Hitachi YUTAKI Series - DHW Control

Controller pack
Service Manual
86
DHW control functions
SMGB0066 rev.0 - 12/2009
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
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DHW diverting valve system DHW pumped system

TheDHWfunctionhaspriorityovertheHeatingCircuit,whichmeansthatwhentheDHWstoragetankisbeingloaded,
the heating circuit will be switched off.
TheDHWfunctionwillbeblocked(temporarilydisabled)whentheTariff/TimerinputisconguredforDHWandtheinput
isopencircuit(oralternativelyshortcircuitasdenedbyparameter–see“DHWTimeProgram”).

P1 System DHW Choice (default 0)
P1=0 No DHW function -
P1=1 System with DHW diverting valve -
P1=2 System with DHW pump -
 

WhenDHWcontrolisenabled,thesystemcontrollerheatstheDHWtanktemperaturetotheDHWsetpoint(P10).When
theDHWtemperaturedropsbelowtheDHWsetpointminustheDHWdifferential(P11),thisfunctionswitchesonthe
DHWPumporopenstheDHWvalve,andsetsasupplysetpointequaltoDHWsetpoint+DHWsupplyoffset(P12).The
DHW loading is complete when the DHW temperature rises above the DHW setpoint.
Supply Setpoint for DHW loading = DHW setpoint + DHW Supply Offset (P12)
DSET = DHW setpoint (P10)
SDHW = Supply Setpoint for DHW loading.
TDHW = DHW tank temperature

DHW loading starts (power-on or DHW timer signal)
Supply water temperature set to P10+P12
(*)
DHW tank temperature (TDHW) rises above P10
DHW loading stops
Supply water temperature is determined by heating circuit
requirements.
DHW tank temperature (TDHW) falls below P10 - P11
DHW loading starts
Supply water temperature set to valve P10+P12
(*)
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note
The Heat Pump outlet temperature setpoint will be equal -
to the Supply Water Temperature Setpoint + P31 (Heat
Pump supply offset) to account for pipe losses. The Heat
Pump outlet temperature setpoint is always limited to 55º
C or 50º C depending on the outside temperature.