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. Additional features of the 95% AFUE NFB series include advanced user interface controls, built-in zone controllers, 10:1 turndown ratio from a sophisticated gas flow-control system, easy field gas convertibility, extremely low NOx levels, cascade capability up to 16 units, common venting capability up to eight units and remote accessibility when installed with NaviLink Wi-Fi control system.