hot water only pipes banging ! turn on c/heating stops this

[slackjawgaze]

Hi
I have a potterton profile 50l boiler.

When i turn on the hot water only - after 5 minutes the pipes start banging really loudly increasing in volume !!!

I f i then turn on the central heating the noise stops straight way !

Can anyone explain 1. why it stops the noise ?
2. What i can do to fix this problem ?

thanks

Carl.

 

[Slugbabydotcom]

1.)For some reason the water isnt moving fast enough through the boiler when on HW only. Could be sludge, blockage, knackered diverter or zone valve.[or maladjusted balancing valve causing a slightly different scenario]
When the CH goes on the pump drags the water through faster thus stopping the 'kettling' thats going on in your boiler
2.)Check out as above and / orTell us more, but before you do read > this