E20
Defro
Internal Control Board Error / EEPROM Fault
Boiler displays E20, no heating, pump may run but burner does not start, often after power disturbances.
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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
Corrupted firmware on Defro PCB, Voltage spikes or unstable power supply, Faulty main control board memory, Incorrect parameter configuration
How to Fix / Troubleshooting
Safety: Isolate power before handling electronics.
- Power reset: Turn off the boiler at the main switch and at the circuit breaker. Wait at least 2 minutes, then restore power and attempt a reset from the control panel.
- Check supply voltage: Ensure the boiler is connected to a stable mains supply within the specified voltage range. Avoid using undersized extension leads.
- Factory reset (if available): Some Defro models allow a factory reset of parameters via the installer menu. Only perform this if you have the installation data and understand the implications.
- Service intervention: If E20 remains, the PCB may require reprogramming or replacement by an authorized Defro service center.
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Repair Difficulty
Professional Required
5/5
Required Part
Defro main control board
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