28Cdi diverter valve

[garyo]

I've had hot water issues recently (luke warm water, central heating warming up instead of hot water etc) so last night I removed the plate exchanger and stripped the diaphram end of the diverter valve. It was in good condition, and this wasn't a surprise because I'd put a new diaphram in 18 months ago.

The valve end seemed sticky though - I could just about move the metal disc back and forth with a screw driver, but it felt seized up. With some more wiggling it gradually got easier to move and free'd up a little, but still didn't feel quite right. So I've purchased a completely new diverter assembly so will replace the lot. Does that seem like the right course of action?

Is the old diverter scrap or should I try to clean it out, descale it, keep it as a spare?

Thanks

Gary

 

[45yearsagasman]

Not worth repairing the old valve. Just make sure when fitting the new valve you use new washers and O rings and use silicone grease( not sealant) and nothing else. Good luck with the O ring at the back.

 

[MJN]

I descaled/scaled my diverter which went on to last 5 years (before we moved out) so it's not necessarilly a right-off.

No harm in giving it a try and see how it finishes up - the efficacy will be self-evident.

Mathew

 

[45yearsagasman]

Two differing opinions. Make your mind up time.

 

[MJN]

I wasn't necessarily disagreeing with you, merely pointing out that as it doesn't take long to dismantle and clean there's little to lose in attempting a a refurbishment of the old one.

Mathew

 

[garyo]

Thanks chaps - not sure I'm looking forward to the O ring at the back

 

[garyo]

Well, I've fitted the new diverter valve and unfortunately the problem is exactly as it was before - tepid hot water unless the hot taps are barely turned on.

I'm wondering if the new valve could be faulty in some way. When in hot water mode, should the CH pipes remain cold, or is there always a proportion of flow though these?

I've replaced the DHW temperature sensor, so I'm starting to wonder about a PCB fault?

Thanks

Gary

 

[Agile]

What did you do about the plate heat exchanger?

Tony

 

[Maxsys]

Have a look at my post here, plate exchanger sorted it for me, with guidance from Tony

//www.diynot.com/forums/plumbing/worcester-28cdi-hot-water-problems.299152/

 

[45yearsagasman]

Cleaning the plate is fairly easy and should have been done during repair process, although a new one is a better bet. The heating pipes SHOULD NOT heat up during hot water demand.
The best way of testing this is to turn off CH and let it all cool down and then demand hot water and feel the flow pipe under the boiler. It should remain cool during demand. I will heat up only after HW is turned off to dump excess heat during pump overrun.

 

[Agile]

You repaired/replaced the diverter valve and the water is still tepid.

You did that because the rads where heating up at the same time.

A blocked plate HE can do that ( as well as many other things ) and should have been checked when changing the diverter valve.

I would be measuring the flow and return and DHW temps on DHW to see what might be wrong! But from what you have said the problem seems that the diverter valve is letting by.

Was this a proper brand new diverter valve ???

Tony

 

[garyo]

Thanks Max. I changed my exchanger for a refurb model last year, but I do live in a hard water area so perhaps that's the problem. I still have my old one so will descale it and swap them back over to see if that solves the problem.

Agile - the diverter valve was brand spanking new, fitted with new o-rings all round, but I didn't sanity that it was all moving freely internally etc.

I'll leave the heating off for the day and then run a conclusive test tonight to confirm whether the CH pipes are definitely warming up.

Thanks for your help!

Gary

 

[Agile]

I would recommend that you dont do anything unless the temps have been measured.

The rads heating may be something else.

Close the CH flow isolation valve and see what difference that makes. Again I would always be measuring temps to compare!

Do you have any dripping taps?

Tony

 

[garyo]

Hi Tony,

No, no dripping taps.

I'll close off the CH isolation valve tonight too and see what affect that has.

If it's of interest - this fault came on over the period of around two days - it seem too quick to be scale related - but perhaps it could well be a blockage that's gone through in the the exchanger. I've checked both circuits in the exchanger by running tap water through them though any they both seemed to flow freely.

I have a contact thermometer so will try to measure the input/output temps on the boiler tonight.

Gary

 

[ollski]

I've had the boards fail on the cdis like this before, turn the hw pot down below half and the boiler will work perfectly but over about half way up the boiler fails to modulate and drops out. Won't explain hot water going round rads though.