Navien’s NCB Series combi-boilers are offered in three models: the NCB-180, NCB-210 and NCB-240. The maximum heating input for hydronic heating is 80,000 Btu/hr., 100,000 Btu/hr., and 120,000 Btu/hr., respectively. DHW flow rates for each model at 77 Delta T are 3.4 gpm, 4 gpm and 4.5 gpm, respectively. They incorporate the use of dual stainless-steel heat exchangers for hydronic heat and a stainless-steel flat-plate heat exchanger for DHW with capability to use 1/2” gas connections and 2” PVC venting.