Hitachi RHUE-3AVHN, Руководство по обслуживанию

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Controller pack
Service Manual
92
Heatpump control functions
SMGB0066 rev.0 - 12/2009
4.5.2. Heatpump Setting Control Signal
function •
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.
Calculation •
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.
Parameter Settings •
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. -
4.5.3. Heatpump Sensor offset
function •
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 flow 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.
Parameter Settings •
P31 Heat Pump Sensor Offset (default 3K)