vokera Excell 80 SP hot water ok but no heating

[eggheed]

Hi can anybody help
hot water working ok but when set to heating the boiler lights up for about 30 seconds then goes off (pilot stays on).
can feel that some of the hot water has just started to go down the flow.
Fan and pump seem to run ok.
thanks

 

[Agile]

It sounds as if the diverter valve has stuck in the SHW position.

Thats fairly unusual on your model though!

Tony

 

[bengasman]

could be air in the calorifier. what most people would call the heatexchanger. 10 mm spanner if i remember correctly to loosen up the nut. not sure if i am thinking about the right model, but seem to remember ally parts so be careful

 

[DP]

Bengasman, you are thinking of the Flowmatic.

Air in this chamber would not give you heating. Nor would you get hot water. Air acts as a cushion to stop flow switch operating.

 

[eggheed]

As there is water actually going into the flow pipe could it have any thing to with the thermister which is on the pipe coming from the exchanger
does this thermister do the hot water as well as the heating.
thanks

 

[eggheed]

have stipped valve does not seem to be any problems with that. all pins are moving in and out also making the swiches.
If there was a problem with the fan would the hot water not work aswell ?
thanks

 

[MarkBarl]

Just a though on trying the simple first. What about the room stat?

 

[eggheed]

no room state fitted (good try) all trv's
the system worked last winter and worked a couple of weeks this winter but has now decided it just wants to do the hot water
thanks anyway.
Any more help would be much apricated

 

[gas4you]

Is fan speed the same for DHW and CH on this boiler?

If not perhaps the fan is struggling to satisfy the aps on CH

 

[eggheed]

The fan seems to be the same for both.
Is there two pressure switches in the pressure switch unit one for hw
other for ch.
if so could the ch one be faulty.
If it works ok for the hot water does this not mean the fan is ok
thanks.

 

[bengasman]

i managed to solve same sort of poblem once on one of these by giving the venturi a good clean.and the flue

 

[DP]

Here is how you will fix the problem.
1) Get hold of the boiler manual.
2) Also lay your hands on a multimeter.
3) Using the diagram at the back of the manual, start looking for the 240 volts that should operate the boiler in CH mode. Simple.

 

[eggheed]

Good advice will try these over the weekend
let you all know how a got on.
found the service information on the vokera website(http://www.vokera.co.uk/ )under literature then discontinued products,all the electrical diagrams and fault flow charts are there.
Many thanks.

 

[eggheed]

job done but can't believe how
before i posted the problem i noticed the diverter pin was sticking a little so i turned off the water and the flow and return isolaters,removed pin and cleaned then refited then turned everything back on,still did not work hence the post,
over the weekend cleaned fan unit ,ventura also did a full electrical check making sure 240v was present where it should be at all switches and outputs from the board which it was,still did not work.
thought i would take pump out to check the blades were ok. turned the return isolater and heard a gush of water as if it had opened even though the marking on the valve was in the shut position, tried the boiler on heating and it worked. so now i have one isolater in the off position (return) the other in the on position (flow)one line vertical and one horizontal.
looks like original problem was diverter but since closeing the valves one has got stuck or spun round inside. will replace both.

 

[eggheed]

Many thanks to you all who posted to help me,boiler must have been going off with temp after 30 secounds as there was no flow through system, at least the boiler has had a good going over
I would be interested to know if anybody else has had problems with these valves
Once again THANKS.