sizing to a calculated heat loss. Considerations: Check the exact K2 generation and size for warranty, vent and condensate requirements. Condensing efficiency depends on low return-water temperatures; high-temperature radiation may limit real-world savings. Requires a condensate drain and, in many homes, neutralization, plus manufacturer-approved vent materials.

Specifications on this page come from the manufacturer documents linked below; always confirm figures for the exact size being installed.

Condensing boilers like the K2 reach their rated efficiency only when return water runs cool enough to condense flue gases. We check your radiation and design water temperatures so the unit actually condenses in your home, not just on the spec sheet.

Every U.S. Boiler Company installation starts with a free in-home assessment covering the heat-loss calculation, venting and chimney condition, gas or oil supply sizing, and permit requirements for your town. Learn more about our boiler installation process, or see current rebate and incentive programs that may apply.