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kdflan · Joined: 11 Apr 2008 Posts: 12 Location: birmingham england

hi guys am new to this forum and have a query about hot water problem
boiler is a worcester bosch 240 rsf boiler of a friend. had a problem couple of months ago where ther was no pilot ignition and found problem was a faulty fan . replaced this and has been fine for a while now, but last few days she has said that the water was running luke warm and only working when ch was on . she has now told me there is no hot water at all
and having loked on here was lead to believe is might be aproblem with the divertor valve or expansion tank but cannot find the message posted when looking again. could anyone run me through a fault find so i can rule out the most likely culprit thanks Shocked

thescruff · Moderator Joined: 03 May 2003 Posts: 4418 Location: Bath

I don't know much about these boilers but I would suspect the HX is scaled up.

One of our guys will post later.

AlanE · Posted: Sat Apr 12, 2008 12:19 pm Post subject:

Heat exchanger or diverter valve.

kdflan · Joined: 11 Apr 2008 Posts: 12 Location: birmingham england

if it is the heat exchanger how do i descale it and is it a major job
ps i am a bit rusty on pc,s so will try to make sure my next question is in the right forum place and not personal . thanks

kdflan · Joined: 11 Apr 2008 Posts: 12 Location: birmingham england

and also i presume its the water to water exchanger and not the gas to water exchanger?

thescruff · Moderator Joined: 03 May 2003 Posts: 4418 Location: Bath

AlanE · Posted: Sat Apr 12, 2008 8:46 pm Post subject:

Replacement heat exchanger is listed as £252 + VAT by HRPC and is still available.

It is not a modern style plate one. You could try removing it and flushing it through with a limescale remover, but you would need to keep the cleaning fluid moving for best results, but I would not expect HE to cause problems over course of few days rather gradually over time.

Check diverter valve is operating correctly when tap is opened. I would suspect this is stiff/siezed or simply not working because diaphram is defective.

kdflan · Joined: 11 Apr 2008 Posts: 12 Location: birmingham england

tried the divertor valve .when the taps are on calling for hotwater the pin at first moved out a fraction to touch the microswitches .then stopped moving at all.which judging by other replies is the diaphram is no good . when i pressed and held the microswitch buttons the water heated to a good temperature for a while . tried it again a while later and it wouldnt run hot at all so does this mean that it is still the diaphram as i presume by holding the microswitcdhes in im simulating the diaphram moving, or could ther be another reason .just want to get an idea b4 i go and buy the diaphram .

cheers guys

AlanE · Posted: Tue Apr 15, 2008 7:53 am Post subject:

The diaphram carries out two operations in fact:

1. Changes water flow from radiator circuit to the DHW heat exchanger.

2. Operates microswitch to tell boiler there is a DHW demand.

Operating microswitch manually may not produce hot water at the tap, it will depend entirly on what position the diaphram has left the diverter section of the valve.

Problem could be defective diaphram OR the diverter valve is partially siezed up so even a good condition diaphram could be incapable of operating it. (or both)

Bearing in mind age of boiler it might be a good idea to simply change the diverter valve complete.

kdflan · Joined: 11 Apr 2008 Posts: 12 Location: birmingham england

cheers lads . i got a new daiphram and changed that and the boilers working fine now so thanks for your help Laughing