Why are radiators hot in middle of night when boiler is off?

[Homervanderjazz]

Hi,

I have a W Bosch combi boiler and have noticed that in the middle of the night the radiators all over the house get piping hot. This is despite the wireless thermostat not activating the heating. I left it for an hour last night thinking the radiators May simply start to cool down. They did briefly but then started getting hot again.

I then went down to the boiler which wasn’t even showing as being on, I.e the red light was not on which it normally is when the heating is on. Ended up having to manually shut the boiler off.

This was happening earlier in the year and as it’s still under warranty a WB engineer came out to have a look. He said he couldn’t find anything wrong with it but had changed one of the valves. It worked normally for a bit but then same thing started to happen again.

I am going to contact WB again but it would be useful to know if anyone has experienced anything like this and what the fault is likely to be? Thanks.

 

[muggles]

Could be a faulty diverter valve. You've not told us what the model is so this is going to involve a bit of guesswork, but is hot water pre-heat switched on?

 

[ericmark]

I bought this thermostat for my mother, it turns out there is no hand shaking or any other system to ensure it fails safe, be it flat battery or a mobile phone poles just as it sends its signal then it does not switch states. It did seem after some time it did resend signal, but I have walked into the house at 27°C when set to 20°C, it slowly got worse and worse and in the end it would only work opposite to receiver 4 foot away.

At first I thought it was my mum fiddling, as by time I got there it was working again. However for radiators to get hot there is likely more than one fault. Most radiators have thermostatic radiator valves fitted (TRV) and really the room should have never exceeded 22°C. So my cure was to swap heads on the TRV as well as change thermostat, so even if heating stuck on all that happens is the boiler cycles.

Electronic heads start at £10 and allow you to program each room independently, so once fitted even if mother turned wall thermostat to 30°C the rooms would not over heat.

 

[Homervanderjazz]

Could be a faulty diverter valve. You've not told us what the model is so this is going to involve a bit of guesswork, but is hot water pre-heat switched on?

Hi it’s the 32CDI Worcester Bosch. I don’t know what you mean about the pre-heat switch tbh. I can take a picture of the control panel when back in the house and will post it.

 

[Homervanderjazz]

Thought would post an update, the boiler is still under warranty so had Worcester Bosch (WB) out to look at it. They have done a visual inspection and concluded it is the external timer fault. The external timer is made by Salus so WB won’t touch it.

So, my question is do I just buy a new timer myself and pair it with the boiler as a start? Or should I call a heating engineer who will be able to do a full assessment/diagnosis as I am not convinced by the line WB are taking; they only seem to have done a visual inspection. Thanks for any input.

 

[Deleted member 267285]

I would suggest you try the following which may help. Turn boiler off and wait for it to cool down (no heating at all through radiator pipe work) needs to be cold to the touch. Run the hot water and then feel the flow pipe on boiler, it this gets hot it would indicate to me that the diverter is faulty or debris is keeping it open.

 

[ianmcd]

WB will not honour your warranty if it has salus controls installed , if it was me I would fit WB controls and then they have to honour the warranty

 

[Homervanderjazz]

WB will not honour your warranty if it has salus controls installed , if it was me I would fit WB controls and then they have to honour the warranty

Given they now know I have Salus controls installed is it not a moot point?

 

[ianmcd]

Given they now know I have Salus controls installed is it not a moot point?

not if you change it

 

[ericmark]

Salus badge is found on many thermostat this

one is also badged as Horstmann see previous post and it has issues losing wireless contact with base station. Also Worcester Bosch are know for problems producing RF noise, the receiver needs to be some distance from the boiler, think it's the boiler fan which causes the problem.

The honeywell

did not have a programmed mode, however it does have fail safe, if thermostat not seen in ½ hour it auto closes down.

If it were mine I would down load instructions for thermostat and see if it fails safe or not, I am assuming wireless, if hard wired then unlikely the thermostat.

Most of my radiators have electronic heads on the TRV and these would stop the radiators heating up even if the boiler started to run, most have two settings Eco and Comfort I have Eco set at 17°C and Comfort set at 20°C and at the scheduled times they swap between the two settings or press of button on TRV head or on phone bluetooth program. The wall thermostat also has a schedule set so either a very cold night, or both wall and radiators thermostat would need to go faulty.

Old house had a programmer with the wall thermostat, so in that case either programmer faulty or the frost thermostat would need to be faulty and again TRV electronic head as well.

So what thermostat have you got? Is it programmable, is it hard wired or wireless, have you read the instructions, if so does it fail safe?

 

[Homervanderjazz]

 

[Homervanderjazz]

Salus badge is found on many thermostat this

one is also badged as Horstmann see previous post and it has issues losing wireless contact with base station. Also Worcester Bosch are know for problems producing RF noise, the receiver needs to be some distance from the boiler, think it's the boiler fan which causes the problem.

The honeywell

did not have a programmed mode, however it does have fail safe, if thermostat not seen in ½ hour it auto closes down.

If it were mine I would down load instructions for thermostat and see if it fails safe or not, I am assuming wireless, if hard wired then unlikely the thermostat.

Most of my radiators have electronic heads on the TRV and these would stop the radiators heating up even if the boiler started to run, most have two settings Eco and Comfort I have Eco set at 17°C and Comfort set at 20°C and at the scheduled times they swap between the two settings or press of button on TRV head or on phone bluetooth program. The wall thermostat also has a schedule set so either a very cold night, or both wall and radiators thermostat would need to go faulty.

Old house had a programmer with the wall thermostat, so in that case either programmer faulty or the frost thermostat would need to be faulty and again TRV electronic head as well.

So what thermostat have you got? Is it programmable, is it hard wired or wireless, have you read the instructions, if so does it fail safe?

I have now uploaded pics of the thermostat and the Salus control unit on the boiler. I would have thought if the batteries were low it would start to lose contact but there is no low battery symbol. I then thought maybe it was because I had it too far from the boiler so last night I left the thermostat right next to the boiler. However the same thing happened again and the boiler randomly turned on the heating at night.

Not really sure what to do to be honest. I appreciate your post and advice given but I don’t think I am technically enough minded to find a fix myself in all honesty. That leaves me either calling someone to try and fix the fault or changing to WB controls which you have noted may cause other problems. I will see if it has a fail safe.

 

[ericmark]

Reading the manual it seems it does have a fail safe for battery going low, but does not say anything about RF interference, it also it seems has both on/off and pulse width modulated mode, and reading the instructions I would agree with

WB will not honour your warranty if it has salus controls installed , if it was me I would fit WB controls and then they have to honour the warranty

The unit connects into the boilers electronics so it's impossible for anyone other than Bosch or Salus to know what it's doing.

 

[Homervanderjazz]

Reading the manual it seems it does have a fail safe for battery going low, but does not say anything about RF interference, it also it seems has both on/off and pulse width modulated mode, and reading the instructions I would agree with

The unit connects into the boilers electronics so it's impossible for anyone other than Bosch or Salus to know what it's doing.

Sorry but I don’t know what you mean by the following- it seems has both on/off and pulse width modulated mode. Can you please explain?

 

[Homervanderjazz]

not if you change it

Do you have a rough idea of how much something like this may cost? Thanks