Hitachi YUTAKI Series - Heatpump Maximum Return High Limit; Heatpump Operating Limits

93
Heatpump control functions
SMGB0066 rev.0 - 12/2009
Controller pack
Service Manual
4

note
It is important to minimise this effect as much as possible during installation. The following precautions should -
be taken
1. Fully insulate the supply and return pipes. -
2. Ensure that the supply temperature sensor is tightly strapped-on to the pipe with the metal clip provided. -
The metal clip should be used directly around the sensor element itself (since it itself improves the heat transfer) -
and then insulation should be placed around the sensor and xed securely in place.
 

TheHeatPumpitselfensuresgoodcontroloftheoutletwatertemperature,andswitchesoffthecompressorwhenthe
returnwatertemperaturegetstoohigh.However,insomecircumstanceswithbi-valentsystems,theboilermaybe
operating at high supply and return temperatures. If the return water temperature to the Heat Pump rises above 65°C it
willgenerateasystemfault(“excessivelyhighwatertemperature”).Topreventthishappening,theSystemControllerwill
directly switch off the heat pump if the return temperature rises above a set limit.
Return water temperature (TRET) > EP13 + 0.5K Heat Pump is switched off
Return water temperature (TRET) < EP13 - 0.5K Heat Pump may be switched on.

EP13 Heat Pump Maximum Return Temperature (default 60°C)
This value should not normally need to be changed.

note
Engineering Parameters (EP) are only available for service engineers. -
 

HeatPumpoperationisonlypossiblewithincertaintemperaturerangesasdenedbelow.Parametersareprovidedin
ordertoadjusttheworkingareaifrequiredtodosobyHitachi.
The Heat Pump water temperature setting sent by the System Controller is always constrained to lie between the
maximumandminimumlimitsdenedbytheoperatinglimits.
Iftheoutdoortemperatureisbelow-20°C(P14inCong3,4,5/EP14inCong1,2),theheatpumpwillalwaysbe
switched off.
