Navien’s NCB-H condensing combi boiler series includes five models ranging from 160,000 BTU/H for DHW and 60,000 BTU/H for heating to 210,000 BTU/H DHW and 150,000 BTU/H heating. The series uses dual stainless steel heat exchangers for heating and a separate flat panel stainless steel heat exchanger for DHW. Features include 15:1 turndown ratio (TDR) for DHW and up to 11:1 TDR for heating.