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Joined: Aug 2002
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I am hoping someone can help me determine the maximum allowable current carrying capacity for Aluminum Busbar. I need to install some busbar. I have 1/4" X 4" and 3/8" X 4" to choose from. What is the ampacity of each? Would you please tell me how to figure this out and cite reference, if possible? Thank you all so much! I really like this board!
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Joined: Oct 2002
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Joined: Apr 2002
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Gregory, a conservative rule of thumb for Aluminum is 700 amperes/in². Based on that, ~700/1150A. {Suggest Belleville washers while you're at it.}
Copper—1000 amperes/in² See 99NEC 374-6(a).
[This message has been edited by Bjarney (edited 01-07-2003).]
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Joined: Jul 2001
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There are several factors to consider.
What temperature rise above what ambient? What is the conductivity of the conductor (an old book shows two types of aluminum EC - 61%IACS and EC-T61 - 57%IACS)? What is the orientation of the bars, flatwise or on edge? Are bars mounted above each other (stacked)?
For example: 30 deg C rise over 40C ambient, still but unconfined air EC-T61 aluminum Edgewise orientation, bars spaced at least one thickness apart. AC 60hz current
3/8 x 4 = 1170A 1/4 x 4 = 960A
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Joined: Aug 2002
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Thank you all for your replies.
JBD, I was wondering where you found the info to calculate the ampacity? Why does it matter which way they are stacked?
Thank you!
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Joined: Nov 2000
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Heat rises? Just a guess...
-Virgil Residential/Commercial Inspector 5 Star Inspections Member IAEI
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Joined: May 2001
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It sure is nice to have an old Anderson Reference book. Mine is a '64 version also, and I use it many times to get information not readily available. I wish they would reprint it, or publish it on the web.
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