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Copper butt Connector with Aluminum wiring

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  • Copper butt Connector with Aluminum wiring

    Hi,
    i’m installing ground mount solar and running 4 awg aluminum wire. One of my strings ran short, so I connected more aluminum wire using a copper butt connector and the heat shrink tube. I was just reading that you should not combine aluminum and copper.

    Is it really a big deal? I already pulled the wire through my conduit. Of course I can pull it back out and replace it with an aluminum butt connector – but that’s a pain.

    thanks in advance for any help
    Steve

  • #2
    Most of the butt splices rated for aluminum, are tin plated copper, not plain copper and I think aluminum no-ox joint compound is supposed to be used.

    Because of thermal mis-match, the copper/aluminum couple will eventually fail, start heating up from high resistance, and melt it's way through insulation till something stops working. If it was my project, I'd pull that wire out and re-do it properly with rated parts. It will save you the bother of doing it in 6 years with all the wires melted into a glob.

    Power transmission runs lots of power, for hours at a time, and the cables get much hotter than household wires that generally only run intermittently.
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      I think it is a big deal. I also think you should check the code to see if splices are even allowed in conduit. My understanding is they are supposed to be in junction boxes.
      9 kW solar. Driving EVs since 2012

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      • #4
        Originally posted by Ampster View Post
        I also think you should check the code to see if splices are even allowed in conduit. My understanding is they are supposed to be in junction boxes.
        I also do not think splices are allowed in conduit. I think they're supposed to be accessible.
        I believe this is the relevant code section:

        300.13 Mechanical and Electrical Continuity — Conductors
        (A) General Conductors in raceways shall be continuous between outlets, boxes, devices, and so forth. There shall be no splice or tap within a raceway unless permitted by 300.15; 368.56(A); 376.56; 378.56; 384.56; 386.56; 388.56; or 390.6.

        So -
        I think it's time to buy some longer wire and re-pull

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        • #5
          Thanks so much for the quick replies

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