On Sat, 13 Sep 2008 04:25:59 -0700, Michael B wrote:


.... and the exhaust from the first was directed to
the fire box of the one above. That one sent its output to a couple of
bedrooms rather than having 'dueling fans'.
Indeed, that second one recovered considerable heat from the first one,
and the exhaust from it was still warm enough to maintain good venting.

Michael:

Do I presume correctly the second furnace was not connected to the gas
line, and no fire in the firebox? The only heat in the 2nd firebox came
from the exhaust of the first?

Wasn't there a problem with chimney back-drafting in winter? Or did this
happen down South where you don't get temperatures below 10 degrees F?