Vaillant Combi VCW-Sine 18 T3WF H

[Agile]

Mac, if you are still around?

It is possible your investigation of the PCB circuit might have even traced out the circuit diagram. If so a copy would help me.

I am dealing with one of these boilers which does the following:-

Lights at low flame then ramps up to maximum.

Then fails to reduce to low flame. ( NTC sensor is OK and control pot is OK )

As I recall the 2N3055 is in series with the gas valve. So I am presuming that its OK as it allows start up at low flame. ( Easily tested transistor anyway ).

There will be two circuit functions, the first reduces flame to minimum and the second at a higher temperature will turn off gas completely.

Did your investigation go as far as identifying these two circuit functions?

Tony

 

[The831Bunny]

Does the burner extinguish when you put the NTC wire to earth (boiler chassis)? If not then electronic PCB.

 

[Agile]

No it does not!

But in this case I am interested in extending my knowledge of how the pcb works in order to repair it.

This is all for a family with a combined income of well over £100k but they dont want to replace boiler yet! Its just a personal anorak interest of mine to see how the PCB operates. I suppose its rather sad but I have enough time on my hands and this kind of thing interests me.

It would be far more useful for me to find out why the Worcester boiler PCBs dont bring it back on after a CH anticycle delay.

But the Sine 18 is a bit like a Lagonda car. Interesting but not encountered every day!

Tony