Installation Manual

6 720 644 930
30
Installation instructions
3.12 Space heating applications
Bosch 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. 40. Use of a
Bosch tankless water heater in a combination DHW
and space heating application will result in the product
warranty being reduced to 3 years.
Fig. 39 Pressure drop curve
Warning: If the set point temperature is
above 120°F, precautions should be
taken to protect users of potable water
from scalding.
Warning: Propylene glycol may be
used for freeze prevention ONLY on the
space heating side of the heat
exchanger. Do not use ethylene glycol
(automotive antifreeze).
Warning: 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-handling system. The
flow switch should be used to disable
the blower on the air-handling system
when domestic water is used.
Warning: Ensure the primary pump is
properly sized to provide adequate flow
for the system heat load.
i
For Pump sizing please refer to the
pressure drop curves, Fig. 39. 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.
Flow(GPM)
Pressure(FeetofHead)
0
0.0 1.0 2.0 3.0 4.0 5.0
10
20
30
40
50
60
70
940ES
6720644930-01.1V