Went through the same issues about two years ago. If you don't mind will
respond at the bottom of each of your questions.
MLD
"Todd H." wrote in message ...
Greetings,
It's that sad time to replace a furnace and possibly the A/C at the
same time. I've done my googling of past threads and gathered bits
and pieces, but thought I'd offer up my situation all the same. The
location is Chicago, IL, home is a 15 year old 2-story colonial around
2300sf, with a 15-year old 100,000 BTU furnace and a 3ton A/C unit.
Summers get hot and obnoxiously humid, but aren't that long. Winters
are, well, Chicago winters.
I had a 100,000 BTU (original furnace) that was replaced with a 60,000 BTU.
The original furncae was very over sized and obviously my house didn't have
the benefit of a heat load calculation. When it was built (1961) they just
threw in something that was sure to be more than what was needed--gas was
very cheap then.
I'd like some thoughts on the conceptual stories being spun by two
quotes I've received thus far. Sadly, the two companies seem to have
divergent advice on several points!
o Company A: a large well-respected 2-location Carrier dealer
in Chicagoland that has a training budget and a large staff
of technicians. Thought of well by every home inspector I've
come across.
o Company B: The other company, a lesser known, a 2 co-owner
Frigidaire dealer recommended by a friend who knows them very
well. The friend is one of those sorts who can do ANYTHING
to his house and just got done rebuilding it literally from
the foundation up largely on his own, and chose these guys for
HVAC.
The questions:
1) Carrier vs Frigidaire. Carrier I've had and had pretty good luck
with. Frigidaire...never even knew they did HVAC. Thoughts? I'm
leaning heavily Carrier or Bryant on this one.
Didn't get or hear very good comments about Carrier, Bryant seemed to be one
of the better ones along with Trane. I ended up with a Trane 92+% variable
speed, two-stage furnace. As important as the Brand of furnace are the
people who install it. I had isssues of crappy work that had to be redone.
2) 80 vs 90% The larger Carrier dealer interestingly was
recommending 80% for my 15-year old home. They said if it were new
construction 90% would make a lot of sense to save on running a
flue to the roof, but given that we already have one, it was
probably more cost effective to go with 80%. The Frigidaire
dealer said the 90% was the way to go with the number of degree
days we have here in Chicagoland. I'm more inclined to lean
toward 90% because I don't see energy getting anything but more
expensive in the future.
Being in a cold climate you would be much better off with a 90+% furnace.
Sure, you need to put inlet and outlet pipes (PVC) through the side of you
house--you'll also most lilely need a condendate pump. With an 80% about
10-12 cents of every heating dollar is going up the chimney. Also add the
folllowing to your heating costs--
The combustion air for the 80% is being supplied by inside air--air that
you've already heated to 70+ degrees and are now throwing up the
chimney--wasted $$$$.. This combustion air also has to be replaced (and
heated, more wasted $$$$) so the result is a more drafty house and one that
requires a great deal of humidifying--
3) Variable speed vs fixed speed fan. Carrier dealer recommended
against variable speed for my ductwork. He did not recommend the
variable speed motor for my ductwork because it went from square
ducting to round ducting ,and something about the turbulence
caused by the transition causing the motor to run at higher speeds
for longer than it should--some mention perhaps of a sensor of
some sort? How do Carrier's variable speed motors work?
The Frigidaire dealer was very pro-variable speed, although they
couldn't seem to explain to me my question about "what dictates
the speed the fan runs during a cycle? Is there a sensor? Is it
timed?" They told me a lot about dip switches for setting mins
and maxes, but never did manage to "get" that I wanted to know the
control algorithm for the fan speed so I could make sense of maybe
why they were all for variable while the Carrier guy was not.
4) Dual stage furnace vs single stage. The Carrier dealer, who'd
ruled out variable speed based on my duct configuration, said a
2-stage would bring me more comfort and evenness of heating temp.
The Frigidaire dealer wasn't pushing 2 stage since variable speed
addressed the comfort issue.
I don't have a two stage thermostat so can't take advantage of some of its
features. Having said that--I think that you would still be much better off
with a two-stage furnace and variable speed fan. With this configuration,
when the stat calls for heat it starts off on the first stage (somewhere
around 60-70% capacity, not too sure ) and low fan speed. Since I don't
have a two-stage stat, I've set the dip switches such that if the set
temperature is not satisfied after 10 minutes, the second stage kicks in and
the fan ramps up to it's high speed setting. On cold days the furnace comes
on more often but most of the time it doesn't get to the second stage. The
end result is a more even house temperature with the typical hills and
valleys no longer evident. Additionally, since the combustion air is coming
from the outside the house is not as drafty and requires less
humidification. Don't have to fill the humidifier water bottles as
frequently as before the new furncae installation.
5) 13SEER vs 15SEER. If it only cost $300 more, would ya do it?
Carrier dealer had this option for mein the quiet Performance
series (I like quiet given the configuration of my yard and its
use i the summer). Both dealers seemed to feel the federally
mandated 13SEER was plenty efficient for our area. In the Carrier
dealer quote, I had 13SEER comfort and 13SEER performance options
with a $300 spread between them for the better noise package.
Another $300 gets me to 15SEER and quiet.
6) R410A vs R22? Carrier dealer recommended the R410A versions of
their units vs the R22 as it was only $75 more to get the more
eco-friendly refrigerant that'd be around for the forseeable
future, plus the R410A units were a lot more reliable and had
longer warranties because they cooperate with lubricants a lot
better than R-22. The Frigidaire dealer was quiet on this issue
as they didn't appear to have any R410A units available.
7) Do furnace and A/C simultaneously? Or not? One one hand I'd like
to hold onto the $2500-$3500 the A/C would cost rather than
dropping that into the bucket now. The Carrier dealer said I
would only save about $250 in installatoin labor by doing them
both at the same time. The Frigidaire dealer seemed to push at
least replacing the A/C coil with the heater even if we waited on
the outside unit. The A/C currently seems to work well now,
though we do have a pretty good temp difference upstairs and down
even when running our current single speed blower 24/7. I don't
see a new unit making any difference in comfort, but we would see
a few months of energy savings.
Company #3, another larger place, comes tomorrow.
Thanks so much for any thoughts or advice with these issues!
Best Regards,
--
Todd H.
http://www.toddh.net/