hot water supply

[stephen22]

I would be grateful for some advice about my indirect CH/HW system in a 30y-old house.

About 15y ago I had a new boiler fitted, in a different place from the original, so the supply to the inner cylinder of the water tank goes up from the boiler, then has to diagonally cross the floor in the 1st floor bedroom to reach the airing cupboard. There is no HW pump.

Recently I had to drain the system because of a leak, and now although the radiators are working, no hot water is reaching the tank. The pipe up from the boiler is hot only in its lower half.

I bled the downstairs radiators first, and with very little difficulty. I have just noticed that the venting pipe had come adrift and the end was underwater in the expansion tank, which I suppose wouln't have helped the flow.

I'm getting old and can't remember for sure, but I think we had similar problems when I had some thermostatic valves fitted a few years ago. I guess there's a bubble in the pipe that crosses the bedroom floor. How can I persuade some hot water to go up my pipe?

Stephen

 

[chrishutt]

Yes, you seem to have an air lock in the primary gravity circulation pipes, probably where they run under the floor.

The best solution might be to convert the system to be fully pumped. This would require some pipework alterations near the boiler and cylinder, and the addition of a motorised valve and cylinder stat, but the advantages of bringing the hot water under proper control are substantial, not least that the pump will clear air locks.

In the meantime, you can only clear the air lock by introducing some force, like the pressure of pump or the mains, or by waiting for the air lock to be absorbed by the water (days, weeks?), or by opening the pipework where the high point is suspected to release the air. Have you got an immersion heater that you can use meanwhile?

 

[stephen22]

Thanks. Makes good sense. I do have an immersion heater.

Meanwhile, any wrinkles for intoducing a force to nudge the hotwater circuit?