Vent Backdrafting

[Chefwong]

Hot Water Tank (natural) + boiler in the same room/chimney.
I just recently picked up on what seemed like burning dust when the hot water tank was in play. In looking at the plastic plugs, it did somewhat confirm it looks to be backdrafting. However the boiler has been running -constant- for the the last week we have been @ home and I cannot pick up nary of anything from the boiler.

Removed the ductwork on the tank and it all looks good.
Haven't had a chance but will need to do a A/B test by opening a sill window to see if it changes whether I can smell the backdrafting from the hot water tank

Any other pointers you guys can share

 

[Chefwong]

When it rains, it pours. Got to the house tonight. No hot water. Pilot out so I picked up a new thermocouple. Swap it.


Pilot is fine. Turn to fire it up. She lights up but after 5 seconds, she shuts down.
Further poking - looks like the glass vial - air - shutoff device blown, hence no air.
I suspect the backdrafting did oveheat the vial to pop


Boiler is in the commonstack and no signs of backdraft.
Just on the HW tank, when I picked up the stinky exhaust, I could see the plastic plugs on the water and anode - had a little melt to it, which indicate backdraft. If I hold a match, it wicks up and out