Wire size, 3ph Delta, 120/240

Discussion in 'Electrical Forum discussion & Blog' started by Homeownerinburb, Jul 10, 2012.

  1. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    There is required by code, and then there is custom and practice, which, I grant you, is an amorphous thing.

    Where the 3 phase is being used to mostly deliver 120/240, in what is essentially the equivalent of single phase practice except that we have a third leg to give us some more options on the 240 and the potential to deliver 3 legs at 240 (there is a water heater going in), then black and red for the two low phases and orange for the high phase would not mix up even a home remodeller like me.

    And it seems to be what the rest of the building was wired to, and it seems to me that is very important, assuming it is not stupid in some way.
  2. Rich B

    Rich B DIY Senior Member

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    283
    Location:
    New Jersey
    As I have posted many times.....I work in the backup generator field in the NY-NJ area. We service and repair units from 5-10 KW all the way up to very large units over 500 KW
    We have 120/240 3 phase in our building.....It is Delta and one leg to neutral is about 210V while the others are 120.
    Any 2 will be 240
    We supply generators when needed to buildings thruout the area.
    Most buildings are 120/208 Low Wye or 277/480 High Wye....
    The color code usually used is black, red and blue for the lower voltage (120/208) and brown, yellow and orange for the higher voltage( 277/480).

    I can reconnect most any 12 lead reconnectable generator for either voltage and have many times. I can also do one for the 120/240 Delta configuration and did that on a 400 KW unit that we use for our own building.....

    We have rarely serviced or worked on or seen pretty much anything other than the 3 voltages I mentioned and we cover a lot of area......
  3. ActionDave

    ActionDave Electrician

    Messages:
    346
    Location:
    Colorado
    Orange is strongly suggested by code, but not required. Best to follow what is common in your area.
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
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    The only time the high leg will see current will be on a three phase appliance or a single phase appliance that does not utilize the neutral. It must be able to carry the same current as the other line that is supplying one of these loads in the event of a short circuit. This is the reason that it must be sized the same as all the other ungrounded conductors.
  5. Rich B

    Rich B DIY Senior Member

    Messages:
    283
    Location:
    New Jersey
    RED LEG Delta is what I call it and thats how I ID it.....with red tape....
  6. Homeownerinburb

    Homeownerinburb New Member

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    525
    Location:
    Los Angeles, CA USA
    "It"?

    Sorry, what is the it? The phase that is 208v to the neutral between the other two phases?

    I'd certainly not use red. It is very traditionally the opposite end of the phase in single phase from the black.

    Which is why I like having the two low phases in open delta red and black. They make sense with 120v for me.
  7. ActionDave

    ActionDave Electrician

    Messages:
    346
    Location:
    Colorado
    Seems like sometime back in the 70's the high leg was labelled red. I'm not sure. I was not pulling wire in the 70's. I was playing with army men and doing anything I could to got out of going to school.
  8. Homeownerinburb

    Homeownerinburb New Member

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    525
    Location:
    Los Angeles, CA USA
    I was trying to get smoochy with girls.
  9. Rich B

    Rich B DIY Senior Member

    Messages:
    283
    Location:
    New Jersey
    Series High Delta 120/240 60 Hz 3 Phase power. My voltage reconnection chart tells me I could make that 139/277. I assume it too would have a "high" leg to neutral since it is the same wire configuration and that is a voltage that must be used somewhere but not around here. All one would need to do is adjust the voltage regulator to get to that output voltage on a generator assuming it (the regulator) was capable of running at that odd voltage. As I said.....Black, Red, Blue are the colors used on 120/208 or 120/240 voltage power being supplied in buildings in this area.

    We use red to ID the higher phase to neutral. Red stands out and I like it that way....Unless your colorblind you should be able to quickly recognize this is a good way to ID a phase that should not be used with a neutral to create a circuit.

    You do whatever you like or is required in your area......
  10. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,532
    Location:
    North Carolina
    The internal parts of a generator are outside the scope of the NEC but once it leaves the generator it must comply with the NEC.

    As Dave has pointed out with his post of 110.15 of the NEC if a color is used to identify the high leg it MUST be orange or if one wanted they could put a tag on it that shows that it is the high leg.
    The only other colors that are mandated by the NEC is white or gray for the grounded neutral and green or green with yellow strips for the equipment grounding conductor.

    The ungrounded (hot) conductors can be any color that the installer chooses. It has been a standard of practice (SOP) throughout the country to use Brown Orange and Yellow for 480/277 but then if there is a transformer that steps this system down to a 240/120 delta system then the orange color cannot be used for the 480/277 as the high leg of the 240/120 will be required to have this orange color. If the high leg of the 240/120 is identified with a tag the 480/277 still can’t be orange as this color is set aside to identify the high leg. If the building does not have a system with a high leg and is supplied with only a 480/277 wye system then the use of the “BOY” is allowed although I strongly object to this SOP (standard of practice).

    I have installed many of a system using the standard black color that the conductors of size 4 and larger comes in and identify the phases using marking stickers as Phase “A”, Phase “B”, and Phase “C” looking at the panel from the front from top to bottom, left to right, or front to back.

    In the premises wiring system electricians are not allow to just choose which color they want to use to identify the high leg, neutral, or the equipment grounding conductors. These conductors are mandated as to what color is to be used by 110.15 for the high leg, 200.6 for the neutral, and 250.119 for the equipment grounding conductor.
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,532
    Location:
    North Carolina
    With a system of this voltage the high leg would be the square root of any line voltage squared minus the voltage from one end of the center tapped winding to the center tap squared when the system is not under any load. This would be the square root of 76729 minus 19321 or a high leg of 239.5 without load.

    This is also true for any high leg system like a 240/120 delta system. 240*240=57600, 120*120=14400. 57600-14400=43200. The square root of 43200= 207.84 and we round up to 208.
    Once under load the voltages will change on any system be it delta or wye depending on the load applied and the configuration of the load three phase or single phase.

    Also remember that the neutral of a wye system where nonlinear loads are served there can be no reduction of the neutral conductor due to the possibility of high harmonic currents on the neutral conductor.

    Edited the second time to add;

    The laws of physic are not up for debate. Math does not lie.

    If you are seeing 219V on the high leg to ground then the 120/240V nominal system is also high they would be 126 phase voltage and 252 line voltage.
    Last edited: Jul 17, 2012
  12. Rich B

    Rich B DIY Senior Member

    Messages:
    283
    Location:
    New Jersey
    Okay......Somewhere in my past .....the term Red Leg Delta was used and most everyone I work with recognizes the meaning of this term.....We are wrong and from now on I will no longer call it Red Leg Delta....and in the future will use Orange tape on the high leg.....

    Since the NEC writes the rules.....I abide by them once I know what they are so Orange is in Red is out.....LOL
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,532
    Location:
    North Carolina
    Throughout the years I have heard it called high leg, wild leg, red leg, stinger leg, odd out, 208 leg, and a few others that don’t come to mind right now but it has for as long as I have been in the electrical trade identified with an orange color.
    Reached up and grabbed a book at random and it was a 1975 edition and in 215-8 there it was - orange in color. In 200-6(c) of the 1962 cycle it is only required to be identified but no color is mentioned.
    The NEC has always called it high leg. All these other names have come from the field. The white wire is called in the field “neutral†but Article 200 of the NEC calls it the grounded conductor. What we call in the field the grounded conductor is the equipment grounding conductor or bonding conductors.

    It is because of this misnaming that keeps so much confusion about grounding and the thoughts that current somehow flows to earth. It is also this misnaming that causes some folks to want to put red tape on the high leg of a delta system. Don’t think that you are the only one.

    A few years ago I had a class of people seeking their electrical licenses. Most of these men were working in the construction field and had just gotten their experience requirements fulfilled and preparing to take the state mandated test. There was one older man that had worked in maintenance for a textile factory for most of his life and had been laid off due to his plant closing. This class was a 6 hour a week for 10 weeks and this old man walked out three times because he disagreed with the NEC. It was saying something different than what he had learned in the maintenance shop over the years.
    It took him several tries before passing his electrical test to get his license and to my surprise he retired and is now drawing SS and has not renewed his license. I see him from time to time and he still disagrees with the NEC. He says that the book is written by a bunch of educated idiots that don’t know a damn thing about electricity.

    I have always said that using the proper terminology when discussing electrical is very important and was to be very adamant about it here on this site. I have relaxed a little over the years and am bending my opinion toward using the proper terminology when discussing things on these discussion forums but I am learning that I am not doing anyone a favor by doing so. I know that using the proper terminology in the classroom always leads to a better understanding of the subject matter even when I have students get up and walk out in disagreement. Had that old fellow tried to learn the terminology a little better I know that he would not have to take the test so many times before passing?

    All this is just to say that I understand why you used red tape as a lot of folks refer to the high leg as the red leg thus the thoughts that it is required or allowed to be identified with red tape.
  14. Homeownerinburb

    Homeownerinburb New Member

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    525
    Location:
    Los Angeles, CA USA
    There is a field outside of electricity and construction in which I am quite adept. Never mind the field. There I must say:

    "Not to be pedantic, but" and "I appreciate that it is a fine distinction, but" and "for the benefit (and safety) of us all, perhaps we can agree to use"

    No. You are utterly correct. You have buckets of experience. Don't back down.

    And I still think back stab receptacles are crap.
  15. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    I never trusted the back stabs until the boss posted a internal view. Now I trust them.

    In californication, that debased state, with smoke detectors like mosquitos in the house and fire sprinklers, who the hell cares anyway.
  16. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Outlets must tolerate plugs being shoved into them and jerked out of them repeatedly.

    I don't trust backstabs to stand up to that.
  17. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Thats relates to the quality of the contacts to the PLUG. Not to the method of feed wire insertion.
  18. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,532
    Location:
    North Carolina
    I respect Homeowner’s opinion of not trusting this type of installation but I know without a doubt that it is just as good as any other method when done correctly.

    When the installer gets in a big hurry and does not make a proper installation it wouldn’t matter which method is used it will fail.

    When the installer is green it doesn’t matter which method is used there will be a failure if not done correctly. I will venture as far as to say that I have found burnt insulation on conductors from a loosely tightened screw for every back stab I have found that has failed.

    Where the mistrust comes into play is when the repair person sees one that has failed and immediately blames the back stab when the truth of the matter is the receptacle was way overloaded. When that same person sees a receptacle that will no longer hold the blades of the male plug they say the receptacle is worn out but the truth is the same thing has happened here that happened to the back stab. Experience will teach this.
  19. ActionDave

    ActionDave Electrician

    Messages:
    346
    Location:
    Colorado
    I am in the anti-backstab camp, but I have to admit you have moved the needle in my "Reason to Not Like Backstabometer" from Full Hate to Still Hate but Must Be Looked Into More.
    Last edited: Jul 25, 2012
  20. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,792
    Location:
    Long Island, NY
    Wow! that is the most diplomatic thing I have ever heard here:) Nice
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