Vokera Linear 24 problem

[ksm1826]

My Vokera is not working, it was giving warm water intermittantly but now nothing.

It flashes error code 07 when its not reading a temperature of 94.
Turn on tap it drops to 16 turn it off and within a second it jumps to 94 again.
Some time ago (after paying fortunes for parts) I bought a fuly working unit to save as spares so can quickly try any ideas you may have.

So far I have changed

PCB
DHW Heat Exchanger
HW Flow switch
Still keeps coming back to the same symptoms.

Would appreciate any help before I really start to stink !!

 

[bellairaphon]

dhw ntc

 

[bellairaphon]

no sorry primary ntc

Nath

 

[ksm1826]

Bit technical for me Nath could you explain?

cheers mate

 

[nickso]

primary thermistor on the right hand side of primary heat exchanger.

 

[ksm1826]

Ok I have found that and will swap it 1st thing, thanks guys

 

[Agile]

Some of us still think there is a blockage or flow restriction.

But instead of checking that you have shot off and changed the PCB all to no avail.

Check the non return valve first.

If thats really clean then remove the pump head and look for dirt in the impeller and do the finger test while its off. ( See FAQ ).

Tony

 

[ksm1826]

The story so far,

I have changed the flow switch for a spare.

I changed the PCB for a spare whilst inside and the pump isn't running constantly anymore.

I have changed the dhw he for a spare and on the face of it that seems ok

I have now changed the Primary Thermistor, which was actually pretty manked up inside, the boiler is now working and the water temperature held constant at the setting I chose for about 15 minutes so I guess that was one of the faults. The heating side seems to be ok too.

There is still this temperature thing going on when nothing is running (?) only now instead of 94 its reading 70 and I can't remember what it used to read before.

I would still intend to check the Non Return Valve when I find out where it is and best way to check it if only because I am in there and might as well do it now.

 

[ksm1826]

30 minutes later the temp is reading 50 so ran some water until temp went to 55 turned off and it immediately jumped to 84 the begand to slowly but steadily drop again, within 3 minutes it was down to 73 and still falling.

 

[DP]

I would still intend to check the Non Return Valve when I find out where it is and best way to check it if only because I am in there and might as well do it now.

Don't bother with above.

The thermistor was the cause all along. Temperature of 70 indicates correct operation so you need not fret.

 

[ksm1826]

Appears to be working ok now so gonna bolt it all back up.
Been ok all day so I'll take a chance on it, many thanks all of you for your help

 

[Agile]

30 minutes later the temp is reading 50 so ran some water until temp went to 55 turned off and it immediately jumped to 84 the begand to slowly but steadily drop again, within 3 minutes it was down to 73 and still falling.

Surely Danny it should not be that high when running hot water if the pump, NRV and plate are all operating correctly.

Tony

 

[DP]

Flow temperature of 55 would suggest cold water clocks in at 20 degrees C. Cannot see that happening with water run for 30 minutes.

If hotwater flow is restricted to achieve 55, primary will be higher.

Tony we have had a long debate on primary temperatures previously. You may want to check primary temperature on a Biasi 24S when HW flow is restricted.

 

[Agile]

In this case the hot water temp of 55°C was matched by a flow temperature of 84° a differential of 29°C.

In that case I would expect that the plate was rather blocked/scaled.

The trainer at Vaillant where Alex morrow and his ARGI gang went today, considered a differential of about 20° was typical and when demonstrating the measured was 19°.

The day was primarily about Vaillant W/C controls.

Tony