Can wire size be TOO BIG

backroad
backroad Solar Expert Posts: 185 ✭✭
in Off Grid Solar & Battery Systems #1
Now I'm trying to understand why my old system would not keep up with my 3500-4000 watt needs. WE live far enough out that the county doesn't even bother with us. The main wires that ran from my solar shed (and they were above ground) were very, very large. The diameter of the cable and insulation was about 2" and it was designed to feed a very large shovel in the mine I work for and carried 7200 volts.. I have no idea about guage of it. Wire run was about 150 feet to the house. Could there possibly have been a large loss because of this.

It's now been done away with and rewired up to code and underground.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Can wire size be TOO BIG

    you'd have to get a better idea of how large that wire was to figure how it stands in your system. old wire can also mean breaks in it or at least higher points of resistance due to abuse and use.
    now i did try addressing some of this in a pm to you, but in stating a 3500-4000w need, is that continuous or the total whs you need in a day as there's a big difference between the 2?
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  • backroad
    backroad Solar Expert Posts: 185 ✭✭
    #3
    Re: Can wire size be TOO BIG

    The "old shovel cable" has been used and very abused. They never get rid of the good stuff as it's very 'spensive to replace. The outside insulation is very weathered and spilt. it weighs about 11lbs per foot. Now if only scrap copper will go back up to where it was.

    The estimate that I came up with was 3500-4000 PER DAY.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    Re: Can wire size be TOO BIG

    It's only too big, when it wont fit into the socket.

    Too large won't create losses, but if used, and bad spots, you could have loss. What was carried in the wire:
    PV array,
    battery voltage to inverter, or
    inverter to household
    Powerfab top of pole PV mount | 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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  • backroad
    backroad Solar Expert Posts: 185 ✭✭
    #5
    Re: Can wire size be TOO BIG

    Inverter to house....and I really can't call it wire. At 11 lbs a foot, it's huge cable. Not that this really matters at this point. I'm just trying to come up with an idea of why my previous system was not doing it's job sufficiently.
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #6
    Re: Can wire size be TOO BIG

    the cable might not be very big actualy if it was intended for 7200 volts it probably has a layer of armor in it? the actual copper may be on the smallish side.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: Can wire size be TOO BIG

    it's too bad your old system isn't in place as a simple voltage drop measurement with loads on could've solved whether or not your wire is at fault.
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  • backroad
    backroad Solar Expert Posts: 185 ✭✭
    #8
    Re: Can wire size be TOO BIG

    Ya know, now thnking back just a bit, my microwave never really did do very well with the old system. It even seemed to lack power even when the 8kw generator was running. Hummmmm.......
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #9
    Re: Can wire size be TOO BIG

    yeah high voltage cable is usually fairly small. I forgett what the voltage was on your system but that may have been the root of the troubles?
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