H02
Wiser by Drayton
Heat HubR Hot Water Relay Output Fault
Heat HubR or app shows H02; hot water relay does not operate when scheduled.
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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
Failed hot water relay on Heat HubR PCB, Loose wiring to cylinder valve or boiler hot water terminals, Burnt relay contacts, Incorrect configuration of hot water channel in app
How to Fix / Troubleshooting
Safety: Isolate mains power before opening the Heat HubR or touching any wiring.
- Check schedule: In the Wiser app, confirm that the hot water schedule is enabled and currently calling for hot water.
- Verify wiring: With power off, inspect the hot water relay terminals on the Heat HubR and ensure the wires to the hot water zone valve or boiler are secure.
- Relay operation test: Restore power and manually turn hot water on via the app. Listen for a relay click. No click indicates a relay or control fault.
- Check external controls: If the relay operates but the cylinder or boiler does not heat, check the external motorised valve, cylinder thermostat, and boiler inputs (qualified engineer only).
Persistent H02 with a non-operational relay usually requires Heat HubR replacement.
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Repair Difficulty
Professional Required
5/5
Required Part
Wiser Heat HubR hot water relay
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