Boiler does not start - unless increase pump speed -

Joined
11 Dec 2012
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Location
Staffordshire
Country
United Kingdom
Hi

My CH boiler occasionally does not start. I've noticed that when I increase pump speed to 3 (normal setting 2) the boiler will immediately start and is OK for some time then. And I can reduce the speed to normal 2.

Seems like the pump gets the signal to start but not starting and then boiler does not start either.


That is for central heating.

Can the pump be faulty?

What else can be a problem?

thanks
 
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You have a zone valve in the circuit and the increased pump speed is
making it work. The valve isn't operating enough to switch across and switch on the boiler.

Sorted.
 
You have a zone valve in the circuit and the increased pump speed is
making it work. The valve isn't operating enough to switch across and switch on the boiler.



Sorted.

Thanks for that

Is it the mid position valve? This was changed a year ago. Do I need to change it again?
Or is it something else?
 
As it seems to work OK on setting 3 I would isolate the pump and split it and have a look at the impellor it may be full of crap and a good clean might be all it needs, wont cost anything to try this and may save you buying a new pump, if not what have you lost ?
 
Thanks for the advice.

checked the boiler - Potterton profile 30

I have replaced the valve today. Had to increase the speed to 3 for the first couple of times to start the boiler (when the pump was cold)
Then as the pump got warmer it was OK. So not so sure yet whether this was the valve.
Will wait and see.

In case I have to replace the pump - I've got CP53 model.

I read somewhere that to replace the pump I would have to unscrew two fixing screws in front of the pump (diagonally opposite if you know what I mean) and it will make the whole job much easier. Do I have to order exactly the same size or any pump will fit to those 2 fixings. Trying to avoid removing the whole pump from the pipes
thanks
 
As it seems to work OK on setting 3 I would isolate the pump and split it and have a look at the impellor it may be full of crap and a good clean might be all it needs, wont cost anything to try this and may save you buying a new pump, if not what have you lost ?

Will check daytime tomorrow. Now it's a bit too cold to remove the pump... it's freezing outside!
 

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