Vaillant VCW GB 242 EH Boiler - Is it Diverter Valve?

[trelo]

There is a small slot head screw going through the water section support plate, it pushes tight on the lip on just near where the pin comes out in the centre, it's a little difficult to describe! Back that screw out a few turns till it clears that lip and it should come off. Obviously un-do the pipes aswell. Watch you don't round that screw, sometimes they seize up

Thanks for that... I spotted that screw after my last post
The other concern is the new water valve has a missing feature. Please look at video clip of me attempting to look like i know what i'm doing
here is the clip:
[/url] http://www.screencast.com/users/And...em/media/fef9ec52-f570-43ec-bd10-e5478bd69365 [/url]

Please 'FULL SIZE' the video when you get there to get a better view...
and sorry its a bit slow...i'm a bit knackered

 

[Andygasman2010]

Don't worry, it doesn't have one anymore. You can throw away the expansion vessel.

 

[Agile]

The pin in the water section goes up inside a larger sleeve.

This sleeve has a screw and locking nut so that the "push" on the servo valve cam can be adjusted.

Its important that the moving surface on the sleeve is lubricated with silicone grease so that it moves freely and particularly returns after a DHW demand.

The spring on the cam has to be fitted correctly and is often in poor condition after many bodging attempts.

When the sleeve and its adjustment is inconveniently fitted behind the thin tubes you need your inspection mirror to see whats going on.

Tony

 

[trelo]

The pin in the water section goes up inside a larger sleeve.

This sleeve has a screw and locking nut so that the "push" on the servo valve cam can be adjusted.

Its important that the moving surface on the sleeve is lubricated with silicone grease so that it moves freely and particularly returns after a DHW demand.

The spring on the cam has to be fitted correctly and is often in poor condition after many bodging attempts.

When the sleeve and its adjustment is inconveniently fitted behind the thin tubes you need your inspection mirror to see whats going on.

Tony

Thanks for that...
funny you should say but i did order a new spring when i got the water valve... the old one looked worn

 

[Agile]

Its not really funny.

After you have been to a few of these you soon realise that after lubricating the sleeve it still needs the spring to be in the original shape otherwise it does not bring the cam fully back to its rest position.

Tony

 

[Andygasman2010]

This sleeve has a screw and locking nut so that the "push" on the servo valve cam can be adjusted.

Don't adjust this pin though. Adjusting this pin would just be masking some other reason why it's not pushing/returning propperly, best fix the route problem.

 

[trelo]

Ok Chaps.... The problem hasn't gone away! Its still not hot (DHW) I've changed all parts that could possibly be causing the DHW to be luke warm. Flow rate is fine (8 litres in 56 seconds) Gas rate seems ok (38 seconds for 1 revolution of test needle on gas meter) I still believe that the flow into the HEX just ain't right, its not hot enough although its only a weeks old? Could i have an excess of muck in the system and its just fouled up immediately?

 

[Andygasman2010]

I'm affraid one of your checks must be inaccurate. To keep the burner on maximum gas rate you could pull the wire off the NTC. This will make sure that the burner stays on full and is not modulating at any point, unfortunatly if i remember correctly, it's fitted behind the combustion case. it might be worth getting an RGI in now anyway, he'll be able to do this for you and also check the burner pressure at the same time.

A quick check you could do would be to monitor the green LED during hot water operation, if it was modulating it would be dim at low gas and bright at high gas. You could also just look at the burner.

Try and prove all these things 100% because we're running out of things now!

 

[Agile]

I agree that all those tests, if correct, would indicate correct operation AS FAR AS THEY GO !

To assertain the problem a thermal survey is needed and that would require a reasonably accurate CONTACT thermometer.

Tony

 

[Agile]

Don't adjust this pin though. Adjusting this pin would just be masking some other reason why it's not pushing/returning propperly, best fix the route problem.

Thats fine advice if the setting is the original.

Unfortunately the last one I went to had been worked on by British Gas who had replaced the servo valve. Changing that had not fixed the problem and they were going to return after a further few days to replace the diverter valve.

They had disturbed the setting adjustment and left the locking nut loose and the spring wrongly fitted.

Correcting the setting of the adjustment and correctly fitting the return spring sorted out the problem ( and saved BG a new diverter valve which would not have fixed it anyway ).

Tony

 

[Andygasman2010]

Don't adjust this pin though. Adjusting this pin would just be masking some other reason why it's not pushing/returning propperly, best fix the route problem.

Thats fine advice if the setting is the original.

Unfortunately the last one I went to had been worked on by British Gas who had replaced the servo valve. Changing that had not fixed the problem and they were going to return after a further few days to replace the diverter valve.

They had disturbed the setting adjustment and left the locking nut loose and the spring wrongly fitted.

Correcting the setting of the adjustment and correctly fitting the return spring sorted out the problem ( and saved BG a new diverter valve which would not have fixed it anyway ).

Tony

Diverters are changed far to readily on this boiler, i don't think i've seen a faulty one yet! They're usually changed due to an engineer not knowiing quite how this boiler works and so having a guess

I'd still recommend leaving that pin alone, especially when the symptom is luke warm water.

I think we've hit a brick wall with this fault though, looks like trelo needs to get an RGI in or just redo all the tests we've given him.

 

[Agile]

I agree that it should not be adjusted if it is already set correctly. That will depend on who last touched it !

If he could do a thermal survey then I can identify the fault(s).

Unfortunately he seems to think he can identify the faults himself whereas he would be better doing the tests we prescribe and just giving us the results.

I would love to not go to those people but because I am able to explain what the real situation is then I can enjoy making them feel a bit of a fool! More sensible people dont try to work out whats wrong and leave it to a professional.

Tony

 

[Andygasman2010]

By "thermal survey" do you just mean accurate flow/return temps, incoming mains and hot water temp? If so, i agree! Accuracy is the key.

Trelo, i'd like to get to the bottom of this, it'll bug me otherwise ha! Post back when you do, i'll be interested to know.

 

[trelo]

appreciate all the help guys.... I think i'm gona call vaillant in... from experience they naturally have been the only guys to fix problems first time.... i've had numerous people in before (non vaillant) and they just didn't have a clue.
I know this may sound stupid to you guys but because I've worked this boiler so many years I know from gut instinct something has gone a miss in the heat output department because I feel even the CH over time (last few years)has deteriorated. Not so bad that the rads don't get hot but because they take longer to get hot and they don't feel as hot as they used to a few years ago.
I've mentioned before on this post that i 'feel' the flame height is not rising as much as it used to (in DWH mode). The green light looks dim and it doesn't change between DHW and CH mode. In fact its doesnt change during both modes either.
From a lay persons view not much else can be wrong. Heat from flame heats the primary HEX which pump then circulates hot water to either secondary HEX or CH. If CH is reasonably ok but not DHW. This must surely mean that something is happening when in DHW mode. Simply that water is not getting heated enough from flame or there's a blockage in the HEX (or diverter not doing its job)or somewhere else in circuit in DHW mode.
Thanks again
Andy

 

[Andygasman2010]

I've mentioned before on this post that i 'feel' the flame height is not rising as much as it used to (in DWH mode). The green light looks dim and it doesn't change between DHW and CH mode. In fact its doesnt change during both modes either.

I didn't get this info, i'm sure i remember you saying all is well with the green light.... If the green light is dim that means the burner has modulated down. You said gas rate was ok and green light was bright. (the gas rate/burner pressure will be the same on DHW as for CH, although it will modulate more when on DHW)

To the left of the boiler there is a branch of pipework that goes to the main heat exchanger and i think the DHW heat ex, not sure, but there is a Y shapped section that can get blocked up. Strip that out and check it.