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Old 05-10-2009, 05:41 PM   #16
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gettting a new furnace help


Quote:
Originally Posted by beenthere View Post
So what would a 2,000 sq ft rancher, with a 2,000 sq ft basement come out to.

In an area with 5,560 HDDs???

What would a 2,400 sq ft 2 story with a 1,200 sq ft basement come out to, at the same 5,560 HHD's???
Lemme' check.

X BTU/sq. ft./HDD

X/(2000 + 2000)/5560 = 5560X/4000 should equal 4.4, so X should equal 3.2 BTU if this house is as lossy as that in the study.

X/(2400 + 1200)/5560 = 5560X/3600 should equal 4.4, so X should equal 2.8 BTU if this house is as lossy as that in the study.

This study
http://www.focusonenergy.com/files/D...udy_report.pdf
talks about
Btu/ft2 - HDD

I take this to mean BTU/ft²/HDD, which equals (BTU-HDD)/ft² but if they mean
BTU/(ft²-HDD) there is a whole different meaning.

The first meaning is that, for a house of given insulation value, as the HDD goes up the BTU usage goes up, and this makes sense, physically.


Last edited by Yoyizit; 05-10-2009 at 06:04 PM.
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Old 05-10-2009, 05:55 PM   #17
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gettting a new furnace help


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Originally Posted by chemist1961 View Post
so i used 398.7 cubic meters, feb - 28 day billing period with 664.10 degree days. House is 2800 ft including unfinished 1100 ft basement basement, 80,000btu he furnace rated 95% efficient. How much am i losing?
I fine tuned the programmable tstat in march
xxxxxxxxx

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Old 05-10-2009, 06:29 PM   #18
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Any form of HDD to calculate heat loss.
Is BOGUS.

HDD doesn't take daily or nightly conditions into account.

15 HDDs when they come form day light hours.
Requires far less heat/BTUs, then when they come from the dark/sunless/or cloudy days.

But, someone somewhere always tries to come up with a cheat formula.

A heat loss calc is the way to determine what size furnace.

Multiply your per sq ft per HDD using a 65HDD factor and see what you come up with for both houses.
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Old 05-10-2009, 07:02 PM   #19
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That Wisconsin study is scrambling what brains I have left.

398.7 cubic meters = 140 therms of NG in 28 days = 5 therms/day
2900 sq. ft. gives 5/2900 = 170 BTU/day/sq. ft.
170/664 = 0.26 BTU/day/sq. ft./HDD

My house, 838 therms of NG in 90 days = 9.3 therms/day
3100 sq. ft. gives 9.3/3100 = 300 BTU/day/sq.ft.
300/2658 = 0.11 BTU/day/sq.ft.

Mr. 61, I doubt that my 1964 house uses twice the energy yours does. I think your NG provides more therms per cu. ft. than my NG does or you have your heat turned down. We use 73F/64F during the winter.


Mr. There, averaging over a whole winter cancels out day/night/cloud cover variations unless I live on the equator and he lives in a place with perpetual winter cloud cover.

What you trade off with averaging is accuracy.

Maybe with Manual J I get +/- 10%.
Averaging over a winter with Canada and DC maybe gives an error of +/- 20%.
Places with climate extremes may give an error of +/- 100%, which means you have to take other factors into account besides just HDD and sq. ft..

Without data from more Canadian and DC houses, I can't say whether 0.11 and 0.26 is a Statistically Significant difference.
"In statistics, a result is called statistically significant if it is unlikely to have occurred by chance."
That bookmarked study may tell me, if I can figure out their data taking methods.

Last edited by Yoyizit; 05-10-2009 at 07:27 PM.
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Old 05-10-2009, 07:07 PM   #20
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LOL... Lot of studies. And papers written on using HHD to determine load, or fuel use.
but, none of them ever check the house with an accurate load calc later.
They just refudge the math to fit the results. Of teh homes they used.
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Old 05-10-2009, 07:25 PM   #21
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Quote:
Originally Posted by beenthere View Post
LOL... Lot of studies. And papers written on using HHD to determine load, or fuel use.
but, none of them ever check the house with an accurate load calc later.
They just refudge the math to fit the results. Of teh homes they used.
I would hope that engineers fudge less than politicians, but who knows?
My use of statistics to find fudged data is what got me out of a job; half the people but almost no companies tolerate whistleblowers!
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Old 05-10-2009, 07:29 PM   #22
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gettting a new furnace help


An engineer is like any other person.
One will do all the work.
Another will take what ever short cuts he can. And fudge the numbers.
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Old 05-12-2009, 06:10 AM   #23
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Must be the high test NG I'm running. Purely Canadian content, we export the low grade stuff. Sounds like I'm on the right track with the upgrades. Interesting calcualtion, thanks
I'm close to parrallel with Wisconson so similar weather but yes I do have the T stat programed for daytime, nightime, etc. My sled dog came equipped with a fur coat so she doesn't complain. I'm far from being a miser, but we run heat at 68 maximum during the day when home, lower to 62 night time by 11 pm, mid 50's when at work. I just leave the heat running late enough to keep the wife close and cuddly at night as it cools, but avoid the thermal fleece and socks and chilly sheets when we roll down the blankets for bed Every man needs a plan....
Gotta say I love the new furnace an it will only get better as I insulate the attic and basement walls

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