Air in system

[gilly1807]

Hi,
My Vaillant combi compact WCWGB221H is running fine, (both heating & hot water). But I keep getting air in the towell rail in the bathroom.
I have to bleed this about once a week and yet I dont lose any pressure on the pressure gauge. (1bar when cold, 1.5 bar when up to temp).
The system has been emptied a few times for repair over the last few months, inhibitor is always replaced, rads are always warm top and bottom. Any suggestions
[/b]

 

[JPC]

auto air vent ??

 

[gilly1807]

Thanks Jamie I will try that.

 

[chrishutt]

I will try that.

Try what? If the pressure is never less than 1 bar air cannot enter the system, even at the AAV.

The air collecting in the towel rail may be given off as a result of heating up fresh water (which would have air dissolved in it). Has the problem persisted long after the last refill of the system?

What repairs have you had done recently? There might be a link. Are you sure that the filling loop has not been left open?

 

[gilly1807]

Combustion chamber and heat exchanger were replaced by BG about 3 months ago.
I have since drained down system to replace a broken TRV.
It has been getting air in the towel rail for about 12 months. BG says its rust in the radiators creating gas, but I was under the impression that you had to have sludge in the rads to do this.
The rads are working fine both top and bottom.

 

[chrishutt]

BG says its rust in the radiators creating gas,

How could that be if the system is sealed and with inhibitor added? And how should this gas (hydrogen) only collect in the towel rail and not in the radiators where it would have formed? Doesn't make sense - they're bull$hitting you! Sounds like you have a BG contract - have they ever carried out any other work on the system?

You haven't answered my other questions? Any idea why BG changed the heat exchanger (which one?) and combustion chamber (that's unusual)? When the system has been drained what did the water look like - black and sludgy or clear?

 

[gilly1807]

I do have a contract with BG.
BG changed the central heating heat exchanger because it had a leak.
They changed the combustion chamber because that to had a leak on what to me looked like a pipe that wraps around the chamber but is part of it (welded to it).
The water in the rads is not as clear as tap water but certainley not black or sludgy.
The filling loop is aways disconnected after use so that a cover can be refitted to hide pipe work. It wont fit if the filling loop is connected.

 

[gilly1807]

Air is in the towel rail as we speak, the last time the system emptied was about 6 weeks ago. I have to bleed the towel rail every week.
The top 4 to 6 inches of the rail are usually cold till bled.

 

[chrishutt]

Just to prove that the air in the towel rail is not gas from rusting (hydrogen), hold a lighted match or similar naked flame in the gas as you release it from the air vent. If it's hydrogen it will burn. If it's only air (which it is) it won't. Then call BG back, tell them to stop bull$hitting you and sort it out. It's what you pay them to do.

 

[JPC]

i meant for op to fit an auto air bleed valve...like alladin (this doies not offer a cure but deals with cold radiator issue whilst allowing you to ignore the problem
[/img]

 

[gas4you]

If you keep bleeding the towel rail and not having to top up system pressure (as your post makes it sound) then water can only be getting in vis the filling loop or a hole in the plate heat exchanger.

 

[chrishutt]

If you keep bleeding the towel rail and not having to top up system pressure (as your post makes it sound) then water can only be getting in vis the filling loop or a hole in the plate heat exchanger.

But the filling loop is disconnected and it's air that's entering, not water. I suspect that air is being drawn in somewhere upstream of the pump (AAV?) as a result of some severe restriction to circulation.

I suppose if the cap were screwed down on the AAV that possible source of the air could be checked. If the OP keeps calling BG back they'll keep changing parts until they eventually change something that fixes it.

 

[gilly1807]

Its not nitrogen opps I mean HYDROGEN in the towel because it will not ignite with match.
Regarding air getting in the system before the pump has anyone got any ideas where this might be.
BG keep telling its from sludge and probaly want to charge for a power flush. (£440).
I rather put that towards a new boiler.

 

[chrishutt]

BG keep telling its from sludge and probaly want to charge for a power flush. (£440).

But now you know they're bull$hitting you, so you can call them back and tell them to sort it out. Why pay for a maintenance contract and then let them get away with cheating you?

And it's hydrogen, not nitrogen!

 

[gilly1807]

Thanks for all your suggestions.
I will speak to BG and see if they can help.