What is pumping over?

[ajsdoc]

I have an ideal Mexico boiler with gravity hot water and pumped central heating. Recently had TRVs fitted, system drained and refilled with inhibitor by a plumber.

Was in loft at the time the heating came on and a small amount of water came out of the vent pipe ver the small feed and expansion tank in the loft. Only a small spurt which stopped immediately. Have been experimenting and this only happens on switching the heating on, it does not continue.

Is this "pumping over" or is this normal. I've read pumping over is less than ideal, but I'm not sure if his refers to the continuous outflow of water from the vent pipe or the situation I describe.

I've read can be linked to pump speed, this is on 3 - should I turn it down, do nothing or call a plumber, could it possibly be linked to the recent TRVs I had fitted ( I imagine I Previously had a fully open system, now some radiators closed down to TRVs)?

Advice appreciated.

 

[45yearsagasman]

Pumping over is more likely in a fully pumped system when due to blockages or wrongly configured pipework causes water to be constantly pumped up the open vent pipe into the expansion tank. Your symptoms would give no cause for concern as it only happens momentarily when the pump starts.
You could try shutting the newly fitted valves and see whats happening in the loft, and if there is no flow from the vent then there should be no concern.
Did you have TRV,s fitted to ALL rads?

 

[ajsdoc]

Thank you. No, one radiator left free of TRV in the hall (where thermostat is) I'll experiment with turning all TRVs off, thank you.

 

[ChrisR]

Make sure all your rads are free of air, it can behave like spring and cause what you have.

 

[ajsdoc]

Interesting. I have had to bleed the radiators a couple of times since the TRVS were fitted a couple of weeks ago (plumber mentioned this may be necessary and should be expected.). It always seems to settle in one radiator in the bedroom ( which I find unusal as a towel rail in the ensuite is higher but doesn't seem to need bleeding!)

 

[robin7]

You could always try turning the pump speed down to 2

 

[ChrisR]

Air coming out of the water is like the bubbles in a pan. They come out in the boiler and settle in the first radiator, not the highest. Can be surprising which one that is. It can also take a surprisingly long time to get it all out.

Also check carefully round the new valves for any sign of a leak - they can take air IN and not let water out. Maybe check they're tight.

 

[ianmcd]

Also make sure that your system is switched off when bleeding, dont bleed it with the pump running