Korean boiler manufacturer KD Navien will expand its product line in the United States and Canada in the fourth quarter when they begin selling the Navien Heating Boiler series. The NHB will be offered in four sizes: NHB-55, NHB-80, NHB 110 and NHB-150, with turn-down-ratios respectively of 7:1, 10:1, 11:1 and 15:1.