Vaillant VCW Combi problem and free beer

26 Jun 2004
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United Kingdom
The ignition pressure is set at about 4.5 mbar, as per spec, and it jumps to about 6 mbar when the green LED comes on. But this is way short of the 23 mbar it should reach.

Thanks again,

Thats why its so important to check the inlet gas pressure first as obviously any restriction or low pressure would prevent the burner pressure going up to the correct value.

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Hello all,

Sorry I've dropped off the map for a couple of days - we've been insainly busy as the local competition has to close for a kitchen refurb :D

Well, I've sorted it out, thanks to everyone who helped.

The working inlet pressure was 40 mbar, so that wasn't the problem, but credit for Tony for suggesting this should be the first thing to measure, and could have explained everything.

The diaphragm pump output was only 1 mbar when measured, so I stripped it and found a build-up of rubber on the valve seats. A quick clean-up later, and I reinstalled and rechecked the pump pressure - got a damp leg when the manometer emptied itself over me :oops: Don't know what it runs at, but it's at least 40 mbar :LOL:
Burner pressures are now set as per the MIs for LPG (4.4mbar and 23mbar respectively).

So, first prize goes to Chris, who correctly identified the likely problem in post 2, and very graciously provided me with a pdf of the manual.

Having sorted this one out, on telling the staff this morning, the cleaners reported to me that the DHW has been running luke-warm for about a month :eek: so now I'll go and work on that side of things. Plenty of good threads to pick over on the forums here to work out what's going on I think (split DV diaphragm??)

My Corgi man is so impressed with the help you've all given me - he was sceptical you'd be able to do a long-distance diagnosis, that now it's working he's offered to do a full service for me for a couple of pints, so you guys have really saved me a bundle.

I'd like to say a big, big thanks to all for your help, I know you all have day jobs, and giving away your precious knowledge for free is something you really don't have to do.

Thanks again,

DIYnot Local

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