Air lock in central heating

[zebedee]

Welcome to autumn..

Put the heating on this morning and the rad in the basement, one in the 1st floor main bed and one in the attic bed and the one in the bathroom work. the one in the living room, the one in the conservatory and the one in the other 1st floor bed don't.

I've bled all rads and most are fine, but for the one in the living room, which is hissing, but there is also a load of water coming out, which is annoying as I don't have a tray or sufficient towels to catch it - it must be like a fizzy drink in there! Is there any trick to get the air in that rad to settle out so I can draw the air off, or should I just buy a big tray and keep it running through the air valve until no hissing or will I have to drain the system completely and carefully refill it (please no, life is too short!)

cheers

Z

[JVaughan]

I had a similar issue when I increased the number of radiators in our house. I found the easiest was was to lock off all your radiators and re-bleed each one, re-isolate it afterwards. This should help to move the airlock out of the system. Also it depends on what system you have ... some systems are pressureised, in which case, again you would have to isolate each rad and bleed the system.

[SS HSV]

Thats really cool I've always wanted an air lock. Very James Bond

Oh

[JVaughan]

The system should be gravity fed from the attic ... well, most are. if you bleed water out of them, they fill themselves back up.

Others have a pressue gauge on the boiler that fluctuates when the system is in operation ..

care to describe yoru system in a littl emore detail ?

[zebedee]

Its a pressurised one, no header tank. I've boosted to 1.5 bar and bled, as I say it seems that one rad is 'fizzy' (i.e. full of air bubbles) because rather than air coming out, lots of water comes out too, with a bit of hissing giving the presence of air away.

[scoobykev15]

you have switched the pump off haven't you cos it wont bleed properly if you haven't!

[zebedee]

what I did was close all the other valves off, then closed the exit valve on the problem (fizzy) rad, bled it and let a lot of water out and the cold pipe (it has a long horizontal run) started to heat up to the supply valve so I closed the bleed valve and then opened the exit valve and voila - it now works. Hopefully the air is not circulating in little bits so I'll bleed the top rad tomorrow and hopefully get it all out. Will do the same on the other 2 as they don't seem to have woken up yet!

[Ferg]

Firstly I would make sure that any thermostatic radiator valves you have are opening correctly. Is the pin under the head moving up and down?

If it is, put the heating on and turn off every radiator except one that isn't getting hot. It should now! If not, close any bypass valves you may have (in the airing cupboard, probably) and make sure the system is on heating only if it is a non-combination boiler. Once you get one hot, close it and open another that isn't working. If the system hasn't been drained you shouldn't have a major lock.

[psn]

Turm off all the radiators then one by one turn each of them on and you will then see where the lock is

[zebedee]

i think closing the exit valve and 'pressurising' the rad whilst bleeding the air valve and letting the water flow through was enough to fill the supply pipe fully and disperse the air into the rad instead of the supply pipe. Probably not the right way to do it, but seemed to work.

I guess the air is now merrily bubbling around the system to the top rad, so I'll bleed them all tomorrow.

Cheers guys, its sorted!

[Ferg]

What probably happened was that the air lock was in the return, but as long as the flow was open the pressure kept the air in the return. Once turned off it allowed it to bubble back into the rad.