VAILLANT DHW DOMESTIC HOT WATER NOT WORKING VCW GB 242 EH

[Whizzard17]

Hi. This is my first post!

I have the aforementioned boiler which has been working pretty well for the last 20 years. However, over a period of two days I lost the DHW.

Basically on the Saturday I found that I had to draw more hot water for the DHW to kick in and on the Sunday it stopped completely.

I had a quick look at some of the other post similar. I could see that the Diverter valve was not moving (to the right) to make the micro switches.

If I manually made the micro switch at the Servo Valve the heating kicked in (only did this momentarily to check).
Also noticed that when I checked operation of CH - which worked - the pressure went up from 1bar (normal) to almost 3bar.

Only way I knew to reduce this was through pressure relief vale, PRV.

Has someone out to take a look. Mentioned the pressure issue when CH was on and he opened up something to check for air and water came out. I didn't see this test point. He told me that the CH Expansion vessel was knackered and I'll need a new one - although he did say that wasn't anything to do with my DHW problem - which I had assumed anyway.

He turned on the hot tap in the kitchen to check and nothing came on.

Checked the Diverter valve and this didn't move. He manually pulled it out to the right to make the two micro switches but still nothing. He then called Vaillant tech support who informed him that if that didn't work then could be faulty Diverter and/or micro switches.He said that if when replacing these and it still didn't work could be circuit board (didn't say which one).

With that he quoted me Almost £600 to replace the expansion vessel (which would be fitted externally as per Vaillant Manual, also cheaper option as don't have to remove boiler and will fit under work top in kitchen cupboard), new Diverter valve and two new microswitches. Also quoted me to fit a new boiler around £2500.

He didn't look at servo valve or water section which I read should be an area to look at due to possibility of a split diaphragm.

Also I noticed that the DHW secondary heat exchanger (new type metal one Pt Number 065-034 fitted around 5-6 years ago) had a lot of scale built up around two of the sleeve nuts - looks like there is/was a small leak.

I have taken some photos of the heat exchanger and other parts. My tools are around my brothers at the moment but I want to check the water section as I this looks relatively simple from the manual and a diaphragm I can source for less than £5.

I work as an Automation engineer so I have reasonable technical ability but gas training is limited.

If anyone could suggest a logical testing method I would be extremely grateful i.e. like a flow diagram - does "a" work if "yes" then etc, if "no" then etc,etc.

Don't really have the funds at the moment to fork out so if I can get by until the winter that would be great as I won't be using the CH now its warming up.

I'm assuming I won't need to change the CH expansion vessel if I'm not using the CH? If accidentally turned on where should I release pressure as I'm sure through the PRV is not the best way.

Thanks.

View media item 44344 View media item 44343
View media item 44341 View media item 44342
View media item 44340 View media item 44346
View media item 44345

 

[Agile]

If you were in my local area then I would fit a new boiler for you for closer to £1600.

It sounds as if you did not pay him for his visit so he has to then over charge for subsequent work.

Tony

 

[GuessMan]

IF I where to undertake this repair, you would be quoted for:

New diverter valve (possible)
New water section support (possible)
New weep tubes X4 (possible)
New water section
New servo valve
New plate heat exchanger kit
Expansion vessel
Pipe & fittings for above
Chemicals
& one day labour.

That would be roughly £1100!

Time for a new boiler as I couldn't sleep charging that much for a repair on a boiler, that is about to be dropped by it's manufacturer. A boiler is never a choice purchase, this workhorse has given you 20 years, put it out to grass or face ever increasing vet bills, keeping it limping along.

 

[namsag]

No hot water first thing to check is that the actual water section is working on turning tap on the pin in it should rise and move the cam behind the servo valve to hit the micro switch.
If it doesnt then its needs a new diaphragm .
Divertors on these are usually miss diagnosed and it is usually the srvo valve at fault

600 quid for an external expansion vessel well they cost 30 quid i cant see it being that awkward to fit so getting ripped of big style.

These are not complicated boilers but seperate water section and divertor seems to confuse many

 

[Whizzard17]

First of all massive thanks for the rapid response.

Agile (Tony) - unfortunately I did pay a call out fee just over £60 but he did say they'll knock it off if I install the boiler with them!

Guessman - Yeah sounds daunting whe put like that. Might just have to bite the bullet. Was hoping to make it through to Winter though!

Namsag - Yeah I thought the quote was a bit high! I will check the water section and the associated diaphragm. Will I be right in assuming that I can leave the expansion vessel as I'm not using the CH? Might be time to change the heat exchanger though. Worried that there is a build up of scale on the inside. I've changed it before and it was awkward due to the proximity of the boiler to my kitchen wall but shouldn't be a problem.

Thanks again

 

[namsag]

If you wanted to make a makeshift expansion in the mean time half empty a rad that will give a bit of room for expansion

 

[Whizzard17]

Hi. I've tried to remove the water section as per the instructions but it won't budge. Am I supposed to remove the servo valve at all? It doesn't say so.Thought it was as simple as loosening off the 5 nuts? HELP!
View media item 44403 View media item 44404 View media item 44405

 

[Whizzard17]

My bad!! Realised the drawing showed a cut-out section. Found the screw and have dropped out section. Unfortunately most of the screws are seized up so will have to let the WD work its magic first. Will let you know how I get on tomorrow I reckon.

 

[petit_pablo]

The majority of RGIs dont understand how these boilers work, unfortunately the guy you had out sounds like he is one of the majority.

Did you check the servo valve to see if was moving and whether the cam was hiting the microswitch?

Good luck if your already diving in!

 

[mickyg]

if you can replace the diaphragm yourself for a fiver you may aswell, as its most likely fault. Will be that, the servo or blocked tubes. The DVs very rarely fail, especially not like that.
Lucky you didnt call out Guessman, by name, and by nature !
Fit an external vessel, should cost about £100 all in to have done.

 

[Agile]

Its easy enough to add an EXV yourself.

If you really intend to change the boiler this year then just let some water out of one rad to create an expansion area.

You may well have a problem getting those screws out. Boiling in a pan of water might make it easier but you do need a screwdriver with an exact fit.

The leaks on the plate are historic and not worth bothering about this year.

Tony

 

[Whizzard17]

Thanks for all the help guys. Removed the Water Section and the diaphragm was in poor condition.
Had slight build up of scale around the pin although this was moving freely enough.
Removed most of the scale and replaced the diaphragm. De-isolated water supplies, etc and turned on hot tap...HEY PRESTO!! HOT WATER!! Saw the servo valve moving sweetly!!
Bit annoyed that the Service Engineer didn't spot that or even look at that and even more annoyed that Vaillant's tech Support didn't either!!
From initially looking at replacing the Diverter, Micro switches andthen PCB to spending just over £5 myself -RESULT!!
Question remains, do I notify the enigineer that I've fixed it? This guy and the company he works for have serviced my boiler last 3 years and I haven't had any issues. Don't think he'd try and bullsh*t me as he knows what I do for a job and that I have fixed a few issues with this boiler previous myself.
Will leave the CH Expansion vessel for now as won't be using the CH for a few months now. £100 to fit seems reasonable.
Thanks again guys.