Hi,
My friend's Vaillant VCW 242E has been getting more and more reluctant
to produce hot water in the last few months. By "reluctant" I mean
that the hot tap has to be opened wider and wider before the burner
fires and hot water issues forth. This has got so bad lately that it
is impossible to use the shower unless the boiler is first given a
prod by opening the hot water tap in the kitchen full blast.

We have taken the front off the boiler and observed that the command
to fire the burner is controlled by firstly a microswitch and then a
gas valve(?), both of which are operated by a pushrod which is
connected to the incoming cold water supply. It seems that whatever
controls the pushrod is no longer giving it the required "ooomph" at
low to medium flow rates.

We have hypothersised it is the diaphragm at fault here - would we be
correct? Looking at the availability of spare parts, I have found

http://www.uk-plumbing.com/vaillant-..._852_1244.html

Which seems to list a number of different diaphragm options for this
boiler.

My questions a

1. Are we right in suspecting the diaphragm is at fault here?
2. If so, which of the options on the page referenced above should we
choose?
3. Will we need the service manual in order to fix the problem or
should it be pretty obvious disassembly-wise to remove and replace?

Thanks in advance

Luke

In message
,
Luke writes
Hi,
My friend's Vaillant VCW 242E has been getting more and more reluctant
to produce hot water in the last few months. By "reluctant" I mean
that the hot tap has to be opened wider and wider before the burner
fires and hot water issues forth. This has got so bad lately that it
is impossible to use the shower unless the boiler is first given a
prod by opening the hot water tap in the kitchen full blast.

We have taken the front off the boiler and observed that the command
to fire the burner is controlled by firstly a microswitch and then a
gas valve(?), both of which are operated by a pushrod which is
connected to the incoming cold water supply. It seems that whatever
controls the pushrod is no longer giving it the required "ooomph" at
low to medium flow rates.

We have hypothersised it is the diaphragm at fault here - would we be
correct? Looking at the availability of spare parts, I have found

http://www.uk-plumbing.com/vaillant-...agms-c-938_852
_1244.html

Which seems to list a number of different diaphragm options for this
boiler.

My questions a

1. Are we right in suspecting the diaphragm is at fault here?

Almost certainly the diverter valve and yes, probably the diaphragm

2. If so, which of the options on the page referenced above should we
choose?

You'll see that some of them are kits and some of them diaphragms - a
complete mess like most 242 parts

Personally, armed with the exact model and serial number (e.g. is it a
242E or 242EH?) I would email them and ask them which one (I would buy
the diaphragm kit as should include the seals etc. It's not something
you want to repeat next year because a seal has gone or something), then
the responsibility lies with them to get it right


3. Will we need the service manual in order to fix the problem or
should it be pretty obvious disassembly-wise to remove and replace?


No - the manual only goes as far as replacement of the diverter valve
IIRC

SO ...

You want to repair your diverter valve

Make drawings and photos at every stage. I can't emphasise how important
this is - there are so many things that could go one way or an other

Do it in one sitting then you have less time to forget

its much easier once you've done a few

Other than that, it's straightforward

Isolate the boiler, drain down, remove the diverter valve, mend and
replace



--
geoff

On Wed, 2 Dec 2009 21:23:51 +0000, geoff wrote:


My questions a

1. Are we right in suspecting the diaphragm is at fault here?

Almost certainly the diverter valve and yes, probably the diaphragm

Is there a small chance that lubricating it would help?

I have a 240, and the diverter valve pin that actuates the microswitch started
to stick. A drop of light lubricant (no, not WD-40!) sorted it, now going on for
a few years.


Personally, armed with the exact model and serial number (e.g. is it a
242E or 242EH?) I would email them and ask them which one (I would buy
the diaphragm kit as should include the seals etc. It's not something
you want to repeat next year because a seal has gone or something), then
the responsibility lies with them to get it right


3. Will we need the service manual in order to fix the problem or
should it be pretty obvious disassembly-wise to remove and replace?


No - the manual only goes as far as replacement of the diverter valve
IIRC

SO ...

You want to repair your diverter valve

Make drawings and photos at every stage. I can't emphasise how important
this is - there are so many things that could go one way or an other

Do it in one sitting then you have less time to forget

its much easier once you've done a few

Other than that, it's straightforward

Isolate the boiler, drain down, remove the diverter valve, mend and
replace

And you may need some stuff to descale the innards, depending on your water. And
gaskets for the stuff nearby. They will start to leak if disturbed when the
shops are closed...

In message , Thomas Prufer
writes
On Wed, 2 Dec 2009 21:23:51 +0000, geoff wrote:


My questions a

1. Are we right in suspecting the diaphragm is at fault here?

Almost certainly the diverter valve and yes, probably the diaphragm

Is there a small chance that lubricating it would help?

I have a 240, and the diverter valve pin that actuates the microswitch started
to stick. A drop of light lubricant (no, not WD-40!) sorted it, now
going on for
a few years.

Usually, the diaphragm kit includes the pin, which does wear with use

If you must lubricate - silicone grease



Personally, armed with the exact model and serial number (e.g. is it a
242E or 242EH?) I would email them and ask them which one (I would buy
the diaphragm kit as should include the seals etc. It's not something
you want to repeat next year because a seal has gone or something), then
the responsibility lies with them to get it right


3. Will we need the service manual in order to fix the problem or
should it be pretty obvious disassembly-wise to remove and replace?


No - the manual only goes as far as replacement of the diverter valve
IIRC

SO ...

You want to repair your diverter valve

Make drawings and photos at every stage. I can't emphasise how important
this is - there are so many things that could go one way or an other

Do it in one sitting then you have less time to forget

its much easier once you've done a few

Other than that, it's straightforward

Isolate the boiler, drain down, remove the diverter valve, mend and
replace

And you may need some stuff to descale the innards, depending on your
water. And
gaskets for the stuff nearby. They will start to leak if disturbed when the
shops are closed...

--
geoff

On 3 Dec, 20:12, geoff wrote:

On Wed, 2 Dec 2009 21:23:51 +0000, geoff wrote:

My questions a
SNIP QUESTIONS ABOUT DIAPHRAGM REPLACEMENT

SNIP USEFUL ADVICE FROM GEOFF & THOMAS


- Show quoted text -

Thank you both for your replies. We had already lubricated the
diverter valve pin a month or so ago, admittedly not with silicon
grease but with 3-in-1. It seemed to have a temporary effect but the
problem remains.

We are going to buy the diaphragm kit as recommended by Geoff and
replace it. As suggested we will take photos and make copious notes
etc and should hopefully be okay. Will report back afterwards.

Thanks again

Luke

Hi, The problem could be two fold, yes the diaphram needs to be replaced if
over 5 years old and its easey [keep away from the gas side] also look at
the radiator again a simple job of replacement it could be fured up with
scale and you can get the part from the manafacturer also are you in a hard
water area ? That could be a furing up of the pipes, fit a cheap scale
inhibitor
Best wishes for hot water

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