Worcester Bosch 24CDi Boiler - Cold Water Flow Switch

Our CH boiler has stopped heating water for the household taps the CH is still working normally. The symptoms are as follows:-
1. Turned of the ch and turned on hot tap it did not switch inself on but initially got a small amount of hot water. Did it again and this time just cold but again it did not switch itself on.
2. Switched on ch and waited until boiler not running, turned on hot tap and it did fire up the light came on and I got a shot of hot water which then went cold?
3. A small amount of water is dripping from under the boiler.
A friend reckons we need to replace the cold water flow switch. What do you think?
Cheers,
Bren
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I think you should find out where your drip's coming from and find out if your cold water flow switch is working (I can't remember whether it just goes short circuit with flow or whether it gives out pulses
What is the diverter valve doing ?
--
geoff

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 25 Nov 2009 18:32:49 +0000, Bren wrote:

I think you need to replace your friend ;-)
IIRC the CDi has a plate heat exchanger and diverter valve: you should be able to see the pin of the diverter valve actuator moving out from the brass body of the valve towards a microswitch (partly shrouded in a plastic cover). It's probably not moving far enough to operate the switch and you need to replace the diverter valve - or, more easily & cheaply, its diaphragm (available from BES, besides others).
--
John Stumbles -- http://yaph.co.uk

Things don't like being anthropomorphised.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

and
you
There is no cold water flow switch as such on the 24cdi.
First place I would start would be the change over valve. Most likely to be damaged diaphragm.
If the diaphragm is damaged then the cold water demand will not allow the pin to activate the micro switch which switches on the burner.
It is not a simple diy job to fit a new diaphragm or change over valve. Would be better to get a boiler technician in to diagnose/sort the problem out if you or your friend are unsure.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Most likely a perished diaphragm in the diverter valve.
I documented my own such repair at http://www.newtonnet.co.uk/house/boiler / if you want an idea of what's involved. I receive several e-mails a week as a result of that page from people who have done the job themselves and so whilst it is not the easiest of jobs it does appear to be within the ability of many.
The drip however is something else - you need to find out where that's coming from.
Mathew
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Most likely a perished diaphragm in the diverter valve.
I documented my own such repair at http://www.newtonnet.co.uk/house/boiler / if you want an idea of what's involved. I receive several e-mails a week as a result of that page from people who have done the job themselves and so whilst it is not the easiest of jobs it does appear to be within the ability of many.
The drip however is something else - you need to find out where that's coming from.
Mathew
Thanks for the replies.
The consensus seems to be that the diverter valve is at fault or, more specifically, the diaphgram. In view of the potential problems and complexity of replacing the diaphgram would it not be easier and simpler to replace the whole valve? I am assuming that a replacement valve comes with a fitted diaphgram. I realise that it is more expensive than just replacing the diaphgram but I am not confident of my abilities to just replace the diaphgram.
Bren
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Contrary to what my site may say I would actually recommend replacing the whole diverter as it could save you another problem further down the line. It will indeed be easier and you will almost certainly be removing the diverter anyway (it is possible to replace the diaphragm in-situ but it takes the right tools and a certain amount of manual dexterity and having done both ways wouldn't recommend it.
I know my site disses the repair-by-replacement approach but when I wrote all that I had all the time in the world... Now that I have a few more responsibilities (and money) I am gradually changing my ways! I probably ought to update the text to something more balanced. Furthermore, new diverters often sell via eBay for <30 so the difference is hardly an issue anyway.
If you are going to give it a go make you sure go in armed with an o- ring and washer pack. Reusing the old ones really is a Bad Idea(TM) as it *will* leak. In fact, it may well leak with the new ones for a brief moment whilst everything settles in! (Silicone grease on the o- rings will help enormously to minimise/eliminate this).
Mathew
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Contrary to what my site may say I would actually recommend replacing the whole diverter as it could save you another problem further down the line. It will indeed be easier and you will almost certainly be removing the diverter anyway (it is possible to replace the diaphragm in-situ but it takes the right tools and a certain amount of manual dexterity and having done both ways wouldn't recommend it.
I know my site disses the repair-by-replacement approach but when I wrote all that I had all the time in the world... Now that I have a few more responsibilities (and money) I am gradually changing my ways! I probably ought to update the text to something more balanced. Furthermore, new diverters often sell via eBay for <30 so the difference is hardly an issue anyway.
If you are going to give it a go make you sure go in armed with an o- ring and washer pack. Reusing the old ones really is a Bad Idea(TM) as it *will* leak. In fact, it may well leak with the new ones for a brief moment whilst everything settles in! (Silicone grease on the o- rings will help enormously to minimise/eliminate this).
Mathew
Hi Mathew,
After my last post I had another look at the instructions on your website and it looks like I would have to dis-assemble half of the boiler to get at the valve in question - not to mention tackling the water leak. It seems from other posts that the water leak may be unconnected with the diaphgram problem. I was told that it was just a question of taking off the front panel of the boiler, disconnecting a valve - replacing it with another and Robert's your mother's brother!
It now seems to be a lot more complicated than that in view of the fact that I would have to remove a lot of bits before I could even get to the valve in question.
I have only basic plumbing and electric skills which I have picked up through life. I can solder joints and for e.g. plumb in a kitchen sink or install an electric shower. I have even rewired a couple of houses by reading the Readers' Digest DIY manual (this was in the 70's and 80's) but I have never worked with anything as complex as a boiler where gas, electronics and plumbing are involved.
So, I am fairly competent regarding DIY but am now wondering if I should even attempt this job. I was told that I did not have to worry about gas or electricity as they were not involved. All I had to do was unscrew a couple of nuts, replace the valve, and do them up again.
What do you think?
Bren
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Replacing a diaphragm is almost very easy
The almost bit is that one thing you didn't document
--
geoff

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.