Boiler turning on when not asked

[Jola13]

Anybody have any idea why my boiler should be firing up when not being told to by the heating/water control panel ? I keep coming down in the night and finding it burning away with no control from the panel. The radiators are not hot but the pipes in the airing cupboard are. No wonder my first gas bill was so expensive ! What can I do ?

[buildersmate]

Has it has suddenly started doing it? I imagine not. If not...

Most modern (conventional) domestic heating/water systems have 2 routes by which the boiler is called upon to heat the system. The first is the CH system, and the second is the hot water system. These work independently of one another but are typically both under the master control of a timer/controller unit - often mounted near the boiler. There are many different types, so I am going to have to make generalised assumptions about what you have. The most common type has two on/off periods that can be set up per day. This allows you to have the 'Heat on Twice' and 'Water on Twice' or 'Heat on Twice, Water All Day'. There are various other combinations and I am sure you have seen this sort of device. From what you say, your system has been wired such that 'Water is on Constantly' - not very helpful. Assuming that you have a thermostat on the boiler (about the size of a matchbox with a dial - strapped to the middle of the hot water cylinder) and a controller similar to that which I describe, an electrician (preferred) or a plumber will very quickly be able to suss out what is wrong and rewire it correctly. Post again if you have a different system to my assumption, but it beyond the scope of this site to help you solve this problem yourself.

[joannewatson]

My boiler does this also, however, the boiler is situated in our garage so the boiler turns on when the temperature is under a certain amount so the pipes don't freeze. Its really annoying because if its a really cold night it wakes me up all the time!

[Jola13]

Hmmm maybe thats it then. It's got dual HW/CH timer thingie where they can be independently controlled. Is there a check I can do myself on this thermostat (know where that is) ? Is this gonna bean expensive job ? Having said that it needs sorting as I've only been there a month and the first month gas bill was �100 !!! Thanks

[buildersmate]

Yes. With the controller in a position where you know the system should be off (e.g. heat on twice, water on twice, during the middle of the day when neither should demand heat, turn the thermostat up. It has a dial on it and usually markings to show approx. temperature. Most are simple mechanical types and you will hear (or feel) a slight click as it switches across. If this then results in the boiler firing up (which it shouldn't because the controller is set to water on twice), it is wrongly wired. It's a simple case of switching a couple of wires over and will take an electrician less than his minimum call-out charge to sort out.

[Jola13]

Thank you SO much. I will try this tonight when I get home - I can't afford �100 a month !!! I'll post again tomorrow if you are around to let you know what it does. just to be sure ... shall I turn it temp upwards or dwonwards ? Its currently set at 65deg (I remember noticing it before)

[buildersmate]

Turn it up. The sensor will detect that the water in the cylinder is less than the temperature you are asking for, so it will switch over to try and turn the boiler on to supply the heat. However this instruction should be over-ridden by the controller, which you should set to any position where you know that hot water should not be demanded - heat on twice water is twice is fine provided you are outside the periods of time you have set for the morning / evening. If the boiler starts up, it would appear that your system has been wired such that any time, night or day that the cylinder thermostat detects a lower than 65 degree figure. This does waste fuel and explains why your boiler starts up in the middle of the night, but it may not fully explain your high bill because if you have a reasonable well-insulated cylinder, not too much heat escapes.

[buildersmate]

missing words, fifth line from the bottom ...than 65 degree figure, it fires up.

[Jola13]

ok thanks I'll try that and get back tomorrow. by the way thank you for your time AND explaining things is such a clear un-techie way !!! very much appreciated !

[Jola13]

Unfortunately this didn't seem to do anything at all. I turned it up and waited for few minutes. How soon would it kick in ? :-(

[buildersmate]

It would kick in immediately. In which case it is probably wired right. So go back to what Joanne Watson said above. Do you have a froststat somewhere on the system, and is that working. That is the only other simple reason I can think of why the boiler would fire up at night. Is it still happening now that the nights are not as cold as they were? Froststats usually are not adjustable - they are preset to about zero degrees C and override absolutely every other setting. They are more commonly installed in systems where the boiler is in the garage or elsewhere unheated. It could be such a froststat is wrongly calibrated. Otherwise, I'm afraid you have stumped me.

[Jola13]

oh ok thank you ! But I have no idea where to find the frost stat ?!!?!? Not sure on how regularly it does it (more or less now its warmer) - as not there all time. Just one of the bloomin intermittent problems I guess that are so hard to trace/fix. :-(

Thanks for all your help anyway.

[pilotlight]

Jola, Some boilers have " built - in " frost protection. From the correspondence, it sounds as though the frost thermostat could be the scource of the problem.

If your boiler is less than 2 years old, you will probably still be under manufacturers warranty - call them. If not , you will probably require the services of a competant boiler engineer to resolve the problem.

Hope this helps.

[ranad56]

I had the same problem, make sure your eco button is lit up,and ifyour using ipad oriphone with passivheating app.. go into home, and untick economy.and comfort settings. fixed mine.