Worcester Heatslave 26/32 CH operation problems

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FAO IANMCD please.

Ian,
As someone with 70-years reputation for fixing just about anything,
including professionally to this day, it's a bitter blow that I can't
fix my own boiler, and neither so far has my plumber / heating engineer
Steve been able to, though he did do some good diagnosis, and is still
involved, but VERY busy.

My boiler was installed in 2013, and worked beautifully till about a
month ago.

Then it misbehaved and would not do the business. Even with TIMER and
STAT and MAINS all live, it wouldn't do the job.
There is no doubt the TIMER and STAT are good.
First, the Burner motor would buzz but not start. This was easily
checked for capacitor failure (which it was) and a new capacitor of the
OEM type was bought and fitted. Now the Burner motor runs again. I
bought two 4.5mFd capacitors so I have a spare.
Sometimes it was possible to make the boiler work the CH, but usually
not. The DHW was fine after the burner motor revived.
Steve correctly said the Diverter Controller was a suspect, so I got him
to fit a new one.
I checked the old one and beyond any doubt the contacts in the internal
NO microswitch are done.
It did not make a clean CLOSED contact when the DV motored from A-DHW to
B-CH.
Very poor contact was being made, which might not do any good for the
next thing along the line.
(I have since fitted an absolutely identical microswitch to the old DV
controller)
So now it has a brand new DV controller and also new DV valve itself for
good measure.

But it is still misbehaving.

The DHW works perfectly well, BUT . . . using DHW stops the CH dead.
The boiler WILL NOT switch the diverter valve back to B-CH position, and
the circulation pump does not appear to run.

I have discovered that the following procedure will get the CH going.
1. Make sure TIMER and STAT are both ON demand. This is easy.
2. Go out to boiler and lift off the front panel using the new handle I
invented.
3. Try the DV controller lever, and at this stage it always seems LOCKED
in A-DHW position.
4. Switch the control panel main switch to the lowest SERVICE position.
5. Now the DV controller is NOT LOCKED, and can be carefully moved
(once) as far left towards B-CH as it will go.
6. Now release the lever and it will smoothly return under spring
pressure to A-DHW.
7. Now switch the panel power switch back ON, and IMMEDIATELY the boiler
starts to motor the DV Controller to B-CH, the circulation pump starts,
and shortly the burner comes to life and away we go.

As long as I do not use a DHW tap, it will usually keep going all day
with the STAT set well up, say 22~24°C which the space never reaches.
Using DHW will mean no more CH until I do 1 - 7 all over again.
Usually it won't re-start the CH if the STAT stops it for a while, even
if I turn the STAT up to about 30°C!

So . . . what am I doing wrong, or what am I missing?

I'd be delighted if this fault can be identified, because then Steve can
set about and fix it.

Best Wishes,

Charles
(Just along the A71 near Newmains)
 
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ADDENDUM.
I should have said that the DHW is working just as it should, night and day.

My apologies for struggling to find my way around the forum.
Just put it down to old age.

Charles
 
Ian might miss this. His name in the title thread or a tag would be better, I’ll do it for you. @ianmcd

Thanks.
 
Last edited by a moderator:
Many thanks. That was kind.
I'm only 79, so I am not well up on how these forums work.
My CH has been running non-stop all day, and will be till I turn the electric blanket to full turbo-boost, and go to my bed !
Before I turn in I will set the ROOM STAT to about 20°C.
The CH will stop right away.
The TIMER will be left ON overnight, with the STAT set at 20°C.
As the house cools down the temperature at the STAT will lower, and when it gets to just under 20°C, correct me if I am wrong, but the STAT should close (I am sure it will) and the boiler should go into CH mode, move the DV valve to B-CH, start the circulation PUMP and fire up the Burner motor and ignition.

It's Christmas . . . I can dream!

Charles
 
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My best guess would be the programmer. These do funny things when the boiler is asked to change over in my not too limited experience. You need to watch with the multimeter whilst replicating the changing requirements.
 
I am not familiar with this boiler.
Is it an oil fired combination boiler?
By diverter controller, do you mean the valve actuator?
Did Steve make sure the diverter valve shaft was free to rotate?
If the above is true then this diverter will be a true diverter valve with just two positions...CH and HW.
The CH function will be active only after the HW demand has finished, and there may be a small HW storage tank built into the boiler
(for others reading this I am thinking it may follow along the lines of the Worcester Highflow 400).
It may simply be a case of waiting 5 minutes or so after HW has been used....but you'd surely know this after 10 years with the boiler, so this may be irrelevant and erroneous.
Could it be that the shaft of the diverter valve is semi-seized? You should be able to actuate it by hand only once the valve actuator is removed.
 
One thing you have explained is it won’t go to B for heating, but B is for hot water and A is for Heating.
 
Could the dhw flow switch be jamming in th call position. ? This will keep the pump on but the diverter won’t open to c/h and burner wont fire as no temp drop across the dhw stat. (Assuming a g/star model)
One could unplug the flow switch from the pcb to test this
 
Last edited:
Meldrewsmate,
It is a kerosene external boiler, sealed system.
You point out "I am not familiar with this boiler".
It seems clear to us there is a specific problem, and it is clear to us so far that the usual fixes aren't dealing with it.
This is going to need a really expert Heatslave 26/32 specialist.
Thanks for your reply.


CBW,
Please read the original post carefully and believe me. I have set it out carefully.

This has been going on for nearly six weeks so far. It only became serious when the temperature outside went arctic.

My boiler has a BRAND NEW Diverter valve Controller and a BRAND NEW diverter valve assembly, three days ago.

For CERTAIN, on my DV valve the default rest position for the indicator peg is A for DHW.
The DV controller is spring-loaded to return to this position, that is, A-DHW
When It does decide to go to central heating, the DV motor is actuated, which drives the DV valve across, clearly shown by the indicator peg moving positively to position B for CH.
This actuates the microswitch inside the DV Controller, which moves from OPEN to CLOSED circuit.
This tests perfectly by continuity meter.

So, now boiler has BRAND NEW DV valve and Controller.

For interest and learning, I re-built the old DV controller with a brand new OEM microswitch inside it.
I also stripped and refurbished the old DV valve itself.
Now I have a working spare DV valve and controller, both perfectly fit to go back for another ten years.

This issue is apparently not a typical 'run-of-the-mill' problem, but hopefully someone on the forum will actually KNOW or be able to DEDUCE why this is happening, and tell me.
Thanks for your reply.

CharlesY
 
Charles, it's not easy to deduce and diagnose remotely. I detect that you are anxious to have your problem solved, but quick to dismiss the well intentioned and genuine help on offer. There is much experience on this forum.
Did you consider the advice from @Hairymelon? His seems an easily performed diagnostic for someone who is experienced in fixing things.
 
Could the dhw flow switch be jamming in th call position. ? This will keep the pump on but the diverter won’t open to c/h and burner wont fire as no temp drop across the dhw stat. (Assuming a g/star model)
One could unplug the flow switch from the pcb to test this
 
Charles, I have read it several times, including the additional posts, and you keep saying at rest it’s at position A for hot water and mention position B for central heating. Please see image of Danfoss, but there’s generally an industry standard:

1672089498574.jpeg
 
Thanks Hairymelon.

Almost certainly NOT. What happens when I open a DHW hot tap depends on the flow switch working.
However, I will check it at the first opportunity. That is quite easy to do.

For example :
1. the CH has been working all today, but crucially I HAVE NOT RUN ANY DHW ALL DAY.
2. I know for sure that if I run DHW it will do two things immediately
(a) STOP THE CH PUMP and BURNER and release the DV valve so it returns to A-DHW position
(b) nice hot water will flow from the hot tap and if need be the burner will fire up to keep it flowing hot.
This is more or less proof positive that the DHW flow switch is functioning as it should.

3. Overnight when the CH is OFF and the DV valve is at A-DHW, the burner fires up once in a while to keep the DHW hot.

4. I know from experience that if the CH stops, it is most unlikely to start again by itself. In the morning, when TIMER AND STAT call for heat, the CH WILL NOT ACTIVATE unless I perform the procedure outlined in the first post.
Again, please believe me when I say that the TIMER and the STAT are working fine.
If they were not, the CH would not run at all, never mind all day today.

It's a real mystery.

CharlesY
 
I would also check there is a hot water off wired into the timer and if there is one, make sure it hasn’t come loose/detached
 
Charles, I have read it several times, including the additional posts, and you keep saying at rest it’s at position A for hot water and mention position B for central heating. Please see image of Danfoss, but there’s generally an industry standard:

View attachment 290221
Chris,
That is NOT my model of DV valve. My one is a competely different make, model and fittings.
Mine is a DRAYTON "Hansen Class 'F'" DIVERTER VALVE
27904 8-718-684-238
and I have it IN MY HAND.
Position A is the default rest position and is the DHW position FOR CERTAIN.
Position B is CH position, and the valve has to be powered to achieve that state.

Here is a photo of the DV controller opened-up ready for the change-over of the microswitch.
You can see the springs, and that the indicator lever peg is all the way down, in position A.

CharlesY
 

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  • Diverter Valve switch in situ.jpg
    Diverter Valve switch in situ.jpg
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