The NFB-C is available in two sizes: NFB-301C (301 MBH) and NFB-399C (399 MBH). 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. The 97.5% thermal efficiency NFB-C series includes a 15:1 turndown ratio; top and bottom piping connections for installation flexibility; an advanced 7” color touchscreen display with easy, intuitive navigation for setup, troubleshooting and operation; extremely low NOx levels; 3” venting up to 60’ or 4” up to 150’ with PVC/CPVC/PP/SS approved materials; and Modbus/BACnet and LonWorks to BMS communication capability. Navien.