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3 phase Delta High Leg Single Phase Load

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    Originally posted by Smart $ View Post
    So are you saying Monica's error was the reason for your's...

    Finding it in hindsight don't count
    Nup! Monica asked the question; someone else answered it, and this proves that the word means different things. Strictly speaking, I think the word means horizontal line or something like that. They quit teaching Latin just before I started high school, so it's all Greek to me. Natheless,

    1/2/2 = ?

    (1/2)/2 = 0.25?

    1/(2/2) = 1?
    Last edited by rattus; 01-30-10, 04:59 PM. Reason: Expand
    Don't mess with B+!
    (Signal Corps. Motto)

    Comment


      By the way:

      BTW, here we have an excellent example of the voltage phasors, Van and Vcn, being 180 degrees out of phase. Then,

      Van + Vba = Vcn + Vbc = Vbn

      or,

      120V@0 + 240V@120 = 120V@180 + 240V@60 = 208V@90

      If one draws the phasor diagram it is immediately obvious that the equation above is correct.
      Don't mess with B+!
      (Signal Corps. Motto)

      Comment


        High leg use

        I have seen the high leg (wild leg) range from 180 to 215 volts to ground.
        This is just a cheap way for the utility company to build transformers.
        This is the can you see used in Residental area's a lot around here.
        They just drop that tap, and send the 240volt phases to the residence.
        I always tell my men, If you are on a commercial job and measure 240 volt expect a high leg.
        I have seen this use on lighting circuits, expecially now that electronic ballasts are in fixtures.
        They have auto sensing and will work just fine on the wild leg as long as it is between 100-277volt. you just have to use 277 volt switches, and mark everything well.
        This is becoming common place. due to panel space limitations with the high leg taking 1/3 of the spaces, and only being able to use with a 2 pole operation.
        I would be concerned about using this to run a motor load, or some other equipment, because the voltage may not be stable.
        Because the NEC is only concerned with clearance for rated voltage, and equipment rated to voltage, I don't think this would be addressed in the NEC.
        Tony
        OK Contractor.

        Comment


          Originally posted by TonyEEINC View Post
          ...I would be concerned about using this to run a motor load, or some other equipment, because the voltage may not be stable...
          What do you base this on?
          BB+/BB=?

          Comment


            I have a question to ask. The type of load wasn't really specified. Wouldn't it have to be a load designed to be connected phase to neutral? Otherwise you would be using the neutral as an ungrounded conductor; then 240.22 would apply?

            Comment


              Originally posted by Stopmoving View Post
              I have a question to ask. The type of load wasn't really specified. Wouldn't it have to be a load designed to be connected phase to neutral? Otherwise you would be using the neutral as an ungrounded conductor; then 240.22 would apply?
              Last edited by Smart $; 02-07-10, 04:55 PM.
              [COLOR=RoyalBlue]I will have achieved my life's goal if I die with a smile on my face.[/COLOR]

              Comment


                Originally posted by mivey View Post
                Sounds like a legend to me as they will just charge for what you use. Like with any load, you should tell them your loading so they can size the transformer correctly.
                Depending on the type of metering the POCO is using, they may not be charging for this use. If I remember metering correctly from my POCO days, a 2 stator meter will not see the usage on the high leg. A 3 stator meter would have to be used and, since it is more expensive, they are not typically installed. Where I worked, we used all 2 stator meters and prohibited connection of load to the high leg.

                Comment


                  Originally posted by egoy View Post
                  Depending on the type of metering the POCO is using, they may not be charging for this use. If I remember metering correctly from my POCO days, a 2 stator meter will not see the usage on the high leg. A 3 stator meter would have to be used and, since it is more expensive, they are not typically installed. Where I worked, we used all 2 stator meters and prohibited connection of load to the high leg.
                  BB+/BB=?

                  Comment


                    Assuming that the source is a GROUNDED system 3 phase DELTA:

                    In a "2 wire" circuit that is composed of one GROUNDED conductors, it is best (a code requirement no less) to install the circuit protection in the NON-GROUNDED conductor only.
                    In this case A 208V. 2 wire circuit is composed on one GROUNDED conductor same as a 120V 2 wire circuit. The circuit breaker or fuse should be installed only in the NON-GROUNDED conductor or "high-leg".

                    Comment


                      Vin, welcome to the forum!

                      Originally posted by vinform View Post
                      The circuit breaker or fuse should be installed only in the NON-GROUNDED conductor or "high-leg".
                      As long as the protection in the grounded conductor cannot open independently (i.e., by use of a 2p breaker), it is permitted.
                      Master Electrician
                      Electrical Contractor
                      Richmond, VA

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