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Topic Title: central heating fault
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Created On: 10 April 2013 09:54 PM
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 10 April 2013 09:54 PM
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SKElectrical

Posts: 910
Joined: 01 February 2009

Hi
Conventional boiler & separate cylinder
2 x 2 port zone valves
Stat works
Programmer works
HW fires up the boiler
but boiler won't fire up when CH is demanded.
When CH is turned on (and the HW is already turned on) then the rads get hot.

I reckon I know what the fault is but would appreciate your diagnosis.
 10 April 2013 09:58 PM
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DOUGIE1000

Posts: 4168
Joined: 13 August 2005

You checked motorized valve micro switch?

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Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!
 10 April 2013 09:58 PM
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slittle

Posts: 3523
Joined: 22 November 2007

I'd be looking at the CH valve, assuming it's wired normally my money would be on the microswitch in the valve motor.

Change the valve head ?

Stu
 10 April 2013 10:02 PM
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SKElectrical

Posts: 910
Joined: 01 February 2009

Originally posted by: DOUGIE1000

You checked motorized valve micro switch?


My thoughts too.

Thanks lads
 10 April 2013 10:21 PM
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peteTLM

Posts: 3169
Joined: 31 March 2005

the output from the valve is the orange wire, which has to go live to fire the boiler. Put it into a strip con by itself and see if it goes on.
This is the output from the microswitch as everyone else has suggested.

-------------------------
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Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 10 April 2013 10:31 PM
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dickllewellyn

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Depending on the valve head, you can sometimes take the cover off and get access to the micro switch to switch it manually. Sometimes the valve works, and the switch works, but the little rubber balls inside the vave body can deform so it doesn't quite go right over, or bits of grit can get caught and cause the same issue.

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Richard (Dick)

"Insert words of wisdom and/or witty pun here"
 10 April 2013 10:37 PM
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daveparry1

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Probably the synchron motor failure, very common fault,

Dave.
 10 April 2013 11:32 PM
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Martynduerden

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Possibly a swollen ball, if the valve opens but does not activate the microswitch it's one of three things

Swollen ball
Dodgy micro switch
Missing power to micro switch (from wherever)

The power could be linked from the motor live so if the motor operates the last is unlikely, especially as there are two valves!

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Martyn.

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www.electrical contractors uk.com
 11 April 2013 05:14 PM
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SKElectrical

Posts: 910
Joined: 01 February 2009

Well I was wrong. Having ruled out y plan (3 port valve), I had assumed 2 x 2 port zone valves.
Anyway, there were no valves at all. The HW is gravity fed, from the back boiler to the cylinder, and the central heating is just a pump controlled by the room stat.
Pump had failed.
Old, & Odd.
 11 April 2013 05:35 PM
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daveparry1

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Nothing odd about it SK, it was a very common way of doing it in the 60's and 70's, plenty still running that way,

Dave.
 11 April 2013 05:41 PM
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SKElectrical

Posts: 910
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Originally posted by: daveparry1

Nothing odd about it
.


You need to turn on HW to fire up and CH to run pump. It's fairly odd these days! !
 11 April 2013 05:48 PM
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AJJewsbury

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You need to turn on HW to fire up and CH to run pump.

Standard 'gravity primary' - most programmers used to have an optional mechanical link between the switches so that you couldn't select CH without HW.
- Andy.
 11 April 2013 05:55 PM
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daveparry1

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Thanks Andy, saved me the bother of explaining it! Funny how some people these days consider things that were once very common and standard methods strange just because they haven't met them before,

Dave.
 11 April 2013 06:36 PM
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Grumpy

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Ooh steady Dave, that reply has just the vaguest whiff of smugness and we wouldn't want that on this site would we? Isn't everything strange if you haven't met it before?
 11 April 2013 06:49 PM
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daveparry1

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Yes I agree Grumpy, my apologies to you SK,

Dave.
 11 April 2013 06:51 PM
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Grumpy

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Good man! Now I feel empowered to ask a string of gormless questions that I've been saving up!
 11 April 2013 09:42 PM
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AJJewsbury

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vaguest whiff of smugness

I'm not sure if that's better or not than the feeling I had of just being old (again) being able to remember such things first hand. My excuse is that I started taking things apart to see how they worked at a very early age, and I'm sticking to it!
- Andy.
 11 April 2013 09:53 PM
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daveparry1

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Sounds like you started the same way as I did Andy! I suppose it's because we didn't have all the toys and gadjets that kids have now, eg Playstations, computers phones etc,etc? (I think we must be from a similar era)

Dave.
 11 April 2013 10:19 PM
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AJJewsbury

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(I think we must be from a similar era)

It sounds like it! for me it was an era of make-do-and-mend, and when it can't be mended - given to Andy to take apart! I still remember vividly getting into awful trouble after being given an old clothes iron, taking it apart outside and finding it full of hundreds of sheets of mica, which then promptly blew around the garden and lodged in every tree and bush in the neighbourhood. I must confess I did have a computer though - it came as a kit of components and empty circuit board and I had to spend 2 solid days soldering it all together!

- Andy.
 11 April 2013 10:26 PM
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daveparry1

Posts: 6227
Joined: 04 July 2007

With me it was old radio's and tv sets, then went on to repairing them for friends and neighbours etc. from the age of about 13!
IET » Wiring and the regulations » central heating fault

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