The CREST® line of condensing boilers was expanded to include three models with 750,000-Btuh, 1-MBtuh, and 1.25-MBtuh-inputs. The new boiler models deliver 96.2 percent thermal efficiency and up to 20:1 modulation turndown. The boilers are designed with a top-mounted, micro-metal fiber burner, engineered specifically for fire-tube technology. The wave fire-tube configuration creates turbulence as flue gas products flow down the tube, scrubbing the energy. As water flows up the vessel, super-heated flue products flow down the fire tubes. With one pass, heat is transferred and flue gases reach condensing temperatures. The system ensures smooth, quiet modulating combustion from as low as 5 percent of the maximum firing rate up to 100 percent as the heating load increases. By matching the actual system demand, modulation reduces operating costs, enhances long-term reliability, and provides improved seasonal and operating efficiencies.