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Thread: Bus Bars: AL vs. CU

  1. #1
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    Bus Bars: AL vs. CU

    This topic has probally been beaten to death already, but here goes:

    Anyone know the pros and cons of using aluminum bus bar in switchboards, panelboards and transformers? My initial reaction was no way. But i cannot find a good reason not to.

    Any links to articles would be helpful

    Thanks.
    C

  2. #2
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    While everyone loves copper, aluminum is less costly.
    I have worked around switchgear and bus-duct for the last 30 years.
    I have never seen a reason not to use aluminum buss.

    I can't remember a time when I have seen an aluminum buss fail.
    Maybe it's my alzheimer's though.
    Tim
    Master Electrician
    New England
    Yesterday's Technology at Tomorrow's Prices

    Answers based on 2011 NEC

  3. #3
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    I would GUESS that they both pass the same UL testing and standards. Copper is probably the better product, but if I'm paying the bill, aluminum is just fine.

  4. #4
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    I suppose there are horses for courses. I came across this forum when I was looking for figures for aluminium busbar ratings.
    This because I was bidding for a project that requires Al bars to be used.
    It's an upgrade to add to an existing rectifier system which currently uses Al bars. In the event, I went to site and physically measured the existing (live) bars - with a plastic ruler I might add....and lived to tell the tale.
    One of the constraints is that there is a 100ft span with no intermediate supports and Ali conductors for the same current are about half the weight of copper.
    That's one of the main reasons why it is commonly used for overhead transmission lines.

    That said, I can't think of any panel board or motor control center where we have used aluminum. Maybe just because customers prefer copper?

    I have been told recently that Cuponal is the way to go.
    It was probably by a sales rep who was obviously being absolutely objective....

  5. #5
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    30+ years in the business, The MCC and switchboards and I-Line panelboards have been probably 75% aluminum. Just about the only time I have used copper for these has been on government projects (taxpayer money).
    Just because you can, doesn't mean you should.

  6. #6
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    Aluminum is actually a better conductor than copper. The bad rep that aluminum carries came from all of the AL wiring used in residences where subsequent work was done without regard to dissimilar metals issues. Also, wires tended to evpand and contract at different rates than the terminal devices, so any sloppiness on the part of the installer would tend to make things worse.

    For bus bars though, these issues just don't hold water.

  7. #7
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    Quote Originally Posted by Jraef
    Aluminum is actually a better conductor than copper.
    Not sure where you got that from nor in what context you intended it....
    Electrical conductivity of copper is about 1.5 times that of aluminium and thermal conductivity about double.
    On both those counts, copper would be considered to be the better conductor.

  8. #8
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    Quote Originally Posted by jim dungar
    30+ years in the business, The MCC and switchboards and I-Line panelboards have been probably 75% aluminum. Just about the only time I have used copper for these has been on government projects (taxpayer money).
    Interesting, that. It just seems not to common practice, at least in UK.
    The only place I have seen aluminium bar used is for projects like the rectifiers I mentioned above. These are usually pretty high current with long runs to the load so there are significant financial savings to be made by using aluminium.

  9. #9
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    Quote Originally Posted by Jraef
    Aluminum is actually a better conductor than copper.

    then why do aluminum conductors have to be larger when using the same size over current protection as copper conductors?

  10. #10
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    Sorry, I was thinking of wire conductors and that aluminum is used because it has a lower resistive density, meaning it can carry more current per pound than copper. That makes it a better conductor for overhead cables, but would be relatively irrelevant in bus bar applications.

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