Glow-worm
Hot Water Control Wiring / Configuration Fault
Thermostat does not control hot water cylinder even though schedules are set
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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
Cylinder relay output not wired to cylinder valve or boiler, Hot water function disabled in installer menu, Faulty hot water relay in wiring center, Mis‑assigned zone outputs
How to Fix / Troubleshooting
Safety: Isolate mains power to the wiring center and boiler before inspecting hot water wiring.
Steps:
- Confirm in the thermostat settings that hot water control is enabled and that a cylinder is configured.
- At the wiring center, trace the hot water ON output from the Glow‑worm control to the cylinder valve or boiler input. Verify continuity and correct connections.
- Command hot water ON from the thermostat and listen for the hot water relay click in the wiring center.
- If no click is heard, test the relay coil and replace the wiring center or zone module if faulty.
Remedy:
- Correct any wiring errors and replace defective relays or zone modules.
- After repair, test hot water operation through several on/off cycles.
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Repair Difficulty
Hard
4/5
Required Part
Glow-worm wiring center / hot water relay output
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