Vokera Excell 80SP - diverter valve

[Drew21]

Hi, I'm new here but not new to DIY. I have a problem with my Vokera 80SP and am looking for info to make a positive diagnosis and then some info on how to fix...

this boiler is pretty much on it's last legs but I need to keep it going for 6 months or so until I get the go ahead on an extension, at which time I will be fitting a new boiler in a new location.

Problem is a lack of hot water from the taps, rads are fine and the gas burner is (currently) working fine. Stuff that has been replaced over the past few years: DHW flow sensor diaphragm, flue pressure differential switch, plus I have cleaned the flue out several times. I don't think any of these fixes are related though, the differential pressure switch was replaced about 2 months ago and this was the last time I worked on the boiler. Also I fitted a couple of new rads last summer and so fully drained and refilled the system then, I did put inhibitor in the new water though.

I can get hot water out of the boiler by closing the two valves (flow and return) on the rad system, so because of this my thoughts are that the diverter valve is the cause rather than the DHW heat exchanger being scaled up. Though could a very blocked heat exchanger cause the diverter valve to not operate? Even with the rad system blocked off, the hot water in the shower is not as hot as it once was...

When I turn the hot tap on, the DHW flow switch operates the lever as it should and the lever looks to operates the diverter valve and the DHW micro-switch, and then the fan operates and the boiler fires fine... but still no hot water. Putting my hand on the rad flow pipe shows that this pipe gets hot, though not very quickly. I kept my hand on it for a minute or so before I got bored.

Let me know if you need more info to diagnose??

on fixing the diverter valve, a refurb kit is peanuts so I was planning to get in there and fit new bits. No-one has serviced this part for at least 4 years.

So, is there an exploded diagram of this anywhere that would help me understand how it works and what I should be looking for.

and/ or, are there any instructions I could use to help me

this job looks a lot more involved than work I have done before on the boiler so any help or advice is appreciated.

thanks in advance,
Drew

 

[scatmanjohn]

Sounds like two problems.

1, diverter passing, service kit available to sort.

2, Plate heat exchanger fault (sludged)

 

[Drew21]

thanks for coming back to me so quick. is the plate heat exhanger the domestic one or the primary heat exchanger in the burner?

is it an easy thing to clean out? Do I just run cold water through or do I need to soak it with some kind of cleaning solution/ descaler??

 

[scatmanjohn]

The plate heat exchanger is the domestic one.(looks like a sardine tin)

On some versions of that boiler it can be a bit of a fiddly job to get it out.
(two large hex keys are req'd)

I don't bother to try and clean them out, i just replace with new.

Some others on here may be able to advise on cleaning it.

 

[Drew21]

yeah, I can see it just in behind the diverter valve manifold, looks a bugger to get out!!

given the boiler only needs to do a few more months I'm inclined to try and clean it in situ as best I can and have done.

any tips/ info/ piccies of the diverter valve rebuild job very welcome


thanks for your input

 

[ChrisR]

DV internals have changed at some point, so the new often don't match the old. I remember I had to "phone a friend" and ask where one of the washers went! Otherwise that part's straightforward, unless you do the gland seals up too tight - they shear off.

 

[nickso]

and the dhw heatex is easy to get out too. drain both circuits, remove two screws and thats it. getting the old o-rings out is sometimes the hardest bit.

 

[DP]

Why bother if the boiler is only there for six months?

I suspect the problems are more deep seated like main heat exchanger blocked on air side (heat from barner not getting through sufficiently) and general lack of attention.

If the OP is asking on how to and he has tinkered with the boiler, chances are other things have been allowed to detriorate.

Pity, great boiler destined for the skip. I would be attaching a Megaflow if HW were poor. At least there would be backup if boiler were to fail.

 

[scatmanjohn]

and the dhw heatex is easy to get out too. drain both circuits, remove two screws and thats it. getting the old o-rings out is sometimes the hardest bit.

Unless its the version thats not held in with 2 screws that is

 

[Rob]

Unless its the version thats not held in with 2 screws that is

and what a poxy job that is!

 

[scatmanjohn]

Unless its the version thats not held in with 2 screws that is

and what a poxy job that is!

You know the one.

 

[nickso]

Unless its the version thats not held in with 2 screws that is

and what a poxy job that is!

You know the one.

is this the one with two allen bolts? ive heard of this fabled beast but as yet failed to work on it.

 

[scatmanjohn]

Unless its the version thats not held in with 2 screws that is

and what a poxy job that is!

You know the one.

is this the one with two allen bolts? ive heard of this fabled beast but as yet failed to work on it.

Lucky you

 

[nickso]

Unless its the version thats not held in with 2 screws that is

and what a poxy job that is!

You know the one.

is this the one with two allen bolts? ive heard of this fabled beast but as yet failed to work on it.

Lucky you

two allen bolts doesnt sound hard at all, but ill take your word for it

 

[Drew21]

DV internals have changed at some point, so the new often don't match the old. I remember I had to "phone a friend" and ask where one of the washers went!

Great news

...so anyway, once I get it all apart and can't get it back together again I'll post back!!

Back to my original post, I'm guessing that there is no easy to find exploded diagram of this valve then.

many thanks all, I'll keep an eye out for the nasty allen bolts