Hi all. We live in IL and looking to replace our old furnace. We
have had a
estimates and now we are trying to decide between an 80% and 90%
efficient heaters and 1 stage / 2 stage / variable models. The price
difference between 80% and 90% seems to be about 600-800 for Trane.
The price difference between different stages is also several hundred
$$$. How do we make a decision whether it is worth money to go with a
more expansive model. I'm looking for a dummy-oriented advice as my
knowledge here is pretty mich zero
Take a look at the fuel use from the previous year. How much did it cost
you? If it was $2000, you'd save about 10%, or $200 in a year. Payback
will be about 4 years, then you save that every year after. As the cost of
fuel goes up (and it will) the savings will be even greater.
You are not taking into consideration the fact that the 80% furnace uses
inside air for combustion and the 90% furnace brings in outside air. The
inside air has already been heated, that has cost you $$$ and you're
throwing it up your chimney . This air has to be replaced and the new air
is coming into your house from the outside--cold air that has to be heated
to room temperature--more $$$$. It gets into your house through cracks,
windows, under doors--so your house gets drafty. All this newly heated air
has to be humidified because it is going to be very dry. My point being
that the $$$ difference between the 80% and the 90% furnaces is more than
the 10-12% in furnace efficiency.
That's the dumbest thing I've heard in awhile. That air your talking
about that is already heated and gets put up the chimney, did you ever
stop to think that it must pass the burners to get there in the first
place? Now if by chimney you mean the real chimney, any idiot knows
to close the damper when the fireplace is not being used. As for a 90%
furnace getting air from outside, bullshit. They can get air from the
living space also. Stick with something you know cause hvac ain't it!
Most, but not all new 90% furnace installations DO bring in outside air,
in a PVC pipe to supply the burners, particularly in new custom homes as
extra attention is paid to proper sealing.
Manufacturers have recommended this practice for a LONG time, same as
fireplaces that bring in combustion air from the outside so that you
keep the doors closed most all the time.
I have a 90% furnace and it does have an air intake tube that takes air
from the outside but my understanding is that is for the combusion
process. The air that is being heated comes from the return vents
(totally separate). I admitady dont know about HVAC here but this is
just my understanding.
I went from a 70% efficient to a 90% efficicent and I save about
$300/year on heating a 1200 sq foot home comparing 2004-2005. Now, I
also did two other things when doing this furnace replacement. I blew
in an extra 12 inches of celulose in the attic and put in a chimney
balloon for my fireplace since my damper was leaking cold air real bad.
These probubly helped the savings as well.
Once again--the air used for combustion on an 80% furnace is supplied by air
that is already in the house. A 90% furnace brings in air from the outside.
In my search to install a new furnace I didn't see one manufacturer that did
it otherwise. The exhaust air from a 90% furnace has just about all the heat
squeezed out of it-- that's why it can safely be vented outdoors. You can
put your hand in the air stream and it feels luke warm. If you vented the
90% exhaust gases into the chimney you'd have a problem sooner or later.
Why? First of all there would be problems creating the proper draft because
of the relatively cool air moving up the chimney--not too good to have
poison gas reentering the house. Second, because of the condensation that
would form in the chimney. I don't know who Al Moran is but I do know that
he isn't too bright.
Well, this is contrary to what the installers told me here when my 18
year old 65% furnace died and I was forced to replace it with an 80%
(the cost delta between 65% and 80% will NEVER, NEVER be recovered in
the lifetime of this furnace even if gas prices TRIPLE!!!)
I had stuffed fiberglass insulation around the plenum of this up flow
furnace. They removed it and said that combustion air comes from the
attic. Very little air comes thru the crack at the bottom of the door
to the closet where the furnace is installed.
90% furnaces are condensing and the flue must be PVC and routed
HORIZONTALLY outside. The water that condenses and drips outside is
caustic, and limestone or marble chips need to be placed under the drip
zone to protect neighboring plants. 90% furnaces should NEVER be vented
out a chimney.
ahh my other home exhausted the 90+ furnace above grass, it wasnt lush
green but it survived
they sold you a 80 furnace and promoted it as such.
but you lost 15% efficency For the life of the furnace, how much did
you save ?$500?
With rising gas costs that payback will occur and if you sell a 90+
furnace is a sales advantage:)
At today's gas prices I pay roughly $100 for the ENTIRE heating season.
65% to 80% if it costs $500, 15years x $15 = $225 PAYBACK IS INFINITE
65% to 90% and it gets MUCH worse!!!! yes, gas bills decline but cost
delta rises faster
Coming from a MINISCULE heating area, efficient furnaces are NOT WORTH
So you live where heating costs are 100 bucks a year. A 90% furnace
may not make a difference there it's true but live in the north or
northeast and 100 dollars doesnt cover near a month worth of gas
Robert Gammon wrote:
We are basically saying the same thing. However, very little condensate
drips outside. Essentially all the condensate is fed to a condensate pump
and then directed through plastic tubing to a drain. How does attic air get
to your furnace? If the furnace is not in the attic is there a pipe that
feeds attic air to your furnace? I guess it's one way of getting rid of
damp attic air before it condenses within the attic.
The furnace is installed in a closet that has NO CEILING. Its OPEN TO
Common construction practice in single story homes here.
Furnace site on top of the return air plenum, sandwiched between the
laundry room, kitchen,and bathroom.
Condensation of cool winter air in the attic is not an issue.
As the Building Science Corp web site puts it, roof insulation under the
shingles is NOT needed here, but go 200 miles north and everyone needs
insulation under the shingles.
Less than 20 hours a year are spent below freezing temps here, and some
years its less than half that figure.
All the +90% furnaces I install are set up for sealed combustion, but it
doesn't mean it's used.
That's the way I do it.
You must be in the really deep South..
Can you smell the BS?
Partially correct. The venting has to be PVC, but it can go vertical. Most
people put acid loving plants (azalea's?) under the vent. I've never seem
marble chips under a vent outside. I do have a condensate neutralizer next
to my condensing furnace.
Oh, I have seen 90% furnaces vented out a chimney. They just run the PVC
inside the chimney.... We have one like that scheduled for next week.
Other than insults, do you have anything useful that you could add to the
topic under discussion?
The amount of insight and expertise that you bring to the table indicates
that you must have an IQ somewhere between your shoe size and your hat size.
SORRY YOU ARE MISS INFORMED:(
Furnace and hot water chimneys draft constantly even when they arent
heating air. They are constantly exhausting already heated room air up
the chimneys.ust like leaving a window open 24 / 7 all year long/ True
the exhaust rate increases when the burner is on but they are always
venting and sucking cold air from the outside in.
You dont know enough about HVAC:(
plus consider the furnace chimney may require future repairs that can
be expensive. or if the home is really old a new 80% furnace the
existing chimney may be too physically large and need a stainless
90% furnaces frequently draw cold air from a pipe for combustion,
saving even more. plus cold air is more dense burns better......
the dual speed is worth it. go slightly larger on furnace BTUs it will
normally run slower going full bore only on the coldest days.
do get a long term warranty on the entire furnace.
remember furnaces are part of the investment of a home, last a long
time and energy prices continue to rise.
extra efficency today saves bucks now and forever and are a sales
feature if you decide to sell.
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