Eliminates the standby losses associated with conventional tank type water heaters. This coupled with its 80% efficiency can reduce the cost of heating water by 20 to 50%. The water is heated on demand as the flow of water triggers the heater on, which provides an endless supply of hot water.
Water connection 1/2" NPT, gas connections 1/2" NPT. Min. water pressure 15 psi, max water pressure 150 psi, minimum flow to activate burners: 3/4 gpm. Thermostatic control combined with water flow rate modulates the flame to regulate the output temperature to preset temperature. Models ending in S modulate down to zero and are therefore suitable for use with solar water heating systems. Models ending in HN are spark-ignited by a Micro-Turbine which is activated by a request for hot water in the house. The models ending with EF have a built in Power Vent, ideal for horizontal through-the-wall venting. GWH 635ES with 6.35 gpm @45 degree F rise is powerful enough to supply two showers simultaneously. Available in natural gas or propane (specify at the time of ordering).
10 year limited warranty.
Model 38B: 40K BTU/H NG or LP Model 125B S: 117K BTU/H with zero mod. NG or LP Model 425 HN: 117K BTU/H no pilot NG or LP Model 425 EF: 130K BTU/H electronic ignition, power vented NG or LP Model 635 ES: 175K BTY/H electronic ignition, power vented
Power Vent Kit for Thru Wall 110V 1.25A 80 & 125 & 425
Bosch Pro Tankless Gas Water Heaters 
Eliminates the standby losses associated with conventional tank type water heaters. This coupled with its 80% efficiency can reduce the cost of heating water by 20 to 50%. The water is heated on demand as the flow of water triggers the heater on, which provides an endless supply of hot water. 