Global Pro Tankless Supply is just about out of stock on the Bosch 450ESR NG recirculating heater. The 120,000 BTU Bosch Protankless 450 ESR NG Tankless Recirculating Water Heater is temperature modulated and has an electronic ignition. Theis recirculating water heater is designed and approved for heating and recirculating potable water in conjunction with an indirect tank. The 450ESR recirculating water heater is not approved or designed for closed loop heating applications.
The Bosch 450ESR unit is not a traditional tankless water heater. It has no flow switch to respond to water flow. Instead it is a recirculating water heates 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.