Circuit breakers

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  • Circuit breakers

    I have a 12v 7.5amp washdown pump. All breakers for switches on same panel are Push-Button Reset-Only Thermal Circuit Breakers. Do i go with a 7amp or bump to10?

  • #2
    I'd rather exceed the demand than not supply enough; especially given the cost involved.
    I can't help but think if I was a better person I could've been a dog. 🐕

    Chet
    Amesbury, MA (work in Boston)
    1987 2855 Bayliner Contessa SB
    How can I help you?

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    • #3
      Depends on the size of the wire. Probably 14g or 16g wire.

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      • #4
        With 14 wire, 20 amp would not be too much.
        Small town S. W. Ga./St. James Fl.

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        • #5
          Originally posted by Tori645 View Post
          I have a 12v 7.5amp washdown pump. All breakers for switches on same panel are Push-Button Reset-Only Thermal Circuit Breakers. Do i go with a 7amp or bump to10?
          A little more info is needed.
          Length of run from pump to breaker. Then we can determine breaker and wire.
          But, in the offset, if the pump is a 7.5a, then a 7a breaker is not enough.
          the pumps draws 7.5a, who knows what spike startup is or pressure cut out?
          Less wire gauge and longer run, pump will draw more.
          Engine Sales and Service
          Ph +1 954.463.1515
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          954.463.4904
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          • #6
            Originally posted by Parker Yacht View Post
            Less wire gauge and longer run, pump will draw more.
            That puzzles me;
            doesn't Ohm's Law say it would be less ?

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            • #7
              14 ga wire
              less that 3ft to switch/breaker

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              • #8
                Originally posted by Lucky Dog View Post

                That puzzles me;
                doesn't Ohm's Law say it would be less ?
                Maybe I said it wrong or didn't say correctly.
                By less, I mean more IE: 16-18-22ga would draw more than 12-10-8ga.
                Less being smaller ga.
                My apologies.
                Engine Sales and Service
                Ph +1 954.463.1515
                Fx +1
                954.463.4904
                Toll Free: 800.622.6747

                [email protected]
                www.parkeryacht.com

                Member of the MSHS Group

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                • #9
                  Originally posted by Tori645 View Post
                  14 ga wire
                  less that 3ft to switch/breaker
                  10a Should cover it.
                  Engine Sales and Service
                  Ph +1 954.463.1515
                  Fx +1
                  954.463.4904
                  Toll Free: 800.622.6747

                  [email protected]
                  www.parkeryacht.com

                  Member of the MSHS Group

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                  • #10
                    Ok..thx

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                    • #11
                      The larger the wire gauge, the more amperage/current it can carry.. More surface area.. The smaller the wire, the less current it can carry because of resistance.. Same effect with longer wire runs.. Lots of resistance in long runs of wire.. So with longer distance, this creates friction and heat, which creates resistance. With greater resistance, you get reduced current capacity.
                      Wire Size (AWG) Diameter (MILs) Area (CM)2 Feet Per Pound
                      Bare
                      Ohms Per 1000ft
                      25°C
                      Current Capacity
                      (Amps)
                      4 204.3 41738.49 7.918 0.2485 59.626
                      8 128.5 16512.25 25.24 0.7925 18.696
                      10 101.9 10383.61 31.82 0.9987 14.834
                      12 80.8 6528.64 50.61 1.5880 9.327
                      14 64.1 4108.81 80.39 2.5240 5.870
                      18 40.3 1624.09 203.5 6.3860 2.320
                      20 32 1024.00 222.7 10.1280 1.463
                      22 25.3 640.09 516.3 16.2000 0.914
                      24 20.1 404.01 817.7 25.6700 0.577
                      28 12.6 158.76 2081 65.3100 0.227
                      32 8.0 64.00 5163 162.0000 0.091
                      40 3.1 9.61 34364 1079.0000 0.014
                      2019 Tidewater 252 CC Twin F150's
                      2016 Tidewater 230 CC VF250 SHO- SOLD
                      Mobile, Al.
                      Dauphin Island, Al.

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                      • #12
                        It's basically about creating heat. Resistance creates heat. A bad connection will get hot. If the wire stays cool, it is big enough.

                        Stranded wire will carry more current than solid. Electricity flows on the surface of the wire, and stranded has more surface. Stranded wire is also easier to "pull".

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