Hi, I have a combicompact VCW GB 242 EH and the old girls got issues...The radiator temperature is fantastic but the hot water isn't. It started several months ago with the hot water getting less hot. After a while we were having to reduce flow at the taps ( flow rate is perfect ) to get the temp to increase - this worked for a while. Now we have to reduce the flow so much that the boiler shuts off or it will work for 10 mins then shut off. Sometimes the taps do still get really hot for the first minute then go stone cold. My wife is bored of fiddling with taps and cold showers! My plumber said that the expansion vessel loses pressure but he just wants to sell me a new boiler! Could this be the problem or does it have other faults? I've got attached to the old girl over the years, she's had pumps, flue motors and regular love and affection and i can't help feeling she can be saved again. Any ideas will be greatly appreciated. Thanks for reading...
vaillant boiler hot water problem
- Thread starter paul2728
- Start date
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Does this happen on all hot water taps or just bath mixer taps, if just on bath mixer taps then sespect taps before boiler?
The expantion vessal is only to do with heating not hot water! sound like the diverter valve or hw microswitch!
The expantion vessal is only to do with heating not hot water! sound like the diverter valve or hw microswitch!
My plumber is a git! It happens worst on shower mixer but also bath mixer and normal taps so i think it is boiler. I've got the heating on now and if i turn tap on slow it is really hot - does this mean that diverter is ok? When i go higher flow temp decreases. Is the diverter the valve with the temp adjust dial on it? Thanks for your help.
Two things I'd look at: -
Blocked plate 2 plate heat exchanger; or do you still have the black plastic tank on the left? If so definitely needs changing.
Failed diapragm air pump or gas valve not giving correct gas burner pressures.
1st isn't cheap, 2nd is a job for a RGI who knows these boilers.
Blocked plate 2 plate heat exchanger; or do you still have the black plastic tank on the left? If so definitely needs changing.
Failed diapragm air pump or gas valve not giving correct gas burner pressures.
1st isn't cheap, 2nd is a job for a RGI who knows these boilers.
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Heat exchanger is the newer type and if i grab the outlet from it with taps on it can get really hot. Also flow is fine so should this unit be ok? I don't understand how sometimes it can be really hot for ages but then it can be ok for a minute then goes cold. Or it can run a whole bath with reduced flow at a reasonable temp. With the shower we always turn it on max flow, count to ten then reduce flow for a reasonable temp shower. Sometimes this is fine for a long shower. Other times it won't heat up for half a dozen tries or it'll be ok ut only for 5 mins. I'm really anal about the time we leave it and the flow rate but the result is different everyday! When the heating is on you get instant hot from shower for 5 seconds then cold. Does this mean diverter is diverting but then something shuts burner off?Help!!!!!!
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You have a faulty servo control valve and probably is is just a matter of renewing the rubber diaphram. If you open the lower door you will see half of a white dial with red pointers on it, at the bottom centre of the control box, this is attached to the servo valve. Your installation manual will confirm this. I would advise you to get some one with knowledge of these boilers to repair it, as they are built like tanks and, without leaks, they will outlast many of the boilers now on the market.
spraggo
I've been doing a bit more diagnosis and it was looking like the valve you mentioned. I was reading about how flow rate will affect heat so checked mine - 20 litres in 60 seconds. I reduced this to 14 litres but this meant that the plunger on top of that valve was not acting on the hw microswitch. A quick adjust on the plunger rod has meant that the microswitch is actuated at 3/4 of the max new flow rate and shuts off at about 1/4 flow. Does this sound about right? It's cured it for now. Max flow gives comfortable temp and if i reduce it gets really hot. Anew valve and a gas safe fitter will follow shortly but i'm happy for now. Thanks for your help you've saved me a fortune!
Wonderful long hot shower this morning.... But the heating didn't cut in! Pump runs but burner didn't fire. Have I reduced the water pressure coming in too much or over adjusted diverted valve? Any ideas guys? Thanks
You have probably displaced the return spring on the lever cam when you adjusted the pin, as previously stated, renew the diaphram and re-adjust.
spraggo
Spring Is there ( fiddly to fit) and I'm awaiting part and plumber. In the mean time I'll re- adjust- it it because it cant pull down to the required level? Thanks for your help, it's -2 outside so I'm not popular with wife- guess she could go have a hot shower!
It's not the servo! This model will only heat 7.6 l/m if u have 20 u either have a passing shower valve or the flow reg has gone in the water valve changing diaphragm won't help, change the valve 011299 leave divertor alone these can't cause this fault an put servo back as it was
Ur confusing the bloke spraggo water section is what he wants an what ur talking about 011299 the servo is is black plastic valve above 012646 nothing to do with that mate 
Thanks guys, I re- adjusted last night. Heating fine and shower better but not brilliant. I'll order the other valve but at least it's ok for now. I am confused but I am learning! Thanks again I'll keep you posted.
F
F
OK, to save any further confusion. The part that the white dial is attached to is known as the water section, Part No 011299, which obviously contains the, rubber diaphram which needs to be renewed.
The cam with the spring and micro switch etc is known as the servo valve,
Part No 012646, which needs to be adjusted so that the push rod on the water valve has a 5 -7mm gap between it and the cam on the servo valve when the hot water taps are turned off.
spraggo
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