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Installation & Service Manual
™
F I R E T U B E
6B
Domestic water piping (Combi Only)
Table 6E DHW Pressure Drop Chart
DHW PRESSURE DROP
Combi Sequence of operation
Th e cold domestic water enters the plate heat exchanger through
the DHW inlet connection, fl ow switch, and strainer. Cold water
fl ows through the plate heat exchanger, where it is heated by hot
boiler water, and then discharged through the Domestic Hot
Water (DHW) outlet connection.
Heated boiler water is supplied from the primary combustion
heat exchanger through the diverter valve into the plate heat
exchanger. Th e boiler water heats the colder domestic water,
and is then returned to the primary heat exchanger through the
pump.
While operating in DHW Mode, the diverter valve prevents
water from fl owing through the boiler outlet connection to
the heating system. Boiler water is circulated inside the unit
between the plate heat exchanger and the primary combustion
heat exchanger.
Th e diverter valve is normally in the DHW position when the
unit is in Standby, thus isolating boiler water from fl owing to the
heating system. When there is a space heating call, the diverter
valve will move to the space heat position allowing boiler water
to fl ow from the primary combustion heat exchanger through
the boiler outlet connection to the heating system, bypassing
the plate heat exchanger. Th e internal pump is used to circulate
water in both Space Heating and DHW Modes.
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