Central heating airlock

[dave1]

After changing some rad valves today I've had a nightmare airlock on the central heating. I've put it down to the position of the vent and cold feed as when the heating on the air has nowhere to go. I've drawn a diagram of the setup what do you think?

 

[hammers4spanner]

Are any rads getting warm??

 

[dave1]

Managed to get some hot then open others up and all goes cold again. I'm thinking of moving that vent and cold feed to before the pump, what do you think?

 

[lame plumber]

did it work prior to your arrival, if it did, wack that boiler temp up, let it rattle for a while and blow the airlock out. if its an old non condensing floor stander, if your feeling brave, whip the overheat stat for a short time, it will shake n rattle but probably clear any airlocks, other wise set up the neutral point correctly.

 

[dave1]

Cheers lame, customer said it worked before although has said they have had trouble when draining it previously. I've said to leave it a day or so and see how it settles down. It's a logic in there.

 

[lame plumber]

dont go boiling low water content boilers then

 

[dave1]

Do you think I'm Barking up the wrong tree with the pipework?

 

[hammers4spanner]

Possibly if it was working before customer has said they have also had issues before .Tried a wet vac on a couple ?Checked the pump as well impeller may have an issue on drain down.I have used a filling lop in the past to blast water into system has worked for me.If not try what you said .

 

[townfanjon]

Personaly I would cut out the cold feed , vent section and check for gunk

 

[dave1]

Update, most rads have started working two or three not heating properly now. Advised customer to turn off all hit ones and leave the three to blast through for a while.
Still think moving the vent and cold feed to before the pump would help.