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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Air in radiators - why? https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1102617868 Message started by HandyJon on Dec 9^th, 2004, 6:44pm

Title: Air in radiators - why?
Post by HandyJon on Dec 9^th, 2004, 6:44pm

Got a problem with our CH system. There's loads of air getting into the system such that the upstairs radiators need to be bled every other week. Now I can't find any sign of a leak anywhere so I don't think it's a leak. There is inhibitor in the system - it was put in at the beginning of the year when the one of the valves was replaced (had a problem where no hot water but CH worked which led to the valve being replaced and the system being flushed). Since the replacement of the valve nothing has been done to the system, not even turning it off, and it worked without problems immeidately after.

Any ideas? Even if it is obviously a leak, just let me know and I'll look harder for it.

Title: Re: Air in radiators - why?
Post by HandyMac on Dec 9^th, 2004, 10:02pm

Might be worth adding an auto-bleed valve to the water circuit. Typical place is on the pipe feeding into the HW cylinder in the airing cupboard, which is a high point.

That way as water makes its way around the heating circuit (carrying air) the auto-bleed valve can evacuate the air automatically and hopefully keep it out of the radiators.

HM

Title: Re: Air in radiators - why?
Post by thescruff on Dec 9^th, 2004, 10:07pm

But that doesn't solve the probem HM.

Suspect the system is out of balance, blocked cold feed, valve fitted wrong, pump on the wrong setting.

more info on type of system required.

scruff

Title: Re: Air in radiators - why?
Post by HandyMac on Dec 9^th, 2004, 10:08pm

Actually I know it doesn't fix the problem. But started writing my answer before engaging brain.... :)

HM

Title: Re: Air in radiators - why?
Post by HandyJon on Dec 11^th, 2004, 7:11pm

wrote on Dec 9^th, 2004, 10:07pm:

Suspect the system is out of balance,

Nope, no rad valve has been touched in three years

Quote:

blocked cold feed,

possibly, but once bled the system fills again so there is water getting into the system from the cold water tank.

Quote:

valve fitted wrong,

Possibly, but it was working properly immediately after it was replaced at the begining of the year.

Quote:

pump on the wrong setting.

Possibly since the motor might have been fiddled with when the valve was changed, but the system had no bleeding problem (sorry about the swearing! ;)) immediately after the valve replacement and none till 2 months ago.

Quote:

more info on type of system required.

It's a condensing boiler feeding the CH system. Not a combi boiler since the hot water is stored in a hot water tank. No TRVs on the rads. The pump's setting is set to 2. Pump is a Grundfos Selectric UPS 15-50. Anything else you need to know, let me know.

Title: Solved
Post by HandyJon on Dec 16^th, 2004, 9:43pm

Worked it out. Was painting the rad in the bathroom, as you do, so I turned it off when I noticed that the base of the valve was a bit damp and there was some discolouration. It seems that it's leaking when hot and you don't see any patches because it all evaporates with the heat.