Galvanizing Flaking Off Single Vent

[Michael Thomas]

What might cause this? Draft was fine, flame pattern was normal, no chemicals in area at time of inspection.

[Bob Harper]

While the draft may indeed be "fine", it could be too strong. There is a phenomenon known as the "curtain effect" with draft hood equipped appliances. The draft is so strong, the in rush of dilution air blocks the exhaust gases, which back up and vent out the base. This flaking could be from excessive heat buildup.

Then again, it could be from a bad batch of pipe. What other signs are there? Did you test with a CO analyzer around the base for backdrafting?

Weil-Macs can be a PIA to vent.

[Michael Thomas]

Bob,

Thanks as always. "Curtain effect" is new to me.

"Did you test with a CO analyzer around the base for backdrafting?"

Above my pay-grade (and level of competence) at this point.

Per tag the last service on this boiler was '01, there is a slight (water) leak at pump, and a service tech will be out Monday.

I'll be in the area and I'm going to meet him if possible, I'll see what he has to say.

BTW, that boiler is on the same chimney (let's hope not the same flue) the FP for which I just posted the damper picture.