boilerThe Cleaver-Brooks ClearFire-C down-fired, stainless steel, fully condensing hot water boiler achieves efficiencies up to 99 percent and NOx levels to less than 20 ppm, says the company. The modulating pre-mix burner precisely controls the air/gas mixture, and the linkage-less burner provides up to 5:1 turndown. The ClearFire-C comes in seven sizes, from 500 MBtu to 3,300 MMBtu.