... back Chamber (Wet-Back). 3.100% Corrugated Furnace. Product Features of WNS Oil/Gas-fired Hot Water Boiler1. This horizontal wet-back boiler ... adapted to various fuels, including light oil, heavy oil, residual oil, natural gas, coal gas, and liquefied petroleum gas;7. Polished stainless steel presents pleasing ... and high pressure style, for customer’s option. WNS Oil/Gas-fired hot water Boiler