IRVINE, Calif. — Navien has begun distribution of the new NFB series high-efficiency condensing fire tube boilers. The NFB series is now available in two models, NFB-175 (175,000 Btu/h) and NFB-200 (199,900 Btu/h), both featuring new, patented fire tube heat exchangers. The in-house-designed and -manufactured heat exchanger is form-pressed and robotic-laser-welded to minimize the number of weak points that could be prone to thermal stress and corrosion. Oval tubes within the heat exchanger contain internal turbulators designed to improve the heat transfer rate and structural integrity of the assembly. A specific water flow is generated by baffles inside the heat exchanger to extract the maximum amount of heat from flue gases while the non-metallic base provides additional protection against corrosion caused by acidic condensate. Additional features of the Energy Star Most Efficient 95 percent AFUE NFB Series include advanced user interface controls and built-in zone controllers. For more information, visit