Controller pack
Service Manual
100
Electric heater control functions
SMGB0066 rev.0 - 12/2009
Enable/disable
•
This function can be disabled by setting parameter P32=OFF.
Parameter Settings
•
P32 Supply-Return Difference Limit (default 3K)
A high value will prevent the electric heater switching on until a large temperature difference is seen by the System
Controller. With a low value or with the function disabled, the electric heater may start more often, for example during
defrost cycles.
note
This check is ignored if the Heat Pump is switched off or has an internal fault.
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4.7.3. Electric Heater Waiting Time
function
•
It is important with mono-energetic systems that the Heat pump should first try to satisfy the heating demand by itself.
For this reason an electric heater waiting time applies. This means that when the heatpump cannot meet the heating
demand, then the electric heater is switched on only after the waiting time has elapsed.
The waiting time starts:
When the heat pump is switched on, or
When the electric heater switches off (but only also when the Supply Setpoint SSUP < heat pump maximum temperature
– heat pump sensor offset).
This means that when the heatpump should normally be able to meet the heating demand on its own, the electric heater
waiting time applies, but when the supply setpoint is so high that the heat pump cannot meet the heating demand on its
own, the waiting time does not apply.
Parameter Settings
•
P19 Waiting Time for Electric Heater (default 30min.)
A higher value of P19 will reduce the number of times that the electric heater is used at lower supply setpoints, but the
desired supply temperature may not be reached quickly if there is a high heating load (slower response). Conversely, a
lower value of P19 will increase the number of times the electric heater is used at lower supply setpoints, but ensure that
the desired supply temperature is reached more quickly (better response).
4.7.4. Electric Heater return High limit Check
function
•
The return high limit check is used to help ensure that the heat pump operates as much as possible even when higher
supply temperatures are required, thus emphasising energy economy operation. The electric heater is disabled when the
return water temperature (TRET) rises above the maximum heat pump outlet temperature minus the return limit offset
(P33). A +/-0.5K control differential applies.
TRET > Heat Pump maximum supply temperature – P33 + 0.5K
Electric Heater disabled
TRET < Heat Pump maximum supply temperature – P33 - 0.5K
Electric Heater enabled
Since the electric heater is switched off then the return temperature rises too high, the effect will be that in some system
conditions it will not be possible to reach 65°C supply temperature. If it is important to allow 65°C operation, then the
parameter can be reduced or set to OFF, but the result is that in some situations the electric heater will operate on its
own and the heat pump will not be used. This will cause higher energy costs.
