Raypak Digital Low NOx 399K BTU Cupro-Nickel Pool Heater Natural Gas has a polyester-coated, non-corrosive cabinet that is more durable than solventborne- and waterborne-coated metal cabinets. Every piece of sheet metal goes through a 7-stage wash system, making certain the powder paint has a perfect bond. Underneath the tough, yet beautiful finish you will find galvanized metal that offers superior rust prevention and years of durable service. Its wind-resistance design eliminates the need for fans to combat drafting problems. Polymer headers prevent rust stains from harming your pool's surface, providing you with years of trouble-free swimming pleasure. This gas pool heater also features a cupro-nickel heat exchanger, stainless steel tube sheet, and 2" CPVC water connections. The Unitherm Governor helps reduce condensation from low inlet water temperatures and automatically regulates the water flow to help keep the water temperature in the heat exchanger about 105ᵒF. This Raypak gas heater is equipped with an automatic bypass built into the heater, making it capable of handling water flow at a rate up to 125 gpm. The burner tray is built to last and its innovative design allows for the easy removal of the tray and burners for servicing. A ceramic fiber combustion box keeps your heater running efficiently while keeping the outside jacket cool. By using this space-age material the heater will not retain residual heat after it is turned off, allowing it to be installed without the use of costly metal heat sinks. Rheem heaters are energy-smart and consistently achieve the highest efficiency ratings. Low Emissions units use combustion control to minimize levels of nitrogen oxides (NOx).