Vokera Linea 24 Hot water problems.

[emailpatch]

open circuit it reads 1meg closed i.e when the water is switched on it reads 1.4 to 0.8 it varies, and I've swapped the CH and DHW thermistors over about an hour ago. If it were the Flow switch why would it divert the water down the CH and not just just turn off the gas burners, and why would it fire up the burners every time the hot water tap was turned on.

 

[Agile]

Has swapping the sensors made any difference?

Tony

 

[emailpatch]

Working fine at the moment but it usually does for a couple of days, will let you know Tony, but call me pessimistic but I've no confidence in this boiler now.

Steve.

 

[DP]

Some posters needs to check the MIs as they assumptions are incorrect.

Remove the motor and place a nail or screwdriver on the brass section that actuates the diverter spindle. For CH brass section will be retracted (with motor in position, diverter spindle will not be operated/ not depressed). For HW mode, the brass actuator will push out till the nail/ screwdrive mentioned above is ejected. In HW mode the diverter spindle will be depressed when motor in place.

I take it the boiler has been serviced which should include servicing the diverter valve. If this item is stiff to operate, HW delivery will be effected.

Craigmcgonigle- You may want to check you figures. At 15 ohms the burner would be OFF

Removing the motors puts the boiler in CH position. Depressed diverter spindle will give HW mode.

 

[kevplumb]

go danny

 

[ChrisR]

Yep, the spindle should also be extended whenever the beast is NOT heating the rads or on overrun -see below.

The low resistance measurement is predictably inconclusive.
The problem is clearly when the flow switch is ON not when it's off, so the high measurement is not an issue.

You could pull both connectors off the flow switch and if they're 1/4 inch spades, use a paperclip to connect them together.
However, if the voltage across the wires stays low when the ch starts getting hot the flowswitch doesn't appear to be at fault. This is another benefit of measuring the voltage - to measure the resistance you'd have to turn it off. If the voltage is correct when the behaviour isn't, that isn't a snapshot.

The boiler would be expected to circulate after through the CH after a HW demand, to dissipate excess heat, but not for long. You're seeing that.
It's possible that the sensors are telling the boiler it has overheated, but I'd have thought it would turn the burner off!

The remaining possibles include the other circuit board(s), which is/are involved in turning CH on (overriding hw) as mentioned above. Broken tracks on potentiometers can do odd things.

 

[emailpatch]

Which other circuit board, the one foremost at the front underneath the main board, where the dials go into?
This is giving out stupid displays.

Steve.

 

[ChrisR]

Does this seem familiar??!

Does the display ever show "CO" - combustion analysis mode, which would put it into CH operation. Can do that if the knob in the middle isn't in quite clicked in the right position or there's problem with the potentiometer on the board (daresay that wasn't the board you changed??). (Has your knob/spindle broken yet - it will...)

---

This is giving out stupid displays.

Is there anything else Toi ain't telling us?

Did you change the bit in fetching cherry, which the aforementioned knob engages with?

 

[emailpatch]

Thats not Cherry its more a girlie pink, no I havent changed that one just the main pcb behind it, I have checked all the spindles though and they are all intact for now, checked the operation and all dials seem to respond to command.

 

[emailpatch]

Can I wire this out to test?

 

[Agile]

The open resistance of the DHW flow switch IS important to measure!

If its low due to dampness etc. then it can give rise to a false demand for DHW !

I once wasted some time because I only measured the reed switch on a Genesis on a low resistance range and failed to check it properly on open circuit. It was actually 48 k and that was still enough to intermittently creast a false demand.

Steve, how is it doing after the sensor swap?

Tony

 

[ChrisR]

If its low due to dampness etc. then it can give rise to a false demand for DHW !

But he doesn't have that problem.
So, it isn't an issue.


What are you getting on the display??

Can I wire this out to test?

Wouldn't have thought so, but if you get to it and wiggle things you might find the fault appearing.

 

[emailpatch]

HW still working normally after swapping the thermistors Tony, but worked for a week after swapping the pcb last time, so not holding my breath, starting to think that it could well be a problem with either the wiring harness or the girlie pink pcb, will keep you both informed if or when it packs up again.

Display is reading really low temps when the HW outlet pipe is really hot, when i restrict the flow which increases temperature of the water the display temp falls ect.

Steve.

 

[ChrisR]

Did you get the incorrect temps before changing the pcb/sensor?

Was the "new" pcb off ebay??!

No point asking what coloour they are...

 

[Agile]

The temperature display is not the exact DHW temperature. Its derived from the system water temperature. Its based on a temperature sensor reading.

Have you measured the two sensors when cold? Should be about 13k at 16°C

Tony