Vaillant VCW GB 240 H - CH fine but no DHW

[dejavous]

Hello there,

I've just moved into a 'new' house that has a Vaillant VCW GB 240 H combi boiler. The boiler works fine for heating but hot water in the taps is not working properly.

If the heating is off and I turn on a hot tap, the boiler kicks in and the water warms up just a little but doesn't improve beyond lukewarm. The shower is very cold and barely heats up at all. I've been doing some searching online and some comments here suggested that the diverter valve may be responsible? I asked my other half to leave the shower running, the boiler stays on, the water from the shower stays barely tepid and she reports that the radiators don't heat up any.

When the heating is on and the radiators are hot, when I turn on the tap in a sink the water comes out quite warm. The shower starts off hot and then cools to a luke warm temp. If I turn it off for a minute and then restart it, the shower is warm again before cooling down.

Using my highly scientific jug and basin I get about 10l/m flow rate if that information is any use.


Any ideas on what I can do to repair this or if is even possible to repair? It's really old and information about it has been scarce. I've been quoted anywhere from £120 to £280 for an engineer to come and take a look at it which I'm loathe to spend unless there is some hope of repair. Does anyone have any recommendations for an engineer that is familiar with these boilers that might have more success than someone who has never seen one? I'm based Swindon.

Also are there any suggestions for how I could diagnose what the problem is. If I could identify the source of the problem there is a chance that I could find the part and get an engineer to replace. Any tips or information gratefully received.

 

[Bunnyman]

I think you may hav researched the wrong model, the vcw range was deemed obsolete in march 2012, however many independents mend these but Vaillant themselves won't.the divertors rarely fail on these, 8litres a min is the max flow you are looking for. If ou truly hav 10l/m then maybe the water valve reg is bust or the shower is passing? Only the engineer on site will know. If the flow rate is ok it maybe a gas pressure fault ( common on this model) which we can't help with here I'm afraid

 

[dejavous]

I think you may hav researched the wrong model, the vcw range was deemed obsolete in march 2012, however many independents mend these but Vaillant themselves won't.the divertors rarely fail on these, 8litres a min is the max flow you are looking for. If ou truly hav 10l/m then maybe the water valve reg is bust or the shower is passing? Only the engineer on site will know. If the flow rate is ok it maybe a gas pressure fault ( common on this model) which we can't help with here I'm afraid

Thanks for the reply. The model is definitely the VCW GB 240 H, it's a very old boiler. When I said 'new' house, I meant new as in we recently purchased, it's Victorian. Sorry for the confusion.

Checked the flow rate again and something is not right, tried again at the kitchen sink with some proper measuring implements this evening and it was actually just about 13l/min which from what you tell me is way too high and probably why the water isn't heating properly. With the tap at a rate of about 8l/m the water gets warm but not hot, reduced to 6l/m it's much better.

So that would suggest that the water valve regulator is the issue? Is that a significant job to fix or replace? Thanks.

 

[bell824]

i would suggest that the biggest issue you have is the flow rate/temperature rise!

with combi boiler's the faster the water runs then the less it heats and as bunny says this boiler is designed to run at 8lpm with a 42 degree rise, so at 8lpm then your (very cold about 5 degrees at the moment) would only reach a maximum 47 degrees for a new boiler, so your faster running water reduces that efficiency,

try turning your sink tap down and see if it gets hotter, as for the shower it may be worth getting the cartridge checked out it may be scaled and allowing to much cold water through!

 

[dejavous]

Yes indeed, when the tap is turned down the water does indeed get hotter.

There is another issue which may or may not be related to the excessive flow rate issue, the boiler doesn't kick in until the flow rate is about 7l/m and cuts out when it gets to about 3.5-4l/m.

I don't have a service manual yet, Vaillant are sending me on a copy. Any tips on what do I need to do to get this sorted? Is it something that I can adjust myself or a plumber/gas engineer can service or will it need parts replacing? Thanks.

 

[bell824]

This is a delicate unit that not a lot gas engineers can understand so I would not recommend an attempt at DIY . My advise would be get an engineer experienced in this unit out.

 

[dejavous]

This is a delicate unit that not a lot gas engineers can understand so I would not recommend an attempt at DIY . My advise would be get an engineer experienced in this unit out.

Fair enough. Do you or anyone know of an engineer in the Swindon area that would be familiar with the boiler or where I can find one? Thanks.

 

[Bunnyman]

How far from Bristol?

 

[dejavous]

How far from Bristol?

I'm in the centre of Swindon, so 40miles or about 45min depending on where in Bristol.

 

[Bunnyman]

send me ur email i giv u number of ex vaillant oxford