Hitachi YUTAKI Series - Heatpump Setting Control Signal; Heatpump Sensor Offset

Controller pack
Service Manual
92
Heatpump control functions
SMGB0066 rev.0 - 12/2009
 

WhenthereisademandforheatingorDHW,theSystemControllerwillsendtotheheatpumpasignalfortherequired
Heat Pump outlet temperature. The System controller uses the 4-20mA connection to represent the outlet water
temperature setpoint. The heatpump will modulate the appliance according to its own control strategy to achieve the
correct output water temperature.
A conversion table from water temperature setting to mA signal is provided at the end of this guide.

Heat Pump Supply Setting = SSUP (supply setpoint) + P31 (Heat Pump Sensor Offset)
The Heat Pump Supply setting is always constrained within the maximum and minimum heat pump supply temperatures.
These limits depend on the current outside temperature; see “Heat Pump Operating Limits”. Heat Pump Sensor Offset is
explained in the next section.

EP6 Heat Pump Supply Setpoint at 4mA (default 20°C)
EP7 Heat Pump Supply Setpoint at 20mA (default 55°C)
These parameters should only be changed with the approval of the manufacturer.

note
Engineering Parameters (EP) are only available for service engineers. -
 

Inpractice,theremaybeadifferencebetweentheheatpumpoutlettemperature(measuredbytheHeatPump)andthe
supply temperature (measured by the system controller). This can be caused by:
Different measuring position. The Heat Pump is outside and some loss of heat is possible between the heat pump 1.
and the supply pipes inside the house.
Different types of sensor. The Heat Pump measures the outlet temperature using an immersion-type sensor directly 2.
inthewaterowafterthecondenser.TheSystemControllerusesastrap-ontypesensor,whichdependingonthe
ambientconditions,willtypicallymeasurealowertemperaturethananimmersion-typeinthesamelocation.
Thisdifferenceneedstobetakenintoaccountforoptimumcontrolperformance,andparameterP31isprovidedsothis
canbeadjustedaccordingtotheinstallation.

P31 Heat Pump Sensor Offset (default 3K)