How to rid central heating pipework of airlock???

[Frenchy316]

Hi everyone, I wondered if someone could help me with a problem that I have? I have recently replaced a cracked radiator on an unvented system. After installation I bleed the new radiator, turned the heating back on and now all of the downstairs rads are not heating up properly, yet the valves are hot. The upstairs ones are piping hot, so I tried bleeding each rad and balancing the system to no avail. I then thought it could be an air lock, so I drained the system down, and refilled in two stages, bottom rads first followed by the upstairs ones, again downstairs are cold. The first rad on the system is upstairs, so should I fill the top ones first? Many thanks in advance.

 

[bennythedip]

Do you have any way of isolating upstairs and downstairs? Are there any zone valves or lever valves?

 

[village idiot]

check to make sure all the valves on downstairs rads are fully opened.
Then with central heating on full blast, turn off all radiators upstairs. This time, it may work. well, you have already tried that anyway

 

[Frenchy316]

Do you have any way of isolating upstairs and downstairs? Are there any zone valves or lever valves?

Hi I'm not 100% sure to be honest, where would they be situated, near to the boiler? all I could see was the pump and motorised valve on the flow pipe from the boiler. Thanks

 

[Frenchy316]

Do you have any way of isolating upstairs and downstairs? Are there any zone valves or lever valves?

I can't say I've noticed any, all I could see was the pump and motorised valve on flow from the boiler, would they be situated anywhere else? thanks

 

[bennythedip]

If you have a hot press/airing cupboard would check there. Have you tried turning off all rad's except one upstairs and see if it heats?

 

[tamz]

Drain it and refill again this time make sure the motorised valves are manually opened. Always fill from the bottom up.

 

[Frenchy316]

Drain it and refill again this time make sure the motorised valves are manually opened. Always fill from the bottom up.

I will try this thanks, it may be nothing, but when I first turned the heating back on the motorised valve vibrated quite badly for a few seconds and made a grinding noise when in operation before settling down again?

 

[Frenchy316]

If you have a hot press/airing cupboard would check there. Have you tried turning off all rad's except one upstairs and see if it heats?

Yeah where the unvented cylinder and boiler is housed there is a motorised valve on the CH flow pipe. I was thinking of filling the downstairs rads one at a time, starting with the furthest and seeing them heat up individually? Many thanks for your valuable advice!