Vokera Mynute 20SE

[craig51]

HI All

I have a Mynute 20 SE system boiler. No R/S etc, just a mechanical clock on the front. With the boiler turned on, and the programmer on, it wont light.

So far I have determined.

Pump Runs
(Slightly loosened the bleed screw and felt/heard it run)
Fan Runs
(Can hear it)
Pressure switch is OK
(When running, I removed one of the tubes and blew down it to make and break the switch. I can hear it click on and off)

So even with all the above, it will not try to spark.

So i think its either the PCB, or the igniton. What do you guys think?

 

[glasgowgas]

HI All

I have a Mynute 20 SE system boiler. No R/S etc, just a mechanical clock on the front. With the boiler turned on, and the programmer on, it wont light.

So far I have determined.

Pump Runs
(Slightly loosened the bleed screw and felt/heard it run)

Should have removed bleed screw totally and looked at shaft to determine if its actually turning
Fan Runs
(Can hear it)
Pressure switch is OK
(When running, I removed one of the tubes and blew down it to make and break the switch. I can hear it click on and off)
Should never do this, potentially just humped the APS
So even with all the above, it will not try to spark.

So i think its either the PCB, or the igniton. What do you guys think?

you now need an RGI

 

[craig51]

APS is cool, checked resistance and it is making and breaking ok, and the voltage is cool aswell.

I didnt take the bleed screw all the way out as i can feel the pump working and hear it humming away when i hold a screwdriver on it and to my ear.

I have my ACS, but I am dont have much experience with breakdowns, just servicing.!

 

[glasgowgas]

Should have removed bleed screw totally and looked at shaft to determine if its actually turning

 

[craig51]

OK, I will do this tomorrow then. If it is working, what would you put your money on?

I dont have a fault finding flow chart so its a bit hard.

As it isnt even trying to spark, it must be either the ignition or the pcb.

 

[glasgowgas]

if your gas safe registered apply for the CC, loads of gas related topics in there

if pump dont run, pump proving switch dont make, no sparky sparky

capiche?

all vokera manuals can be downloaded from their website FOC

 

[craig51]

Excellent, i will do all 3!

 

[craig51]

OK, i am some where nearer to finding this fault.

As above, checked the pump and its defo is ok.

So, I downloaded the fault finding flow chart from vokera and did the following

Check 240Vac coming in - Yes
Turn on mode selector switch
Does pump run - Yes
240V on 1 of boiler stat - Yes
240V on white/black of safety stat - (there wasnt a black, only two whites, so tested a white and yes there was 240V)
240V on white of safety stat ( Going off the diagram, there where two stats just behind the gas valve. As previous step the one with white wires was getting 240v, and this stat had two brown wires. So i tested it anyway and got 240v)
Flow diagram now states go to flow diagram A

240v on terminal 10 of EB - No
240V on brown of flow switch - No
240V on white of flow switch - No

solution - Check wiring from safety stat to flow switch???

How? it looks OK to me. If the last step was no, then it states check water circulation and flow switch.

So, i personally cant see it being the wiring, so its either the flow switch internals, as when the pump runs i observed it making and breaking, heard it make and break, and i also manually did it. What i should have done, but ran out of time, was check across C and NO and NC to make sure it was making and breaking inside. Or, its the PCB!

Any opinions etc. Pm if you like.

 

[fanboy]

Craig, does the pin on the pump proving switch sit pushed fully against the microswitch when boiler is off/on?, cause as far as im aware, the pin has to retract back into its housing to let the microswitch lever away from the switch. If this doesn't happen when pump is running, you could have a lazy pump, torn diaphragm or slight blockage.

 

[craig51]

your right, when its off if i recall, the pin is all the way out, but when fired up, the pin goes in and turns the switch off i believe.

 

[Agile]

They work oppositely to most other boilers and that fools a few people.

It might be better to say that the retracting pin puts the switch "on" as thats easier to think about. ( Even if its actually breaking a circuit )

Its not when its fired up its when the pump is powered.

Tony

 

[craig51]

So, anyone want to take a stab at the possible issues wrong with this then? Its either the switch which i doubt, but i will test today, or the pcb. ANy others?

 

[Agile]

There are a lot more items involved in boiler operation.

Fan, fan proving device, gas valve, electrodes.

As has been advised, these need a competent gas registered engineer to diagnose.

Tony