Terry Beck
09-09-2007, 09:32 PM
For example, this is a 5-year old American Standard Freedom 90 Cat IV condensing furnace, with the normal PVC exhaust vent to the exterior. Normally when I see similar furnaces of this age, they all have a PVC vent pipe that extends to the exterior for combustion supply intake. Does the manufacturer (or some code) require a direct vent connection to the exterior? I wasn't able to locate a manufacturer's installation guide.
In this case, it is installed in a non-vented (not conditioned) crawlspace, but they did provide one 6" vent at the rim joist for combustion air to the crawl. (Don't need comment on the rust in the attached picture; I have already recommended a service tech to repair any condensate leaks. I just needed a picture for illustration of the furnace type.)
As a side note, I do see older Cat IV furnaces (i.e. 1980s) with no visible option for an air intake vent that would extend to the exteror, so I have to assume some older models just used room air for combustion supply.
In this case, it is installed in a non-vented (not conditioned) crawlspace, but they did provide one 6" vent at the rim joist for combustion air to the crawl. (Don't need comment on the rust in the attached picture; I have already recommended a service tech to repair any condensate leaks. I just needed a picture for illustration of the furnace type.)
As a side note, I do see older Cat IV furnaces (i.e. 1980s) with no visible option for an air intake vent that would extend to the exteror, so I have to assume some older models just used room air for combustion supply.