b vent on furnace located in basement 2 feet from chimney

[WARREN40]

i installed a furnace in Detroit michigan and the inspector wants a b vent installed is this code it has a 6" flue

[Jerry Peck - Codeman]

Hi Warren,

The type of vent has to do with the type of appliance, not the size of the vent.

Is it a natural draft gas furnace? If so, then a Type Gas Vent is what is required, the size based on many variables.

If it is a condensing gas furnace then it would need a different type of vent.

I've contacted someone for additional input, if you could provide the type of furnace for him it would help with the answer.

[Hearthman]

Warren, you didn't provide much info. so I'm not sure what you're dealing with or asking. Are you saying the AHJ wants you to install a B-vent in lieu of a listed liner in the chimney or is he asking you to use B-vent as a vent connector to the masonry chimney?

You must also consult the mfrs listed instructions. Some furnaces require a B-vent connector even in a conditioned space venting into an interior chimney. The codes and mfr much be consulted for specifics in vent connector sizing.

Modern 80% fan asisted furnaces run on such low stack temps, there is very little heat lost to warm the stack and thus create draft. The use of B-vent prevents stack connector losses, which helps draft while reducing condensation of flue gases. If this furnace does not have a post-purge cycle, one can easily be added, which will purge much of the moisture out of the stack and reduce condensation.

Is there a gas water heater common vented with this furnace?

Hearthman