165
Troubleshooting
The heat pump in DHW mode stops working but the setpoint is not reached, the room heating requires
heat but the unit remains in DHW mode
Possible causes Corrective action
TBH or AHS not available
The heat pump will remain in DHW mode until either t_DHWHP_MAX or the
setpoint is reached. Add TBH or AHS for DHW mode, TBH and AHS must be
controlled by the unit
Room heating is insucient when the outdoor temperature is low
Possible causes Corrective action
The backup heater does not
start.
• Check that the “OTHER HEATING SOURCE/ BACKUP HEATER” option is
enabled, see chapter “8.2.7 Additional heating source settings” on page
90 and paragraph “7.8 Dip-switch setting” on page 64.
• Check that the backup heater's thermal protection has not tripped.
• Check that the booster heater is not operating; the backup heater and
booster heater cannot operate simultaneously.
• Check fuses or safety thermostats in the case of an external backup
heater and, if necessary, replace them after ascertaining the reason for
the intervention.
Too much heat pump
capacity is used to heat
domestic hot water (only for
installations with domestic
hot water storage tank).
• Check that parameters “t_DHWHP_ MAX” and “t_DHWHP_RESTRICT”
are configured correctly.
• Check that the 'DHW PRIORITY' function on the user interface is disabled.
• Enable parameter “T4_TBH_ON” on the user interface/ FOR SERVICEMAN
menu to start the booster heater for heating domestic hot water.
It is not possible to switch immediately from heating mode to DHW mode
Possible causes Corrective action
The tank volume is too small
and the position of the water
temperature probe is not
high enough
• Set dT1s5 to 20 and set t_DHWHP_RESTRICT to the minimum value.
• Set dT1SH to 2.
• Enable TBH, TBH must be controlled by the unit.
• If AHS (boiler) is available, switch on the boiler first, if the demand for the
heat pump switched on is full, the heat pump will switch on.
• If TBH and AHS are not available, try changing the position of the T5
probe.
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