Just read the venting literature for the American Standard sealed
combustion, haven't read it lately so I thought I better see if there is
They are now saying you can come off the top of the furnace and go to the
bottom and vent out the crawl space, that is if you slope it correctly and
put a trap in the lower part of the vent. Hmmmm, we already knew this, but
thanks A.S, been doing it for years.
You can now get the fresh air from the attic, Hmmm, Done it but don't like
to. There is a possibility of a leaking gas valve, and if the attic is
hotter than outside the make up air pipe in the attic could act like a
chimney and cause the gas to go into the attic. Realistically however, that
would have to be a BIG leak!
You DO NOT have to get the fresh air from the same side of the house. I
wonder if that only applies to the variable speed vent furnace or all of
On the subject of venting, we installed a new power vented H2O tank which
had a few nuisance calls. Of course the factory was of no help. Mark found
that our venting was too short and the flame was lifting off the sensor due
to the air rushing into the chamber because of suck a great suction from the
ventilator. He put an orifice in the exhaust and adjusted the inch's of
water over fire. Works perfect now.
For those who don't know it, an 80 and 90% furnace is orificed in some
manner to control the negative pressure over fire, not much different than
an old 60% with a barometric really. If you installed a condensing coil in a
70% furnace and you can make it close to a 90% with consistent control of
pressure over the fire box. Had a lot of problems with YORK back in the late
70's/ early 80's. Tore the things apart and under the combustion vent motor
was a plate, you would use the proper plate according to your fuel. Had
problems with flame roll out, since I couldn't increase the secondary air I
increase the negative pressure over fire by increasing the orifice size on
the plate between the vent blower and exchanger. There was some efficiency
loss but never had the problem again. Two buildings over a YORK truck was
working on a unit and we spoke with him, he was having the same problem.
Mark and I kept our mouths shut........ they make the big bucks, let them
figure it out!
Just thought I'd pass on this info, I'm kind of laid back tonight wondering
which customer will cut my jewels off this week because we can't get to them