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#83064 01/07/03 02:31 PM
Joined: Aug 2002
Posts: 19
G
Member
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: Mar 2001
Posts: 2,056
R
Member
Did a search and came up with this, but it is for copper.
Try an internet search. http://www.stormcopper.com/design/Ampacity-Quick-Chart.htm

Joined: Oct 2002
Posts: 67
C
Member
Try NEC 366.7 (A)

Joined: Apr 2002
Posts: 2,527
B
Moderator
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).]

Joined: Jul 2001
Posts: 599
J
JBD Offline
Member
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

Joined: Aug 2002
Posts: 19
G
Member
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!

Joined: Nov 2000
Posts: 2,236
Likes: 1
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Heat rises?

Just a guess...

[Linked Image]


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI
Joined: Jul 2001
Posts: 599
J
JBD Offline
Member
Yes, orientation affects heat transfer.

I got my basuic info from an old (1964) reference from Anderson Electric.

For current aluminum bussing information try: http://www.alcoa.com/afl_tele/en/pdf/catalog/catalogs/BusCondCatalog.pdf

Joined: May 2001
Posts: 176
W
Member
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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