Controller pack
Service Manual
98
Electric heater control functions
SMGB0066 rev.0 - 12/2009
Parameter Setting
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P15 Maximum Outdoor Temperature for Boiler Operation (default 0°C)
Enable/disable
•
To disable this function and allow boiler operation at all outdoor temperatures, set the parameter P15=OFF.
note
The boiler is always available for DHW loading, independent of outdoor temperature.
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4.7. ElECTrIC HEATEr ConTrol fUnCTIonS
4.7.1. Electric Heater Control
Configuration Specific
•
Electric Heater control is available only in configuration 2 (CONF 2).
function
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When the heatpump cannot meet the heating demand the 3-stage electric heater can be switched on to raise the supply
temperature up to a maximum of 65°C. The electric heater control decides whether to switch on one or more of the
electric heater stages based on a proportional plus integral action (P+I) control algorithm and the difference between the
Electric Heater Setpoint and the Supply Water Temperature (TSUP).
The electric heater will only be used when
the outdoor temperature is below the bivalence point (maximum outdoor temperature for electric heater operation)
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or the electric heater has been manually released (after a heat pump fault)
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In addition, two further checks are made before the electric heater is allowed to switch on. The purpose of these checks
are to help ensure that the electric heater only switches on when the heat pump is working at its maximum capacity.
the Supply-Return Difference Check
1.
the Electric Heater Return High Limit Check
2.
These checks are not carried out if the heat pump is switched off or has an internal fault.
note
The boiler is always enabled when there is DHW loading required
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Electric Heater Setpoint & Supply Setpoint Control offset
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If the heat pump is switched off, or has an internal fault, the Electric Heater Setpoint = Supply Setpoint (SSUP)
If the heat pump is switched on, the water setpoint used for the electric heater control depends on the value of the
Supply Setpoint. When the supply setpoint is low, the electric heater will only be used if the actual supply temperature is
much lower than the desired setpoint. To achieve this, the electric heater setpoint is offset lower than the supply setpoint.
When the supply setpoint is higher than can be achieved by the heat pump alone, the electric heater setpoint is equal to
the supply setpoint. This function is intended to help reduce the number of times the electric heater is used, to emphasise
energy saving operation.
