E05
Wiser
Hot Water Channel Output Fault
Thermostat shows E05 and hot water control is unavailable
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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
Faulty HW relay in Heat Hub, Shorted hot water valve coil, Miswired cylinder thermostat, Blown internal hub fuse on HW channel
How to Fix / Troubleshooting
Safety first: Hot water controls are mains powered. Isolate the heating system at the consumer unit before opening any wiring centre or Heat Hub.
- Check cylinder thermostat: Ensure the hot water cylinder stat is correctly set (typically 55–60°C) and not stuck or physically damaged.
- Inspect HW valve (if S-plan/Y-plan): Listen for the hot water motorised valve when HW is requested. If it hums loudly, is hot to touch, or does not move, it may be shorted or jammed.
- Check wiring (qualified persons only): With power off, inspect the HW relay terminals in the Heat Hub and wiring centre. Look for loose wires or signs of burning.
- Isolate suspect loads: Temporarily disconnect the HW valve or cylinder stat from the Heat Hub HW output and power up. If E05 clears with the load disconnected, the external component is likely faulty.
- If E05 remains with loads disconnected: The HW relay or internal fuse in the Heat Hub is likely damaged. Replace the Heat Hub.
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Repair Difficulty
Hard
4/5
Required Part
Wiser Heat Hub hot water relay / internal fuse
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