Cold Rads

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Hi,

We have a gravity fed system, and last week we had a problem where the bleed valve near the boiler let all the water out of the system. We fixed the valve and then refilled the system from the feed tank.

Now all radiators are cold, the pump seems to be working - it is making a noise & vibrates, all of the radiators have water in them and no air.

Any ideas would be wonderful.


Thanks
 
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Sounds like an air lock in the primary circuit.

Is there a vent above the boiler? Or near the cylinder?

BTW, make you sure that you vent with the pump off.
 
i have followed the pipes out of the boiler ( the ones that go up ) and they are just pipes with no vents on them etc.

I don't need to do anything with that bleed valve that we fixed now the system is full do i ?


Thanks for your help.
 
Erm, what is this "bleed valve" exactly, and where is it, and what does it look like? :confused:
 
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I assume it is a bleed valve as it is under the floor boards to the side of the boiler, and the floor board above it says bleed valve under here ? but that could obviously be completely wrong as i have no idea who wrote that. The valve is like a big version of the bit you bleed on a radiator, you have to use a wrench to turn it as there is no handle it just a larger version of the bit you turn to bleed a radiator.

Thanks.
 
Hm. That sounds more like a lockshield gate valve. Or is it a drain off cock?

If it's lower than the boiler then it can't possibly release all trapped air from the heat exchanger.

Supposing for now that there is no blockage, it's possible that you have the kind of system that's just a bit hard to vent. When faced with these I sometimes fill the system from the bottom, if there's a suitable drain cock to get a hose on without leaking at a 'mains flow'.

Alternatively, shut all the rad valves, both ends, and manually open any motorised valve on the DHW circuit, disable the pump (electrically disconnect), and fire up the system on DHW only. Turn the boiler thermostat dial up to maximum (remembering where it was before you move it), and let it get stinking hot.

However, you MUST be sure that the boiler is not totally empty of water before doing this. It's unlikely, but please make sure.

The object of this is to use the increased pressure of fast-expanding air pockets to force water around the system. A kick-start, so to speak.
 

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