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Thread: 220 volts

  1. #1
    Join Date
    Jun 2018
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    Default 220 volts

    I have a 220 compressor running in my shop and I wanted to run a 220 welder of the same plug. so I bought some wire and wired it but my welder didn't work but the compressor does when I plug it in. so I took apart the welder and couldn't find a problem. So I checked the plug and found from one side to ground was 120 volts and I expected to find 120 volts on the other but I didn't. I found 240 volts on the other side.

    What could cause this problem? Makes no sense to me. Any ideas for me to follow up on and why would the compressor work? Thanks

    Bill

  2. #2
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    Feb 2012
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    Lala land, OH
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    Are you sure your air compressor is 220v?
    a 20A 120V plug/outlet (NEMA 5-20) and a 240v (also known as 220v) (NEMA 6-20) plug/outlet look similar. A 6-20 outlet has no neutral in it.

    What outlet does it currently have (see like below)
    What is the breaker/fuse and wire size for this outlet?

    What is the nameplate rating on your air compressor?
    What is the nameplate rating on your welder?
    Does either specify a circuit size on the nameplate?

    Do you intend to run them both at the same time (you will need separate circuits if so)

    https://upload.wikimedia.org/wikiped...ified_pins.svg

    Measuring from hot to hot will give you 240V, measuring from any hot to ground or neutral will give you 120V. Use the above image to see what outlet you have and verify it's wiring.

  3. #3
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    Welland Ontario
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    The only way to get 240 volts to ground is if one of the hot leads is on the ground. It sounds like you have swapped a hot and ground.
    Operation Overlord.

  4. #4
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    Jun 2018
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    Mine is the nema 1050 . I will look at the compressor when I get to the shop. when I said ground I's most probably a neutral. I never knew you could make one line a 240 volt line from a regular house setup without going between both 120. How is it possible?


    Quote Originally Posted by Mr T View Post
    Are you sure your air compressor is 220v?
    a 20A 120V plug/outlet (NEMA 5-20) and a 240v (also known as 220v) (NEMA 6-20) plug/outlet look similar. A 6-20 outlet has no neutral in it.

    What outlet does it currently have (see like below)
    What is the breaker/fuse and wire size for this outlet?

    What is the nameplate rating on your air compressor?
    What is the nameplate rating on your welder?
    Does either specify a circuit size on the nameplate?

    Do you intend to run them both at the same time (you will need separate circuits if so)

    https://upload.wikimedia.org/wikiped...ified_pins.svg

    Measuring from hot to hot will give you 240V, measuring from any hot to ground or neutral will give you 120V. Use the above image to see what outlet you have and verify it's wiring.

  5. #5
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    Kent, WA
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    A NEMA 10-50 is 2 hots, a neutral, but no ground. Its an "old school" range plug. You should measure 240V from X and Y on the receptacle, and 120V from X to W and Y to W. This is a combination 120V/240V receptacle, but you probably don't need the 120V capability unless the compressor is actually 120V.

    What type of cable is wiring this receptacle? The neutral is required to be insulated in this receptacle, so you should have a red, black, and white. If there is a bare ground it does not connect to the receptacle (just the box if it is metal).

    A NEMA 6-50 is 240V only and would have 2 hots and no neutral (but it has a ground). Electrically, it is the same as the 10-50 except that the 10-50 neutral is intended to carry current and the 6-50 ground is not. The 6-50 ground screw is electrically connected to its mounting strap. The N terminal on the 10-50 is electrically isolated from its strap. Grounds and neutrals go to the same bar in your panel, the difference is intended use (safety ground green or bare -vs- return current on white wire).
    Last edited by suemarkp; 06-12-2018 at 06:54 PM.
    Mark
    Kent, WA

  6. #6
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    Jun 2018
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    I went to the shop and this is what I found. The compressor is 220 volt 7 HP and has been running for more than 10 years. Looking at the 10-50 plug I have three wires. Top one is black, right bottom is red, bottom left is white. with my VOM set on 250volts, from top to bottom left I get 120 volts, from top to bottom right I get 250 volts. So I went to the box and found the red one is grounded and both white and black breakers are reading 120. to me the red one on bottom right should be a neutral on the top 0f plug (forget about colors right now) and the bottom two would be the 120's. I have no idea of what is happening behind the wall but something must be. Because Its been there and running for years I don't want to just change wires nor do I want to take done the wall. Any idea's. I'm going to leave it and write on the wall miss wired. Any ideas welcom

  7. #7
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    Sounds wired wrong as previously mentioned. Wrong wire locations at the breaker and the outlet. Only white should be on the neutral bus (green or bare too if it's a neutral/ground bus and not a subpanel). Is there a chance that the compressor plug or wiring box is also miswired, possibly by intent in order to make it work with the bad circuit?

    I would check your compressor wiring and verify its wired up correctly. Once that's fixed you can fix your breaker and outlet wiring. Red and black should go to the breakers, white goes to your neutral bus (which could double as your ground bus if it's your primary service panel). Your outlet appears to be arranged so that your neutral is on top. So, white to the neutral (top), and red and black to the 2 hots (x and y).. The order does not matter for the hots. If it's wired correctly then you should have 120V from white/neutral to either of the 2 hots and 240V from hot to hot..

    ===> Make sure you verify your compressor wiring before you plug it in! If the compressor has the neutral and ground connected together and it is miswired, plugging it into a correctly configured outlet may put 120V on the outside case of the compressor, creating a shock hazard.


    You may want to consider upgrading this outlet since you are messing with it.. You will need a new 3 conductor + ground cable run (red, black, white + green or bare ground). You will need to replace the outlet (should be a 14-50 outlet for a 50A circuit) and new line cords of course. If you do not need a neutral for either item then you can go to a pure 240V circuit (red, black, green or bare ground with a 6-50 outlet.... A white wire can not be used as a ground). If you think you might need a neutral now or in the future, leave it a 120/240V circuit.

  8. #8
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    Kent, WA
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    Just to clarify if you don't know:

    On a 240V circuit, each of the two breaker screws will measure 120V to the neutral bar. But there should be 240V between the two breaker screws. This is where the red and black are supposed to go.

    The pin in the outlet that looks like a corner _| is where the neutral goes. The slant ones, / and \ get the red and black (doesn't matter which one goes to which).
    EDIT: Confused with the NEMA 10-30 which has a corner prong, but the 10-50 is all straight. The neutral on the 10-50 goes to the straight up and down prong |, and the hots go to the diagonal ones / and \.
    Last edited by suemarkp; 06-17-2018 at 11:44 AM.
    Mark
    Kent, WA

  9. #9
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    Jun 2018
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    I put in a separate plug wired correctly on a different breaker just for the welder and it works fine. So because the compressor has been running the way it is for 10 years I'm going to just use it the way it is. Must not be harming the unit or it would of done so already.
    Thanks everyone for your input. I'm done with is project.

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