1 cold loop on my central heating system.....

[Les1]

I have just changed a motorised valve on my heating system. Refilled it & turned it on & found 0ne loop only working with 2 radiators on it.

Next morning programmer started it up and the 2 rad loop was cold but the rest was really hot & working fine. Cannot seem to get the air out of the 2 rad loop. Tried purging at the Air valve but it doesn't appear to have air in it. Any ideas would be most helpful. I have tried turning other radiators off but no joy.

Thanks, :annoyed:

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[Gas]

Have you closed off all working rads? Closed off the by-pass? pics of the install might help use identify the problem.

 

[Les1]

Thanks Gas,

I have tried closing off all hot rads. I do not follow the bypass, could you please explain.

I could draw the layout but it has 4 loops, 1 serving 1 rad to kitchen, 2nd feeds 4 rads bedroom & bathroom, 3rd dining room & rear bedroom (2 doubles) this is the cold loop, 4th is on it's own a large double in sitting room.
Does this help I am not a heating engineer which is probably obvious...

 

[Gas]

Haven't got much to go on here, but you can sometimes force an airlock through by turning off the bypass (if you have one, next to the pump) turn off any HW demand + working rads and turn the pump to full whack, or, if any of the 2 rads have 1/2ince bleed valves, remove and stick a flex on and drain to outside

How many port valves have you got? did you clean the header out before draining, assuming you have a vented system, yes?

 

[tomma]

Are any of the rads drop fed ?

 

[Les1]

Haven't got much to go on here, but you can sometimes force an airlock through by turning off the bypass (if you have one, next to the pump) turn off any HW demand + working rads and turn the pump to full whack, or, if any of the 2 rads have 1/2ince bleed valves, remove and stick a flex on and drain to outside

How many port valves have you got? did you clean the header out before draining, assuming you have a vented system, yes?

Thanks again ,

I have one port valve if you mean the motorised valve which operates the system when programmer cut in. It is a vented system with drop feeds. All rads are drop fed. I have drains on all radiators would that help to try to release the air & drain from there?

 

[Les1]

Thanks for your reply.

This is a bungalow with ground floor water cylinder & header tanks in the roof. All runs are in the roof dropping to all radiators.

 

[tomma]

Try shutting the valves on each radiator put your hose on the drain off then open each valve in turn tll you get a good flow of water thru this normally gets rid of the air in the droppers.

 

[Gas]

and if you have not got drain offs on either rads, then disconnect one rad and stick a washing machine hose on the valve and drain in to a bucket

 

[Les1]

Thanks to you both, I thought yesterday that I had it cracked. Got both rads red hot. This morning they are barely warm but I will try the air purgers first but thanks for your help.

One more thing I turned the circulation pump up to 3. Should it stay at that or drop it down to 2 again if I manage to sort this.

Thanks again,