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  1. #1
    Join Date
    Jul 2011
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    4

    Default Converting dryer plug to welder plug

    Hi, new here, hope this is in the right category. My 220v welder has a nmea 6-50 plug that is hot-hot-ground. It draws 19.8A. I have a dryer circuit I no longer need for a dryer that is 30 amp, hot-hot-neutral. Can I use the neutral as a ground/will it act as a ground/is it safe?

  2. #2
    Join Date
    Apr 2011
    Posts
    362

    Default What a good idea...

    ...I wonder why no one else ever thought about doing that? Oh wait, there are about 3000 threads on the subject. Try a search for general questions such as this…and welcome to the forum. This is NOT aimed at just you but all us newbies that drop by.
    MillerMatic 211 Auto-set w/MVP
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  3. #3
    Join Date
    Dec 2007
    Location
    Los Angeles
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    2,861

    Default

    Quote Originally Posted by rwaters View Post
    Hi, new here, hope this is in the right category. My 220v welder has a nmea 6-50 plug that is hot-hot-ground. It draws 19.8A. I have a dryer circuit I no longer need for a dryer that is 30 amp, hot-hot-neutral. Can I use the neutral as a ground/will it act as a ground/is it safe?
    yes and yes.
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  4. #4
    Join Date
    Jul 2011
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    4

    Default

    Quote Originally Posted by Doughboyracer View Post
    ...I wonder why no one else ever thought about doing that? Oh wait, there are about 3000 threads on the subject. Try a search for general questions such as this…and welcome to the forum. This is NOT aimed at just you but all us newbies that drop by.
    Thanks. Oh wait, no thanks. Instead of replying with all that nonsense a simple answer will do just fine next time. Are you the "newbie" in charge of regulating other "newbies" on you virtual discussion board or what dude? Guess there's one in every forum.There are nowhere near 3000 posts, I found a few dated ones.

  5. #5
    Join Date
    Jul 2011
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    4

    Default

    Quote Originally Posted by Broccoli1 View Post
    yes and yes.
    Thank you for the reply.

  6. #6
    Join Date
    Sep 2006
    Location
    Abilene, Texas
    Posts
    639

    Default

    Welcome to the forum rwaters and I'm glad that you got your answer. Some welding forums will actually help you w/out flaming you. PM me if you want to know more.
    Jim

  7. #7
    Join Date
    Jul 2011
    Posts
    162

    Default

    I'm not a licensed electrician but I have studied the National Electric Code to know the intent of neutral and ground connections. Neutral is intended to carry current, ground is an emergency connection.

    With this stated, a 3-pole, non-grounded connection is intended to have the majority of the current through the hot legs of the split-phase connection. Both have a potential of 120 volts AC to ground. Across the legs, the potential is 240 volts AC and the majority of the current is through these legs. But a small percentage is used from one leg to the neutral. This can lead to a problem IF the neutral is broken and the device is also grounded through the neutral as there WILL be 120 volts potential in the frame. Also, if the neutral conductor is the same gauge as the legs and there is a fault, that conductor could become over-loaded since both legs could short to it. As since there is no circuit breaker on a neutral, there is potential for fire. Consider 240 VAC heater elements are switched by one leg only. If there is a short from the heater element to ground, the leg that is unswitched will continue to draw, even when the machine is off! There are no safety controls for this on older appliances

    On an inverter machine, using the neutral as ground is far safer since the possibility of both legs dumping to ground is highly remote. If one leg shorts to ground, it will trip both legs of the breaker. And the master power on a welder disconnects all power, not just one leg of 240 split phase.

    I ran a rough failure modes effects analysis of this before wiring my Dynasty 200DX to a NEMA 10-50 plug. The existing wiring on the receptacle is 10 AWG for all thee conductors. The neutral is tied to the same point for all the grounds in the wiring. If there were faults in both legs to ground, the ground conductor in my welder would certainly overheat with 100 amperes through a 10 foot section of 12 AWG copper. But such is the case if it were connected to a proper NEMA plug/receptacle of 240 VAC or even 3-phase.

  8. #8
    Join Date
    Sep 2005
    Location
    16919 Pole Rd. Brethren, MI 49619
    Posts
    4,383

    Default

    There may be some issues if this outlet is fed from a sub with 4 wires, if the circuit originates from the service main not a deal at all. If this is unused circuit change the recept to match welder.

  9. #9
    Join Date
    Jul 2011
    Posts
    21

    Default

    Quote Originally Posted by Keith_J View Post
    Also, if the neutral conductor is the same gauge as the legs and there is a fault, that conductor could become over-loaded since both legs could short to it. As since there is no circuit breaker on a neutral, there is potential for fire. [...] If there were faults in both legs to ground, the ground conductor in my welder would certainly overheat with 100 amperes through a 10 foot section of 12 AWG copper.
    I think you're misunderstanding how the 240V split phase system works. The two legs are both 120V AC relative to ground, but to give 240V between the legs, at any moment in time they are the opposites of each other. That is, at a given instant, one might have +170V and the other -170V. If either one shorts to ground, the ground conductor carries the full fault current. If both short to ground, the ground conductor carries virtually no current, as the two legs cancel each other out, not add together - the fault current is between the two legs, with only a slight residual through the ground conductor.

    Not having a circuit breaker in the neutral is an important safety requirement, not a fire risk. The current through the neutral will never exceed the current through either one of the legs.

    --Bushytails

  10. #10
    Join Date
    Sep 2005
    Location
    16919 Pole Rd. Brethren, MI 49619
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    4,383

    Default

    There may be hundreds of amps going thru this 12 for split of a second,,, long as it handles it to clear the breaker all is fine, 12 is good to 50A circuits depending on the ungrounded conductor size. Shorts blow fuses or trip breakers.

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