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.

 

[Vee]

Do you have an automatic bypass on the system. You may need it if the radiator you removed acted as manual bypass.

 

[Last Plumber]

It sounds like a spring return motorised valve slamming shut.
Vee may well be right with the bypass but you need to identify the cause first.
If you have a motorised valve, check it when you turn the heating off to see if it’s that, which is making the bang.

If not let us know and we’ll think of something else

 

[Paul Cooksn]

Do you have an automatic bypass on the system. You may need it if the radiator you removed acted as manual bypass.

I don't think it has one. Where would it usually be located. i can take pictures if required.

 

[Last Plumber]

It may not have one. I was going off the description you gave. Difficult on a forum.
Normally, airing cupboard or near Boiler !

If it hasn’t got one, maybe an auto bypass is the answer.

Any chance of photos of Boiler and airing cupboard ?

 

[Paul Cooksn]

It sounds like a spring return motorised valve slamming shut.
Vee may well be right with the bypass but you need to identify the cause first.
If you have a motorised valve, check it when you turn the heating off to see if it’s that, which is making the bang.

If not let us know and we’ll think of something else

It has two motorised valves. I can hear the motors opening and closing when both the heating and hot water are in use. The bang is really hard to identify, it seems to be coming from around the pump but difficult to say for sure. Is the hot water being pushed up into the header tank part of the same problem.

When I removed the radiator I capped the ends and have also tried connecting them together similar to how the radiator would function but no joy.

Thanks for your advice.

Paul.

 

[Last Plumber]

It has two motorised valves. I can hear the motors opening and closing when both the heating and hot water are in use. The bang is really hard to identify, it seems to be coming from around the pump but difficult to say for sure. Is the hot water being pushed up into the header tank part of the same problem.

When I removed the radiator I capped the ends and have also tried connecting them together similar to how the radiator would function but no joy.

Thanks for your advice.

Paul.

It has two motorised valves. I can hear the motors opening and closing when both the heating and hot water are in use. The bang is really hard to identify, it seems to be coming from around the pump but difficult to say for sure. Is the hot water being pushed up into the header tank part of the same problem.

When I removed the radiator I capped the ends and have also tried connecting them together similar to how the radiator would function but no joy.

Thanks for your advice.

Paul.

Honeywell ( silver box top ).?

 

[Paul Cooksn]

The boiler is in the garage 15 meters from the airing cupboard. Since this problem the bleed valve no longer works and is full of water. If you undo the screw water overflows from the nipple.

Cheers.

It may not have one. I was going off the description you gave. Difficult on a forum.
Normally, airing cupboard or near Boiler !

If it hasn’t got one, maybe an auto bypass is the answer.

Any chance of photos of Boiler and airing cupboard ?

 

[Last Plumber]

Yes it needs a bypass.
If you try holding the valve open whils someone turns heating off you’ll see if it stops the bang

 

[Paul Cooksn]

View attachment 31460

The boiler is in the garage 15 meters from the airing cupboard. Since this problem the bleed valve no longer works and is full of water. If you undo the screw water overflows from the nipple.

Cheers.

The

Yes it needs a bypass.
If you try holding the valve open whils someone turns heating off you’ll see if it stops the bang

How would you do that, I'm not sure. Presume you would take the cover off but then what?
Many thanks.

 

[Last Plumber]

No. 230V in box.

There’s a lever on side where wire exits.
Auto - Manual

 

[Christopher buzzard]

Opposite side to the label on the zone valve is a little lever. When your heating is on there should be no resistance on the lever and it should move left and right freely. Heating off and you should feel tension on the lever and when you move it is should move back to close position on a spring action. Switch your heating off and hold the lever open. If there's no bang once the pump has shut off then you def need a auto bypass. There is also a little nib on the valve where you can hook the lever onto so it won't return to close, if you are doing this alone.

 

[Last Plumber]

Do what C Buzzard said.
It’s what I was about to write.

 

[Paul Cooksn]

Opposite side to the label on the zone valve is a little lever. When your heating is on there should be no resistance on the lever and it should move left and right freely. Heating off and you should feel tension on the lever and when you move it is should move back to close position on a spring action. Switch your heating off and hold the lever open. If there's no bang once the pump has shut off then you def need a auto bypass. There is also a little nib on the valve where you can hook the lever onto so it won't return to close, if you are doing this alone.

I'll try it in the morning and be in touch then (kids asleep). Thanks for your help and advice, much appreciated. Regards. Paul.

 

[Last Plumber]

I'll try it in the morning and be in touch then (kids asleep). Thanks for your help and advice, much appreciated. Regards. Paul.

No worries, do let us know how you go on!

 

[king of pipes]

Vent your pump to it sound like a typical air locked system , good luck kop

 

[Paul Cooksn]

No worries, do let us know how you go on!

Hi I did what you said. When the heating is off I checked the tension on the lever and there isn't any. When it's on there is tension so I held the lever open and turned the heating off and it still bangs.

Could it be an air lock.?

Cheers.

 

[Paul Cooksn]

Vent your pump to it sound like a typical air locked system , good luck kop

I've bled the pump. The air vent above the pump is faulty and leaks water through the bleed nipple. I know it's supposed to be left undone but I can't as it will FLOOR the airing cupboard.

 

[Last Plumber]

When the heating is on, there shoul be no tension as the valve is open. If it is calling for heat that is.
i.e. programmer on, room stat up above room temp.

Maybe you meant that ?

If it still bangs with the valve left open, it needs looking at, I can’t guess without witnessing it.

I don’t think it’s an air lock but that is my opinion.

 

[Paul Cooksn]

When the heating is on, there shoul be no tension as the valve is open. If it is calling for heat that is.
i.e. programmer on, room stat up above room temp.

Maybe you meant that ?

If it still bangs with the valve left open, it needs looking at, I can’t guess without witnessing it.

I don’t think it’s an air lock but that is my opinion.

Sorry was checking the wrong one. You are right, no resistance when on. I held it open, turned off and no bang. Can still hear water going into header tank? Does this mean the valve is faulty.

Cheers

 

[Paul Cooksn]

Are these bypass valves or air bleed valves. They are a few meters from the boiler.

 

[Last Plumber]

Sorry was checking the wrong one. You are right, no resistance when on. I held it open, turned off and no bang. Can still hear water going into header tank? Does this mean the valve is faulty.

Cheers

It can be a faulty valve yes but in your case I would suspect that the lack of a system bypass is causing the valve to slam shut as the pressure increases on closing. (valve damage may have occurred as a result of not having a bypass).

My advice:-
Install a system bypass (22mm Auto) and see if it stops the bang. If not replace the valve. You need the bypass anyway.

 

[ShaunCorbs]

Agree with the above but as your draining down I would replace the valves at the same time, if you can afford the slightly extra cost

 

[Last Plumber]

Agree with the above but as your draining down I would replace the valves at the same time, if you can afford the slightly extra cost

Good point!
Do that!
Replace valve and install a Bypass.

 

[ShaunCorbs]

Are these bypass valves or air bleed valves. They are a few meters from the boiler.



View attachment 31464

Looks like auto air vents

 

[Last Plumber]

Bit dark but I agree wi Shaun

 

[Paul Cooksn]

Great help guys thanks very much. One more question where should I fit the bypass valve. Close to the boiler or in the airing cupboard.

Cheers.

 

[Paul Cooksn]

Bit dark but I agree wi Shaun

They were hissing air when the system was refilling so guess they are air vents.

 

[ShaunCorbs]

They were hissing air when the system was refilling so guess they are air vents.

Airing cupboard

I would fit it in between the port valve tees and straight onto the return

 

[stratplus]

Airing cupboard

I would fit it in between the port valve tees and straight onto the return

Yes it needs a bypass.
If you try holding the valve open whils someone turns heating off you’ll see if it stops the bang

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.

 

[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?

 

[Paul Cooksn]

What speed is the pump on now?

Pump is on 2 as the system is quite large 12 rads.
Cheers.

 

[Last Plumber]

I

Pump is on 2 as the system is quite large 12 rads.
Cheers.

If it works well it's fine. You want them on the lowest setting that works and gives the right flow and return temps.

With the valve:-
screw it shut, turn on the heating and hot water so both Motorised valves are open and the pipes start to get hot. Slowly open the Auto by-pass 1/4 turn at a time, (a few seconds in between turning), until you feel hot water flow through the by-pass. Then close it back around a half turn.


That's the best explanation I can give on a Forum. I would be going to greater lengths to set things up and balance the system if I were doing this in person but it will do!

 

[Paul Cooksn]

I


If it works well it's fine. You want them on the lowest setting that works and gives the right flow and return temps.

With the valve:-
screw it shut, turn on the heating and hot water so both Motorised valves are open and the pipes start to get hot. Slowly open the Auto by-pass 1/4 turn at a time, (a few seconds in between turning), until you feel hot water flow through the by-pass. Then close it back around a half turn.


That's the best explanation I can give on a Forum. I would be going to greater lengths to set things up and balance the system if I were doing this in person but it will do!

Thanks I'll do it on Saturday and let you know how it goes.

Cheers.

 

[Last Plumber]

Thanks I'll do it on Saturday and let you know how it goes.

Cheers.

Please do come back and tell us how you went on.

 

[Paul Cooksn]

Please do come back and tell us how you went on.

Hi.

I fitted the valve where suggested and unfortunately it still bangs, perhaps even louder. I can't get water to run through the valve unless I restrict the hot water flow, even with it turned down to 0.1 bar, the lowest it will go.

Picture attached.

Cheers.

 

[Ric2013]

Does the light on the pump flash or stay solid?

 

[Paul Cooksn]

Does the light on the pump flash or stay solid?

Stays solid then switches off completely.

Cheers.

 

[Ric2013]

Okay. That's fine. If you were running it in flashing mode, then it would not be running fixed-speed, and the automatic bypass valve wouldn't be able to work as it should.

 

[Paul Cooksn]

Okay. That's fine. If you were running it in flashing mode, then it would not be running fixed-speed, and the automatic bypass valve wouldn't be able to work as it should.

I'm not sure it is. I can only get water to flow through when I restrict the flow on the hot water.

I would have thought 0.01 bar would be open all the time. Any suggestions.

Cheers.

 

[SavageW]

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

 

[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.