Vaillant VCW 20/1 T3 W PCB Problems

[gorselands]

Update: Boiler now flaming (HW & CH) then goes out after a few seconds.

Mike

 

[The831Bunny]

Make certain you have not crossed the PD valve tubes. The bottom tube above the pump goes to the top connection on the PD valve. For future ref, the boiler can be drained via the 10mm nipples at the isolation valves.

Bleed points: AAV, Brass 10mm nipple on Main Heat Exchanger, Hex nut on top of Domestic Heat Exchanger. As the MHE bleed is within the combustion chamber it's not a place a DIYer can enter. The chamber cover is difficult to refit, and is often left sealed incorrectly.

 

[gorselands]

Thanks The831Bunny.

HW now working ok. CH flaming for a few seconds and then flames die. Have bled everything you suggested except MHE bleed.

Left CH on constant and just checked again. CH has come back on and rads warm. So all is working.

The other identical boiler next to it (big old house) CH comes on and stays on without the delay period. Any idea what's causing the delay before it flames again and stays on?

Mike

 

[gorselands]

Just to say everything is working fine.

A big thank you to all those who helped me.

Until the next time!!!

Mike

 

[gorselands]

Spoke too soon. New PDV leaking round the stuffing box. Spotted it before it got to electrics.

Mike

 

[gorselands]

Just ordered a replacement PDV. Should I remove stuffing box and use silicon grease on the threads? I wouldn't have thought it was necessary on a new part and don't really want to disturb it but maybe it's common practice. I checked for tightness when saw it was leaking but it wouldn't go up anymore.

Mike