Always lots of air in our CH system

[Richtop8]

When I turn on our CH there's a lot of noise from one specific part of the system - the pipes on the landing, and one radiator. It sounds like air, and the landing radiator needs bleeding regularly (about once a month), even though it isn't the highest point in the system. The two upright rads in the bathrooms are a good 50cm higher but rarely have more than a quick "pfffft" of air if I open the bleed valves. All the radiators get hot from top to bottom (except when the landing one needs bleeding) and the noise stops after a couple of minutes running.

Wondering what could be causing one radiator to fill with air so quickly, and why there could be so much air trapped in one part of the system. I can't see any sign of a leak. Any ideas?

 

[John.g]

Have you a sealed or open vented system?

 

[Richtop8]

Have you a sealed or open vented system?

You'll have to forgive me - I'm not great with the terminology - but I think it's vented. There's a dome-shaped air separator at the highest point in the airing cupboard, out of the top of which comes a pipe that goes all the way to the header tank where it curves over the tank. The system was installed around 1990, although the boiler has been replaced within the last ten years. When the boiler was changed a Valiant magnetic filter was added, and this has been drained a few times.

 

[John.g]

You might post a photo of that, it sometimes gets full of sludge causing those problems you are getting, if your boiler is a heat only boiler it will have a circulating pump installed close to this and after it, the boiler would be the "4" series like a 418 or 424 etc, if so post a photo of this pump as well.

 

[Richtop8]

This is the boiler. It was installed about eight years ago. It's been maintained pretty well and has a magnetic filter installed above it.

This is the separator in the airing cupboard. I used a very powerful magnet to try and dislodge anything clogging it up. The magnet did something because you could hear stuff moving and going down the pipe when it was released. I did this a few times until there was no more sound when it was taken off.

This is the pump. It’s below the separator (about 20cm). Between the separator and pump is the feed which comes down from the header tank. The pump was changed when the boiler was installed, so is also about eight years old.

 

[John.g]

Try and look into the small feed and expansion tank in the Attic and see if water is flowing out of the vent pipe or drawing air into it, you will have to hold a "glass" full of water with the vent pipe immersed in it to see this. If neither, get someone to start the boiler and see if any spurt of water from the vent, then get them to stop the pump and watch again for any spurt of water, you may have to wait for ~ 3 minutes for the pump to stop after boiler switch off.

How may rads have you got?

 

[Richtop8]

Try and look into the small feed and expansion tank in the Attic and see if water is flowing out of the vent pipe or drawing air into it, you will have to hold a "glass" full of water with the vent pipe immersed in it to see this. If neither, get someone to start the boiler and see if any spurt of water from the vent, then get them to stop the pump and watch again for any spurt of water, you may have to wait for ~ 3 minutes for the pump to stop after boiler switch off.

How may rads have you got?

I'll give that a try.

Sixteen rads. Two have never worked. We had the system power flushed when the boiler was fitted, and we were told this would sort it, but it didn't. One is in the hall and the other is a small secondary rad in the living room, so it's never been a big deal, but there are problems somewhere.

I go around with the key a few times a year, but most rads have no air or just a tiny bit. It's only the one noisy rad that seems to fill with air, but thinking about it, that might be the first one the pipes go to. It's the closest to the air separator/pump.

The pipework to the rads is microbore. Does that make them more likely to block with crud? I assume it does.

 

[gmartine]

If you're prepared to flush the system you could leave some system cleaner in there for a few weeks while the CH is on and see it that unblocks anything. I'll leave John to advise about the F/E tank and pump but I'd seriously consider getting the system sealed, it does save alot of ball ache with air ingress.

 

[Timmy D]

Pump prob set to high and could be drawing air down the vent.

 

[Bev GG]

I had a similar problem, air building up in the boiler, power flush temporarily solved it but after a couple of months the problem returned. Called a local company who sent an engineer and they claimed the heat exchanger was blocked due to the system being fed through a water softener. Viessman technical told me that was rubbish and that they recommend feeding the system with softened water as the heat exchanger is stainless steel. The company then told me that a replacement heat exchanger was not available. Turned out that the engineer had got the model number garbled and Viessman confirmed that the part was available. The company quoted £2500 to replace the boiler.
Needless to say at that point I threated to report them to trading standards and refused to pay their callout.
I then decided to try to fix it myself, having studied the installation guide I found that it was incorrectly installed. The pump is on the wrong side of the boiler and it was fed with a switched live from the thermostat to the permanent live on the pcb. I rewired it (I am a qualified electrician) and now it is working fine.

 

[Alucard]

Hi to John.g.
You recommend ...Try and look into the small feed and expansion tank in the Attic and see if water is flowing out of the vent pipe or drawing air into it, you will have to hold a "glass" full of water...

I can do this test, as my CH system that has a similar issue, but only at the bathroom radiator.
Please can you enlighten me on what the outcome proves and what the solution would be?
As I have noticed the copper pipe that runs upto the expansion tank gets warm /hot. would this draw air the the system as it cools down?

Best regards

 

[John.g]

Hi to John.g.
You recommend ...Try and look into the small feed and expansion tank in the Attic and see if water is flowing out of the vent pipe or drawing air into it, you will have to hold a "glass" full of water...

I can do this test, as my CH system that has a similar issue, but only at the bathroom radiator.
Please can you enlighten me on what the outcome proves and what the solution would be?
As I have noticed the copper pipe that runs upto the expansion tank gets warm /hot. would this draw air the the system as it cools down?

Best regards

Have you the same vent/cold feed arrangemant as Richtop8 above or something similar without the "dome",
depending on what arrangement you've got you may have to cut out a section and throw away the dome (think its called a Airjec or something like that, as sludge builds up in it)

Before doing anything look at your pump and check its mode & setting, if it has LEDs and you are unsure what they show, just post a close up photo of them wthe pump/boiler running. It may be set too high.

How mant rads??.

 

[Alucard]

Hi good afternoon l
My CH system has 10 rads.

I do not have a "dome" arrangement, the expansion goes via 25mm copper pipe to the expansion header tank. It has a bend downwards and an air gate to the surface of the liquid.

The Pump is a Grundfos type: UPS2 15-50/60. It has 3 pump settings low, medium and high.
On the low settings I get less air than on the medium and most air on the high setting.

It is presumed to be air as it is not flammable gas.

About 5 years ago I flushed out the CH system by taking out the Grundfos pump to get access to the connections for the circulating pump instalation. There were no leaks during the circulation cleaning period. So I presumed all fittings were sound and leak free.

Do you have any observations on what causes the air ingress and how to fix it?

Thanks

 

[Alucard]

Hi good afternoon l
My CH system has 10 rads.

I do not have a "dome" arrangement, the expansion goes via 25mm copper pipe to the expansion header tank. It has a bend downwards and an air gate to the surface of the liquid.

The Pump is a Grundfos type: UPS2 15-50/60. It has 3 pump settings low, medium and high.
On the low settings I get less air than on the medium and most air on the high setting.

It is presumed to be air as it is not flammable gas.

About 5 years ago I flushed out the CH system by taking out the Grundfos pump to get access to the connections for the circulating pump instalation. There were no leaks during the circulation cleaning period. So I presumed all fittings were sound and leak free.

Do you have any observations on what causes the air ingress and how to fix it?

Thanks

 

[Alucard]

Hi apologies
The expansion copper pipe is 15mm not 25mm...finger trouble

 

[John.g]

Hi apologies
The expansion copper pipe is 15mm not 25mm...finger trouble

The vent pipe is/should be 22mm and the cold feed is 15mm, are you sure its not the cold feed you are looking at.
Is the pump located upstairs in the hot press and the boiler downstairs, if so, and if you have zoned CH and HW then you will have at least two motorized valves fairly close to the pump, they may be located above the pump or below it, between the pump and these you might see something like the above arrangement (without the air jec).
Also go to the attic and have a look at your small cistern (Feed & expansion or F&E cistern for short) and see where the vent goes up and over it and also the cold feed which will come from the side or end of this cistern, you can then follow it and see where it is teed into the system.

Might look something like this: (This pump is pumping downwards)

 

[Alucard]

Apologies for the delay in replying.
F&E tank photo attached plus images of:
Grundfos pump set at lowest speed
2-way Motorised valve and controller also shows 15mm F&E feed.

Do you recomend the "glass" of water test on the 22mm vent pipe.

I presume that if the water is sucked into the vent that is where the air gets in.

Any other thoughts?
Thanks

 

[Alucard]

For clarification
15mm F&E pipe
22mm vent pipe
Gas boiler is downstairs, pump upstairs in the hot press.
Zoned CH and HW with a 2-way Motorised pump and controller.

Thanks again.

 

[John.g]

That Drayton 3 way mid position valve installation doesn't look right to me, can you check that the direction (up or down) the pump is pumping, there should be a arrow on the pump body, also there may be AB stamped on one the valve body ports and maybe a A & a B on the other two, B should go to the cylinder heating coil inlet (top) and A should go the the rads.

 

[Alucard]

Hi good afternoon ,
I'm having trouble sending my reply with the attached images. I will try later.

Thanks

 

[Alucard]

Hi good evening,

TheGrundfos pump arrow on the front is pointing anticlockwise so is pumping up.

I removed the Drayton 3 way mid position motor controller to check if marked A or B and it was not marked.

 

[Alucard]

Hi good evening,

TheGrundfos pump arrow on the front is pointing anticlockwise so is pumping up.

I removed the Drayton 3 way mid position motor controller to check if marked A or B and it was not marked.

See image sent. The arm is shown in the down position = Central Heating. Whin the controller moves the arm a 1/4 turn up it is in the Domestic Hot Water position.

 

[Alucard]

See second image sent, showing the 3 way connections.

 

[Alucard]

Bottom is from the pump outlet. The Left side is to the CH and the top to DHW

 

[Alucard]

Note in image 3, that the DHW is to the mid point on the cylinder to the bottom of the coil.

Hope this assists.
Thanks