half full rads

Helpme · 11 Nov 2004

Help please!!

I have moved into a house recently with an oil fired boiler and rads. It is a gravity fed system. When the hot water was on, the upstairs radiators were hot. I fitted a non return valve after the boiler to fix the problem, and also fitted thermostatic radiator valves.

My problem now is that I can\\\'t get the upstairs radiators to fill up. They are all half full. I have turned rads off, rads on etc but when I try to bleed them, nothing happens. I have checked the header tank and it is operating OK. I can\\\'t get the system to fill up. Is this an air lock? If so, how do I get rid of it?

Grateful for any help.... :

kevplumb · 11 Nov 2004

take the nrv out

brumylad · 11 Nov 2004

is there a motorised valve (silver metal box with brass valve under it) in your primary (gravity) pipes between the boiler and the hot water cylinder ?

Your system might be a C-plan.

Plus is there a manual air vent in the highest primary pipe as it enters the cylinder. This might need bleeding.

kevplumb · 11 Nov 2004

the only way to stop the rads upstairs heating is ti do the job properly

Helpme · 11 Nov 2004

Thanks for your advice. I had a plumber around to service the boiler and he recommended to move from a gravity fed to pumped system, for 450 quid. When probed further, he said I would be better off getting a non return valve from screfix for 4 quid. Is the spring in the NRV cancelling out the pressure differential in the header tank?

He looked upstairs and couldn't find a motorised valve. There is only one thermostat in the house and this goes to the boiler, via the programmer, not to a motorised valve.

I did think of taking out the NRV because I now have thermostatic valves upstairs, but the plumber said if I don't fit a NRV it would send the problem with hot rads from the upstairs to downstairs.

How do I find and check the primary pipe.

Thanks again

kevplumb · 11 Nov 2004

Is the spring in the NRV cancelling out the pressure differential in the header tank?
eh ???

Helpme · 11 Nov 2004

probably talking out of my bum, but would the spring pressure cancel out 1M of static pressure from the header tank?

Anyway, I welcome your advice on what I could do. I could take out the NRV but I can't work out why this is stopping my rads from filling up? And I the NRV is an a very difficult place to get to.

Is it simply an air lock. If so should I stick a hosepipe onto one of the drain valves on the downstairs rads?

Cheers

croydoncorgi · 11 Nov 2004

With a valve preventing reverse flow, it's quite likely that there's an airlock stopping water flowing the opposite way to fill the rads.
You ARE trying to bleed the rads with both pump and boiler turned OFF?
Filling the system with a hose through the drain-off MIGHT work.

But why is the plumber who fitted the check valve not completing his work???

PEDANTICVINDICTIVEMAN · 11 Nov 2004

Without knowing how the system is piped difficult to say what the problem is, wondering why the nrv is difficult to get at to remove if you managed to retro fit it, need to make sure the cold feed isn't blocked for starters, I would probably try doing what you said and put a hosepipe onto the drain cock and backfill from the mains to see if this helps.

kevplumb · 11 Nov 2004

if the nrv is difficult to get to how did you manage to fit it ??

oilman · 12 Nov 2004

Bear in mind the system has probably worked fine at sometime, so adding gadgets is not dealing with the problem. Cold feed blockage is possible and a partial blockage elsewhere is another. If the cold feed is on the return of the DHW circuit, and the blockage is there, the return path could be via the radiators.

PEDANTICVINDICTIVEMAN · 12 Nov 2004

I'm sure I said this

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half full rads

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