E20
Dimplex
External Control / BMS Communication Error
E20 displayed; unit reports communication fault with external controller (if fitted)
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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
Disconnected communication cable, Incorrect wiring polarity, Faulty external controller, Damaged communication port on PCB
How to Fix / Troubleshooting
Safety: Isolate power before working on control wiring.
- Check cabling: Inspect the low-voltage communication cable between the Dimplex water heater and any external controller or BMS. Ensure correct terminals and polarity.
- Verify settings: Confirm that communication parameters (protocol, address) match between devices as per Dimplex documentation.
- Test standalone: Temporarily disconnect the external controller and run the heater in local mode if possible. If E20 clears, the issue is external.
Note: If the error remains with no external controller connected, the PCB communication interface may be faulty.
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Repair Difficulty
Hard
4/5
Required Part
Control Wiring / Main Control PCB
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