Heating Bangs when switching off.

[Paul Cooksn]

When you say restrict the flow on hot water,is this when the system is running eg demand from heating/hot water? The hot water coil should have a balancing valve on it that should be restricted (which from the pic you have one after the 2port) to stop the heat just whizzing around the coil and giving less to heating

The balancing valve is fully open. When I mentioned restricting the flow I shut it off. Are you saying this valve should be half turned off or similar. Is this likely to contribute to the banging.

Cheers.

 

[SavageW]

It should be restricted yes,but are you only getting flow through the by-pass valve when there is still demand for ch or hot water an your closing the balancing valve?

 

[Paul Cooksn]

It should be restricted yes,but are you only getting flow through the by-pass valve when there is still demand for ch or hot water an your closing the balancing valve?

If I run the water and heating separately or even both of them together I can't get any water to pass through the bypass valve. I can only get it to pass through when I close the balancing valve with the hot water on demand.

 

[Paul Cooksn]

Another point I forgot to add. If I turn the pump off at the fused spur, it doesn't bang. Don't know whether this has any bearing on the fault but thought I would mention it.

Cheers.

 

[Last Plumber]

What size of pump is it, I can't read it

 

[Paul Cooksn]

What size of pump is it, I can't read it

Photo attached. Cheers.

 

[Last Plumber]

Nothing unusual about that size.

 

[Last Plumber]

You don't really want water passing through the bypass when the valves are open so I wouldn't worry too much about that if the flow and return temps are ok at the Boiler.
I'm surprised it still bangs but you do need to rule things out like the lack of a by-pass before you can start to think of other possibilities,

I'll put my thinkin cap back on.

 

[Paul Cooksn]

You don't really want water passing through the bypass when the valves are open so I wouldn't worry too much about that if the flow and return temps are ok at the Boiler.
I'm surprised it still bangs but you do need to rule things out like the lack of a by-pass before you can start to think of other possibilities,

I'll put my thinkin cap back on.

Cheers, it seems to be dragging on this but any suggestions I will try and I really appreciate all the help and advice.

Flow and return seem normal and all radiators get nice and hot.

I even tried balancing the system by restricting flow in the first radiator to warm up and so on.

I tried refitting the bypass valve with a normal 22mm isolation valve which I fully opened and it still banged. This would suggest an auto bypass is not required or not working even though the water is passing through and the pipes are hot.

When I am bleeding the system, when there is air present it doesn't bang. It's only when all the air is removed it starts to bangs.

Could the system just be full of glag as the filter is really dirty every week with bits of swarf/metal in it.

Thanks again.