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250.118 - using emt conduit as a ground

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    #91
    Originally posted by Gary11734 View Post

    As I said, NO WAY would this ever get into the code. NEVER! I guarantee the code will finally get rid of the conduit as an effective means to clear a fault... It's just a matter of time...
    Please explain how a single fault clearing path through a single wire equipment ground is more effective than multiple paralleled paths through bonded metal conduits

    Comment


      #92
      Originally posted by Gary11734 View Post
      NEVER! I guarantee the code will finally get rid of the conduit as an effective means to clear a fault... It's just a matter of time...

      That'd be an awful tall order to fill seeing as how conduit has already been proven to be a better conductor than the wire type.

      Jap>

      Comment


        #93
        Originally posted by Gary11734 View Post
        Plastic boxes/wire, and grounding are comparing apples and oranges...
        It isn't when your talking about conserving resources.

        Those who don't learn how to adapt to the ever changing cost saving options that are available in the electrical industry will eventually find themselves behind the 8 ball on most project business.

        Not everyone has industrial or commercial clients that will turn a blind eye to the difference in price every time.

        Jap>

        Comment


          #94
          Originally posted by jap View Post
          That'd be an awful tall order to fill seeing as how conduit has already been proven to be a better conductor than the wire type.
          Agreed, but if it happens, it will be from the argument that conduit fittings might be installed improperly at many places more difficult to inspect. We've all seen conduit runs sagging years later with loose fittings.

          Yes, we've all seen improperly terminated wire EGC's, too, but that will be ignored.

          Comment


            #95
            Wow 10 pages on a EGC in EMT!
            As your self appointed resident code historian I will add that;
            1/2" EMT (properly installed to NEC minimum) has a rating of 40 Amps as an EGC, 3/4" EMT has a rating of 60 Amps, 1" EMT = 100 Amps.
            The conduit sizes were part of the equipment grounding conductor sizes from at least 1930 - 1965, what is T250.122 today.

            The photo is from the 1965 NEC.

            Cheers
            Attached Files
            Comments based on 2017 NEC unless otherwise noted.

            Comment


              #96
              Better yet.

              Let's do an expirement.

              Let's consider we're all mostly above average and are able to run conduit with all the fittings tight from beginning to end. I realize that might be a challenge,but, I feel we can do it.

              Let's run 100' of 1/2" EMT straight from a panel to a 120v receptacle outlet, let's say on 2x4's or some other non conductive surface.

              Now, let's pull wire to that receptacle, but, we're only going to pull 2 insulated wires a hot and a neutral in the conduit.

              To add to the fun, we're going to strip about 5' of insulation off of the hot conductor at about the 50' mark so it will be sure to contact the inside of the conduit when we pull it in.

              We terminate the wiring on both ends and turn on the breaker. Dead short and the breaker trips because it used the conduit as a return path.

              Now we pull in a green insulated EGC,terminate it at the panel and receptacle, and turn the breaker on again, and, once again dead short and the breaker trips.

              What did installing the wire type EGC do to help clear the fault? Not a damn thing.

              Now, let's separate the EMT from the metal box at the receptacle end and turn the breaker back on.

              Again, dead short and the breaker trips. What did the wire type EGC do to help clear the fault that time?. Not a damn thing.

              Now lets leave the EMT seperated from the receptacle box, and, we're going to go back and separate every joint in the conduit by an inch simulating a shotty install and turn the breaker back on.

              Hey!!! the breaker held that time even though we have a section of EMT at about the 50' mark That's energized with 120 volts. Since the seperated pipe can't clear that fault, what will our wire type EGC do to help clear that danger? Not a damn thing.

              You can pull a wire type EGC and bond to your hearts content, but, depending on where the fault occurs,and where the conduit return path may have failed makes all the difference in whether or not it's actually going to help.


              Jap>

              Comment


                #97
                Originally posted by jap View Post
                Better yet.

                Let's do an expirement.

                Let's consider we're all mostly above average and are able to run conduit with all the fittings tight from beginning to end. I realize that might be a challenge,but, I feel we can do it.

                Let's run 100' of 1/2" EMT straight from a panel to a 120v receptacle outlet, let's say on 2x4's or some other non conductive surface.

                Now, let's pull wire to that receptacle, but, we're only going to pull 2 insulated wires a hot and a neutral in the conduit.

                To add to the fun, we're going to strip about 5' of insulation off of the hot conductor at about the 50' mark so it will be sure to contact the inside of the conduit when we pull it in.

                We terminate the wiring on both ends and turn on the breaker. Dead short and the breaker trips because it used the conduit as a return path.

                Now we pull in a green insulated EGC,terminate it at the panel and receptacle, and turn the breaker on again, and, once again dead short and the breaker trips.

                What did installing the wire type EGC do to help clear the fault? Not a damn thing.

                Now, let's separate the EMT from the metal box at the receptacle end and turn the breaker back on.

                Again, dead short and the breaker trips. What did the wire type EGC do to help clear the fault that time?. Not a damn thing.

                Now lets leave the EMT seperated from the receptacle box, and, we're going to go back and separate every joint in the conduit by an inch simulating a shotty install and turn the breaker back on.

                Hey!!! the breaker held that time even though we have a section of EMT at about the 50' mark That's energized with 120 volts. Since the seperated pipe can't clear that fault, what will our wire type EGC do to help clear that danger? Not a damn thing.

                You can pull a wire type EGC and bond to your hearts content, but, depending on where the fault occurs,and where the conduit return path may have failed makes all the difference in whether or not it's actually going to help.


                Jap>
                You need to read my first post on this.

                The question was;

                IF WE ALWAYS PULLED A GROUND WIRE IN since the first days of Edison and NEVER used the raceway system to clear a fault, then, could we now say today we want to eliminate the wire and use only the conduit? I say, NO. It would NEVER pass the code gurus in today's climate.

                Now, we have back data of one hundred years that conduit can be an effective means to clear a fault. But, that doesn't matter. Today, more is better and they will eliminate the conduit system for the wire in due time...

                And, we are basing the grounding means of conduit on a workmanlike manner, not some trunk slammer doing moonlighting. The conduit system is an efficient means to clear a fault but we will eliminate it in due time for that precious green wire. Now, of course, IMHO!

                Comment


                  #98
                  Originally posted by Gary11734 View Post
                  You need to read my first post on this.


                  Today, more is better and they will eliminate the conduit system for the wire in due time...
                  Unlikely, metallic conduit is the better EGC and the NFPA recognizes this in NFPA 99 comentary, there is also the GEMI research.

                  https://steeltubeinstitute.org/steel...ysis-research/

                  Roger
                  Moderator

                  Comment


                    #99
                    Originally posted by Gary11734 View Post
                    The conduit system is an efficient means to clear a fault but we will eliminate it in due time for that precious green wire. Now, of course, IMHO!

                    Electricity itself will never let us eliminate the conduit system as an efficient means to clear a fault.

                    It's going to utilize it regardless of whether a code rule ever gets put in place to add an additional green wire to it.


                    JAP>

                    Comment


                      Originally posted by Gary11734 View Post
                      What codebook year did we not worry or care about if we cleared a fault?
                      You never seen K&T or two conductor NM cable? Obviously equipment grounding wasn't so much of a priority at one time.
                      I live for today, I'm just a day behind.

                      Comment


                        Originally posted by tortuga View Post
                        Wow 10 pages on a EGC in EMT!
                        As your self appointed resident code historian I will add that;
                        1/2" EMT (properly installed to NEC minimum) has a rating of 40 Amps as an EGC, 3/4" EMT has a rating of 60 Amps, 1" EMT = 100 Amps.
                        The conduit sizes were part of the equipment grounding conductor sizes from at least 1930 - 1965, what is T250.122 today.

                        The photo is from the 1965 NEC.

                        Cheers

                        I just love stuff like that.
                        It's so easy to read.

                        Thanks for posting.

                        JAP>

                        Comment


                          Originally posted by tortuga View Post
                          Wow 10 pages on a EGC in EMT!
                          As your self appointed resident code historian I will add that;
                          1/2" EMT (properly installed to NEC minimum) has a rating of 40 Amps as an EGC, 3/4" EMT has a rating of 60 Amps, 1" EMT = 100 Amps.
                          The conduit sizes were part of the equipment grounding conductor sizes from at least 1930 - 1965, what is T250.122 today.

                          The photo is from the 1965 NEC.

                          Cheers

                          The same chart from 1937:

                          Click image for larger version

Name:	EMT as GND 1937.jpg
Views:	1
Size:	65.8 KB
ID:	2380382

                          The language probably predates it back to the 1920, but it's sometimes difficult to trace as 1937 was the first major overhaul of the numbering system used.
                          Attached Files

                          Comment


                            Originally posted by tortuga View Post
                            Wow 10 pages on a EGC in EMT!
                            As your self appointed resident code historian I will add that;
                            1/2" EMT (properly installed to NEC minimum) has a rating of 40 Amps as an EGC, 3/4" EMT has a rating of 60 Amps, 1" EMT = 100 Amps.
                            The conduit sizes were part of the equipment grounding conductor sizes from at least 1930 - 1965, what is T250.122 today.

                            The photo is from the 1965 NEC.

                            Cheers
                            That was 1965. THHN/THWN didn't yet exist, you almost never were going to exceed the rating based on what size conductors you could fit inside, exception maybe with a feeder tap situation. You also still had service conductors inside raceways with somewhat unlimited current limits.

                            I have easily exceeded the values in that table with more recent installs involving THHN/THWN and motor circuits.
                            I live for today, I'm just a day behind.

                            Comment


                              I bet those guys from way back then would get a kick out of how overly confusing we've made all this electrical stuff.


                              JAP>

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