I'm replacing my oil furnace and I'm deciding between a single stage or a 2
stage furnace w/ variable speed fan. I was just wondering since my house is so
old, will it make any difference to get a 2 stage furnace w/ variable speed fan?
it's about a $1000 dollar difference. Thanks
On Wednesday, July 25, 2018 at 10:26:31 PM UTC-4, Ed Pawlowski wrote:
All a two stage furnace does is fire at a high output or low output.
The higher output is good because it will get the temp up faster from
being setback, when you come home and turn it on, when you've been
away on vacation and turn it on, etc. There are also wifi thermostats
now where you can turn it on from your phone, so that can also get
the temp up on the way home.
The low output is good when it's not very cold out and/or it's just
maintaining temperature. The lower firing allows the furnace to run
longer, move more air, distribute it more evenly through the whole
house. If you get a two stage, make sure you get a two stage thermostat
to go with it. A two stage thermostat, the thermostat makes the call
on which stage to use. If it knows the temp has to go up a lot, it
will call for high, otherwise it will use low. With a regular thermostat
a two stage will make the decision, based on how long it's been running.
After it's run like ~7 mins, if it's still running, then it will kick
up to high.
Variable speed blower, IMO, may be far less desirable. I don't think
fully variable speed adds much. I have an ECM, which like variable
speed, is an ECM motor. The big advantage to either is they use
substantially less electric than a conventional blower. How much
that saves depends on how much you use it and the elec rate. The downside
is that the motors have electronics in them, are more failure prone
and if they fail, instead of looking at a $150 motor, you're probably
looking at $600. I also had an ECM fan motor on the AC condenser outside.
It failed after just a few years. New one was like ~$350. I found
a conventional motor that would replace it for $90. IDK how many years
it would take to make up that difference in electric, but I suspect
it's a very long time, given the usage here. For a furnace blower in
a colder climate, the payback could be sooner, but I still suspect it's
many years. Say it's ten, is it worth it, given that if the motor fails
in six, you have to pay 4x more for a new one?
On Thursday, July 26, 2018 at 10:24:05 AM UTC-4, email@example.com wrote:
And also factor in that for my condenser fan, the $350 price was the lowest
price I could find online. If you can't do the repair yourself, have to
call an HVAC guy, that motor could be $500 plus labor and the replacement
would have the same crappy electronics in it. IDK if an HVAC guy would
put in a split phase motor instead or not. It takes a bit of smarts for
one thing, to look up the specs on the two and find the equivalent one.
The furnace ECM I think is paying back faster, the electric bills in winter
are lower, but I've also put in LEDs, etc that could be part of it. But
the biggest savings were in the gas bill for the furnace and elec bill in
summer with AC. Gas bill went down by ~40%, elec bill probably about the
On Thursday, July 26, 2018 at 9:20:15 PM UTC-4, catalpa wrote:
The $1000 difference he was quoted sounds way high too. The two
stage is essentially a gas valve that opens part way or full.
The variable speed blower, if it's being compared to a regular,
non-ECM blower, there is some more substantial difference there,
but you can buy those furnaces retail with maybe a $300 delta.
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