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Andrew Smith
Andrew Smith, Home Appliance Technician
Category: Appliance
Satisfied Customers: 3757
Experience:  Gas cooker specialist
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I have a Vaillant ecotec plus.My central heating keeps coming

Customer Question

I have a Vaillant ecotec plus.My central heating keeps coming on spontaneously plus when i run hot water,despite the thermostat in my hall being turned down to nil and the heating turned off at the control panel adjacent to the thermostat.Both are contected to the system by wiring,ie not battery remote operated.The system was installed in 2006.
Submitted: 4 years ago.
Category: Appliance
Expert:  Andrew Smith replied 4 years ago.

Plumbers_Mate : Is it only when the hot water is on?
Customer: replied 4 years ago.

Thankyou for your reply.The heating will always come on when the hot water is running.It will stay on for a few minutes,long enough to heat the rads to full temperature and then go off again;most of the time.However occassionaly the heating will come on totally randomly.This can be any time day or night even on hot days.

Expert:  Andrew Smith replied 4 years ago.
Ok, this is because your boiler had a preheat function for the hot water.
What will happen is that your boiler will try and keep a small amount of hot water up to temperature so there is not so much of a delay when the tap is opened.
This means if the tap has not been run for a couple of hours then the boiler will fire to keep it up to temperature, so you will get this happening in the middle of the night also when the tap is not running.

You need to get someone to strip and clean (or usually replace) your divertor valve as it is stuck partly open, this causes heat to leak into the central heating circuit when it running hot water