Heating is contantly on - thermostat broken?

antys · 30 Jul 2007

I have an Ideal Cmbi boiler, just over 2 years old. 3 Days ago we turned the heating on and and now it will not turn off automatically via the thermostat. I have to physically turn off the boiler to stop it from keep pumping out the heat.

The thermostat (Drayton, basic dial one) does not click at any point (as it should when reaching the desired temperature) and is set to the lowest temperature, but the heating continues to pump out.

Does this sound like a broken thermostat, or something more serious?

Thanks in advance, and i know i am just being tight but I do not want to call out an engineer before trying the cheapest option of replacing the thermostat.

big-all · 30 Jul 2007

heeelllooo and welcome antys

if you physicly dont hear the little click at the thermostat its the most likley cause [assuming its a clicking sort

]

could be the disc is disconected from the shaft / cam or the contacts could be welded together

wait for other opinions before turning off at the boiler and taking the front off the stat to have a look incase the stat is fed from somwhere else

Agile · 30 Jul 2007

If this is an Ideal Mini C24 then there are several possible causes of the problem and you will need a competent boiler engineer to identify the problem.

If its an Icos/isar then the display would indicate the function with a "c" on the display for CH but I dont think thats the model you have. Giving the model number is much more helpful!

However, even if the thermostat were faulty you would be able to turn off the CH on the boiler using the timeclock or function selector.

Tony

antys · 30 Jul 2007

The digital interface on the wall does not display anything, ie we select the heating to be in the 'off' position and it continues to heat the radiators up. The only way to turn the boiler off is to switch it off at the wall or the boilder switch itself.

I wondered if it was the Drayton thermostat as there is a warning sticker on the outside saying something like 'this must be connected to power else it will be in an open position and there will be a constant call for heat' or words to that effect.

Thanks for the welcome

I will have to get the model number at lunch as I am at work at the moment

antys · 30 Jul 2007

The boiler is an Ideal Classic SE15FF, Digital interface Drayton Tempus 6 with the Drayton Room Thermostat.

weareleeds · 30 Jul 2007

The ideal classic is NOT a combi boiler what control plan do you have ie y plan s plan etc as valve may be defective

penpusher · 30 Jul 2007

Sounds like you have a stuck microswitch in the central heating zone valve, but really you should have a competent person (a CORGI) look at it. If your boiler is an Ideal Classic SE15FF then its not a combi.

antys · 31 Jul 2007

Ok, i see its not a combi boiler, (didnt quite know what one was but when i rang Homeserve up when it was still in warranty they said it was a combi)

Anyway, purchased a new thermostat exactly same as before and the problem is still there. After searching on these forums i found that the 'click' will only be produced when the system is running.

As the problem with the boiler being constantly on, i think i am going to have to get someone to come and fix it. Was only being tight and trying to pick your guys' brains to see if I could do it for free.

Dan Robinson · 31 Jul 2007

when i rang Homeserve up when it was still in warranty they said it was a combi

Reassuring isn't it ?

found that the 'click' will only be produced when the system is running

Huh?

It still sounds like a stuck microswitch in the zone/diverter valve.

antys · 2 Aug 2007

i do not know how these thermostats work, i thought the 'click' when turning more or less told you the temperature. Although when I turned the whole boiler off there was no 'click' it only works when the boiler is on, thats what i meant to say.

Got someone from Bgas coming on monday to check the boiler so we can have the insurance for 17quid a month off them. Hope the mrs can sweet talk him into saying theres nothing wrong with it. ALthough, it does say they will let you know the problem if there is something wrong with it, and how much they will charge to fix it. So if thats the case, he can tell me the problem and I will get someone else to fix it, hopefully.

The boiler does stop when i turn the setting gauge down on it (like from 6 down to 1) but it still keeps the CH on. I am going to have to hope they dont look too closely at it when they check it!

Dan Robinson · 2 Aug 2007

Turning hte boielr stat down will turn the boiler off. You have one of the controls still calling for heat.

Whether it is the room stat or the zone valve will require a multimeter and some electrical tests.

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Heating is contantly on - thermostat broken?

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