Vokera Linea 24 Hot water problems.

[ChrisR]

HW flow should short purple wires on flow switch or M5 pins 5 and 6
Black wire to actuator should go live and stay there.
Does it?

 

[Agile]

That would have been covered by my para 3 of 3 March 6.47pm.

I dont think that he can have correctly answered all the questions I asked though!

I will repeat them in case he wishes to review the answers given previously:-

If the 230v switches from black to brown with the motor disconnected then thats definately a PCB problem unless there is an external influence at fault.

Are you sure the supply is switched to the other wire and not to both together? If both are powered then it will rotate and cycle the pin every 4 secs. That could be a fault on the relay not spacing the NC/NO contacts.

Have you monitored the DHW flow swith to ensure it remains electrically activated during the fault condition?

This would be an interesting one to visit if the answers really were correct. My past experience of cases like this were always dissapointing as there was always a fundamental incorect answer.

Tony

 

[emailpatch]

This I am sure of, The 230v switches from black to brown ect when the water goes cold definitely not both on together, the hot water will work fine for a couple of days ect, but when it goes off the burners remain lit and the motor actuator pin goes in and out not every 4 secs but intermittently(may stay cold for 3mins putting the water down the CH). I have not checked the DHW flow switch electrically because the burners always lite when the hot tap is switched on, but the boiler sounds like an airplane now with hot water tap on, the water flow seems hampered. I have opened the HW flow tap fully but the flow noise is loud, when the hw tap is screwed to close it cuts off the water within 1.5 turns and the tap will travel another 4 turns could this be sticking backing up pressure ect or am i barking up the wrong tree.
Steve.

 

[emailpatch]

What do i need to do to check the flow switch? just had a look and there are two purple spades on the switch that go to (M5) 5 and 6 pin as previously mentioned, also just removed left hand spade on the switch to stop any short and noticed the boiler kept running, flames an all but the hot water just went luke warm and stayed there, when i put the spade back on the water went hot but the diverter motor started to click in and out, by the time I got my multimeter it was working fine again, should the DHW swtich just meter straight through on demand?
I guess the question I'm asking is what else could it be? Like I said I've changed the Pcb (new) and the motor actuator(new), so whats telling the Pcb and the actuator to swtich between the HW and CH?
Thanks in advance
Steve.

 

[ChrisR]

That would have been covered by my para 3 of 3 March 6.47pm.

No it isn't, and so what anyway?

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When the hot water flow switch is "on" there should be 0 Volts DC across the purple wires
When it's OFF there should be nominally 5Vdc.

To get the actuator into DHW position there should be mains across connector M11.1 and M11.3 (measure with the connector in, at the back of the connector or on the board)

For CH there should be mains between M11.1 and M11.2

--

WHen the CH "erroneously" comes on, is CH switched on at the boiler/ programmer/ thermostat? A dirty signal from the flow switch could make the boiler switch between CH and HW.

 

[emailpatch]

----------

When the hot water flow switch is "on" there should be 0 Volts DC across the purple wires
When it's OFF there should be nominally 5Vdc.

To get the actuator into DHW position there should be mains across connector M11.1 and M11.3 (measure with the connector in, at the back of the connector or on the board)

For CH there should be mains between M11.1 and M11.2

--

WHen the CH "erroneously" comes on, is CH switched on at the boiler/ programmer/ thermostat? A dirty signal from the flow switch could make the boiler switch between CH and HW.[/quote]

Firstly Chris i appreciate all the help I'm getting in particular from you and Tony so don't be falling out.
Just let me clarify, even in just HW mode on the front of the boiler the problem still occurs, for some reason the feed to the motor actuator changes from brown to black ect and sends the heated water down the CH when only the hot tap is on and no central heating. I've changed the motor actuator on advice and now the main pcb but the problem still occasionally occurs. I need to check the HW flow switch as you suggest, and just to clarify, if I put the multimeter onto the two purple wires on the switch I should read 5v? if then I turn on the HW tap this voltage should disappear? and if with the HW tap on this changes from 5v to 0 ect this would point to the flow switch? yes?

Steve.

 

[Agile]

----Just let me clarify, even in just HW mode on the front of the boiler the problem still occurs, for some reason the feed to the motor actuator changes from brown to black ect and sends the heated water down the CH when only the hot tap is on and no central heating.

Chris has only quoted what the boiler should do! Not why it may not be working corectly!

What you said above is new !

On CH if the motoring occurs then it would point towards a failure of the CH demand thus causing the boiler to revert to the resting motor DHW position.

I would ask you to check the resistance of the contacts on the room stat and then disconnect and link the stat connections at the boiler to eliminate the stat.

HOWEVER...

That would not obviously explain why the PCB drives the motor to CH during DHW. That would imply a loss of DHW demand!

So I would ask you to measure the resistance of the DHW demand switch.

When you measure these resistances, its important to measure the closed resistance on a low ohms range and get the real resistance reading.

Also you must measure the open circuit resistance on a high ohms range to ensure its over 1 Meg when open circuit.

The fault is actually very simple but we have to point you directly at it !

Tony

 

[ChrisR]

Chris has only quoted what the boiler should do! Not why it may not be working corectly!

Not quite Tony. While Chris did point out what the boiler should do (about time somebody did ) there was also a suggestion why it might not be working correctly:

A dirty signal from the flow switch could make the boiler switch between CH and HW.

I also suggest you measure the 0V and 5V with a voltmeter as described. If you use a resistance meter you only see what is being presented when you happen to be looking, and with whatever source the meter happens to be using, which can vary enormously.

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...)

When you changed the actuator was there any sign of water coming out of the diverter valve? It could be going along the shaft into the motor and doing something naughty in there.

emailpatch don't worry about any of us falling out - we all have our styles and we all take glee in taking the P out of each other. All resolved over a curry. About bXXdy time for another one, by the way, Tony!

 

[emailpatch]

All the above I've mentioned before but I appreciate you both are not concentrating just on this post like myself.

I agree with you Tony the problem is simple but whats the cause?

Again.....
The pcb that feeds the actuator is swapping the signal (brown & black) when only the hot tap is on but not to any pattern or regularity, it does not make any difference if the switch on the front is set to HW only or CH & HW, the switch does work however because the CH will not work when just HW is selected.
I have changed the motor actuator on advice from here but i knew through logic it couldn't be at fault because the feed to it was changing, valve behind it find no water leaks.
I then changed the pcb thinking that this was at fault (relay ect) but the fault still remains. I will check the flow switch or any other part that could cause this problem but you have to appreciate I need an idiot guide when it comes to checking resistance ect I'm an engineer not a sparky.
Like Tony said something is telling the pcb to change the flow on the motorised valve, not turning the burners off! when only the hot tap is on no CH, I have noticed however that when the fault occurs and the hot tap is then switched off the boiler continues to run for a couple of mins sending the water down to the rads.

NO room stat just the digital clock on the front of the boiler, wire already linked through since new.
And to clarify again the problem only seems to occur on HW demand CH works fine all the time.

 

[Agile]

I also suggest you measure the 0V and 5V with a voltmeter as described. If you use a resistance meter you only see what is being presented when you happen to be looking, and with whatever source the meter happens to be using, which can vary enormously.

...over a curry. About bXXdy time for another one, by the way, Tony!

Although you can measure the voltages if you like, please do measure the resistances as I have requested.

All measurements of voltage or resistance are always a snapshot unless you add a monitoring device.

Its so long since the last curry that the venue has closed! There is another available though. Dan is a significant offender though!

Tony

 

[emailpatch]

Will check the voltages tonight when I get home from work and try to work out how to check the resistance, will post later if you could both make time for the results, Is the flow switch and easy repair what else other than this could it be?
Steve.

 

[emailpatch]

Right here goes!

In standby mode the two purple wires read a constant 10.2v and low and behold when the HW tap is turned on this disappears, but the problem is still there (hot water down the CH not out the tap) voltage doesnt come back! Checked the resistance with the wires off and my meter will not go low enough, when the HW is then turned on via the tap the resistance goes to 1.4 but interestingly does fluctuate down to 0.8 but the boiler fires with both the wires off but the water only gets luke warm. I cant read anything into this hope you can
Steve.

Also just like to add that the display on the front is misleading, when the HW runs normally and I struggle to grip the outlet pipe underneath the front display reads anything between 0 and 66 ect when i restrict the flow via the black outlet tap underneath the temp on the display falls although the pipe is getting hotter as you would expect, just another thing I would throw in as a thought, dont know if its linked but its definately not right.
Steve.

Also when the thing goes wrong and sends the water down the CH, if I then turn off the HW tap that initially fired the thing up it continues to run, even when I turn the selector nob to the off/reset position, I have to phyically isolate at the main power at the wall before it will reset/ turn off, they must be all linked!

Steve.

 

[Agile]

I am waiting for both the resistance readings on the switch with the wires removed.

When you measure these resistances, its important to measure the closed resistance on a low ohms range and get the real resistance reading. Put the test leads together to see what the lead resistance measures.

Also you must measure the open circuit resistance on a high ohms range to ensure its over 1 Meg when open circuit.

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

Did you ever measure or change the temperature NTC sensors? It could be one is intermittent!!! May be easier to change the DHW one in case!

Tony

 

[emailpatch]

I am waiting for both the resistance readings on the switch with the wires removed.

When you measure these resistances, its important to measure the closed resistance on a low ohms range and get the real resistance reading. Put the test leads together to see what the lead resistance measures.

Also you must measure the open circuit resistance on a high ohms range to ensure its over 1 Meg when open circuit.

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

Did you ever measure or change the temperature NTC sensors? It could be one is intermittent!!! May be easier to change the DHW one in case!

Tony

My multimeter does not go low enough to measure the closed reading but when opened the reading starts at 1.4 and does vary down to 0.8. I have just changed over the NTC sensors now.
Steve.

 

[Agile]

Also you must measure the open circuit resistance on a high ohms range to ensure its over 1 Meg when open circuit.

For the avoidance of doubt I am refering to the DHW flow switch!

When did you change the NTCs and what was the result?

Tony