Navien NFC-250 Fire Tube Combi Boiler with Tankless Water Heater

The Navien NFC-250 is a 250,000 BTU fire-tube condensing combination boiler, designed to provide both domestic hot water (DHW) and hydronic space heating from a single appliance. "NFC" identifies the fire-tube heat exchanger architecture (versus the water-tube design in other Navien combis). The 250K BTU class is sized for larger homes with substantial space-heat demand.

Specs: 250,000 BTU input, AFUE 95%, fire-tube stainless steel heat exchanger with self-cleaning design. Up to 9.0 GPM DHW at a moderate temperature rise. Built-in 0.5-gallon buffer with ComfortFlow recirculation for the DHW function. PVC venting up to 100 feet. 15-year warranty on the heat exchanger.

The fire-tube architecture is Navien's premium engineering for the combi market. Combustion gases flow through tubes inside the water jacket, providing better heat transfer and less scaling than water-tube designs. The self-cleaning feature uses the unit's modulation cycles to flush condensate through the heat exchanger.

Right buyer: medium-to-large home (2,500–4,000 sq ft) needing both space heat and DHW from a single appliance. Conversion from aging oil-fired boiler or atmospheric boiler + separate water heater. Typical install cost $9,000–$13,000 depending on existing hydronic system. Wrong buyer: pure DHW applications (the NPE tankless series is the right product), or smaller homes (the NHB hydronic-only boilers or smaller combi units are more economical).