Radiator problem

[Timothy Murphy]

One radiator on the top floor of my house remained cold when I turned on the heating today. I bled it, and a large amount of air came out. The radiator became hot, and I thought the problem was solved. But when I went up an hour later the radiator was cold once more. I tried bleeding it again but it started squirting water at once. I even let about 1 pint of water run from the bleed valve into a container. But the radiator remained cold. All the other radiators appear to be working.

Any advice or suggestions gratefully received.

[F]

An airlock in the pipe before or after it? I've sorted this in the past by turning off all of the other radiators and letting the pump push the air through.

[Tim+]

Does it have a TRV fitted? I presume you checked that it was fully opened?

Also, is yours an open vented or a pressurised system? If your boiler has a pressure gauge (or if there is a pressure vessel and gauge elsewhere in the system) you'll almost certainly have to re-pressurise your system to 1-1.5 bar.

Tim

[Timothy Murphy]

Thanks, I'll try that.

[The Natural Philosopher]

If it did get hot, its probably not an airlock in the pipe. but simply more gas in the whole system, that collects in that particular radiator

Keep bleeding it, and re pressurize the boiler if needed.

Also check pressures hot-to-cold in case the expansion vessel needs re pressurizing.

[Roger Mills]

You need an air-free water path to *both* sides of the radiator for circulation to occur. You only need a water path to one side to bleed it! If there's an air lock in one of the pipes, or if one of the valves is stuck shut, you'll still be able to bleed it - but there will be no circulation.

So, close one valve and bleed it with just the other valve open. Then close that valve and open the other one, and repeat. Once you have water flowing from both sides, open both valves and the heating should then work.

[In case the system has been balanced, count the number of turns required to close the lockshield valve so that you can return it to the same position].

[F]

He bled it again and immediately got water...

[Roger Mills]

Indeed.

Chances are there is an airlock or blockage in the other leg - which wouldn't stop it bleeding but would stop water circulating. See my earlier post about bleeding each leg separately.

[alan_m]

+1 My parents CH used to have this problem and forcing all the flow through the one radiator used to clear the airlock in one of the pipes.

If you have a pump with multiple speeds you may stand a chance of forcing out the airlock by increasing the pump speed temporarily. Put it back to the original speed setting afterwards.