Vaillant ecotec plus 837 boiler heating not switching off

ladymrx

Hi all, we’ve just moved in our new house and it has a vaillant Ecotec plus 837 boiler. We noticed that the heating is turning on randomly during the day and night and we cannot switch it off. We changed the thermostat to 15 degrees, turned heating down on the boiler as low as it goes, and turned the heating level on the radiators to 0, and the heating still goes on and the radiators get hot. How to make it stop? It is not on Comfort mode.

ThisIsWeird

The comfort mode only applies to the DHW side in any case. But, yes, it appears to be off.

The CH coming on to the extent it actually sends some hot water to the rads is clearly 'wrong'. It'll either be an internal fault in the boiler, or it's receiving a triggering signal from your external controls.

How many CH zones are there? Just one? If more than one, then there will be external motorised zone valves, and these do go wrong after a decade or so, and can cause this.

What external controls do you have for your CH? How do you 'time' it for when to go on? How do you adjust the room temp?