Reply90,000 sounds grossly over sized for a house of your size.
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Hey Everyone,
I got a couple quotes and different opinions on sizing for new furnaces. I am replacing 2x25 year old 90,000 btu lennox furnaces.
I am looking at 2 95% efficient furnaces with ECM motors.
My house has the upstairs which is 850 sq ft, the main is 950 sq ft
one furnace runs the upstairs the other runs the main floor and 2 vents in the basement. (not need much heat down there)
one quote said a armstrong air 90,000 for main floor and a 70,000 for upper.
the other quote said 2x 60,000 goodman furnaces. and told me a 90,000 is way to much for the size of the house.
Can anyone chime in and let me know what they feel would be good sizing for the 95% efficiency furnaces for the sizes of my house.
Cheers,
djrocketodd
God Speed, Jim. We'll miss you - 2-26-23
90,000 sounds grossly over sized for a house of your size.
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180,000 on 1800 sqft a bit much. Resizing both will probably require more then just replacing the units. Should be able to handle that space with much less but it's really not that easy to get there from here.
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Do you live in Alaska with paper walls. I've done 1800 sq feet with one 60,000 furnace in northern central Ontario do you self a favor and get a heat loss calc done on your house
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Where is this house located. ???
Sounds very very over sized to me
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In our cold climate for a house of that size we would have 1 70,000 BTU furnace typical construction. So I can't imagine meeting anywhere near what those dealers are suggesting.
Find a good dealer who will do a heat loss calculation.
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I live in Calgary Alberta, so it does get a little cold and the house was built in 1986. I want to keep the split of main and upstairs separate since there is no zoning in the house. Thanks for the input, i felt 90k was a bit overkill as well.
Professional Member*
2 - 40,000 btu units sound just about right.
"Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler
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+1Originally Posted by 2old2rock
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Might even want to go to the next level and get a pair of 2 stage 40-45,000 furnaces. There's not much cost difference and quite a bit more comfort. The upstairs unit will probably never go to high fire.
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Ya. What he said.
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Ditto
Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities
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Love Calgary, awesome town.
x3. Nice suggestion.
Look for turn-down to 20-24k. Then the equipment will only be over sized 20% of the time instead of 90%.
Get a load calc and blower door. Please share cfm50 number, and make sure they use that leakage in the calc.
Professional Member*
A double furnace install is common in Calgary and most builders oversize on new homes here so people don't complain of being cold. It has been known to get to -45*C in the winter here.... Recently.
If you put 2 45's in I doubt they'll shut off ever, when we get those cold snaps.
I agree the 90 is too big, I would look at something in the 60-70mbtu range for the main and a 45 for the top floor. 2 stage and ECM for sure.
A 2 stage 70 will start at 40-44,000btu on low fire to keep your costs down and you'll have that extra capacity when needed.
Make sure they run enough wires so you can actually control the 2nd stage!
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Maybe this will get popular for AC too.... install a 2 stage 2 ton unit and a 3 ton unit when the design calls for 5 tons and you can go from about 1.5-5 tons in up to 5 stages. (1.5, 2, 3, 4.5, 5)Who needs a stinking inverter drive! Then again, you could also just throw in a 2 circuit coil and use a single 5 ton air handler and keep costs reasonable. Hmmm... maybe on my downstairs, rather than a 2.5 ton single stage unit, I put in a pair of 1.5 ton units and to try it out. It would run on 1st stage almost continously for a good part of the summer.
Another thought, I suppose you could use a single AC unit with 2 coils as well. I wonder if you could take for example a 4 ton 2 stage unit, split 2 linesets, then install 2.5 ton coils co they could run invididually on low stage, or both on high stage.
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You seem to be straddling a line here. Do you think the fact they'll never shut of is a good or a bad thing? I can't tell.
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(2) 45's will use about $1/hr at average gas costs. Are you OK with a $720 gas bill caused by a cold snap or would you be willing to bundle up for a month? Bigger furnaces of course would cost even MORE to run !!!
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Good point. Back into it.
$720 running flat out, ever have a bill even 1/2 that?
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I just pulled up a load calc I did on a 2100 sqf house that was built in 1988 and changed the outdoor design temp to 0 degrees and the load for the whole house came out to 57,276 BTU. 72,341 BTU for -20 outdoor design temp. Although your home is obviously different I'd bet the farm that 1 90,000 BTU furnace would be too big, much less two of them
Edit* House had R38 in the ceiling, R19 in the crawlspace, R13 in the walls, double pane vinyl frame windows
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