Bosch tankless water heaters can be used in recirculation applications and there are many different set ups for this such as direct recirculation and indirect recirculation. Certain models of the Bosch tankless water heaters are approved for direct recirculation and are listed below. Please be aware that the heat exchanger warranty of 15 years will be reduced to 3 years for direct recirculation. This is stated in the warranty section of the installation manual. All of the Bosch tankless water heaters can be set up for an indirect recirculation application in conjunction with a mini tank, recirculation pump and aquastat as described in the image below. The warranty for recirculation through an indirect mini-tank and not directly through the heater is 15 years.
Bosch tankless water heaters approved for direct recirculation:
Bosch Therm C1210ES
Bosch Therm C1210ESC (Commercial Unit)
Bosch Greentherm C1050
Bosch Greentherm C950
Bosch Therm 940ES
Bosch Therm 830ES
Diagram for Recirculation Application:
(This schematic is for illustration only and must not be used for actual installation without appropriate engineering and technical advise from a properly licensed professional in the locality where the installation is made).