E15
Immergas Setpoint Transmission Error

Thermostat shows E15 and the boiler does not respond to temperature changes; manual boiler controls still work

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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

Incompatible communication protocol between thermostat and boiler, Incorrect boiler parameter for external control, Firmware mismatch between thermostat and boiler, Partial BUS wiring fault (one conductor broken)

How to Fix / Troubleshooting

Safety: Turn off boiler power before accessing terminals.

  • Step 1 – Check compatibility: Confirm that your Immergas boiler model supports the specific smart thermostat you are using and that BUS control is enabled.
  • Step 2 – Verify parameters: In the boiler installer menu, ensure the control mode is set to BUS/remote thermostat and not to simple on/off or internal probe only.
  • Step 3 – Inspect BUS cable: Check both BUS conductors for continuity with a multimeter. Repair or replace if one is open.
  • Step 4 – Firmware alignment: Update both boiler (if supported) and thermostat firmware to the latest versions recommended by Immergas.
  • Step 5 – Re-pair device: Delete and re-add the thermostat in the boiler’s external control menu if such option exists.
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Repair Difficulty

Hard 4/5

Required Part

Immergas BUS communication cable
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