Changing MIG Power Cord Plug From 50A to 30A? HP?
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  1. #1

    Changing MIG Power Cord Plug From 50A to 30A? HP?

    MillerMatic 180 MIG

    From its manual .....

    230VAC
    Amps Input : 21.7
    KVA 5.0
    KW 4.1
    Max. Recommended Circuit Breaker 25A
    Min. Input Conductor 14ga (I used 10ga when I ran the new branch line)

    The power cord that the plug is mounted on is 12ga.

    Why did this welder come with a 50amp plug (NEMA 6-50P)? Instead of a 30A plug?

    I wish to remove the power cord from the welder, and make a longer one myself with SOOW cord. But I would like to use a 30A plug (NEMA 6-30P), so I could use a 30A (6-30P) receptacle on the wall for other things than this welder.

    I do not understand why I could not use the 30A plug. I do not understand why Miller used the 50A plug.

    Is there something I don't understand amout HorsePower? When looking at the plugs in the Grainger's catalog .... besides amperage and voltage, they list HP for each plug. A 6-50 plug has a power rating of 3HP.. It seems that a 30A only has a power rating of 2HP. What is the Power Rating of my welder.

    Thanks in advance for any info.

  2. #2
    Join Date
    Jun 2008
    Location
    Central California
    Posts
    3,768

    Re: Changing MIG Power Cord Plug From 50A to 30A? HP?

    The hp rating shown by Grainger for the plugs is for use with motors (of the correct voltage and phase to match the plug), so you don't need to worry about it. Your MIG power rating (21.7 amps input) as shown at the top of your post will allow you to use the 30 amp plug.
    The 50 amp plug is probably considered the standard for single phase equipment because the larger machines do need that much current. I have some equipment with plugs for 30 amps so I can use an outlet in the back yard and have an adapter for using it with my 50 amp socket in the garage.

    I do not understand why I could not use the 30A plug. I do not understand why Miller used the 50A plug.
    Maybe 'Mr. Miller' doesn't want to be chewed out by the wives of all the men who use the dryer outlet and keep the women from getting their chores done before the soap operas come on?

  3. #3
    Join Date
    Feb 2008
    Posts
    561

    Re: Changing MIG Power Cord Plug From 50A to 30A? HP?

    The 50 amp plug is just more standard and commonly available than the 30 amp version, besides the breaker is what protects the machine, not the plug

  4. #4

    Re: Changing MIG Power Cord Plug From 50A to 30A? HP?

    There are 746 Watts of energy per one electrical Horsepower.

  5. #5
    Join Date
    Jan 2004
    Location
    Las Vegas, NV
    Posts
    3,175

    Re: Changing MIG Power Cord Plug From 50A to 30A? HP?

    A typical welder receptacle is the NEMA 6-50R. You are by no means obligated to keep that plug on your machine. You are absolutely safe and fine to replace it with a 30A plug and use a 30A receptacle. Miller ships all the 230V machines of this class with the 50A plug only for maximum versatility in the most locations.

  6. #6
    Join Date
    Sep 2006
    Location
    NJ, USA
    Posts
    3,375

    Re: Changing MIG Power Cord Plug From 50A to 30A? HP?

    As Mac mentioned, it's pretty standard for small/medium 240V welders to have a NEMA 6-50P to go into a 6-50R.

    A 30 amp breaker/plug/receptacle would be fine for that machine.

    But so would leaving the 6-50P on the welder and putting in a 6-50R in/on the wall. If you had to, you could even run that circuit with a 30 amp breaker, but then you have to label it "Welder Use Only!" or some such, because the breaker and receptacle no longer 'match'.
    The best laid schemes ... Gang oft agley ...

  7. #7
    Join Date
    Jan 2004
    Location
    Las Vegas, NV
    Posts
    3,175

    Re: Changing MIG Power Cord Plug From 50A to 30A? HP?

    The "welder use only" label would definitely be needed if the wire size was smaller than the breaker would otherwise require, but I do like the recommendation of a label, somehow making sure someone doesn't see a 50A receptacle and think they can swap out your 30A breaker for a bigger one without first making sure the wire size is compatible for the larger job. Good point.

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