Central Heating on when thermostat turned down

[Dr Acula]

I'm currently experiencing an issue with my boiler/thermostat.

I have an Ideal icos boiler (unsure but model either HE15, HE18 or HE24) and use a Nest thermostat. Over the last few weeks i have started to notice that the boiler is coming on even when the thermostat is turned down to a very low temperature.

I have both restarted and reset the Nest to make sure that wasn't the issue and that hasn't resolved anything. The Nest still turns the heating on/off when it is turned up/down unless the central heating comes on of it's own accord, at which time the boiler seems to do as it pleases.

I haven't noticed that it's coming on at specific times. It seems to be quite random. The boiler looks to be working fine as there are no error messages and the display shows what it would normally show when the heating is on/off.

The system also has a BoilerMate 2000 storage tank.

Any help would be greatly appreciated. If any further information is required i will do my best to provide it.

 

[Ted777]

I wonder if it's a faulty frost thermostat in the boiler, or if it's cold enough that the frost thermostat is doing its job and firing up to make sure nothing freezes.

 

[bernardgreen]

deleted Ted777 got in first

 

[Dr Acula]

Is there any way i can check this?

 

[D_Hailsham]

Where is the boiler located?

 

[Dr Acula]

In an open plan kitchen/living room. The main room in the house.

 

[D_Hailsham]

So the boiler should not be getting so cold that the frost stat kicks in.

What shows on the display when the fault occurs?

 

[stem]

It's rare if the boiler is located indoors, but sometimes you can find remote frost thermostats in the loft / garage or anywhere else there is pipework that is likely to freeze.

Alternatively if you have motorised valve(s) on the system, they are used to switch the boiler 'on' and 'off' using an internal microswitch that operates the boiler when the valve(s) move to an open position. These switches can stick in the 'on' position even when the valve is closed.

I'm not an expert on the BoilerMate thermal store, but I believe that they are kept hot regardless of the radiators being on or not, so it may be just keeping that hot.

 

[Dr Acula]

The display shows a C and the burner light is illuminated. And that's what it is normally like when the central heating is on.

I've turned up the thermostat up to a warmer ambient temperature to avoid is getting too cold in the room to see if it the frost thermostat.

 

[stem]

Over the last few weeks I have started to notice that the boiler is coming on even when the thermostat is turned down to a very low temperature.

Are the radiators actually 'on' when the Nest thermostat is not calling for heat? By this I mean is your house getting too hot because the radiators are on when they shouldn't be? or is it just that the boiler is running when the Nest is not calling for heat?

If the former is the case, then you may have a fault. However, if it's the latter, that is how a thermal store (BoilerMate) works. The boiler remains in the ‘on’ position 24 hours a day, 7 days a week, but fires only when needed to maintain the temperature of the thermal store. That way, the thermal store is always hot and ready to go when heat is needed for the radiators or for hot water.

 

[Dr Acula]

The radiators get hot even when the Nest isn't calling for heat. I've kept an eye on it for the last few days and it seems pretty random but I've also noticed it when the hot water has been running, the boiler kicks in and then the radiators start to heat up.

 

[FlyingFish]

If your confident the Nest is operating correctly and the boiler is showing no fault codes, then I would say good luck (sorry, not helpful). The fault may lie with the boilermate, and through experience, they are not a repairers favourite appliance to work on. It might just be the few I've seen over the years and the trouble people have had getting them repaired. Ive fixed a handful but they are not a 'fun' appliance If your getting someone out to look over the system then it might be worth a call to Gledhill to see if they have any recommended people near you.

 

[mcmoby69]

It's a learning stat. 1st couple of weeks it's a bit random. Leave it alone it will be OK. It's cleverer than the average punter.

 

[Dr Acula]

It's a learning stat. 1st couple of weeks it's a bit random. Leave it alone it will be OK. It's cleverer than the average punter.

It is but we disabled that as my parter's work schedule varies day by day and week by week so that wasn't practical.

Also even when we were using that function the display would still show up orange to show central heating was on. This does not.