E20
Baxi Multi-Zone Control Communication Fault

Thermostat shows E20 and indicates a zone configuration or multi-zone communication error.

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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 Baxi zone controller, Faulty wiring between thermostat and zone modules, Duplicate zone addresses, Failed zone expansion module

How to Fix / Troubleshooting

Safety first: Isolate mains power before opening any zone controller or wiring center.

Steps to check:

  • 1. Verify zone layout: Confirm the number of zones and that each Baxi zone controller or actuator is correctly addressed and configured in the thermostat installer menu.
  • 2. Inspect wiring: Check the low-voltage bus wiring between the main thermostat, Baxi zone controller, and actuators for loose or broken connections.
  • 3. Test each zone: Call for heat in each zone individually and observe which zones respond. This can help identify a specific faulty module.
  • 4. Reset zone controller: Power-cycle the Baxi zone controller and re-run any auto-detection or configuration routine.

When to call a professional: Multi-zone systems can be complex; if E20 persists, a heating engineer should test and replace any faulty zone modules.

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Repair Difficulty

Hard 4/5

Required Part

Baxi multi-zone controller
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