Why is my central heating coming on? }:-/

[^woody^]

My CH is controlled by programmer not a timer, which should only call for heat at certain temperatures during different set periods during the day.

A few weeks ago the heating was coming on at some random times despite the actual room temperature being above the set temperature.

So I turned the temperature to off for all periods, but the boiler is still coming on at different times for different periods of time.

Ideal ISAR
Horstmann Centaur Stat 7

 

[picasso]

Pic of zone valve/s possible ?

 

[^woody^]

No zone valves. Everything is straight off the boiler

 

[dilalio]

So you have a combi boiler?

Run some hot water and see if the rads start warming up.

Or identify when exactly the heating is coming on.

Depending on the above it will be a faulty programmer or diverter valve.

Or, perhaps a faulty frost protection, if one is present.

 

[Madrab]

Is the heating actually coming on? Rads geting warm? Or is it just the pump being fired up, if so this is normal during the summer periods, it's an anti sieze process the boiler puts the pump/DV through when CH not is use for extended periods.

 

[McCombi]

Your boiler has a water preheat function built in.

you may have a blocked plate heat exchanger or faulty diverter valve which is causing radiators to heat when the water is preheating due to diverter valve passing heat down heating pipes

 

[^woody^]

I think it may be related to the HW or pre-heat side of things.

When the rads have got hot, I've never seen the CH light indicate in the boiler display. I've put it down to always missing it and it has cycled off by the time I got to look, but having read the replies, it may well relate to the HW being used or pre-heated.

It's never done this before and we have had it years, so I can't imagine it being a maintenance cycle of the pump - the rads get piping hot! There is no frost stat.

 

[jeff the gasman]

Faulty diverter valve hot water preheat switched on is my diagnosis.

 

[shambolic]

It will have a Honeywell diverter valve sticking 174200. Preheat comes on to heat the plate and passes down into heating circuit.
Water also won't be as warm. 20 minute job to change.
If you know what you are doing.

 

[^woody^]

Update ....

It was the diverter valve and all is well now.

Thanks everyone

 

[AGAS]

^woody^ think your missing a thanks