Copper vs Aluminum?

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Brock
Brock Solar Expert Posts: 639 ✭✭✭✭
in Advanced Solar Electric Technical Forum #1
I will helpfully upgrading our array this summer I was looking at upgrading the line from the combiner panel to the charge controller about 45 feet. Right now it is #4 and I was going to go to 2/0 or 4/0, overkill, but then I won’t have to mess with it again.

So I went to look at prices and aluminum is much less expensive as service entrance cable, but I thought I remembered something about not using aluminum for this? Thoughts?
3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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  • LucMan
    LucMan Solar Expert Posts: 223 ✭✭✭
    #2
    Re: Copper vs Aluminum?
    Brock wrote: »
    I will helpfully upgrading our array this summer I was looking at upgrading the line from the combiner panel to the charge controller about 45 feet. Right now it is #4 and I was going to go to 2/0 or 4/0, overkill, but then I won’t have to mess with it again.

    So I went to look at prices and aluminum is much less expensive as service entrance cable, but I thought I remembered something about not using aluminum for this? Thoughts?

    Stay with copper if you never want to mess with it again, Aluminum is not as good of a conductor of electricity as copper and it has a tendancy to get hot at the connections because of oxidation and expansion and contraction. I have seen way to many Al wires burn off.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,696 admin
    #3
    Re: Copper vs Aluminum?

    You can use Aluminum + Copper with the correct fittings, lube/sealent, and tool+die (power companies do it all the time). They have Al/Cu transition fittings available...

    However, there are many folks that would say to stick with copper.

    Perhaps a local electrician and/or electrical supply house can help you. The price of a crimping tool (if you don't hire an electrician) may just push you towards the copper solution anyway...

    I was trying to look up the parts and process on the Net--but was not very successful.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
    Re: Copper vs Aluminum?

    For wire that size, with the lengths you have,, I wouldn't go with Al at all. The money saved is not worth the aggravation IMHO. How many amps are you going to run through it?

    I have, over the years had all kind of odd, hard to find problems with AL,, at the connectors,, even using anti-oxide pastes and proper connectors.

    T
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Copper vs Aluminum?

    as was mentioned the aluminum doesn't handle as much power for the same sized wires, so going to al would mean thicker wires over what the copper would be for the same amount of current to flow through it. the voltage drop calculator's figures would also be wrong for al as it is based on the resistances of copper.
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  • Lefty Wright
    Lefty Wright Solar Expert Posts: 111 ✭✭
    #6
    Re: Copper vs Aluminum?

    Two reasons to avoid aluminum wire.

    Cold flow and oxidation.

    When aluminum is compressed the material migrates and the connection is then loose. Connections should be tightened at least once a year.

    Copper oxide is a conductor but aluminum oxide is an isulator. As the connection loosens (due to cold flow) the oxygen enters and oxidises the metal until you loose the connection. Or until heat generated by the decreased surface area burns up the connection.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #7
    Re: Copper vs Aluminum?

    Edison company ran coarse strand alum wire to my 200A service panel in '90.
    It is attached to the meter terminals with screws - something like a 5/8 giant set screw, with No-Ox goop on them. Been fine AFIK since then, but they know what they are doing with it.
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  • Malasombra
    Malasombra Solar Expert Posts: 24 ✭
    #8
    Re: Copper vs Aluminum?

    Another (maybe?) problem if you use Al is the maximum connection size in diferent items, breakers ,regs, etc.....not familiar with AWG standar, sorry
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  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    #9
    Re: Copper vs Aluminum?

    Thanks I will stick with copper, everything else is copper anyway. Right now I am running two sets of four panels in series (about 70v) to the MX-60 at about 14 amps on #4 wire. I plan to double the size of the array. I know using the calculator I could get by with just adding another #4, but if I am going to put in new wire I might as well put in enough to handle what I can eventually throw at the MX-60 which would be around 60 amps.

    It looks like I can get either #4 copper then they skip to 3/0 copper. The 3/0 is feeder with a #2 ground and looks pretty stiff to work with I will look for it in single wire although that seems to be more expensive since it isn't as common.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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  • jacobs
    jacobs Solar Expert Posts: 72 ✭✭
    #10
    Re: Copper vs Aluminum?

    If installed correctly, aluminum is very safe and trouble free. If it wasn't, utilities would not use it in transmission lines and loops into homes. If you do decide to use aluminum, use plenty of nocorrode and securely tighten joints.
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  • StorminN
    StorminN Registered Users Posts: 12 ✭
    #11
    Re: Copper vs Aluminum?
    Brock wrote: »
    It looks like I can get either #4 copper then they skip to 3/0 copper. The 3/0 is feeder with a #2 ground and looks pretty stiff to work with I will look for it in single wire although that seems to be more expensive since it isn't as common.

    Brock, #4 to 3/0 is a big jump... you should be able to find #2, #1, 1/0 or 2/0 copper... ask at your local electrical supply house...

    -N.
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  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    #12
    Re: Copper vs Aluminum?

    I did actually just stop by a local electricians shop, the problem is their wire (#2, 0, 2/0) was more expensive than the 4/0 at the "box" store. The more I look at it, it would really be a pain to work with that 4/0 wire.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #13
    Re: Copper vs Aluminum?

    #4/0 cheaper than #2? you better look at more places for prices i think.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #14
    Re: Copper vs Aluminum?

    Home depot carries #2 & #4 , I use and purchase it just last month from HD
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  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    #15
    Re: Copper vs Aluminum?

    Ya, Home Depot does have #2 up here as well, the other 3 box home stores didn't. In general their wire was more expensive, but cheaper than 4/0.

    Thanks!
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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