Hot to stop banging when boiler calls for hot water

[Gibbo]

Hi
I have a worcester heatslave external oil boiler which makes a large bang every time we use hot water when the central heating is running. It seems that as the diverter valve moves towards the hot water position there is a single clunk which can be heard all around the house. The diverter valve has had new internals and the actuator was replaced recently for a different problem. Would appreciate any advice on this please.

 

[ShaunCorbs]

Is there an auto bypass fitted ?

 

[Gibbo]

No. Is this recommended. The boiler was installed as recommended by Worcester. They don't mention anything like that.

 

[ShaunCorbs]

I would recommend having one fitted should get rid of the clunk

 

[Paul Gibson]

Is this fitted across the the flow and return of the pump

 

[John.g]

Yes,

What exact make/model of circ pump do you have and see what mode and setting it at, you may be able to reduce its setting which may help to reduce the clunk.
Also check for clunk by shutting the boiler/circ pump down when in CH mode only then c/o to HW mode only, restart boiler, check for clunk.

 

[Deleted member 123817]

Should also have asked if it's a mid position valve that allows HW & CH on together?

 

[SimonG]

Should also have asked if it's a mid position valve that allows HW & CH on together?

No its priority to hot water, all the rads probably have trvs. All shutting down and then nowhere for pump to go, swaps to hot water and 'thud'.

For a quick fix till sorted permanently take trv head off on one of rads.

 

[John.g]

Does a diverter valve parallel the CH & HW momentarily while changing over?.

 

[SimonG]

Does a diverter valve parallel the CH & HW momentarily while changing over?.

Will do.