On Aug 23, 10:16 am, wrote:
The HVAC is in the corner. At the bottom is an air filter which then
has duct work that runs towards the water heater. Then there is a
decent sized duct that runs up, through the first floor, and into the
attic. In the attic there are two round flexible tubes connected to
this. One runs to a air intake vent in the master bedroom and another
to the hallway on the other side of the house.

The openings in the duct work are in this structure. The water heater
sits right next to it.

A picture is here linked below. Bare in mind that this is over a year
old. The basement is finished now. You can sort of see one of the
openings in the duct work at the top -- it's a white grill. The other
is a few feet below that, more slim but longer.

http://farm1.static.flickr.com/54/15...832ab758_b.jpg


Very clear that this is in fact vents in the main return duct at the
furnace. Were these there before the basement was finished? If so,
it's totally bizarre. You would be sucking huge amounts of basement
air, which you don't want to conditon, into the system. And with no
air vents into the basement on the supply side, it's a prescription
for all sort of problems. Drawing outside air into the basement,
drawing conditioned air from the house into the basement, creating
negative pressure affecting combustion, etc.

If it was done as part of finishing the basement, it would make a
little more sense, but still be wrong. I'm thinking they might have
added them as returns for the basement. But they then should be in
the finished space and never that close to the water heater/furnace.

My guess is this was some homeowner added crap, based on some very
incorrect ideas.