Wiser
Stuck Relay / Permanent Call-for-Heat
Heating stays on constantly even when the thermostat is set low or off
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Welded relay contacts in Heat Hub, Miswired permanent live to boiler call terminal, Shorted wiring in wiring centre, Boiler internal control fault
How to Fix / Troubleshooting
Safety first: This condition can waste energy and overheat the property. Isolate power to the heating system before inspection.
- Confirm thermostat demand: Set all Wiser thermostats to OFF or a very low temperature and verify in the app that no rooms are calling for heat.
- Check boiler: If the boiler continues to run, the call-for-heat is being held on by wiring or a stuck relay.
- Inspect Heat Hub (qualified persons only): With power off, open the Heat Hub and check for signs of burning around the CH relay. Verify that wiring is correct and that no links are incorrectly installed.
- Test relay: Restore power and, with no demand, measure voltage across the boiler call terminals. If they remain closed (calling for heat) with no demand, the relay is stuck and the Heat Hub must be replaced.
- If wiring and hub are OK: The boiler’s own controls may be stuck on. Consult a heating engineer.
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Repair Difficulty
Hard
4/5
Required Part
Wiser Heat Hub central heating relay
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