Hitachi YUTAKI Series - Maximum DHW Loading Time

87
DHW control functions
SMGB0066 rev.0 - 12/2009
Controller pack
Service Manual
4

P10 DHW setpoint (default 45°C)
P11 DHW differential (default 5K)
P12 DHW supply offset (default 10K)

CONF1,2: HeatPumpheatstheDHWstoragetankdirectly.IfthestoragetankalsohasaninternalDHWelectric
heater this can also be used if necessary.
CONF2: The3-stageelectricheatercannotbeusedforDHWloading.WhenDHWloadingstarts,the3-stage
electric heater is switched off.
CONF3,5: IftheHeatPumpisnotabletoreachtheDHWsupplysetpointbyitself,theboilermayalsobeusedto
raise the temperature of the DHW tank (see “Using the Boiler for DHW loading”).

P10: DHW setpoint
CONF1,2: IfthereisnointernalDHWelectricheater,settingtheDHWsetpointhigherthan45°Cmayresultinvery
longDHWloadingtimes,andthedesiredtemperaturemaynotbereached.Thisisbecausethemaximum
outlettemperaturefromtheHeatPumpisnormally55°C,andatlowoutdoortemperatures50°C.
CONF3,5: TheDHWsetpointmaybesethighersincetheboilerwillalsobeusedtoheattheDHWstoragetank.
P11: DHW differential
A small DHW differential will increase the frequency of the DHW loading periods while making them shorter. A large DHW
differentialwillreducethefrequencyoftheDHWloadingperiods,whilemakingeachperiodlonger,andwillcauselarger
swings in DHW temperatures.
P12: DHW supply offset
CONF1,2: settingavaluehigherthan10KwillnotaffecttheDHWloadingperiodsincethemaximumoutlet
temperature from the Heat Pump is 55°C.
CONF3,5: settingavaluehigherthan10KwillallowfasterDHWloadingtimessincetheboilercanbeused.
 

IncasethereisacontinuoushighdemandforDHWoveraverylongperiod,ortheDHWsetpointissettoohigh,the
HeatPumpmaynotbeabletoreachthedesiredtemperature.Inthiscase,toensurethatheatisprovidedintheliving
space(heatingcircuit),theDHWloadingisstoppedafterapresettime(parameterP27)andthesystemcontrollerreturns
to satisfy the demand from the heating circuit.

DHW loading starts (power-on or DHW timer signal)
SupplywatertemperaturesettoP10+P12(*)
DHW setpoint not reached after time P27
DHW loading stopped