big wire

ws9876
ws9876 Solar Expert Posts: 448 ✭✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
Most set ups will include copper stranded wire, 10ga /4 ga battery/ maybe some 8 ga etc... if you have all copper would it be bad to include
some alum 4 ga ,very thick utility wire scraps 500+ amp from the bat to the inverter and use some homemade big lugs to accomodate the size. I mean the utility alum wire used in  commercial construction and found in dumpsters sometimes,super stiff ,about 10 strands ...
an 1100 amp installation usually includes 2-3 of these buried direct in the dirt from the transformer to a large main panel.
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  • MichaelK
    MichaelK Registered Users Posts: 236 ✭✭✭
    #2
    Please be aware that Al wiring will undergo oxidation and will have an insulating layer of Al oxide on the outside.  You need to chemically treat the conducting ends with special bonding compound to ensure good electrical connections.  When working with copper, I have made good home-made lugs out of flattened copper tubing that was polished bright, then rosen-flux soldered to the copper wire.  You might accomplish the same thing with aluminum tubing and zinc solder, be please always be mindful of the problem of Al oxide.  You might be better off cutting your wire to length, and finding a professional that can attach lugs for you.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #3
    Aluminum is useful in long higher current runs because it's cost effective, the battery to inverter should be as short as possible to prevent voltage drop so copper is preferred. Aluminum also has a tendency to shrink under compression which can lead to high resistance connections, so it's nessersary to re torque termination lugs which are supposed to be rated for AL if code rules are followed, additionally  surface oxidation is a problem which needs to be addressed with an oxidation inhibitor. Copper is superior in all aspects to aluminum except price.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    To properly terminate aluminum cable, you need to use rated compression/crimp connectors that make a hermetic seal between the aluminum cable and the compression sleeve--Then connect the other side of the sleeve to a copper cable (to terminate to copper that can be used in normal off grid/AC power systems).

    Using aluminum cable in non-aluminum rated connections is usually pretty bad news over time:

    https://inspectapedia.com/aluminum/Aluminum_Wiring_Hazards.php

    What Amp Rating are you looking for? 500 Amp would need something like 1500kcmil aluminum cable which is larger than 1" in diameter... Not exactly easy stuff to work with.

    Unless you have the proper compression fittings and tools and this is a "one off" system--I would suggest that you avoid aluminum (aluminum is very common/standard in US Pole to Home drops... And you can probably find sleeves and tools around somewhere more easily.

    https://www.platt.com/platt-electric-supply/Cable-Lugs/Compression-Sleeves/search.aspx?SectionID=4&GroupID=61&CatID=6940

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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