▶ The use of a flow switch is recommended to ensure DHW
priority and to prevent "cold-blow" situations when the
Bosch tankless water heater is used with an air handler.
Air handler installation must include a pump.
The flow switch should be used to disable the blower on the
air-handling system when domestic water is used.
▶ Ensure the primary pump is properly sized to provide
adequate flow for the system heat load.
For external pump sizing please refer to the pressure drop
curves, fig. 34. Also remember to account for system piping
pressure loss. A minimum of 1.7 GPM is recommended to
provide adequate flow through the water heater when
determining the size of the primary pump.
Greentherm T9900 SE/i tankless water heaters are
approved for use in combination DHW and space heating
applications (open loop setup).
These water heaters are not approved for use in space heating
only applications (closed-loop setup). Bosch supports
applications of combination DHW and space heating in an open
loop configuration if plumbed similar to Fig. 33. Please see
warranty document for additional details.
Greentherm T9900 SE/i – 6 720 813 635 (2019/03)