Vokera Excell SP80 Heating but no hot water ???.

[mickp1]

Hi

I am having problems with my nine year old Vokera Excell SP80 Combi Boiler.

I can only get hot water when the heating is also running. As soon as you turn off the heating you get cold water ?.

The local engineer has been out four times now and has changed the P.C.B, the gas valve (complete) and also a thermistor. None of these parts have made any difference and he has now advised that the system may need de-sludging?.

The system has had fernox in from new so i suspect my engineer is working from pure guesswork.

Any ideas what could be causing this problem?.

Thanks

Mickp1

 

[scatmanjohn]

Your suspicions are correct. Your man has not gone a clue what he is doing.
What you need is someone who knows the boiler.

It will probably need the dhw flow valve and diverter refurbishing.
You can buy a service kit that has all the components that will require.
By the way has your man charged you for his incompentance

 

[compheat]

I would have thought that the DHW diaphragm on the change over/diverter valve would be the first place to look.

 

[mickp1]

No he hasnt charged me as fortunately i have breakdown insurance.

I have however had to have four early finishes at work to let the guy experiment.

Thanks for the advice.

Could there be any other problems that i need to watch for.

 

[compheat]

If the central heating is working ok then its got to be something related to the hot water function, so the diaphragm is the first port of call. You can even test it manually by activating the micro switch.

 

[ChrisR]

Could there be any other problems that i need to watch for.

If anything he's replaced fixes it, flying pigs could be a danger...

 

[mickp1]

Is there anything that i can test safely that would confirm the diverter diaphram is the fault.?.

 

[Paul Barker]

Operate microswithc manually if boiler fires get diverter valve seen to.

Is on bell end of DV, a pin from dv pushes it, remove black plastic part and push something in there to operate it does boiler fire? Stop what you are doing imediately and call competent person saying your DV is ****ed.

 

[scatmanjohn]

Paul Barker.. i think your talking about the Flowmatic.

The Excell has a fulcrum arm which is pushed out by the dhw flow switch.
The other end of the arm operatates the diverter and makes a switch that is screwed onto the diverter housing. (bottom left hand corner on most of them, however some are slightly different).

Could just be the microswitch as they are always going.
I would be fitting a DHW diaphragm,new bobbin,bobbin washer,bobbin o ring, cleaning up all the push rods, new boiler flow switch diaphragm.

And i would so my arse in Debenhams window if that didn't sort it

 

[mickp1]

Scatmanjohn

I think you are right. Your description matches what i see.

Is this a job that the average D.I.Y man can handle or do i need to be making some phone calls to the local heating guys ?.

Thanks for pointing me in the right direction.

So far so good.

mickp1

 

[scatmanjohn]

mickp1.. Watch the fulcrum arm when you turn on the tap. Once it has stopped coming out towards you, try pulling it by hand the rest of the way.
Hold it there, does the boiler fire and give you hot water or is it luke warm.

Be careful where you put your hands it 240v in there!!!

Get back with your findings and i should be able to give you a more accuarate diagnosis.

If its just the diaphragm it is very easy to do.

 

[mickp1]

Tried that.

When you switch on the hot water tap the arm comes out fully towards me. The boiler fires up at this point then runs for a couple of seconds and cuts out. The boiler then fired up again after about 20 seconds, ran for 3 seconds then cut out again. No hot water whilst all this is going on !!.

I tried to pull out the arm as suggested but i am sure it was all the way out.

Does this give you any other clues ?.

mickp1

 

[mickp1]

Scatmanjohn

I have just tried this again with the heating switched off. The arm is working fine and it does seem to travel fully when i open a hot tap. I have tried to ease it out further but if i pull any harder something will snap or bend.

With the heating off the boiler does not fire at all when running hot water. The water coming through the tap is on the verge of turning to ice it is that cold !!.

I hope this gives you a few clues.

Thanks again

mickp1

 

[scatmanjohn]

Hang on a minute?

I thought you said you could get hot water if you had the heating on, now you are saying that you can't get it at all

 

[ChrisR]

Look then at the microswitch, which is operated by a screw in the extreme left end of the fulcrum arm. Might be a good idea to get in there first with the power off, and the hw tap off. You should be able to see what 's going to happen, and operate the switch by poking to see if it clicks ok. Can't remember exactly what the poked bit would look like but the body of the switch will be black plastic about an inch long.
I think it has a metal leaf hanging downwards but...

The arm will move withthe mains electric off.