Alpha CB24 Hot water-not hot enough even on highest temp stg

[ChrisR]

I think the little O rings you mean in the DV must be at cat and dog on the exploded diag
The screw is presumably the lower one on 134, one of the 170’s

Haven’t found a part number for the O ring set.
From Pizartscenter:

165 is
INLET MANIFOLD ASSY
ALPHA 3.013768 MANIFOLD ASSY
Retail Price
(Excluding VAT and quantity discounts)
£73.673

134 is
FITTING- INLET MANIFOLD TO DIVERTER VALVE
1.015633
ALPHA 1.015633 MANIFOLD
Retail Price
(Excluding VAT and quantity discounts)
£15.672

Perhaps the grub screw is like the turbomax one, where it’s best to either use a shock driver to undo it, or whack the end of a well-fitting screwdriver into it before you try to undo it.

 

[Paul Barker]

I think you could get on it with an impact driver. Must get another one.

Yes the cat and dog are the important "o" rings.

Alpha would think I'd gone mad if I didn't just change the whole DV on a job like this. It probably costs them a fraction of the retail price my extra labour for servicing one would cost them more. Iam not aware of any other boiler that uses this DV are you Chris?

 

[eccoboy]

Hi chaps, do I remove the whole of the DV or just the barrel shaped section and leave the section containing the diaphragm in situ?

P.s. pics are very useful, especially the coloured exploded diagram and I have a copy of the manual from the website.

P.s. have checked the grubs and the crosshead screw tonight just to make sure they moved - and they do. Probably tackle this job at the weekend, my missus and 17month old are not keen on being without hot water for any length of time!!

Can I just get one of you to confirm the way I plan on tackling it is correct as per my previous post?

Cheers BB

 

[eccoboy]

Evening fellas, managed to get time to strip it down this evening, the pins in the valve were grotty, cleaned everything up gave it all a really good greasing and reassembled it all (found it easier to unbolt the diverter valve and then tackle it as the allen key grub at the rear of the manifold is impossible to get at)

The sad news is that it doesn't seem to have made any noticeable difference. The hottest temp running at full HW flow is 44c. Is this really as much as I can expect from this boiler? If so its really strange that I used to be able to run a full bath of water on full flow and then have to add cold water to it to be able to get in it without taking my skin off.

Have I missed something, or could it be something else or have we now exhausted all avenues?

p.s. strangely quite liked the challenge of doing it myself with a few bottles of cold beer to keep me company.........

 

[Paul Barker]

Before the heating comes on so the flow pipe is cold, run the hot tap, measure temp and flow rate, measure cold temp. Compare to published performance. If it is not to published spec and flow pipe gets hot more than just the first few inches but gets right along the pipe the DV is still leaching: New DV.

If not leaching anymore but doesn't reach publicised spec, get max gas pressure checked, if satisfactory, you have to wander about the plate heat exchanger, because I think youy have already changed thermisters haven't you?

 

[eccoboy]

Hi Paul, checked the heating pipe it does get hot and it stays hot until aorund the back of the pump area and then it seems to cool off to just slightly warm (this is after I've run off about a third of a bath full of water) Does this mean that the DV still has a leak or is this the usual amount of heat transmission ?

Also yes I did change the thermistors a while ago for the white ones.......

Cheers BB

 

[Paul Barker]

hang on do you mean the flow pipe. The pump is on the return.

In a bad case of leaching the radiators get warm is that happening? If so new DV, The spring isn't shutting off the central heating path and or the or ings aren't sealing. Unfortunatly I am not aware of a generic DV which fits the Alpha so it's Alpha part 3.012752 £103 plus VAT.

 

[gas4you]

Change the diverter valve. All Alphas are prone to these failing. You should get a minimum of 35C temp rise at 9l/min

 

[eccoboy]

Hi chaps, Paul just to confirm that I only mentioned the pump as an indication of travel, not to say that it was linked in any way.

I will probably take down the DV again to make sure that I have not missed anything before going down the road of buying a new DV. I have priced a complete unit today and it really is towards £200 rather than £100+vat.

Might aswell just accept that its alost cause if I was to pay someone to come and fit it........

Not really in the spirit of the site, despite B&Q now offering condensing boilers at less than £500................................

I'll fix it just to defy them.......!!

Still need help, tho will take down DV tomoz n make sure I fixed it as instructed..........cheers bb

 

[ChrisR]

put the part number into google...
I daresay if you strip and clean and grease every part, and change dubious O rings for ones from your local plumber's merchant's stock you'll be able to fix it.
Have you tried shutting the CH flow valve to see what you're likely to achieve? You need to check the gas flow too to make sure it's burning what it should. 1 cu ft in 36-40 seconds.

 

[Paul Barker]

Yikes Chris I ggogled part no. and first place I came to was cheaper than I pay, and I've just ordered one yesterday from Alpha Warehouse direct.

3.012752 Diverter Valve (CB24/28)(HE) £85.84 [url]

 

[eccoboy]

Hi fellas, thanks for your continued help. Checked the gas flow rate as suggested, the flow is 1 cu ft in exactly 40 seconds so no probs there. I also shut down the CH valve and then tried the hot water again but still only getting 40c on full flow.........

Is there something wrong other than the DV?

(p.s. thanks for the link to a less Dick Turpin like supplier too.......!!)

Cheers Ben

 

[Paul Barker]

Sorry but we can't help every time you revert to vague terms. It is critical always to measure the flow rate the cold water temperature for the time of year and the resluting heated water temperature at that flow rate.

If that hasn't altered when you shut the flow or return isolator from when they were both open then the DV is working correctly.

If when these are shut the temperature rise is not acording to manufacturers instructions then you have to evaluate whether the difference is down to the DV as proved in previous paragraph and / or what I have previously mentioned, max gas pressure (though I believe you have gas rated the appliance proving this correct), so finally we have to take a look at the domestic heat exchanger. You will by now be familiar with getting it off.

You have at least served a useful apprenticeship and might now know more than many people who fall out of ACS centres completely unprepared for the age of the combi. They are so obsessed with the past that 50% of the exam is on stuff we come across 1% of the time. Of course they can justufy this approach to examining us because of the dangers of the open flued stuff, and I heartily agree, I wouldn't have an open flued gas appliance in the house. But that is no excuse for completely neglecting the appliances which occupy 90% of homes today.

 

[ChrisR]

I thought I'd take one to bits. Much easier when they're new!

The cat and dog O rings live right up against each other. There would only be tiny movements between either of them and the green shaft; the shaft moves to do the diverting. The tiny relative movements, needed to let the valve seal, are hat lets the dirt in.
When some grot gets in there, the orange cone would move slightly along the shaft to the right so the cat and dog would become separated, and the orange cone's outer O ring would not seal on the inside of the brass body.

The green shaft also goes into the bush under the bird. If that became stiff, it would stop the green shaft, with the cones riding on it, moving to the right when the red shaft in the diaphragm section moves to allow it, on HW flow.

It's actually only the very end of the red shaft which hits the conical tip on the flow switch - must remember to grease.

 

[Paul Barker]

Yes you go tit. It's actuallly the yellow cat which seals off the heating circulation so this is the one, were grit or sludge to get in there, that would be the cause of leaching.