It's called a "condensate pump". One of the reasons 90
percenters are so efficient, they condense the steam out of
the exhaust gas, which puts more heat into the house.

In the summer, the AC drains humidity out of the air, which
also needs to be pumped out.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Jules" wrote
in message
news
Hmm. Ours has an intake and outlet to the outside world -
but it also has
a small shoebox-sized pump beside it, which collects
moisture and pumps
it into the waste water system for the house. I'm not sure
if that pump
is for extracting moisture that's in the air, or from the
gas supply -
but given the way it's floor mounted beside the furnace it
looks like
optional extra equipment, as otherwise surely it'd be built
into the
furnace...

If it *is* optional on furnaces and the OP doesn't have it,
maybe they
need it, whatever its exact function is...

(just idle speculation, not based on any knowledge of how
furnaces work! :-)

cheers

Jules