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Old 12-05-2012, 06:08 PM   #1
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High altitude derating


Trane uses this statement in their product specs for high altitude installations of their residential furnaces,
2 For U.S. applications, above input ratings (BTUH) are up to 2,000 feet, derate 4% per 1,000 feet for elevations above 2,000 feet above sea level.
So my question, for an 8000 ft installation, do you derate 4% per 1000 ft starting at sea level and or do you derate for every 1000 ft above 2000 ft, ie (8000-2000)/1000? Also, is the calculation as simple as for example, 8000/1000 ft * .04 or is it for example, 100,000-(100000*.04)=E1 then E1-(E1*.04)=E2, etc until you arrive at E8.

Thanks for the feedback.

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Last edited by PatchD; 12-05-2012 at 06:31 PM.
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Old 12-05-2012, 06:26 PM   #2
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High altitude derating


Reread their statement again. Very specific and clearly stated how you derate. So yes 4% time 6 would actually be 24% derating not 32.

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Old 12-05-2012, 07:14 PM   #3
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High altitude derating


Yep, 24,000BTUs derate. Will need corrected orifices.
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Old 12-06-2012, 11:58 AM   #4
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High altitude derating


Thanks guys for the response. It's 3 to 1 in favor of the 24%, however, the one saying 32% is from a Trane dealer. He finally responded to a phone call yesterday and says he calculates every 1000 ft from sea level. I must admit though, he didn't leave me with a lot of confidence because he was crunching numbers as we were talking and it didn't seem like he does it very often.

I wish I could hear it direct from a Trane product engineer but they give you know access to their engineers which I find very odd.
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Old 12-06-2012, 01:27 PM   #5
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High altitude derating


Engineers wouldn't get anything done if the had to answer hundreds of home owner questions every day
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Old 12-06-2012, 06:57 PM   #6
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High altitude derating


Say 20 residential engineers. Say just 2000 customers/potential customers calling them a day. When would they get time to do any engineering work.


Just 24%. The instructions tell you that you only derate 4% per 1000 foot above 2000 foot. Your only 6000 foot above 2000. And the furnace is fine for elevations between 0 and 2000 foot.

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