[. . . ] [. . . ] Modulating gas valve ensures constant temperature at varying flow rates Pressure relief valve included Available in natural gas (NG) or liquid propane (LP) 15-year warranty No Electricity Needed. Standing pilot ignition, no electricity required for the 425 PN model. PN Solid Copper Heat Exchanger Standing Pilot Optional Power Stainless Steel Burners Output Control Slide PN ¾" Temperature Control Knob Typical Venting Configuration Power Vent Option Closet Installation of Closet Installation GWH 425 PN with Bosch Aquastar proper venting and combustion air supply shown. CERTIFIED Illustrating the side wall vent option that allows horizontal venting and elimination of the chimney. [. . . ] [. . . ]