Vaillant VCW 242E Reluctant hot water

[Luke]

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

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

My questions are:

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

[geoff]

In message , Luke writes

Almost certainly the diverter valve and yes, probably the diaphragm

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

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

[Thomas Prufer]

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.

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]

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

If you must lubricate - silicone grease

[Luke]

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

[peter richards]

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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