Weird CH behaviour - Boiler or controls?

[johnagall]

I have a 4 year old new build flat with 5 rads (all except one have TRVs) and an Ideal Combi Boiler, which I know is a poor boiler to be relying on.

The heating has been off throughout the spring and summer without problem but during the recent cold snap I have had to switch the system to timer mode where the rads come on between 6-7am each morning and thats it. Again up to this point no problem.

However the outside temp has picked up a bit recently and because the place retains the heat very well I no longer need the rads on so have switched the Thermostat back to the off position (with frost protection kicking in at 16.5 degrees C)

For some strange reason some of the rads are still coming on although not up to full heat. Moreover the rads in the bathroom and hallway were much hotter this morning than those elsewhere. I can't be sure but I think they even came on the other day in the afternoon, when therer has never been a timer set for this time. I only noticed this as I was working from home, which I never normally do.

Any ideas what this could be?

I have boiler protection provided by D&G as I know the boiler isn't to be trusted and they are coming to service the boiler next week. What's more I have just upgraded my cover to include controls as well as boiler but (I think) there's a four week no claim period so if this is likely to be controls then I need to wait.

 

[picasso]

What model of ideal combi boiler do you have?

 

[johnagall]

I can check that tonight for you

 

[johnagall]

Someon has suggested possible diverter valve. How does this sound?

 

[picasso]

The diverter valve would be my best guess, the reason I asked about the model number is if your boiler has preheat and the diverter valve is passing the rads will warm up at any time, without the preheat the rads will only warm when you have used the hot water.

 

[johnagall]

Without the model number to hand right now we cant tell for sure but when you say preheat; does this mean that the combi fires up for a minute or so throughout the day at random points?

Because I know that my boiler does that.

 

[Agile]

The diverter valve can cause problems.

But that would not explain why your boiler is coming on. That would need water to be used to bring the boiler on.

Anyone setting frost protection at 16.5 C will cause the boiler to run whenever the home gets cooler over night. Thats what your problem appears to be !

Tony

 

[johnagall]

In fairness Tony, my Mrs spotted the problem this morning when she got out of the shower so this could have been the reason. I can test that tonight by running a shower to see if the rads turn on too.

 

[Agile]

That does sound like the diverter valve leaking heat to the rads during hot water use.

If that is the case then the hot water preheat will also cause a little warming of the rads. On a recent boiler you may be able to turn that off.

But why dont you want to set the frost protection to the normal temp of about 6 C ?

Tony

 

[johnagall]

The honest truth is that the frost control has never really been needed.

The only time I've used it has been a way of keeping a minimum temp in the depths of winter so that I dont have to rely on a timer too much.

So I set the minimum temp to say 18 deg C and the heat-up cut off temp to 20 deg C to keep the flat at that temp through the night. I would say that this gets used like this one month a year through the night.

 

[johnagall]

The manual that I have shows the boiler as Model:

Ideal Evo HE C22/24 C22/30 C22/35

I've just tested and when I run a hot shower the rad without a TRV is definitely heating up.

Is this something that would likely be covered on my boiler cover plan with Domestic & General?