Vokera linea 28. Error 04, water pressure OK. Micro switch is not pressed.

[garnet]

Hi

I got a problem with my vokera linea 28.
It locks with error 04. Howver the water pressure is 1.4bar.

There is a problem with the pin below. It sometimes dont protrudes out to press the micro switch in front of it. This causes error 04 and if microswith is pressed by hand errror is cleared.

Mostly happens when hot water is used/needed. But I can not fully rule out the same happening when heating is needed.
The membrane in this compartment behid it was changed - same thing.

Any idea what can cause this behaviour?

 

[Stuckinarut]

When was the membrane changed? It’s obviously not making contact with the microswitch and appears to be causing this failure.

 

[garnet]

When was the membrane changed? It’s obviously not making contact with the microswitch and appears to be causing this failure.

Membrane under the plunger/pin is brand new.
This did not fix it.

 

[Stuckinarut]

Are there any small pipes off it at all?

 

[garnet]

Only one small pipe. Going out behind the white pipe/socket where the actuator motor pushes a pin.
There are small pipes within the manifold, but they are part of the metal casing/cast.

 

[DP]

Is the air evacuated from the boiler.
Is the pump running
Happening for heating and hot water also?

 

[garnet]

For the pump, it is running heating works, when not in error 04.
I don't know if there is air in the boiler.
Yes, happens for both heating and hot water.

 

[DP]

One has to appreciate boiler mechanics to understand what is happening in your boiler.

The pump creates pressure difference in water ie negative at the inlet and positive at the outlet.

This difference is seen by the manifold with the microswitch indicating pump is running and there is water in the system which can be heated.

During hot water demand pressure difference across the pump is quite poor due to relatively small hydraulic circuit so the spindle just pushes out and no more. If the cap on the auto air vent is closed, then pump will compress the possible air lock but the spindle will fail to activate the microswitch giving you F4.

During heating, higher circuit means better differential so better chance of not getting F4. Question I asked was, does heating work but not hot water ( not when the fault is showing)

What speed is the pump set to. Should be 3 ( three bars)

BTW it is good manners to click like or thank you

 

[garnet]

One has to appreciate boiler mechanics to understand what is happening in your boiler.

The pump creates pressure difference in water ie negative at the inlet and positive at the outlet.

This difference is seen by the manifold with the microswitch indicating pump is running and there is water in the system which can be heated.

During hot water demand pressure difference across the pump is quite poor due to relatively small hydraulic circuit so the spindle just pushes out and no more. If the cap on the auto air vent is closed, then pump will compress the possible air lock but the spindle will fail to activate the microswitch giving you F4.

During heating, higher circuit means better differential so better chance of not getting F4. Question I asked was, does heating work but not hot water ( not when the fault is showing)

What speed is the pump set to. Should be 3 ( three bars)

BTW it is good manners to click like or thank you

Thanks a lot.
My observation is that during the hot water demand the error 04 appears quite often, but not always. Also it sometimes would get the error during taking a shower rather than from the start of DHW demand.

During heating demand not so often. I don't live where the boiler is so don't have any better information, but it definitely gets into error 04 for both.

Pump is set to 3.

I had some suspicion that it could be something to do with the pump rather than the manifold (new membrane behind the plunger). Actuator motor works. So not much to go wrong there, bar blockage of some of the small passages in the manifold. However it looked clean enough when the membrane was changed.

Would evacuating the air (if any) be the best cause of action?
How can one tell if the pump is working OK, is there a chance for it to work ok at the start and then fail?

 

[DP]

Actuator motor

Actuator motor has nothing to do with 04 fault code

How can one tell if the pump is working OK, is there a chance for it to work ok at the start and then fail?

If the pin moves then pump is moving.
Your info re 04 during heating and hw is sketchy in that solid information is needed which is what the heating engineer acquires while in front of the boiler.
My suspicion is that HW demand is resulting in 04 code failure but for CH boiler works. Have seen this issue on other boilers and have successfully resolved it too.
You could change the pump and good chance it will fix the issue.
If the defect is common for both heating and hot water it could also be an electrical problem.

Would evacuating the air (if any) be the best cause of action?

This would be done by a heating engineer during a service if boiler was drained for any reason. Usually the dust cap is left loose a turn but can sometimes be closed tight if the auto air vent if passing.

How can one tell if the pump is working OK, is there a chance for it to work ok at the start and then fail?

Boiler is a good 20 years of age at a guess. Things do fail or get weak. A weak pump could give you the symptoms you describe.
Pump not running will give you 04 code failure

 

[garnet]

My suspicion is that HW demand is resulting in 04 code failure but for CH boiler works. Have seen this issue on other boilers and have successfully resolved it too.

How did you resolve it? Was it stricly happening for DHW, but never for heating?

 

[DP]

How did you resolve it? Was it stricly happening for DHW, but never for heating?

Now you see why I was asking for that specific information.

Attended a Baxi 105e boiler. Heating worked ok because heating side has greater resistance so flow manifold ( spindle in your text) operated no problem. During hot water demand, the spindle pushed out half heartedly but did not operate the micro-switch. New pump fitted.

Vokera Flowmatic. This boiler is fitted with a 15/50 pump. Any air trapped in the calorifier will mean higher resistance in heating side still provides acceptable flow manifold operation but for hot water spindle fails to move. Calorifier air evacuated, hot water works. Pump goes weak, hot water delivery becomes an issue. Vokera fix is a new pump or additional resistance in hot water hydraulic circuit. This boiler now can be well over 30 years old.

Have managed to resurrect a weak pump in the past when in a corner.

You have a good boiler which reacts well to proper service but person carrying out the service needs to be diligent and not just a boiler slinger.

 

[garnet]

Update and solution.

It turned out the pump was not working intermittently. Almost always when hot water is used, and 50% of the time when heating is wanted.
Pump was not working because the PCB was faulty. No power to pump (interm.)
Also strangelly the boiler will lock out with error 04 from restart immediatelly - now DHW or DH required.
Reading service manual this meant to change PCB.

So in one word: PCB replaced - problem solved.

 

[ATTQ]

Thanks for updating the thread. I've a similar age Vokera so was interested. I recently fixed mine with a new pump capacitor which might have appeared as a similar issue to yours, weak flow. It was still running when it was a fraction of the original capacitance but struggled to heat the distant rads. If yours hasn't been replaced might be worth considering as they are only a fiver and 2 minutes to change. Not sure but I think i read somewhere the pump can be damaged if running with a weak capacitor and they naturally do age. Parts are nice and cheap for these aren't they. And relatively simple. Worth looking after IMO and ignoring advice to get a new one

 

[garnet]

Thanks for updating the thread. I've a similar age Vokera so was interested. I recently fixed mine with a new pump capacitor which might have appeared as a similar issue to yours, weak flow. It was still running when it was a fraction of the original capacitance but struggled to heat the distant rads. If yours hasn't been replaced might be worth considering as they are only a fiver and 2 minutes to change. Not sure but I think i read somewhere the pump can be damaged if running with a weak capacitor and they naturally do age. Parts are nice and cheap for these aren't they. And relatively simple. Worth looking after IMO and ignoring advice to get a new one

Definitely not worth changing the boiler.
In my case the pump was working properly.
Oddly the PCB was changed 7.5 years ago, but definitely this seemed to be the problem now.