boiler switching off, rads not fully hot

[madammim]

Hi everyone

We are having a problem with our heating. I'm not sure if its an air in the system or new controller issue....or something completely different.

The two changes to the system since it was turned off in the summer (when it worked fine) is the replacement of a leaking pressure reducing valve which connects to the unvented cylinder. We've had no issues with getting hot water since it was replaced -but not sure if air could have got into the heating system at that time?

We also lost (or the kids have hidden!) the wireless controller for the heating control only - hot water is a hard wired controller. It was a Honeywell controller (cant remember which model) which talked to the R6660D receiver. We replaced it with a Honeywell CM927 which I was told was compatible - and it seems to be in that it 'paired' ok and does switch the heating on when it is supposed to. I changed some installer settings in it to allow for our oil boiler, as per an installer manual.

The problem is that the heating is set to 18 degrees but we cant seem to get much past 14. The boiler is firing up ok and radiators getting quite warm but not hot. The boiler switches itself off although the flame icon on the controller is still showing as its not reached temperature. When the boiler switches itself off it is not on lock out. And it does come on again in a little while, and so on.

Husband has spent hours bleeding rads - water coming off them but he says he can still hear 'hissing' of air from one, despite draining pots and pots of water off. We have also bled the boiler once.

Is it a case of persevering with the bleeding or could it be something else.

Hope all the above makes sense. Really appreciate any advice - thanks for taking the time to read.

 

[ianmcd]

try turning your boiler thermostat to Maximum and see what happens

 

[madammim]

Hi Ian, thanks for the reply.

I put it on manual this morning and turned it up to maximum (35 degrees). I think the rads possibly got a little warmer but still not very hot, as they used to be. I've had it set at that all day. Controller currently reading 15.5 degrees

 

[madammim]

Sorry Ian, just re-read your post. I think you meant controller on actual boiler. That was set at 5 so have now turned it to max (6) and i'll see what happens.

 

[ianmcd]

yes the thermostat on the actual boiler , it sounds as though it is cutting in too early

 

[madammim]

Boiler still turning itself off when rads only warm and temp only 15 degrees with flame showing. I didn't consider the thermostat could be faulty!

Could air in the boiler or rads be causing this issue? I would like to rule that out if possible.

 

[ianmcd]

yes an airlock could cause your problem, can you see how hot the heat exchanger gets in the boiler before it cuts out ? Basically the way that your boiler thermostat works is that lets say it is set at 4 and for arguments sake 4 is 70 C then once the water within the heat exchanger reaches that temp then the heat source will switch off but the pump should keep running and once the heat has been removed then the heat source will come back on, a little basic but that is the general idea of how it works, if the water in the boiler is at full temp and cuts out then you have a flow problem possibly air or something else, if the boiler cuts off but the boiler is not very hot then most likely a thermostat or boiler fault

 

[madammim]

Thanks for explaining. It makes much more sense now. We'll see how hot heat exchanger gets and go from there. I'll update with progress reports but thanks so much for taking the time to help. Really appreciated.

 

[Agile]

Knowing the flow and return temps of your boiler would be a useful start to diagnosing the fault.

Tony

 

[madammim]

So the heat exchanger is only getting warm - so thinking it could be the thermostat. Is this something we can replace ourselves - husband is an electrician - or is it time to call out Worcester? Grateful for any advice. Thanks.

 

[loafer]

Hmmm!
Air in system? vent rads with key.
Old kapput sludged up rusty rads!? Gentle persuasion with a rubber mallet and a sheet of cardboard!
Kapput diff bypass valve?! or set incorrectly!?

INTERESTING!

 

[madammim]

It's a puzzle! Husband spent hours the other night bleeding rads. Eventually they all got quite hot. But next day we are back to warm rads with heating on full! There is some air and water coming out when we bleed at the boiler. Problem is if we persevere with bleeding at boiler, boiler gets soaked as bleed nipple is on the top. Fed up using all this oil for a barely warm house - thank goodness for woodburner in lounge!