Greenstar 30CDi boiler - overheating

[Simon m]

Hi hope someone may be able to help.
I have Greenstar 30CDi.

When I turn on the boiler it gets to 88 degrees within 2 minutes and the burner on indicator light turns off and the temperature increases to 101 degrees and then slowly drops to 72 degrees when the burner indicator light turns on again and the above process repeats itself. It take approx 5 minutes to complete the above before repeating.

The outlet water pope is hot and the inlet is always cold.

I'm thinking that the pump may be on the out as it is not taking cold water in to prevent the boiler from reaching the 'auto turn off' temperature?

I only have 3 rads turned on and they are a little warm.
Any thoughts on what is going on?

I appreciated any advise you can offer?

 

[Simon m]

I've checked the pump and it runs during the whole process. Is there a sensor that only releases water into the system when it reaches ales a certain temperature?
Possibly the water is being kept in the heating element and is getting too hot and thus causing the burned to stop?

Just a guess as I didn't not know how the system works. Any help would be helpful.

FYI - I get the same result when heating water in the pressurised cylinder.

 

[gigz]

Open all the radiators to see if it still overheats. Sounds like a blockage if the pump IS actually working.

 

[AGAS]

check for a weak pump , why only 3 rads working ?

 

[Simon m]

Thanks for the repy.

I did have all the rads open with the same result. I have a pressurised hot water cylinder next to the boiler and get the same result when the boiled is set to heat hot water for the clynider.

I only turned on 3 rads as when I turned on all of the rads none of the rads got warm.

I took the front cap/screw off the pump and a little bit of water come out and I can see that the pump is spinning.

How can I test if it's a weak pump? Is approx 4 years old.

Thanks

 

[AGAS]

stick your finger in it

 

[steve32]

Heat exchanger blocked new boiler

 

[AGAS]

Heat exchanger blocked new boiler

bit drastic , h/ex not always needed

 

[steve32]

bit drastic , h/ex not always needed

It's a Worcester

 

[AGAS]

It's a Worcester

yes i know thanks

 

[Simon m]

Hi thanks - not the news I was hoping for.
Is there any benefit of adding a cleaner (x800) than the system to try and breakdown/clear the block in the exchanger?

 

[steve32]

Hi thanks - not the news I was hoping for.
Is there any benefit of adding a cleaner (x800) than the system to try and breakdown/clear the block in the exchanger?

Worth a try I have never been successful have you got a mag cleaner fitted.

 

[Simon m]

I'll give it a go tomorrow. Nothing to lose...
Yip - there is a mag cleaner fitted.

 

[cross thread]

check the basics are all boiler/filter valves open

 

[Agile]

When was the boiler last serviced?

I thought that Worcester boilers all had a minimum of a five year warranty?

Tony