PVC exhaust to the top of a B-vent

Nikolai

I am looking for some help with my 3"PVC exhaust inside of a 5" B-vent and use the chimney as the fresh air intake. My questions are; if somebody did something similar and how PVC terminated on the top of the chimney? Thank-you in advance.

Nick

Jason Horner_3

Are you running the intake and exhaust inside the same masonry chimney?

Why not have the combustion intake via a sidewall entrance? Many modcon boilers can have asymmetrical piping, ie vertical exhaust, sidewall intake of different lengths (check w/manufacturer).

Are you using the B-vent to keep the exhaust (I'm assuming that you have a condensing boiler) hot enough so it doesn't 'stall' on the way up because it's too cool?

You'd have to speak with the local code enforcement people to see if they'd allow the exhaust inside the B-vent and the intake to share the masonry flue. Also talk with the manufacturer.

I know that if you have a long vertical run up an existing masonry flue that you will run into exhaust 'stalling' unless the vent pipe is insulated.

You'd probably have to solder a metal flashing plate to the B-vent where it meets the top of the masonry to prevent cold air from getting down between the plastic vent an the B-vent interior wall. Any gaps would have to be sealed with high temp sealant. But check with the local inspectors before you do anything like that.