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Exposed copper on MC4 termination

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  • Exposed copper on MC4 termination

    I have recently encountered what is either the worst example of workmanship in a PV installation or a strange phenomenon of nature and time.

    The site in question had at least 50 MC4 terminations with 1+" of exposed copper between the wire insulation and the plastic connector (see images). These terminations were all located at the negative end of each string where the negative from the last module plugged into the negative source wire going to a junction box. None of the positive terminations had this issue. None of the connections inside the junction box or string inverter had this issue.

    This was obviously an incredibly dangerous fire and safety hazard. The only explanations I can think of are:
    1. Someone who was not trained and had no idea what they were doing was tasked with performing these terminations. Many of the crimps were also loose.
    2. The negative source wire used has somehow contracted over time and pulled out of the MC4 connector to reveal exposed copper. It appears to be standard PV wire with equal ratings to the positive wire and all others used by this installer.

    Neither seem very likely to me. Does anyone have any insight to this phenomenon or any other plausible theories?

    Thank you!!

    Attached Files

  • #2
    Operator error. And they are all trash. Once weather gets into the exposed strands, I would never reuse them.
    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've seen insulation pull away a little over time, but no where near that much. Someone clearly had no idea what they were doing.

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      • #4
        Originally posted by emartin00 View Post
        I've seen insulation pull away a little over time, but no where near that much. Someone clearly had no idea what they were doing.
        Especially when all you need stripped for MC-4 contact crimps is about 1/4"
        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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        • #5
          Possibly one more bright and shining example of what happens when some DIY yahoo or "Larry With a Ladder Solar" does a job where safety and quality concerns take a back seat to low first cost. You get what you pay for - or less.

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          • #6
            Looks like DIY work to me. Every picture screams I have no clue what I am doing and plan to fail.
            MSEE, PE

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