Vaillant Combi-Boiler stops heating - pressure lost needs top-up

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Vaillant Combi-Boiler stops heating - pressure lost needs top-up 10 December 2007, 12:58 PM

khizerharoon Joined 10 Dec 2007 1 posts

I have a 12 year old Vaillant Combi-Boiler serving 5 radiators in a 2 bed house, which was working alright until I decided yesterday to bleed the radiators a bit to let the air out. The top half of a few radiators was different in temperature than the lower half.

While doing that there was some leakage of water probably a few drops from each radiator. The heating continued to work on that day(yesterday), it was making funny noises, but today in the morning when the timer started but the water is not heating up at all either taps or radiator, although the boiler still seems to be trying to do something. So I have mucked something up.

The pressure gauage is below zero and considering I have bled the radiators I think i have cocked up the pressure balance in the heating system. The manual says that pressure gauage in white should be higher or at least equal to another moveable gauage in red. The manual says that if that happens the boiler needs a topup with water.

So what I have done now is moved the red gauge in line with the white one. I need general instructions on how should the top up be carried out.

Something I found online was :

" should b a filling loop somewhere between cold inlet and htg pipework. open valve or tap (different types can b fitted) and observe gauge "

Should the boiler & heating system be turned on while I do it. I can post a picture of the pipes below the boiler, maybe that can help in identifying which pipe it is.

Vaillant Combi-Boiler stops heating - pressure lost needs top-up 29 January 2008, 2:02 PM

Brian Timmins Joined 26 Jan 2008 8 posts

Anyway it "normally" looks like 2 x washing machine taps,either with or without turn off handles,sometimes a screw slot configuration,that turn through 90degrees from off to fully open so turn them slowly.

there is usually a chrome flexi (braided wire armoured) connecting the 2 ,when you find it open 1 slowly ( checking for leaks) then open the other ,you will normally hear the water surging through,keep it open until the white needle is = to the red needle or about 1.5 Bar then shut BOTH valves. The Flexi should be removed to comply with water regs but noone ever does.

The reason for pressure loss is that the air you bled from the rads was replaced with water therefore causing a reduction in pressure et tu a replenishment of water is required to restore the eqilibrium. Hope this helps Brian

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