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Old 09-08-2009, 05:24 PM   #16
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I would not put anything less than a 60k in that home. The amount of reserve would not be that great with the numbers I am seeing for Alberta.

Sometimes it's just better to err on the safe side.

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Old 09-08-2009, 05:34 PM   #17
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I would not put anything less than a 60k in that home. The amount of reserve would not be that great with the numbers I am seeing for Alberta.

Sometimes it's just better to err on the safe side.
All the more reason to do a load calc.

His house might only need 31,000 BTUs.

Making a 45,000 90% a furnace that has a 23% safety.
Or a 50,000 90% that gives him 31% safety.

Why put a 2 to 3 times the size needed monster in. When a load calc will save him money both upfront in install cost. And in operating cost.
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Old 09-08-2009, 05:52 PM   #18
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I would pay a few $$ and do the load calc:Load Calculator and let us know the results.

Why would you buy a mid, you would be far better off with a high efficiency unit in the long run. With that home improvement 15% grant a high is a better choice. Mids are almost as expensive as some high efficiency units. Here is what I would recommend for our climate:

I would recommend a Lennox G61V or G71MPP 90,000 BTU model. Possibly a 70,000 if the load calc warrants it. The reason being that if you use a true 2 stage thermostat the G61 will run a LOT of the time at 56,000 BTU's on low fire and the rest 81,000 BTUs when we get the damn -40F stuff. The G71 is even better as it will run at low fire of 34,000 BTU's and will modulate up to the full capacity (81,000) and be VERY comfortable. The G71 is a modulating unit. Both should use a proper 2 stage thermostat and have 6 wires to it. You should go with R40 in the attic and 3 pane low_e argon windows.
The mid will take the combustion air from your house and that is $$ being sucked in and pouring up the chimney. I would like to know the load calc results before recommending a mid. 110 may be too big and 90 too small. These are Lennox units, Carrier and Trane and other may use, 60/80/100 models. Lennox uses 45/70/90/110.

Guys you need to factor in windchill factor, we need some extra capacity for that.
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Old 09-08-2009, 06:18 PM   #19
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Guys you need to factor in windchill factor, we need some extra capacity for that.
Around here, we usually use a 10, sometimes 15 MPH wind if the house is in the open.
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Old 09-08-2009, 06:20 PM   #20
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All the more reason to do a load calc.

His house might only need 31,000 BTUs.

Making a 45,000 90% a furnace that has a 23% safety.
Or a 50,000 90% that gives him 31% safety.

Why put a 2 to 3 times the size needed monster in. When a load calc will save him money both upfront in install cost. And in operating cost.

May look good on paper, but I know a lot of guys who would have a bad gut feeling about something seemingly as small as that.

I come up with 39900 out by short form. I know this is a good accurate number cause I have had a friend run numbers on his load calc. It's not just ball park . But since a 45k won't have enough juice and a 55k is is not in my equipment line up I would still do a 60k.
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Old 09-08-2009, 06:23 PM   #21
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May look good on paper, but I know a lot of guys who would have a bad gut feeling about something seemingly as small as that.
Thats the problem.
Guys go by gut. Instead of doing the work to measure and do an accurate load calc. And then recheck there measurements and numbers.

So they never find out how reliable a load calc is. They just take short cuts.
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Old 09-08-2009, 06:25 PM   #22
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My brand doesn't have a 50,000 either. So I would be a 60,000 also.

My point was when he is looking at different brands. He can choose one that will be sized closer to what he needs if he wants.
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Old 09-08-2009, 06:34 PM   #23
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Thats the problem.
Guys go by gut. Instead of doing the work to measure and do an accurate load calc. And then recheck there measurements and numbers.

So they never find out how reliable a load calc is. They just take short cuts.
You miss my point. When I say the "gut feeling" I am talking about guys who got burned by load calcs for that small a unit.

I did too. Look at the all threads that gripe about the diff in results form soft ware to soft ware vendor.

I put a 60k 2stg 95% VS in a 1200 sq ft brick ranch that never got off second stage below 40*f. And that is mild for around here.
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Old 09-08-2009, 06:40 PM   #24
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Around here and Edmonton we easily get 30 or more mph winds. Until you have lived in a severe climate you don't ever want to undersize a furnace. The other issue is quality of house construction. Older homes don't have the well sealed vapor barrier in the walls etc as the new ones. My mother has a 80,000 Lennox Pulse in a 40 yr old house like his and her bills are cheap, so bigger does not necessarily cost more. That Pulse is 94% efficient, 28 yrs old and still kickin.
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Old 09-08-2009, 06:40 PM   #25
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My brand doesn't have a 50,000 either. So I would be a 60,000 also.

My point was when he is looking at different brands. He can choose one that will be sized closer to what he needs if he wants.

Even if I had a broader size choice I would still choose 60k cause I just feel in a home 1000 sq ft up to 1500 sqft that size would be the least likely to give you an unwanted surprise on a unusually cold day.
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Old 09-08-2009, 06:48 PM   #26
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Around here and Edmonton we easily get 30 or more mph winds. Until you have lived in a severe climate you don't ever want to undersize a furnace. The other issue is quality of house construction. Older homes don't have the well sealed vapor barrier in the walls etc as the new ones. My mother has a 80,000 Lennox Pulse in a 40 yr old house like his and her bills are cheap, so bigger does not necessarily cost more. That Pulse is 94% efficient, 28 yrs old and still kickin.
That's why i would go with a 60k. I did not want to speak for a part of Canada I know only from what I read. But being to Toronto one winter was enough to make this Greek want to stay South of Windsor. The wind is a bear there so i can imagine how it must be in the more arctic like regions of Canada.
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Old 09-08-2009, 06:53 PM   #27
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Aw common, you like our beer. Its a dry cold and you get used to it. Important to have a good sized heater in your house or fishin shack.
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Old 09-08-2009, 07:01 PM   #28
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Aw common, you like our beer. Its a dry cold and you get used to it. Important to have a good sized heater in your house or fishin shack.
Yeah, get stranded with a butt load of Molson and Labatts and you won't even need embalming when they find you, hell, you won't even be frozen thanks to that good Canadian brew!
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Old 09-08-2009, 07:04 PM   #29
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LOL 30 MPH winds.

Bet there were a lot of blown out pilot calls back in the day.
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Old 09-08-2009, 07:05 PM   #30
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Around here and Edmonton we easily get 30 or more mph winds. Until you have lived in a severe climate you don't ever want to undersize a furnace. The other issue is quality of house construction. Older homes don't have the well sealed vapor barrier in the walls etc as the new ones. My mother has a 80,000 Lennox Pulse in a 40 yr old house like his and her bills are cheap, so bigger does not necessarily cost more. That Pulse is 94% efficient, 28 yrs old and still kickin.
Higher winds require higher infiltration rates to be used.

Thats what many miss. They use average, or tight construction ratings.
When the home is actually loose. While a .7 may be ok for many homes.
In high wind areas, a 1, or 1.25 may be more appropriate. And makes a BIG jump in the BTU requirement.

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