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Old 09-06-2009, 11:11 PM   #1
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I have a 1978, 1200 sq feet house with a 96K BTU output. I live in Edmonton, Alberta Canada and it gets pretty cold in the winter months. Can I replace this furnace with one that has 80K BTU output? It seems like the one I have in there now is over-calculated as I heard that, that was the practice back then. Please advise. Thanks in advance.

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Old 09-07-2009, 04:46 AM   #2
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Maybe.

Best to do a load calc, and find out for sure.
HVAC CALC is advertised here. Its a good program. Try it. It will also let you do what ifs.
What if you add insulation to what ever area. Then it will tell you how much that will reduce your heat loss. So you know if its worthwhile doing and has a ROI.

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Old 09-07-2009, 09:18 AM   #3
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Beenthere,

Thanks. I realize that that is the most exact way of doing it. I figure, the load calculator will arrive at 2 possible scenarios - it will say that if I replace my windows and add an extra insulation in the attic, etc. I can go down to 80,000 BTU output; if I just leave the way things are, the 96,000 BTU is just right. I plan to fix my windows, replace weather stripping on the outdoor doors and I usually caulk my windows prior to winter ( removable caulking ).
There are some generic calculator here on the internet and when I punch in my numbers, 1500 sq feet and the region of Alaska ( it is asking for USA zip code ), it gives me 64,000 BTU.
I also have a brother-in-law whose 1999 house is 2000 sq ft. 2 storey in the same area as mine and he has an 89,000 BTU output. Mine is only 1075 square feet, but since it is a bi-level I estimated it to be 1500 sq ft. because a bigger part of the basement is elevated from the ground as opposed to a bungalow.
And when I asked some people in the trades, they say 80,000 BTU output is plenty. I am really in a dilemma so I thought I post it in here and hopefully get lots of replies and lots of different scenarios.
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Old 09-07-2009, 09:22 AM   #4
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My 2 floor Cape I did the sizing & came up with 68,000 for the original size before my additions
Approx size was 1640 sq ft - mostly 1st floor
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Old 09-07-2009, 09:26 AM   #5
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Use the load calc program to see what you need with your homes current construction.

You mind be suprised to find that your furnace is already 40% oversized.

Generic web based programs just use rules of thumb for the area your home is in. They aren't very accurate at all.
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Old 09-07-2009, 09:57 AM   #6
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Yes - I did the calc with the additions & the current furnace will heat it all
But its over 21 years old & needs to be replaced
I heat a lot with wood so its hanging in there for now
I wanted to wait until the additons were roughed out before new furnace & piping went in
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Old 09-07-2009, 12:31 PM   #7
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Sorry. I was replying to the OP, mindoreno.
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Old 09-07-2009, 12:40 PM   #8
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Mindoreno, does your furnace have a pilot light? Give me the make and model and serial# and I can narrow the process down for you. Wpg is much the same climate as Edmonton.
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Old 09-07-2009, 10:35 PM   #9
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Yuri,
Thanks. I have a Lennox G8-120-1, serial number 6379A86213. It has 120K BTU input and 96k BTU output and it has a pilot light.
My house is built in 1978. It is a bi-level 1075 sq ft. with original big wooden windows. Again some of my refrigeration friends have said that a 100KBTU input with 80K BTU output is plenty. I am looking at buying a mid-efficiency since this is the last year we are allowed to purchase them. I am planning to fix my windows next year. I have a poured in insulation in the attic with normal thickness I am guessing. I am also planning to replace one of my 2 outside doors soon. Besides the size of the furnace, another question is what CFM should I get, 1600 or 2000. I heard that 1600 is plenty and 2000 can be a little noisier. Please advise and thanks very much.
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Old 09-08-2009, 04:16 AM   #10
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You REALLY should do a load calc, instead of just wild guessing. And saying good enough.

A load calc can save you money on your heating bill, by allowing you to get the right size furnace.

CFM of the blower is more dependent on the A/C your house needs.

Newer furnaces need to move more air then older ones did. This makes proper sizing more important then it was for the older furnaces.

Why mid efficiency? Why not a 90%plus. And save even more on your heating bill in the future.

Good chance a 70,000BTU input 90% would be plenty for your home, with its current insulation and windows.
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Old 09-08-2009, 07:02 AM   #11
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I did a short form for you and subed your Alberta temps for Drtroit MI.

70 or 75k (btus in ) @ 95% will give you more than enough heat with a reasonable amount reserve
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Old 09-08-2009, 03:49 PM   #12
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Check out this link

http://www.saskenergy.com/Residentia...naceSizing.pdf

It has the calculation for the size of the furnace vs the size of the house and it takes into consideration the thickness of the insulation on the walls in the main floor and in the basement and also the thickness of the insulation in the attic or ceiling.
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Old 09-08-2009, 03:56 PM   #13
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It just a rule of thumb one also.

Read note 4 on it.

You want to use a free garbage one. Go ahead.
That one will oversize you by a lot.

Pay the small fee, and use This One
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Old 09-08-2009, 04:07 PM   #14
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Quote:
Originally Posted by beenthere View Post
It just a rule of thumb one also.

Read note 4 on it.

You want to use a free garbage one. Go ahead.
That one will oversize you by a lot.

Pay the small fee, and use This One
Prob with a house that small is that most of the mfgs smallest furnaces are TOO small.
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Old 09-08-2009, 04:13 PM   #15
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Quote:
Originally Posted by hvaclover View Post
Prob with a house that small is that most of the mfgs smallest furnaces are TOO small.
Bet checking different brands of furnaces, you can find sizes 40,000, 45,000, 50,000 60,000, 70,000, and 75,000 BTUs.

Without a problem.

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