Persistent air in heating pipes

Kencollins

Hi all,

I have a sealed central heating system , oil fired, was converted from vented.

There is air circulating in the pipes...I can hear it in the pump when the system is switched on, and can hear gurgling in the pipes upstairs when the system is on.

I have tried and tried again to bleed the air out through the radiators, but there is no air in them at all.

The heating pipes go up into the attic, where there is a pressure vessel attached to one pipe, and the fill valve is on the other pipe.

I put in a pressure gauge just inside the fill valve. (the plumber had put in a pressure regulating fill valve set at one bar). The valve allows me to see if the system holds pressure, which it does so there is no leak.

So my question is....how the hell do I get the air out of the pipes? Would it be an option to extend the pipe at the fill valve vertically for about a foot and put a bleed valve on the top if it? The fill valve is at a 90 degree bend, so I could use a T adapter to extend it.

Any ideas?

shane0007

What size circulating pump is on the system? Sounds more like circulation noise rather than air. Pump could be sized to big.

Kencollins

Its a myson standard size heating pump with three settings, I have it on setting two for a two story house with 11 radiators and a hot water tank. The noise at the pump is like a hissing/airy noise. It's not constant though, happens for a second or two, then nothing for 10-15 seconds.

DoneDL

I would fit an Automatic Air Vent, make sure it`s a good quality one or fit a manual vent.

Kencollins

Thanks for the reply!

Where would the best place be for the vent? The pipework I can access is either at the pump, in the hot press (1" pipe that comes up, has a shut off valve, then goes down again), or in the attic (pressure vessel side or water inlet side?)

If you could give me a link or a name of one it would be great, a job to do tomorrow!

Thanks,

Ken

shane0007

Kencollins wrote: »

Thanks for the reply!

Where would the best place be for the vent? The pipework I can access is either at the pump, in the hot press (1" pipe that comes up, has a shut off valve, then goes down again), or in the attic (pressure vessel side or water inlet side?)

If you could give me a link or a name of one it would be great, a job to do tomorrow!

Thanks,

Ken

There should already be on at the boiler & on the coil of the cylinder. The screw caps maybe tightened closed.

Kencollins

http://www.spiraxsarco.com/pdfs/sb/s31_06.pdf

Something like that maybe? I was thinking the best place for it would be just before the pressure vessel. The pressure vessel is lying horizontally, so I could put in a T-piece instead of the elbow and then fir the vent vertically?

Kencollins

I can't see one at all. The only one at the boiler is the 3 bar pressure valve, and there is nothing around the cylinder. Would this be because the system was installed as an open vented system and pressurized at a later date?

shane0007

Kencollins wrote: »

I can't see one at all. The only one at the boiler is the 3 bar pressure valve, and there is nothing around the cylinder. Would this be because the system was installed as an open vented system and pressurized at a later date?

There should always be an AAV on the boiler. When the vent was removed at the cylinder it should have been replaced with an AAV.
This is most likely your problem.

Kencollins

I'm a bit confused now!

Which cylinder are you referring to? The boiler is a potterton statesman if that makes any difference. Would the AAV be in plain view if there was one?

As for any changes, the only thing the plumber did was remove the feed tank in the attic. He put the pressure vessel on one pipe, and the water inlet on the other side.

If I can't find the AAV, would it be any harm to fit a new one? And where will I put it? There is definatly air circulating upstairs as I can hear it gurgling when i'm in bed!

shane0007

Kencollins wrote: »

I'm a bit confused now!

Which cylinder are you referring to? The boiler is a potterton statesman if that makes any difference. Would the AAV be in plain view if there was one?

As for any changes, the only thing the plumber did was remove the feed tank in the attic. He put the pressure vessel on one pipe, and the water inlet on the other side.

If I can't find the AAV, would it be any harm to fit a new one? And where will I put it? There is definatly air circulating upstairs as I can hear it gurgling when i'm in bed!

Your domestic hot water cylinder. There would have been a hockey stick shaped pipe going to the small tank he removed. This is usually removed & replaced with an AAV at the highest point of the system.
There should also be one on the boiler or at least on the boiler pipework.

Kencollins

I think I see what he did now...he used that pipe to put the fill valve on.

Surely not the best way to do it! I guess the best way to fix it would be get a foot of copper pipe and extend the pipe vertically and put the AAV on that?

Hopefully that will sort out the air in a few days then...

shane0007

Kencollins wrote: »

I think I see what he did now...he used that pipe to put the fill valve on.

Surely not the best way to do it! I guess the best way to fix it would be get a foot of copper pipe and extend the pipe vertically and put the AAV on that?

Hopefully that will sort out the air in a few days then...

The norm would be to remove the vent from the tee at the cylinder coil & put an AAV there. You could re-use the feed & connect that from the old ball cock tee for the mains & put a filling loop in the hot press.

Kencollins

I think i will give that a try tomorrow! Its always a pain to have to go into the attic to check the level and top up after bleeding.

Thanks for the help!