Tado Unwanted Boiler Firing

Boiler runs even when all Tado rooms are set to OFF or frost protection.

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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

Boiler internal frost protection or preheat mode, External timer or wiring center bypassing Tado, Zone valve stuck open, Incorrect wiring of Tado relay in parallel with old thermostat

How to Fix / Troubleshooting

Safety warning: Boiler wiring involves mains voltage. Turn off power before inspecting wiring.

  • Check boiler settings: On the boiler, disable any "preheat" or "comfort" hot water modes that may fire the boiler independently of Tado.
  • Inspect external controls: Ensure any old wall thermostats or timers have been fully removed or set permanently to maximum and left on, with Tado as the only control.
  • Check wiring center: At the wiring center or Extension Kit, verify that Tado’s relay is the sole control for the heating call and that no permanent live is feeding the boiler call terminal.
  • Test zone valves: If you have motorized zone valves, check if any are stuck in the open position, which can cause the boiler to run.
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Repair Difficulty

Hard 4/5

Required Part

Tado Extension Kit Wiring
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