E20 error, heater may not start or may shut down with no obvious mechanical issue.

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.

Possible Causes

Multiple unresolved prior faults, Firmware error on Baxi PCB, Intermittent wiring fault, Incorrect configuration parameters

Safety: As with all faults, isolate power before internal inspection.

Steps:

Full power reset: Turn off power for several minutes, then restore. Clear any stored lockouts as per the manual.
Check event history: If your Baxi model has a diagnostic history, review it to see which faults occurred before E20.
Inspect wiring: Perform a general check of all visible wiring looms and connectors for looseness or damage.

Professional: A technician may need to update firmware, reconfigure parameters, or replace the PCB.

Hard 4/5

Main Control PCB

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