Netatmo
Open Thermostat Circuit or No Call for Heat at Boiler
Boiler never starts; no heating even when thermostat is set high and app shows a call for heat.
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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
Loose or broken control wires between Relay and boiler, Relay not switching due to internal fault, Boiler thermostat terminals miswired, Boiler in lockout or summer mode
How to Fix / Troubleshooting
Danger: Always isolate mains power before opening boiler or Relay wiring compartments.
- Check boiler mode: Ensure the boiler is not in summer or hot‑water‑only mode and that no error codes are displayed on the boiler.
- Inspect wiring: With power OFF, verify that the two thermostat control wires are firmly connected at both the Relay and boiler thermostat terminals.
- Continuity test (advanced): Use a multimeter to check continuity of the control cable between Relay and boiler.
- Manual bridge test: With power OFF, temporarily bridge the boiler thermostat terminals. Restore power: if the boiler starts, the issue is with the Netatmo Relay or its control; replace the Relay if it does not close the circuit when calling for heat.
If the boiler does not start even with a manual bridge, the fault lies within the boiler and requires a heating technician.
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Repair Difficulty
Hard
4/5
Required Part
Netatmo Relay Module
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