Air in central heating system

Dis86

Dis86

Dis86

Suspended
Joined
23 Dec 2011
Posts
33,209
Location
Northern England
All,

I'm stumped. Noticed one of the radiators in the bathroom had a cold spot at the top. Bled it and a fair bit of air came out. Note that this radiator is the highest point in the heating system.
All other radiators fine, no air.
Boiler is absolutely fine, working perfectly. Only a year old and recently serviced. Baxi platinum 40kw.
All radiator valves fine, no leaks.
Assuming no pipe leaks. If there was it would either be coming through the ceiling downstairs or within a wall somewhere downstairs so would expect to see something.
No damp patches anywhere.

Finally installed a new radiator in the kitchen in November which is a bit of a monster, about seven and a half feet tall. System was filled and bled after installation. Ran with the pipework exposed for a month whilst other walls in the kitchen were plastered and no leaks visible there.

Only thing I can think is there was possibly an air pocket in the new radiator that's worked it's way free and to the highest point in the house. Would this make sense?
 
My rad that is closest to the pump did this...
Had to bleed it at least once a week with quite a bit of air coming out.

Have fitted an Aladdin valve ( self bleeding) and it has been fine since.
 
Its normal (ish) to some degree or another. Sometimes it can be caused by the boiler temp being set too high, try around 67C.

Sadly Duotecs/Platinums dont have the option to lower the heat output, so it might be that the system cannot take the heat away from the boiler as efficient as it could do, and could cause the boiler to 'kettle' air into the system.

The other means of excess air/gas in a system is from corrosion, so I hope youve dosed up with inhibitor, very important! Overdose is good :) Underdose is baaaad :(
 
Open or closed system and age of?

We have an ancient central heating system with open header tank. If the cold feed is blocked, it could be when you are bleeding it's drawing in air through the vent pipe rather than water from the header tank.

Our system gets terrible trouble with sludge build up, even having a double dose of X100 + X200 to boot after I drained it in the autumn and ran X400 cleaner round it for a month. Plus a Magnaclean in the system to collect iron filings. (Last power flushed 3 years ago). However even though AFAIK the cold feed is okay, still have to bleed the bathroom radiator on a fortnightly basis and you can hear air in the pump when it first starts in the morning, despite occasional bleeding.

TBH I'm fighting a losing battle and sooner probably rather than later am going to need to have the whole system replaced, ker-Ching...
 
Aye, as fish says it's a sealed system combi. System itself is a mix of ages but no part older than 12 years. All the pipework in the kitchen is new and all the pipework from the manifold to the bathroom is a year old.
Serviced annually and fully dosed with inhib. Also has a Magnaclean in it too.
 
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