4 out of 7 rads cold

[DIYFAN]

Help please!

Just replaced 1 rad in hallway, when system turned back on 4 out of 7 rads are stone cold.

3 rads which work are first in the system, 2 upstairs and 1 downstairs.

I have tried:

1) bleeding all rads with pump off, fairly sure all air is out of rads.
2) checked pump when system turned on and can feel vibration, also there is a flow setting (1 to 3) and when adjusting the setting pump flow seems to adjust accordingly.
3) turned off 3 working rads left 4 fully open - with no joy.
4) have tried balancing hot rads, again no joy.

Feed pipes to cold rads are not even getting warm and all valves are manual adjust - boiler is Potterton and is not a combi boiler.

Running out of ideas any other suggestions?

 

[breezer]

you havent bled the pump, also try a search, some one asked a similar question yesterday

 

[DIYFAN]

Thanks for the advice, found the similar question and the suggestion was same as yours - bleed the pump. I tried this and there was no trapped air - clear'ish water came straight out.

Any other ideas?

Any/all help much appreciated.

 

[kevplumb]

whats the system

 

[DIYFAN]

I think its a gravity fed system (i.e. there is a tank in the loft) - is this enough info? (it's a Potterton 'profile' boiler)

It must be pretty obvious that central heating systems are not my strong point!

 

[kevplumb]

[/img]

have you one of these ?? tank in the loft dont really help

 

[DIYFAN]

No we don't have this pump - our pump (DAB) is an in line pump next to the boiler downstairs.

Does this help??

 

[kevplumb]

that was a three port valve

try the pump on full and when you take the bleed off can you see the shaft turning

 

[DIYFAN]

Took the bleed off and the shaft was turning.

 

[ollski]

bleed the pipework, there will be at least one vertical bit of pipe with a screw cap on the top somewhere to bleed it. If you have done that turn off all rads except one cold one, turn your pump up to 3 and force some circulation through.

 

[kevplumb]

look for one of

these

 

[DIYFAN]

Have hunted high and low for a bleed screw cap on a vertical bit of pipe with no success - any idea on where it might be located?

I have turned off all but one of the (cold) rads, the pump is on 3 and just switched the heating on.

 

[ollski]

Have hunted high and low for a bleed screw cap on a vertical bit of pipe with no success - any idea on where it might be located?

Airing cupboard or loft usually.

 

[DIYFAN]

I have checked the entire system (incl. loft and airing cupboard) and there is no bleed screw cap on a vertical bit of pipe.

All I have found is lots of draining points (i.e. above boiler, below pump next to a couple of rads and in the airing cupboard next to cylinder)

Should I drain and re-fill the system again - and see if that works?

Thanks for all your help.

 

[ChrisR]

It may well be that your hot water is heated by gravity circulation. If so there won't be a bleed point, the upper of the pipes from the boiler, which go into the side of the hw tank, will go on up to the loft.

You may have an air lock in your ch system. Try turning the working rads off at the valves, and the pump up to max. This should help to push the air into the rads so you can bleed it.