Page 1 of 2 12 LastLast
Results 1 to 15 of 26

Thread: What kinda plug is this?

  1. #1

    What kinda plug is this?

    I have this plug, I think its 20A 240 volt, but not 100% sure. I put a meter on it, and I get 120, but only when I go from the left or right socket with the top socket. going straight across I dont get any voltage. I suspect its 120 each side, and 240 total.
    My panel has it with a double breaker, is 20A on the breaker. The previous owner had an air compressor here, and its labeled that way.

    I want to use it for my Grizzy planer and tablesaw. Also a compressor too. I will have to unplug each one each time to use obviously.

    I currently have those all wired for 3 prong twist lock, so I would also like to switch the plug out eventually to a twist lock. I am assuming they are wired the same.

    Just want to get educated and see if I need an electrician, or if I can handle.

    File_000 (1).jpg
    Attached Images Attached Images

  2. #2
    Join Date
    Jul 2010
    Location
    State College, PA
    Posts
    376
    I believe that is a 20-amp 220-volt receptacle. See, for example, http://www.homedepot.com/p/Leviton-P...-0IS/100357020

    Your test results seem odd. If it is wired for 220-volt, you should see 220-volts across the bottom two.

  3. #3
    Join Date
    Jun 2006
    Location
    The Hartland of Michigan
    Posts
    7,628
    I wonder if the PO had a 120v compressor, and jury-rigged the outlet. Pull it out of the wall and trace the wiring.
    Never, under any circumstances, consume a laxative and sleeping pill, on the same night

  4. #4
    I'm with Myk here......... I do wonder if both left and right are from the same 120v feed and not two separate 120v feeds needed to make the 240 volts.

  5. #5
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    65,688
    240v 20a fixture, but clearly not wired correctly given the readings you mention. I agree with Myk and Bill...you need to trace things back and pulling the unit out is the first step.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  6. #6
    Join Date
    Feb 2012
    Location
    Little Hocking, OH
    Posts
    676
    Seriously? I'll go check my 220 outlet tomorrow. Both bottom slots are 120v in. Without the meter on a neutral/ground, how would you get a reading by placing the probes in the bottom 2 slots, which should both be hot?

    Where am I wrong here? I know how I wired mine, and they work..

    I say, for this moment in time, this outlet is wired for 220.

    See this https://www.do-it-yourself-help.com/..._diagrams.html go down to your receptacle.

    Oh, the double breaker is how 220 is normally done. When you say double breakers. I assume they are connected, so when you throw the switch to off, both breakers open, no power to either bottom slot.
    Last edited by Mark W Pugh; 02-11-2017 at 9:30 PM.

  7. #7
    I will pull it out of the wall and see how its wired, and also the breaker. I tend to agree with MArk Pugh. If i put a meter across two hots, how would i get a reading.

  8. #8
    Quote Originally Posted by Jim Riseborough View Post
    I will pull it out of the wall and see how its wired, and also the breaker. I tend to agree with MArk Pugh. If i put a meter across two hots, how would i get a reading.
    The transformers customer side winding is center tapped, that tap is your white wire. The ends of that winding are brought out at 120v each, but 180deg out of phase with each other. So measured from the two bottom pins you see the peak voltage between those two, .
    windings, /that's a really poor description, but if you google center tapped transformer there are lots of pics and info online.
    edit"
    If you only have 120 to neutral or ground, and no 240 between those pins, both are connected to the same bus in the panel. they must be connected to different buses in order to get the 120s out of phase as described (badly) above. I've seen guys inadvertently use a half-size two pole breaker. Those contact the same bus. A 'normal' two pole breaker contacts both buses.

    a picture of your panel would help.
    at the tra
    Last edited by Ken Combs; 02-11-2017 at 11:18 PM.

  9. #9
    Join Date
    Feb 2003
    Location
    Griswold Connecticut
    Posts
    6,927
    Jim

    It's a 6-20R, 20 amp, 240vac receptacle.
    It should definitely read 240vac across the receptacle.Not sure why you're getting the readings your getting, unless your meter is over ranged on the setting you have it set to.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  10. #10
    Quote Originally Posted by Jim Riseborough View Post
    I will pull it out of the wall and see how its wired, and also the breaker. I tend to agree with MArk Pugh. If i put a meter across two hots, how would i get a reading.
    It's AC, so the polarities flip many times each second. At the instant that one side is positive, the other one is negative, so when you measure the voltage between them, the magnitudes add.

  11. #11
    Join Date
    Jun 2003
    Location
    Northern Michigan
    Posts
    490
    The panel holding the breaker has 2 buss bars that are both 120 volts referenced to ground but 240 volts referenced to each other. The only way you can get a reading of no voltage across the 2 hot legs of the receptacle is if they are both fed from the same buss bar as this would give you the 120 volt to ground reading but no potential difference across them.

    Start turning off breakers one at a time and take readings on both sides of the receptacle each time. I wonder if they are feeding the receptacle with 2 single pole breakers but have both of them fed by the same buss bar. Have seen this done a couple times. Something is wrong with the wiring and you need to be careful sorting this out if you are not familiar and experienced with electrical troubleshooting. DONT trust the panel labeling as it can be incorrect!
    Last edited by Peter Kuhlman; 02-12-2017 at 12:12 AM.

  12. I agree with the suggestion the meter might be set wrong and possibly nothing amiss with the outlet. it would be possible to rig the outlet to provide only 110v but it wouldn't be possible to plug a 110v compressor cord into that outlet so I doubt that was the scenario. It's a 220 outlet connected (by at least one wire) to a 2-pole breaker, seems he most likely scenario is that it's a standard installation and either being metered wrong or possibly (though unlikely IMO) one wire is loose. Should be easy enough to swap to a twist lock outlet.

  13. #13
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    65,688
    Quote Originally Posted by Jim Riseborough View Post
    I will pull it out of the wall and see how its wired, and also the breaker. I tend to agree with MArk Pugh. If i put a meter across two hots, how would i get a reading.
    The two hot legs are at opposite wave phase, so as long as your meter is set to read AC voltage, it will register the ~240v properly on the meter.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  14. #14
    Quote Originally Posted by Jim Becker View Post
    The two hot legs are at opposite wave phase, so as long as your meter is set to read AC voltage, it will register the ~240v properly on the meter.
    Mr. Becker is correct. The 2 hot legs of typical USA household 240VAC service are each at 120VAC potential (to ground), but their wave forms are 180 degrees out of phase (offset from each other), so the simplistic result is that at any particular moment you measure from the 'peak' of one to the 'valley' of the other - - and get 240V. This 240V is what a meter should 'see', as well as your 240V motor, etc.

    If you measure 120V on L1<>G and L2<>G, but get (zero) 0V from L1<>L2, then the receptacle is incorrectly wired for use with anything. The only way anything will function on this is if it uses the Gnd lead as a conductor. Generally speaking, this would also imply there is a problem with the wiring in the 'motor' allowing current to flow to the ground, but this opens a whole new rabbit hole of speculation and conjecture.

    Photos of meter on a 240V AC circuit, and what it should read on a properly wired 240VAC plug, like the OP's follow:

    This from left leg to ground--
    IMG_0602[1].jpg

    This from right leg to ground--
    IMG_0612[1].jpg

    This from left to right leg--
    IMG_0613[1].jpg

    For some who have responded, please ask yourself why it's called "240V" if you don't measure 240V somewhere.
    Last edited by Malcolm McLeod; 02-12-2017 at 11:31 AM.

  15. #15
    Yea, my bad, I just didnt meter it correct. I rechecked, and I am getting 230ish V.

    Glad I went through this, the plug ground was not connected. I am going to replace with a twist lock type anyway that will allow me to use my existing plugs on my saw and planer. I can rewire a compressor when I get one thats 240

    Glad I have 240V though!!

    File_001.jpgFile_000 (3).jpgFile_002.jpg

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •