E12
Immergas
Second Zone Control Fault
Thermostat displays E12 and cannot control the second heating zone or mixed circuit
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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 Immergas zone control module, Incorrect addressing of zone modules, Broken communication cable between thermostat and zone module, Overloaded zone outputs
How to Fix / Troubleshooting
Safety: Isolate mains power to all zone pumps/valves and the boiler before working on zone modules.
- Step 1 – Identify modules: Locate the Immergas zone control module(s) connected to the thermostat. Note their addresses or DIP switch settings.
- Step 2 – Check addressing: Ensure each zone module has a unique address and that the thermostat is configured to control a second zone.
- Step 3 – Inspect BUS wiring: Verify the low-voltage communication wiring between thermostat and zone module is intact and correctly connected to BUS terminals.
- Step 4 – Test without load: Disconnect the second zone pump/valve from the module and see if E12 clears. If it does, the load may be shorted or oversized.
- Step 5 – Swap modules: If possible, swap the suspected faulty zone module with a known-good one. If the error follows the module, replace it.
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Repair Difficulty
Hard
4/5
Required Part
Immergas zone control module
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