problem bleeding a unvented system

[sly69]

Can anyone help?

I've just replaced TRV's on all the radiators (5) in a top floor flat but can't get two of them to get hot. The problem, I'm very sure, is down to an air lock, the two rads are furthest from the boiler and are connected by pipework which goes up through the loft space and then drops back down. There is no air in the radiators so I imaging air is in the pipes in the loft, how do I get it out?

Thanks

 

[picasso]

check the pipework at the highest point, there maybe manual air vents already fitted , whoever fitted the central heating system will have had the same problem.

 

[sly69]

There are two union type joints in the loft sapce which look like they were put in in case the system was to be expanded but they aren't bleed valves at all - I can't get air out of them either, just water...!

 

[sly69]

Should have said, the unions are just blanked off..

 

[picasso]

are you getting water out of both of the unions ?

 

[sly69]

yes...

 

[twgas]

Turn off the hot ones and the hot water (turn the boiler stat to low to prevent overheating) and see what happens

 

[Servotech]

Can anyone help?

I've just replaced TRV's on all the radiators (5) in a top floor flat but can't get two of them to get hot. The problem, I'm very sure, is down to an air lock, the two rads are furthest from the boiler and are connected by pipework which goes up through the loft space and then drops back down. There is no air in the radiators so I imaging air is in the pipes in the loft, how do I get it out?

Thanks

You need to somehow connect an hose to the feeds on the air locked radiators and then pull water through them until they get hot. You will(if it is air locked) see/hear the air coming out.
This usually involves removal of the said radiator and connecting the hose in turn to each of the valves.
If you have a drain tap fitted it would be easier to use this but if the air locks in the other pipe it won't do it
You need the pump off whilst doing this of course.
Good luck.