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Thread: Wire size, 3ph Delta, 120/240

  1. #31
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Rich B View Post
    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
    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 by jwelectric; 07-17-2012 at 11:58 AM. Reason: to correct math and add spacing

  2. #32
    DIY Senior Member Rich B's Avatar
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    Quote Originally Posted by jwelectric View Post
    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.
    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

  3. #33
    Electrical Contractor/Instructor jwelectric's Avatar
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    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.

  4. #34
    DIY Senior Member Homeownerinburb's Avatar
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    Quote Originally Posted by jwelectric View Post
    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.
    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.

  5. #35
    General Engineering Contractor ballvalve's Avatar
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    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.

  6. #36
    DIY Senior Member Homeownerinburb's Avatar
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    Quote Originally Posted by ballvalve View Post
    I never trusted the back stabs until the boss posted a internal view.
    Outlets must tolerate plugs being shoved into them and jerked out of them repeatedly.

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

  7. #37
    General Engineering Contractor ballvalve's Avatar
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    Thats relates to the quality of the contacts to the PLUG. Not to the method of feed wire insertion.

  8. #38
    Electrical Contractor/Instructor jwelectric's Avatar
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    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.

  9. #39
    Electrician ActionDave's Avatar
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    Quote Originally Posted by jwelectric View Post
    ....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.
    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 by ActionDave; 07-25-2012 at 05:05 PM.

  10. #40
    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by ActionDave View Post
    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 More Must Be Looked Into.
    Wow! that is the most diplomatic thing I have ever heard here Nice
    I am definitely not a pro plumber, but I am a pro crastinator

  11. #41
    DIY Senior Member Homeownerinburb's Avatar
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    JW,

    Went out on a trouble shooting call today. Glad it came. The laborers on the home remodel that I have stumbled across have dug down five feet so far and not yet found the utility's conduit. If we go much further, I am going to tell the general that he needs to pull a permit to dig a deep hole and shore the wretched thing up.

    Wadda ya know? Power out on most of one circuit of four in a one bedroom apartment.

    Looked around for a fair bit.

    And score a point for you: the line went into a box, was stripped of its insulation and wrapped around a screw, and then nutted off to the wire that went off to the parts of the circuit that were not working.

    The line had broken on the outgoing side of the screw. The wire failed because the previous guy had damaged the copper and then possibly twisted it around a lot to get it into the box. The light that the switch served was still working, as the line was intact to the switch.

    Pulled the line off the screw, cut off the exposed copper, bared that and the other, added a third to the screw on the switch, and all was well.

    I had already pulled out a pair of switches thinking the problem was there (the switch not working a light was directly down stream of the other that I described.)

    All four of the screws were loose. I am not a burly guy. I do not have a crushing grip. I twist stuff together as hard as I can. It seems to stay together. What is the problem?

    Your tolerance of back stabs leaves me confused.

    I still insist that the receptacle's female blades in back stabs are flimsy compared to the preferred stuff And I insist that a receptacle that has a yolk strap that passes all the way across the back of the unit is better than one that passes thru the middle of the body. This second arrangement does a very poor job of supporting the the female brass components when the plug gets shoved in there.

    Experience has taught me to trust the unit that is built solidly. I don't object to the back stabs only because they rely on a dodgy contact with the wire (that will weaken in any over amperaging) but because all that I have seen look flimsy in every way.

  12. #42
    DIY Senior Member Homeownerinburb's Avatar
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    JW,

    Went out on a trouble shooting call today. Glad it came. The laborers on the home remodel that I have stumbled across have dug down five feet so far and not yet found the utility's conduit. If we go much further, I am going to tell the general that he needs to pull a permit to dig a deep hole and shore the wretched thing up.

    Wadda ya know? Power out on most of one circuit of four in a one bedroom apartment.

    Looked around for a fair bit.

    And score a point for you: the line went into a box, was stripped of its insulation and wrapped around a screw, and then nutted off to the wire that went off to the parts of the circuit that were not working.

    The line had broken on the outgoing side of the screw. The wire failed because the previous guy had damaged the copper and then possibly twisted it around a lot to get it into the box. The light that the switch served was still working, as the line was intact to the switch.

    Pulled the line off the screw, cut off the exposed copper, bared that and the other, added a third to the screw on the switch, and all was well.

    I had already pulled out a pair of switches thinking the problem was there (the switch not working a light was directly down stream of the other that I described.)

    All four of the screws were loose. I am not a burly guy. I do not have a crushing grip. I twist stuff together as hard as I can. It seems to stay together. What is the problem?

    Your tolerance of back stabs leaves me confused.

    I still insist that the receptacle's female blades in back stabs are flimsy compared to the preferred stuff And I insist that a receptacle that has a yolk strap that passes all the way across the back of the unit is better than one that passes thru the middle of the body. This second arrangement does a very poor job of supporting the the female brass components when the plug gets shoved in there.

    Experience has taught me to trust the unit that is built solidly. I don't object to the back stabs only because they rely on a dodgy contact with the wire (that will weaken in any over amperaging) but because all that I have seen look flimsy in every way.

  13. #43
    DIY Senior Member Homeownerinburb's Avatar
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    I find that backstabs are inferior in every way, including this one.

    They are cheap and flimsy in every way. Never seen one that was not.

  14. #44
    Electrical Contractor/Instructor jwelectric's Avatar
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    Why did I read both of the post above? They are the same post. I know it does me like that from time to time.

  15. #45
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Homeownerinburb View Post
    I find that backstabs are inferior in every way, including this one.

    They are cheap and flimsy in every way. Never seen one that was not.
    I respect you right to believe this and will never try to change your mind. I think that experience will be the best teacher for this.

    There is one thing that I do know for sure and certain, if there was so many problems with using stab-loc devices then the NRTLs through America would have outlawed them long ago.

    I have in the past and will continue to use stab-loc devices as I know that when done correctly they are Just As Good as any other method. I also know that even screws will not save a device that is overloaded. There is no method that can be used that will prevent overloading of a device.

    I can buy a cheap new car or I can buy the most expensive car on the market but either will fail should I decide to lock her in low gear and floor the gas for long enough period. The motor in either will give up.
    The same is true with electrical devices. Installing the top of the line devices and using screws will not prevent the user from overloading the device to the point that the device fails.

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