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Setting up shopmaster 300- Wiring from panel to welder

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  • Setting up shopmaster 300- Wiring from panel to welder

    Hey all, Been a while since i posted here.

    So I am finally getting around to setting up my shopmaster 300. I have 240v service (actually measured it as 250v) to my garage on a 200 amp panel, residential service. This panel is dedicated to garage. Single phase.

    Miller recommends a 125Amp breaker, even thought the machine is rated for 110Amp of incoming power if I remember right. It seems like the code recommends a 2 gauge copper wire or 2/0 gauge aluminum wire. But when i used a wire calculator, actually inputting the length of wire, I seems the 2 gauge aluminum wire is acceptable; I calculated a 1.955 voltage drop with 0.81% voltage drop (3% seems like the norm).

    The run is approximately 25' to the panel.

    Our contractor (long gone) had installed the 2 gauge aluminum wire. Looking to do things legally and if it means pulling that out I will do so.

    Are there any electricians or well seasoned pros that can shed some light on this?

  • #2
    Due to the duty cycle of the Shopmaster you are allowed 6g as the minimum

    http://www.millerwelds.com/om/o322a_mil.pdf
    Ed Conley
    http://www.screamingbroccoli.net/
    MM252
    MM211
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    TA185
    Miller 125c Plasma 120v
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    SO 2020 Bender
    You can call me Bacchus

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    • #3
      So this chart "2-9 Electrical Service Guide" is from the panel to the plug or device?

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      • #4
        Originally posted by H2o View Post
        So this chart "2-9 Electrical Service Guide" is from the panel to the plug or device?
        Both.

        You need a minimum 6g wire to go from the main panel to the disconnect.
        same gauge wire inside a Cord to go from the Disconnect to the machine.

        Since you are using this at 240v you can use SJO cord ( J= Junior) rated for up to 300v

        SO cord is rated 600v
        Last edited by Broccoli1; 12-10-2014, 02:28 PM.
        Ed Conley
        http://www.screamingbroccoli.net/
        MM252
        MM211
        Passport Plus w/Spool Gun
        TA185
        Miller 125c Plasma 120v
        O/A set
        SO 2020 Bender
        You can call me Bacchus

        Comment


        • #5
          One last question, I realize the manual states min gauge size, but does the building code supersede manual? Are there any electricians here that might know?

          I am thinking worse case scenario, for insurance purposes if there was a problem. Some insurance companies like to deny claim, even thought fire had nothing to do with elec set up.

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          • #6
            And are there any issues with using aluminum wires from panel to machine?

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            • #7
              630.31(A)(2) is a chart. Based on duty cycle of the welder, you get a multiplier you use with other articles to get conductor size. A 30% Duty cycle welder needs only .55 times the ampacity as a 100% machine. Keep in mind this only addresses the question of will it overheat? As for determining will adequate voltage be delivered? you need to calculate voltage loss. When power leaves the utility transformer some potential is lost in the form of heat. Each conductor on the way to the welder will lose voltage, each must be calculated. Most utilities deliver 240 Volts, most welders are designed for 230. They will perform acceptably at 5% under their design voltage. A 230 Volt machine works OK at 218.5. If you start with 240, you can lose 21.5 volts and be OK. Too often we hear of people calculating only the welder circuit, that power has to get to the welder circuit first.
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              • #8
                Originally posted by H2o View Post
                And are there any issues with using aluminum wires from panel to machine?
                Aluminum is less conductive than copper, it must be larger to do the same job. A bigger concern is corrosion, more precisely, oxidation. Aluminum in contact with other metals will suffer galvanic corrosion. Terminals must be rated for aluminum, and be larger than if they are used with copper.
                Dynasty 280DX
                Bobcat 250
                MM252
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                Twentieth Century 295
                Twentieth Century 295 AC
                Marquette spot welder
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                • #9
                  Originally posted by WillieB View Post
                  Aluminum is less conductive than copper, it must be larger to do the same job. A bigger concern is corrosion, more precisely, oxidation. Aluminum in contact with other metals will suffer galvanic corrosion. Terminals must be rated for aluminum, and be larger than if they are used with copper.
                  If I read it correctly he had an electrician run #2 Aluminum wire for this circuit- that will be plenty for the Shopmaster.
                  Ed Conley
                  http://www.screamingbroccoli.net/
                  MM252
                  MM211
                  Passport Plus w/Spool Gun
                  TA185
                  Miller 125c Plasma 120v
                  O/A set
                  SO 2020 Bender
                  You can call me Bacchus

                  Comment


                  • #10
                    I recommend Noalox by Ideal for all aluminum terminations. It works. Get out a magnifying glass, make sure all terminals are rated AL_CU. Might have a digit between, that's temp rating. Often temp rating of terminal will limit amperage. A 90 C conductor must be limited to 75C if connected to a 75C rated terminal on either end.
                    Dynasty 280DX
                    Bobcat 250
                    MM252
                    Spool gun
                    Twentieth Century 295
                    Twentieth Century 295 AC
                    Marquette spot welder
                    Smith torches

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                    • #11
                      Thanks

                      Thanks all for all your comments. I did put some dialectic grease on there that i had for cars. Should be same/similar stuff. I put sufficient quantity and really tightened it. Seems like the breaker connection is actually aluminum so it may be less of an issue.

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                      • #12
                        I believe, though I may be wrong, that Noalox has zinc, which serves as an anode to prevent oxidation in the sense galvanizing protects steel.
                        Dynasty 280DX
                        Bobcat 250
                        MM252
                        Spool gun
                        Twentieth Century 295
                        Twentieth Century 295 AC
                        Marquette spot welder
                        Smith torches

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