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Wire size reduction for branch circuits

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    Wire size reduction for branch circuits

    My company installed LED lights in a school. The branch circuit is a 20 amp breaker with 12-2 wire. We installed 40 watt LED panels and a ceiling sensor with 14-3 MC from the switch leg box. The inspector failed us do to the fact the breaker is 20 amp therefore all wire must be 12 gauge. The ceiling sensor only draws 3 amps and has 18 wire hooked up internally. I referenced 240.5 (B)(2) witch states 14 can be used as fixture wire on a 20 amp breaker, but also went to table 402.3 and THWN is no listed. Is there any other code I should reference?
    Thanks all

    #2
    The reference is that the inspector is correct. The sensor is part of the branch circuit not part of the fixture wiring so it must be 12 awg, IMO [MENTION=160324]D_Norris[/MENTION]
    Last edited by Dennis Alwon; 05-01-19, 05:37 PM.
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky

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      #3
      Originally posted by D_Norris View Post
      My company installed LED lights in a school. The branch circuit is a 20 amp breaker with 12-2 wire. We installed 40 watt LED panels and a ceiling sensor with 14-3 MC from the switch leg box. The inspector failed us do to the fact the breaker is 20 amp therefore all wire must be 12 gauge. The ceiling sensor only draws 3 amps and has 18 wire hooked up internally. I referenced 240.5 (B)(2) witch states 14 can be used as [Red]fixture wire on a 20 amp breaker, [Red]but also went to table 402.3 and THWN is no listed. Is there any other code I should reference?
      Thanks all
      Fixture Wire is the wire that is located on the inside of light fixtures. The Branch Circuit wiring is the wiring from the breaker to the outlet box.

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        #4
        I agree, the #14 conductors are part of the branch circuit and must be a minimum of 20 amps unless you want to install 15 amp circuit breakers.
        Rob

        Moderator

        All responses based on the 2017 NEC unless otherwise noted

        Comment


          #5
          Originally posted by xformer View Post
          Fixture Wire is the wire that is located on the [color=red] inside [/color]of light fixtures. The Branch Circuit wiring is the wiring from the breaker to the outlet box.
          But what is the wire in the whip of a troffer? I always thought that was "fixture wire", as I dont see how it could be so small if it isnt.
          Ethan Brush - East West Electric. NY, WA. MA

          "You can't generalize"

          Comment


            #6
            Originally posted by electrofelon View Post
            But what is the wire in the whip of a troffer? I always thought that was "fixture wire", as I dont see how it could be so small if it isnt.

            That would be a fixture tap and fall under 402.5 and 240.5(B)(2).
            Rob

            Moderator

            All responses based on the 2017 NEC unless otherwise noted

            Comment


              #7
              Originally posted by electrofelon View Post
              But what is the wire in the whip of a troffer? I always thought that was "fixture wire", as I dont see how it could be so small if it isnt.
              If it is part of the fixture and its listing it is not under the NEC.

              Roger
              Moderator

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                #8
                Wire from remote ballast can be #14, #16 depending on distance.
                It's considered part of the fixture. Or was code could have changed from the last time I did any work.

                Comment


                  #9
                  190506-2136 EDT

                  Any wiring in series with branch circuit wiring that can carry total branch circuit current, in this case rated 20 A, must be able to handle that rated current.

                  The wire in a load that only connects to a branch circuit only has to carry the current to that particular load. Somewhat the assumption is that the current in the load is only the current of that load, and over normal current is not expected in the individual load. Under some sort of shorting conditions the current in the individual load could be higher than its normal current and might overheat the insulation of the smaller wire. But this is tolerated by the way the code is written. Extension cords are an example of a possible problem, and overloaded extension cords have caused fires.

                  To understand this problem you need to consider that many branch circuits have several parallel loads on the circuit. These loads are individually smaller than the circuit rating. Thus, current to an individual load is smaller than the total circuit load. But when you look at the total circuit, then the circuit current is the sum of all the individual loads.

                  This is why you need to understand circuit theory and analysis.

                  .

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                    #10
                    Just change the breaker to 15 amp.

                    Comment


                      #11
                      Originally posted by xformer View Post
                      Fixture Wire is the wire that is located on the inside of light fixtures. The Branch Circuit wiring is the wiring from the breaker to the outlet box.
                      Fixture wire might extend from luminiare to where it connects to the branch circuit wiring - like a whip from a troffer to a junction box with branch circuit wiring in it.

                      Originally posted by electrofelon View Post
                      But what is the wire in the whip of a troffer? I always thought that was "fixture wire", as I dont see how it could be so small if it isnt.
                      It can be fixture wire it can be branch circuit wire. An allowable tap conductor here doesn't have to be "fixture wire" either.

                      402.10Uses Permitted.

                      [COLOR=#000000]Fixture wires shall be permitted (1) for installation in luminaires and in similar equipment where enclosed or protected and not subject to bending or twisting in use, or (2) for connecting luminaires to the branch-circuit conductors supplying the luminaires.[/COLOR]
                      Wouldn't (2) include the conductors in a "whip" or even conductors ran up a lighting pole to a single luminaire?
                      I live for today, I'm just a day behind.

                      Comment


                        #12
                        Originally posted by infinity View Post
                        That would be a fixture tap and fall under 402.5 and 240.5(B)(2).
                        And 240.5(B)(2) requires the use of fixture wire. Building wire of the same size is not permitted for that application. The only permitted wire types for that application are found in Table 402.3.
                        Don, Illinois
                        (All code citations are 2017 unless otherwise noted)

                        Comment


                          #13
                          Originally posted by don_resqcapt19 View Post
                          And 240.5(B)(2) requires the use of fixture wire. Building wire of the same size is not permitted for that application. The only permitted wire types for that application are found in Table 402.3.
                          I don't see it requiring fixture taps to be fixture wire, it simply states allowable sizes to be used with different branch circuit ratings.

                          410.117(C) allows any conductor type with suitable temp rating for the application to be used as a fixture tap, though that section applies to flush and recessed luminaires.

                          410.62 (cord connected luminaires)also allows, with conditions, the use of smaller conductors than the branch circuit conductors.
                          I live for today, I'm just a day behind.

                          Comment


                            #14
                            Originally posted by kwired View Post
                            I don't see it requiring fixture taps to be fixture wire, it simply states allowable sizes to be used with different branch circuit ratings.

                            410.117(C) allows any conductor type with suitable temp rating for the application to be used as a fixture tap, though that section applies to flush and recessed luminaires.

                            410.62 (cord connected luminaires)also allows, with conditions, the use of smaller conductors than the branch circuit conductors.
                            The wording in 240.5(B)(2) says those sizes are fixture wire. When you buy a pre-made whip with conductors smaller than 14, they are always made up using fixture wire.
                            240.5(B)(2) Fixture Wire. Fixture wire shall be permitted to be tapped to the branch-circuit conductor of a branch circuit in accordance with the following: ...
                            The types of conductors that are fixture wire are listed in Table 402.3.
                            Don, Illinois
                            (All code citations are 2017 unless otherwise noted)

                            Comment


                              #15
                              Originally posted by don_resqcapt19 View Post
                              The wording in 240.5(B)(2) says those sizes are fixture wire. When you buy a pre-made whip with conductors smaller than 14, they are always made up using fixture wire.

                              The types of conductors that are fixture wire are listed in Table 402.3.
                              So I could take any light fixture and use up to 50 feet of 18 AWG fixture wire in a chapter three raceway to connect it to the branch circuit? OR does it have to come from the factory as part of the fixture to use 240.5(B)(2)?
                              Ethan Brush - East West Electric. NY, WA. MA

                              "You can't generalize"

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