6061 Aluminum for a Busbar

Farmerboyz1721Farmerboyz1721 Posts: 39Registered Users ✭✭
Any feedback on using basic 6061 Aluminum for a homemade busbar? 

Comments

  • BB.BB. Posts: 27,931Super Moderators, Administrators admin
    edited April 2016 #2
    While it can be done--I would suggest avoiding doing this unless this was a very temporary usage.

    Aluminum has several properties that make using as electrical conductor "difficult".
    • Aluminum forms an oxide layer within seconds of being exposed to oxygen in air. Good connections need to be "sealed" from the air and need to "break through" the oxide when being connected. There are aluminum crimp connectors that have a special grease and when crimped will exclude oxygen from the electrical connections. Using star lock washers and special grease can make "better" connections with an aluminum bus bar.
    • Aluminum "flows" under pressure. Both under pressure from bults+nuts (you need to retorque connections, especially a few weeks after you first install). And under heat (joint gets hot, aluminum "flows" or extrudes from point of contact. Joint cools and a little separation occurs, and you get oxygen in the joint, reduced area for current flow. Joint gets hotter next time, more flow--Repeat to failure.
    • Do not bolt pure copper (terminal ends, wiring) to ALUMINUM (correction) bus bar surface. Dissimilar metals will tend to corrode. Use tin plated terminal ends (for sample) when bolting to aluminum.
    • No-Ox or similar grease to prevent corrosion of connections.
    • One can plate silver, tin, copper, or nickle on aluminum to improve electrical characteristics (factory built bus bars). I am not sure if this is a DIY type project.
    Here is a link to issues with older homes that have aluminum wiring:

    Aluminum Wiring Hazards

    Properly done, aluminum can make for good bus bars--But as a DIY project (make your own bus bars), I would suggest that you do a lot of research first. Here is a handy table for Aluminum bus bars:

    http://www.wmwa.net/metal-products/aluminum/aluminum-bar/

    Off grid power systems can be "worse" than typical grid/generator powered systems. With battery banks, we have lower voltages and higher currents--Plus you can charge batteries at near equipment capacity for 5+ hours of maximum current... Most AC / home wiring only "sees" a fraction of rated current for short periods of time. And when operated near capacity for long periods of time 9such as charging your battery bank), I would suggest you derate the wiring (be more conservative) than NEC does. (i.e., instead of 1.25x derating, you may want as much as 1.25x1.25 derating to account for charging battery bank).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Posts: 7,923Solar Expert ✭✭✭✭
    in a pinch you can get some copper plumbing pipe, flatten it out and use it,  Much better than aluminum,  There are different thicknesses of copper ( B, K, L or M) and somewhere from 1/2"di thru 1" di should work,  There was some stuff on the web about the resisitivity of water pipe.
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  • BB.BB. Posts: 27,931Super Moderators, Administrators admin
    John P made some tests of copper water pipe in this Discussion:

    http://forum.solar-electric.com/discussion/comment/108378/#Comment_108378

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Farmerboyz1721Farmerboyz1721 Posts: 39Registered Users ✭✭
    I know that copper is better conductor. However, as we know aluminum is much cheaper. I also know that power companies use aluminium all the time for busbars because of cost. But, they use a 6063 or a 6101. This got me to think that if you size it properly, then you could use any kind of  aluminum. 6101 is 57% of copper, 6063 is 53% of copper, and 6061 is 42% of copper. So, for $15 bucks i could get some 6061 and still accomplish the ampacity necessary. Now, it might not last as long as copper but as long as it is being managed i would think it will work.  
  • BB.BB. Posts: 27,931Super Moderators, Administrators admin
    Are you sure about your 6101 (and probably 6063) alloy composition... Everything I could find listed Cu as 0.10% maximum in 6101 alloy.

    http://www.aalco.co.uk/datasheets/Aluminium-Alloy-6101-T6-Extrusions-Bar_356.ashx

    Aluminum is used in long distance transmission lines where light weight and high strength is needed (I think I have seen steel cable centers too in some transmission lines decades ago).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Farmerboyz1721Farmerboyz1721 Posts: 39Registered Users ✭✭
    To clarify what i mean by my % that i stated above. This is NOT about composition but about electrical conductivity. The percentages are based on the IACS (International annealed copper standard). The idea being that the 6061 is 42% of copper, means that it is 42% less conductive then copper. Now, we can use ampacity bus-bar charts of copper and take 42% of that for using aluminum 6061.

    Here is a link to most of my reference for this information. http://www.aluminum.org/sites/default/files/aecd13.pdf 
  • westbranchwestbranch Posts: 5,090Solar Expert ✭✭✭✭
    edited April 2016 #8
    I think you may have this wrong the 6061 is 42% of copper, means that it is 42% less conductive then copper,  can not get to your link, so I would read that to mean that 6061 is 56% less conductive than copper is
     
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  • VicVic Posts: 2,908Solar Expert ✭✭✭✭

    Farmer...,

    YES,  AL is commonly used in buss bars,  terminals,  etc,  in the electrical industry.   BUT,  it is almost always plated/coated with some other metal,  like Tin.  This coating keeps the AL from oxidizing,  and therefore reduces the risks of using Aluminum.

    AND,  to me,  when one says,  "6061 is 42% of copper",  when speaking of conductivity,  read it as,  6061 is 42% as conductive as it Copper.   Could also be read that it is composed of 42% Copper ...

    FWIW,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • solar_davesolar_dave Posts: 2,334Solar Expert ✭✭✭✭
    The composition of 6061 has virtually no copper! ;)
    The alloy composition of 6061 is:
    • Silicon minimum 0.4%, maximum 0.8% by weight
    • Iron no minimum, maximum 0.7%
    • Copper minimum 0.15%, maximum 0.4%
    • Manganese no minimum, maximum 0.15%
    • Magnesium minimum 0.8%, maximum 1.2%
    • Chromium minimum 0.04%, maximum 0.35%
    • Zinc no minimum, maximum 0.25%
    • Titanium no minimum, maximum 0.15%
    • Other elements no more than 0.05% each, 0.15% total
    • Remainder aluminium (95.85–98.56%)
  • Farmerboyz1721Farmerboyz1721 Posts: 39Registered Users ✭✭
  • VicVic Posts: 2,908Solar Expert ✭✭✭✭

    Hi Farmer..,

    That is a sporty table, indeed.   But it is not clear what issue/concern it might be addressing.

    It is beginning to appear that you really DO want to use AL busses,  and perhaps these busbars might well NOT be coated or plated with a metal that will render them less unsafe ...   it this correct ??

    Thanks,  Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Mountain DonMountain Don Posts: 493Solar Expert ✭✭✭
    edited April 2016 #13
    I believe the commercially available aluminum buss bars are tin plated, at least at the electrical connection point.. The tin plate eliminates the aluminum oxide issue. Copper or silver can also be plated on the formed aluminum buss bar.  So perhaps the biggest drawback to using aluminum is the problem encountered when trying to do a cheap(er) DIY aluminum buss bar.  
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