The gas tankless recirculating heaters, Bosch 345 ESR and the Bosch 450 ESR are temperature modulated and have electronic ignition. The ESR stands for Electronic ignition, Sealed combustion and Recirculating. These recirculating heaters are designed and approved for heating and recirculating potable water in conjunction with an indirect storage tank.
The 345/450 ESR are not approved or designed for closed loop heating applications. The ESR units are not a tankless heater as they have no flow switch to respond to flow. Instead it’s a recirculating water heater designed for tank loading applications. When an AquaStat (not included) hooked up to a tank tells the ESR that water needs to be brought back up to temperature, the ESR will tell a circulator (not included) to turn on to create flow through the heater to reheat the water in the tank. Please refer to the installation and applications manual.
The Bosch 345 ESR recirculating heater is a 95K BTU unit and can deliver 3.5 GPM at a 45 degree rise. Efficiency is 82%
The Bosch 450 ESR recirculating heater is a 120K BTU unit and can deliver 4.5 GPM at a 45 degree rise. Efficiency is 81%
The temperature control range for both heaters can be set anywhere from 115°F (45°C) - 190°F (90°C)
The 345/450 ESR comes with a standard ¾” pressure relief valve.
The 345/450 ESR has a special built-in freeze prevention cycle and is controlled by a sensor. Freeze protection is always assured by the operation of the appliance. If the primary NTC (temperature) sensor detects temperatures 9°F below the selected temperature, the appliance starts on minimum power until the sensor reads selected temperature. In the case of minimum set point temperature then it will start at 41°F. The use of non-potable additives like glycol is not approved.
The Bosch 345 ESR and the Bosch 450ESR must be installed indoors according to the provided installation manual. The 345/450 ESR is NOT approved for outdoor installations.
The Bosch 345/450 ESR recirculating heaters must be vented in accordance with the installation manual and require Category III 3” stainless steel sealed venting for the exhaust. These heaters are direct vent units and must be vented directly to the outside in accordance with the installation manual. These heaters cannot be combination vented with any other appliance. The intake should be taken from the outside and 3”PVC or other material can be used only for the intake air.
The Bosch 345/450 ESR recirculating heaters are gas specific so they cannot be converted from one gas type to another.
