Heating Bangs when switching off.

[Paul Cooksn]

Hi,

I have an older style open vented heating system with a Glow worm 50/60 RF flued fan boiler. I have a hot water tank on the first floor and two header tanks in the loft, one large for the hot water and a smaller one for the heating.
Last week I removed a radiator from the landing and capped off the pipes under the floor. Since doing this when the boiler switches off there is a loud bang and the whole heating system shakes. I thought it was an air lock but I have bled the system and all radiators are warm. It only does it when it's on heating, not when on hot water. Another point, when the boiler switches off water runs into the header tank for about 3 seconds.p from the expansion pipe.
I've even tried connecting the pipes I cut off together just in case I had messed up the flow and return but it's still the same. All radiators have trv's apart from a heated towel rail in the bathroom and large radiator in the hall which is by the thermostat.

Anybody have an ideas what it might be. I have also flushed the system and it is clean. It's worked fine for years until I removed the radiator.

Many thanks.

Paul.

 

[ShaunCorbs]

Wouldn’t the rad in the hall and heated towel rail act as a bypass. Neither of these have trv’s.
So removing that landing rad shouldn’t have made a difference. He also joined the pipes from the rad he removed and it was still banging.

If these are piped in before any port valves yes they would

 

[Last Plumber]

Wouldn’t the rad in the hall and heated towel rail act as a bypass. Neither of these have trv’s.
So removing that landing rad shouldn’t have made a difference. He also joined the pipes from the rad he removed and it was still banging.

Not if they’re after the valve and they most likely are.
The bypass needs to be before the valve for when the valve shuts!

 

[Paul Cooksn]

Not if they’re after the valve and they most likely are.
The bypass needs to be before the valve for when the valve shuts!

Hi

I had a plumber attend yesterday and the valve was faulty, when taken off you could hear it making a grinding noise. He replaced the valve and the banging stopped but did say it probably needs a bypass valve fitting between the pump and valves then into the return. After a few hours the banging returned but it was much quieter. The plumber said the new valve is much stronger than the old one.

The bypass is being fitted Thursday so I will let you know what happens.

Cheers for all your advice.

Regards.

Paul.

 

[WYEO54]

Hi Paul
I would suggest that you check that the zone valves are actually positioned correctly for the differential pressure being created by the pump. The type of sound you have described indicates to me that a zone valve is slamming back when closing - this happens when a valve is positioned the wrong way to the flow - but looking at the photo they seem good to me but obviously I cant see the whole system layout design - so its difficult to be sure whats going on?
Best of luck getting it sorted... Bill

 

[Paul Cooksn]

Hi All,

I had the bypass fitted but there is still a slight bang when turning off. It still pushes water into the header tank as well. I also had fitted a new pump as the old one was nearly blocked. I have fitted a magnaclean on the return to the boiler and you wouldn't believe what muck came out of it in 24 hours.

Should I just put the radiator back.

Cheers.

 

[ShaunCorbs]

I would drain down and wack some x800 in the system for a week then drain it down again and fresh inhb

 

[Paul Cooksn]

I already did flush and the water ran clean. I opened all the bleed valves to get all the water out. The pump was old, dated year 2000 so it needed replacing anyway.

 

[Paul Cooksn]

Just updating again on this. I refitted the radiator and now the heating Bangs even more. Really am at a loss. Anybody with any further ideas.

 

[Frog67]

The fact that you have water flowing out the vent pipe when the system shuts down indicates you still have a fault, probably a blockage somewhere near the expansion pipe. You could try turning the speed on the pump down to its minimum to see if the noise reduces. Another thing to try would be to remove the rad again, empty it, refit, turn on the valves but don't bleed it. (it should act as an expansion vessel).
One thing i noticed looking at the pictures is the vent from the boiler looks like its running horizontal along the ceiling, so it may be possible that the system has an air lock.

 

[Frog67]

Forgot to say, that as you mentioned the amount of muck in the magnet suggests that the system needs a good clean.

 

[Paul Cooksn]

Forgot to say, that as you mentioned the amount of muck in the magnet suggests that the system needs a good clean.

Thanks for your advice. The pipe or pipes running across the garage ceiling are the flow and return to the boiler. The vent pipe is in the airing cupboard and goes about 18 inches abouve the header tank in the loft. When filling the heating back up after draining it doesn't bang, it's only when all the air is out the system so similar to your radiator test. Turning the pump down reduced the bang noise.

Cheers.

Paul.

 

[SavageW]

Got a picture of the new by-pass that’s been fitted ? Hard to tell from airing cupboard picture but is the open vent an cold feed teeing in just before pump

 

[Paul Cooksn]

Got a picture of the new by-pass that’s been fitted ? Hard to tell from airing cupboard picture but is the open vent an cold feed teeing in just before pump

 

[ShaunCorbs]

Where's the bypass valve all I see is a full bore ISO valve ?

 

[SavageW]

The valve put in on the by-pass looks like a ball fix turned 1/3 off have you tried opening this fully an seeing if this stops the banging
*shaun beat me to it,but that isn’t correct for a by-pass that’s why you still have the banging

 

[Paul Cooksn]

The plumber said it didn't need one, I thought it might and I asked again whether it needed to be 22mm. I can change it myself if you are able to advise what to get and where to put it. If the valve is fully open then yes it does stop it banging.

One question, I have lived in the house for 13 years without a single bang. Why would this start after removing the radiator.

 

[Paul Cooksn]

The valve put in on the by-pass looks like a ball fix turned 1/3 off have you tried opening this fully an seeing if this stops the banging
*shaun beat me to it,but that isn’t correct for a by-pass that’s why you still have the banging

The plumber said it didn't need one, I thought it might and I asked again whether it needed to be 22mm. I can change it myself if you are able to advise what to get and where to put it. If the valve is fully open then yes it does stop it banging.

One question, I have lived in the house for 13 years without a single bang. Why would this start after removing the radiator.

 

[SavageW]

I didn’t even pick up on that it was 15mm,that won’t help an then with the type of valve that will neither. You’ve said that with it fully open the banging stops.I could only say that since the 13years you’ve been there that the pipework /heatexchanger has become restricted.

 

[Paul Cooksn]

I didn’t even pick up on that it was 15mm,that won’t help an then with the type of valve that will neither. You’ve said that with it fully open the banging stops.I could only say that since the 13years you’ve been there that the pipework /heatexchanger has become restricted.

Cheers for your help. Could you tell me what valve I need and where it should go.
I assume the valve is operated by bar pressure

 

[SavageW]

bypass valve open vented system - Google pretraga ask your plumber who installed your by-pass to come back an rectify

 

[Paul Cooksn]

bypass valve open vented system - Google pretraga ask your plumber who installed your by-pass to come back an rectify

Your a star cheers. Is it in the right place above the valves

 

[Paul Cooksn]

One final question.

Should I fit the new 22mm auto bypass valve to replace what is there or should it go after the pump but before the motorised valves.

Thanks. Paul

 

[Last Plumber]

Has a Plumber put that in?

 

[Paul Cooksn]

Has a Plumber put that in?

Yes.

 

[Paul Cooksn]

Has a Plumber put that in?

Hi sorry couldn't reply properly earlier.

Yes following your previous advice a plumber did fit it, new pump, new valve and I fitted the magnaguard. It stopped for a few days but when the air was completely out of the system it started again. I questioned whether a 22mm auto bypass valve was required and he said this will do the same.
I am perfectly capable of fitting it myself but am not sure where to fit it. Do I install in the same place or before the valves but after the pump.

I even re installed the radiator and it bangs.
Cheers. Paul.

 

[Last Plumber]

It will do there if it is 22mm and automatic. I am presuming you have a 3 mtr min loop from boiler and back to boiler via by-pass?

 

[Paul Cooksn]

It will do there if it is 22mm and automatic. I am presuming you have a 3 mtr min loop from boiler and back to boiler via by-pass?

View attachment 31830

The distance from the boiler to the by pass is about ten meters. I will change the size of the plumbing and use solder joints as it looks a bit messy. I can fit it somewhere else if it works better. I would rather it be correct. Wish I had done the work myself.

Does the pressure have to be regulated by the pump flow speed. Cheers.

 

[Last Plumber]

One question, I have lived in the house for 13 years without a single bang. Why would this start after removing the radiator.

Because the Rad acted as a by-pass and you removed it!

 

[Last Plumber]

The distance from the boiler to the by pass is about ten meters. I will change the size of the plumbing and use solder joints as it looks a bit messy. I can fit it somewhere else if it works better. I would rather it be correct. Wish I had done the work myself.

Does the pressure have to be regulated by the pump flow speed. Cheers.

It's fine there, 22mm with either a straight valve like the one I showed you or an angled one where the elbow is

 

[Last Plumber]

Does the pressure have to be regulated by the pump flow speed. Cheers.

What speed is the pump on now?