Worcester 28 CDI Combi - keeps shutting down

[Stiggsy]

My Worcester 28 CDI Combi Boiler has just developed a fault and I'm hoping one of you knowledgable people might be able to identify the possible cause.

Heating

On start up from cold the boiler is fine and slowley heats the radiators until after around 6-7 mins when it cuts out and won't come on again for approx 10 mins. When it starts up after this it is only for about 1 min and then cuts off for approximatly 10 mins again. Because of this radiators are luke warm and offer very little in the way of heating

Water Supply

The water is similar and is ok from cold until after approx 7 mins when there is a great clunk and then the boiler shuts down and the fan will turn off about 4 times in quick succession. The boiler will not start again until a considerable time afterwards.

It's as though it gets to a certain temperature then shuts down until it has cooled down sufficienty to restart again.

Any ideas ?

 

[gasmarc]

sound like it is overheating for some reason

 

[dontknowitall]

Is there a frost thermostat wired in? It might not be operating properly (or wired in correctly).

 

[diesel_ltd]

is the pump running? possibly air in the pump or faulty

 

[gasmarc]

is there enough water in it should be 1 mbar min when cold

 

[Stiggsy]

Thanks for the replies. Water pressure is 1 bar , pump is running ok and bled for a couple of mins but still no joy.

Wonder if there is some blockage in the heating circuit cutting down circulation & hence causing the boiler to overheat ?

 

[diesel_ltd]

could be a faulty pressure gauge.......

 

[Toddyplumb]

Divertor valve stuck or motor US

 

[gasmarc]

it could be numerous things to be honest, has the boiler been giving hot water ok or has it got slowly worse and if so it could be muck in the system

 

[Stiggsy]

The hot water's ok and appears to control correctly too. It's just that it shut's down after about 7 mins and won't restart until about 10 mins has past. The heating takes a while to run through though compared with how it used to be as I remember and is very hot despite being on a low setting so this would indicate there may be some restriction in the heating circuit. I think the next thing to do is try and de-gunge the heating circuit and see if this makes a difference.

Thanks again for all your replies.

Regards

Stiggsy.

 

[diesel_ltd]

keep us updated

 

[gasmarc]

i think you maybe ****ing into the wind myself

 

[dontknowitall]

That's why I didn't make another suggestion!!