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2008's 310.15(B)(6) "100% Rule" Eliminated

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    2008's 310.15(B)(6) "100% Rule" Eliminated

    Looks like, for now, the rule stating that a conductor must serve 100% of the dwelling unit's load to use Table 310.15(B)(6) is going away:

    6-88 Log #3064 NEC-P06 Final Action: Accept in Principle
    (310.15(B)(6))
    __________________________________________________ _____________
    Submitter: Mike Holt, Leesburg, FL
    Recommendation: Revise text as follows:
    (6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of one-family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder(s) to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard(s) that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit. The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.

    Substantiation: This proposal changes this section back to the 2005 code language. Requiring the feeder to serve the entire load in order to use this section simply does not make sense. For example, consider a 200A service for a dwelling. If the installation consists of a single 200A breaker, 200A feeder and 200A panel, the user can use this section. If the air conditioners for this house are removed from the 200A panel and put outside at the service equipment, there is now less load on the feeder conductors, yet the according to the 2008 revision to this rule, I must now make the conductors larger to serve a smaller load! Obviously this doesn’t make sense.
    Panel Meeting Action: Accept in Principle
    Panel Statement: See panel action on Proposal 6-83a.
    Number Eligible to Vote: 11
    Ballot Results: Affirmative: 11

    #2
    Didn't think I could find more reason to admire Mike Holt than I already do, but this is in my humble little opinion, a great reason to do so. Thank you Mr. Holt for bringing this up and providing common sense reason to the issue.
    85deg. an Sunny today.

    Comment


      #3
      Originally posted by macmikeman View Post
      Didn't think I could find more reason to admire Mike Holt than I already do, but this is in my humble little opinion, a great reason to do so. Thank you Mr. Holt for bringing this up and providing common sense reason to the issue.
      Even though accepted in principle, the current draft is somewhat different...

      310.15(7) 120/240-Volt, Single-Phase Dwelling Services and
      Feeders
      [ROP 6-53].
      (a) For individual dwelling units of one-family, twofamily,
      and multifamily dwellings, conductors, as listed in
      Table 310.15(B)(7), shall be permitted as 120/240-volt,
      single-phase service-entrance conductors and servicelateral
      conductors. [ROP 6-53]
      (b) Feeder conductors for a dwelling unit, after adjustments
      and corrections, shall not be required to have an
      ampacity rating greater than the Table 310.15(B)(16) allowable
      ampacity of the service conductors.
      [ROP 6-83a, 6-85]
      (c) The grounded conductor shall be permitted to be
      smaller than the ungrounded conductors, provided the requirements
      of 215.2, 220.61, and 230.42 are met.
      I will have achieved my life's goal if I die with a smile on my face.

      Comment


        #4
        Hip! Hip! Hooray!

        Outstanding!
        Master Electrician
        Electrical Contractor
        Richmond, VA

        Comment


          #5
          I'm sorry. I don't follow. 334.80 and 338.10 seem to be intact, slightly clarified, but still present.
          At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

          Comment


            #6
            Originally posted by Smart $ View Post
            SE is not even listed as a conductor type in Table 310.15(B)(16).
            I am confused by this statement. The 2008 does list se cable and the proposal to eliminate the conductors from the title of Table 310.15(B)(6) was rejected. What am I missing besides some brain cells.

            6-89 Log #3493 NEC-P06 Final Action: Reject
            (Table 310.15(B)(6))
            __________________________________________________ _____________
            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

            Comment


              #7
              Originally posted by augie47 View Post
              I'm sorry. I don't follow. 334.80 and 338.10 seem to be intact, slightly clarified, but still present.
              See below...
              338.10(B)(4)(a) Interior Installations. In addition to the provisions
              of this article, Type SE service-entrance cable used for interior
              wiring shall comply with the installation requirements
              of Part II of Article 334, excluding 334.80. [ROP
              7-133]
              [ROP 7-133]
              I will have achieved my life's goal if I die with a smile on my face.

              Comment


                #8
                Originally posted by Dennis Alwon View Post
                I am confused by this statement. The 2008 does list se cable and the proposal to eliminate the conductors from the title of Table 310.15(B)(6) was rejected. What am I missing besides some brain cells.
                Hmmm.... brain cells.... what are those???

                I referring to Table 310.15(B)(16), depicted in part below, in the draft (essentially the same as current Table 310.16)



                310.15(B)(7)(b) sends you to this table for comparison of feeder ampacity not greater than the allowable ampacity of service conductors.

                Do you see SE in the table?
                I will have achieved my life's goal if I die with a smile on my face.

                Comment


                  #9
                  Originally posted by Smart $ View Post
                  See below...
                  338.10(B)(4)(a) Interior Installations. In addition to the provisions
                  of this article, Type SE service-entrance cable used for interior
                  wiring shall comply with the installation requirements
                  of Part II of Article 334, excluding 334.80. [ROP
                  7-133]
                  At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

                  Comment


                    #10
                    I will have achieved my life's goal if I die with a smile on my face.

                    Comment


                      #11
                      At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

                      Comment


                        #12
                        Yes. The thermal insulation part. Per 2008, my interpretation of 310.15(B)(6) trumping 338.10/334.80 made no consideration for thermal insulation. Never really thought about it, but it makes sense.
                        I will have achieved my life's goal if I die with a smile on my face.

                        Comment


                          #13
                          Well here's another worthy of debate issue on the subject...

                          Say the "insulation clause" is put into effect. If a Type SE cable were used as an interior feeder and only a short section of it were "in" insulation, the application of [2008] 310.15(A)(2) Exception could "trump" the insulation clause. Actually, the Exception could do that now under 2008 if most of the cable is outside.
                          I will have achieved my life's goal if I die with a smile on my face.

                          Comment


                            #14
                            so the power company will run larger wires to the house? I doubt that. unless i read it wrong they run what ever they think is good enough in the jersey state.

                            Comment


                              #15
                              Originally posted by Smart $ View Post
                              Say the "insulation clause" is put into effect. If a Type SE cable were used as an interior feeder and only a short section of it were "in" insulation, the application of [2008] 310.15(A)(2) Exception could "trump" the insulation clause. Actually, the Exception could do that now under 2008 if most of the cable is outside.
                              That may be true in some instances but if there is fire caulk thermal insulation or sealing foam being used to seal the hole coming from the outside, then the provisions of 310.15(A)(2) exception shall not apply
                              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

                              Comment

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