"Robert11" wrote in message
...
Hello:

Would appreciate any information on the following:

Will be replacing a very old gas, forced hot air furnace with a new
"high-efficiency" type.

Go 94% or higher...go with the highest AFUE you can possibly afford.



Have just read in the Audel's HVAC manuals that for a "high-efficiency"
type
of hot air
furnace, you do not vent thru the chimney (or via a metal vent pipe that
goes thru roof like we now have),
but rather you vent via a PVC pipe thru the side of the house. It wasn't
worded such that you might think that this is an an option, but rather
that
this is the (only) way to do it.


Its the only way to do it correctly, as all your new 90%+ units are set up
that way.



Has to do with the fact that the gas is not very hot from these types of
furnaces, and the condensate would flow back and ruin the furnace, etc.

Is it the "only" way ?

Pretty much....I mean...you can do whatever you want, but running the intake
and exhaust on the new units takes about an hour in most cases, and its not
real difficult. Your installers know what and how to do this.


Is there a "mid-efficiency" forced gas hot air furnace that would enable
venting in the manner we now are doing it (thru the roof) ?

Nope...not unless you call 80% mid....we call mid 90% units, and all of them
vent via PVC pipe.


Sure don't want the expense of trying to configure a new vent thru the
back
side of the house !

If so, how would these "mid-efficiency" furnaces be designated: by SEER
Number, or... ?


AFUE.
SEER is ONLY for AC
HSPF is for the heat mode on a heat pump.
In all cases, higher numbers mean less expense to run.

Any thoughts on this would be most appreciated.


We use a concentric vent on all our new installs where the old unit is
vented via B pipe like you have now.
All it takes is a 4 inch hole in the side of the home, and the intake and
exhaust are in the same opening, but you only see a round "cap" that is on
the outside of the home. The center of the vent is the exhaust and the
backside is the intake...under the home the pipe splits and the intake and
the exhaust are in different pipes leading back to the unit. The vents are
not overly expensive, and they are quick and easy for your installer to set
up. Once they are in place, you just support the PVC every 5 feet or to your
local code and its done.
If you want to see pics of one, in action, let me know as we have several
that we can either put on the website, or mail to you.



Thanks,
Bob