Burners not fireing on Vokera combi

[TrotterD]

Hello,

I wonder if you could help with a problem I have with my combi Boiler.

The make and Model is a Vokera Flowmatic 20/80 RS. The problem seems to center around the burners not activating. I have followed the fault diagnosis and can't come to a conclusion on the faulty part.

If I set the Central Heating Thermostat to the lowest setting and switch it to constant, the pump activates and all the micro switches click into place, but the burners don't come on.

I have checked the voltage on the terminals of the Modulator coil and it reports between 1.5 volts and 2. If I move the pink wire from connection 1 to 1A on the Central Hating thermostat it still doesn't fire the burners up and I get a voltage of between 12.5 and 13. This seems correct according to the manual

I have removed the Modulator Coil and tested the Ohms resistance. It reports 46 Ohms. Which I think is ok. The manual says 50.

If I turn the heating on the burners will turn on to High Fire eventually but just for a short period of time then go out completely, but the pump still works. Its as if it tries to switch to low fire but can't hold it.

The similar symptoms happen when turning on the Domestic Hot Water, so I don't think it is the thermostats as they are separate.

I was thinking it could be the Modulator Coil or the Gas Valve solenoid or PCB.

Sometimes it will work fine and the burners seem to stay on as normal, When it does the radiators get hot.

Any help or advice would be appreciated.

Thanks in advance

Dave

 

[kevplumb]

test the aps on the fan

 

[TrotterD]

Thanks for replying but what is an APS and how would I test this.

Thanks

Dave

 

[kevplumb]

air pressure switch it tells the boiler the fan is running

 

[TrotterD]

Ok I will test this, I think on my boiler it is refered to as a Pressure Differential switch.


Dave

 

[kevplumb]

bit like saunier calling the diverter a reversing valve

 

[DP]

The Flowmatic is like the Vaillant VCW 242/ 282 built like a brick outhouse. They are bombproof but need regular servicing (not the 10 minute lookover).

I would hazard a guess that the APS is OK but the failure is service related i.e. a full service (an overhaul) will put this boiler back on its feed.

Where are you? What is the water quality like? Hard water area?

 

[TrotterD]

I recently serviced it my self last year and replaced all the seals and Diaphragms that come with the service kit. I hoovered it out and cleaned it up like new, because the previous owners of the house looked like they never bothered. It worked great since. I live in Sunderland so we have a very hard water area. Lost of scale. The last problem I had was the Heating manifold sticking when turning on hot water. The pin was all scaled up and wouldn't push the microswitch.

 

[kevplumb]

Sunderland

and you admit it

 

[TrotterD]

Sunderland

and you admit it

Actually, Sunderland is a nice place, I can think of a lot worse places to live..

 

[kevplumb]

try being a monkeyhanger marra

 

[TrotterD]

OK, I have checked for 240 V on the Fan Terminals which is present. I have removed the Air Pressure Sensor and tested that with a multimeter and that seems to switch ok when you suck on the tube.

One thing I have noticed is that the boiler seems to be working correctly now. But there is a clear plastic relay looking thing on the PCB. This seems like it has burn marks inside of it. Any ideas what this relay does and is it a bit suss that it has burn marks in it.

Thanks in advance

Dave

 

[weargas]

Sunderland

and you admit it

oi!! watch it!

 

[kevplumb]

got you out of the woodwork makam

 

[TrotterD]

Hi, I still have this problem with my boiler, I just wondered if anybody had any more suggestions to try, I don't understand the last few comments, but I guess they are not Boiler related.


Thanks

Dave