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Why does my heating keep coming on by itself?
The heating keeps firing up at random times even when the thermostat is set lower than the room temperature. Could this be a thermostat problem or fault on my boiler?
Expert Trade Answers
"Hi there,
It will either be an issue with your thermostat calling or an issue with your motorised Valve (if you have one) if it comes on when your Hot Water is meant to come on, I’d say it’s the latter."
It will either be an issue with your thermostat calling or an issue with your motorised Valve (if you have one) if it comes on when your Hot Water is meant to come on, I’d say it’s the latter."
Answered on 25th May 2026 - Member since May 2021 -
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"Hi, it could be a faulty diveter valve or motorised valve - depending on the type of system you have.
When there is a hot water demand it could be passing into the central heating system."
When there is a hot water demand it could be passing into the central heating system."
Answered on 25th May 2026 - Member since May 2023 -
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"If its a Combi Boiler, It could be a faulty diverter valve. On some boilers, when the hot water preheat function kicks in, a sticking or faulty diverter can allow heat to pass into the central heating circuit, causing the radiators/heating to come on even when the thermostat isn’t calling for heat."
Answered on 25th May 2026 - Member since Apr 2026 -
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