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Worcester 24CDi RSF, no DHW

Discussion in 'Plumbing and Central Heating' started by ChrisOxford, 30 Jan 2013.

  1. ChrisOxford

    ChrisOxford

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    Just had a quick look at the boiler at work which is refusing to fire-up when there is a DHW demand.

    The black plastic disc on the plunger on the diverter valve assembly moves towards the microswitch when a hot tap is opened, but doesn't quite touch the button, let alone actuate it.

    Presumably, the diverter valve assy needs servicing/replacement, but before we get someone in, can anyone tell me how far the plunger is actually meant to move, please?

    Cheers,

    Chris.
     
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  3. nickso

    nickso

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    Right onto the microswitch.

    Diaphragm needs changed. Easy job or nightmare....it's a 50/50 chance.
     
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  4. ChrisOxford

    ChrisOxford

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    Thanks Nickso.

    What can turn it into a nightmare?

    The boss has discovered that a repair kit can be had for under a tenner, so is keen to have a go himself (!).

    C.
     
  5. 45yearsagasman

    45yearsagasman

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    All you need is a first class honours degree in meccano, oh and a lot of patience. There are a lot of parts to remove to gain access to the diaphragm housing, and then you've got to remove the 8 screws, and for a first timer allow 3-4 hours. Even then, that may not be enough.
     
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  6. petertheplumber12

    petertheplumber12

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    Yes it is a fiddle and you need to be GSR surely since cover is being removed.
     
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  7. 45yearsagasman

    45yearsagasman

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    All repairs to diaphragm can be done without combustion cover removal.
     
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  8. petertheplumber12

    petertheplumber12

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    I didn't say combustion cover I said cover. And of course any one can do anything and nobody can stop them I was just being careful not to give advice that shouldn't be done by a novice.
     
  9. 45yearsagasman

    45yearsagasman

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    Not true, but I know what you mean.
     
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  11. ChrisOxford

    ChrisOxford

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    Thanks everyone, points taken.

    Fortunately, have my first class degree in Meccano so will give it a go when the weather's warmer so that if it takes me a day or two to get it right, we won't miss being without CH.

    Anyone else done what Agile's said elsewhere on the forum and done it in-situ, without removing the whole diverter valve, using a right-angled screwdriver? This boiler is mounted high up with plenty of room underneath, so access to the underside is surprisingly good.
     
  12. Gasguru

    Gasguru

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    Be prepared for the isolating valves to leak just by dropping the pressure. It's a boiler off the wall job to replace them. You might want to get Worcester out on a fixed price repair. Most pros hate this job...very difficult to predict how well it will go.
     
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  13. Done dozens of these and I still treat them with mucho anticipation. Get the o ring kit for the associated parts and dont be surprised if after 2 hours and stripping down 3 times it still leaks. Good job for a novice to avoid.
     
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  14. nickso

    nickso

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    If done with the valve in situ it's 45 minutes....if it goes well. :LOL:

    Remember and move the pcb up so the Plate HE doesn't dump water into it.
     
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  15. ChrisOxford

    ChrisOxford

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    Sorry to revive an ancient thread but I finally got a chance to get to work on the boiler, and amazingly, SUCCESS first time, so THANKS for all the advice :D

    I was very lucky that the 16 year-old isolating valves all operated easily and didn’t leak a drop, and the plate HEx came off easily enough too.

    Dismantling the diaphragm housing was OK until I got to the two screws nearest the back, but even these shifted with a Ph2 hex bit held in a ¼” ring spanner, then spun out with a flexible screwdriver. The diaphragm was horribly perished with a huge hole in it, as you’d predicted. It’s worth noting that the screw heads are Philips(Ph), not the more common Pozidrive (Pz). The only RA/offset screwdrivers I could find on sale were Pozidriv unfortunately.You get a much better grip and stand less chance of mashing up the heads if you use the right bit

    I checked the new diaphragm was centred on its spindle by spinning it in the housing, lubricated its edges slightly with O-ring silicone lubricant, then re-assembled the diverter valve. I took the chance to replace the original screws with M5 x 12mm cap head hex bolts which were much easier to tighten to a sensible torque using just an Allen key rather than faffing around with stupid home-made right-angle screwdrivers. You can get a big pack of stainless steel ones on ebay for a couple of quid.

    Hardest bit for me was putting back the plate HEx. Obviously, I used a new fibre washer and 3 new O-rings, but had trouble doing up the union nut on the primary side as it didn’t quite sit squarely against the male threads. I found the best way was to push the HEx half-way and loosely onto its secondary connections, start the nut, then push the HEx fully home, insert the retaining clip and its special tensioning screw on the RH side, and finally tighten the screw and the nut alternately.

    I also changed the filling loop as the old one was FUBAR.

    Amazingly, no leaks at all and the primary holds its pressure (which it hasn’t done for years).

    I had a bit of a shock when I came to test it as the burner fired up then shut down shortly afterwards with lots of banging, and steam coming from the AAV. Fortunately, it was nothing more than the pump had seized from being stood idle and dry for a few days, and freeing off the spindle got things running perfectly again.

    Chris.
     
  16. bazdaman

    bazdaman

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    It's always nice to hear the success stories, most get the advice do the Job without so much as a thank you, you got very lucky using them ISo valves I wouldn't dream if touching them! Just out of interest how long did it take?
     
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  17. petit_pablo

    petit_pablo

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    Fook me :eek:

    Talk about beginners luck! :LOL:
     
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