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4.12 Space Heating Applications - Bosch Greentherm 9800 SE 160/199 Manual

Indoor residential and comme rcial tankless water heaters
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Fig. 25
Recirculation application using the cold water line
and a bypass valve
[1] Cold water supply
[2] Check valve field supplied
[3] Expansion tank field supplied
[4] Circulator pump field supplied
[5] Circulator cable accessory
[6] Greentherm 9800 SE / SEC
[7] PRV
[8] Shutoff valves field supplied
[9] Bypass valve
Recirculation application showed in fig. 25 is
for Greentherm 9800 SE model only.
Models with build-in pump cannot be used.
4.11.1 Recirculation options
House Recirculation
Compatible with dedicated return line and cross over mode
with thermal by-pass valve.
Tank loading
External NTC
– Only compatible with Bosch cable/sensor accessory
(TTNr-TBD). Sensor must be inserted into the tank
pocket and plug in at the tank connector in bottom of
the appliance.
– Compatible with thermostat type solution (example
Aquastat). Thermostat/Aquastat must be connected to
the appliance using the tank connector in bottom of the
Internal NTC
Greentherm 9800 SE 160/199 | SEC 199
– Allows tank loading without using any external sensor/
cable. Temperature readings will be made at the

4.12 Space heating applications

▶ If the set point temperature is above
120°F, precautions should be taken to
protect users of potable water from
▶ 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
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. 27. 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 9800 SE / SEC 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. 26. Please see
warranty document for additional details.
Installation instructions | 33
6 720 816 815 (2016/10)



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