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    GFCI Receptacles

    The code seems very clear on installing GFCI receptacles in Residential applications, but for a commercial installation, what is the maximum number of 120V/20A GFCI receptacels that can be put on a 20A circuit? Where is this stated in the NEC? Thx.

    #2
    what is the maximum number of 120V/20A GFCI receptacels that can be put on a 20A circuit? Where is this stated in the NEC?
    13, Take a look at 220.14(I). This requires that receptacle outlets in a non-residential structure be calcultated at not less than 180 volt-amperes.

    Chris

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      #3
      It's not stated anywhere.


      There are some that believe there is an NEC limit on the number on receptacles that can be installed on 20 amp circuits. I am not among them. (Edited to add that I see Chris is among them, since his post hit the board while I was typing.)

      I believe it is a design choice, and not a requirement. But I am sure everyone will agree that there is no single sentence in the NEC that explicitly states, for any facility (e.g., residential or commercial), that you may not put more than XXX outlets on a YYY amp circuit. I view article 220 as having nothing to do with the design of branch circuits, but rather is only concerned with calculation of load. In order to reach the conclusion that the NEC has a limit of this nature, you have to put several articles together. I do not believe that was the way the code authors intended us to discern their intended requirements.
      Last edited by charlie b; 01-10-07, 01:00 PM.
      Charles E. Beck, P.E., Seattle
      Comments based on 2017 NEC unless otherwise noted.

      Comment


        #4
        Charlie

        I have never heard this opinion expressed before; what an interesting observation. I completely agree.

        Brian Dolan

        Comment


          #5
          I agree with Charlie b. The code doesnt state how many can be put on the circuit. I believe this also is because there general. We dont know whats going to be plugged in to what circuit for how long and at what wattage unless is dedicated or a dedicated circuit right?

          Comment


            #6
            OK I'm listening - please explain how if the load of a recept outlet is calc'd @ 180va that one can put more than 13 on a 20. I'm not argueing, I'm intrigued and I'm learning. My guess is that it is the same idea as the range circuit thread?
            Last edited by bkludecke; 01-10-07, 02:08 PM.
            Bob on the left coast.

            Comment


              #7
              210.19(A)(1) states "Branch-circuit conductors shall have an ampacity not less than the maximum load to be served."

              How do we figure the "maximum load to be served"?

              220.10 states "Branch-circuit loads shall be calculated as shown in 220.12, 220.14, and 220.16."

              220.14 states "in all occupancies, the minimum load for each gereral-use receptacle and outlets not used for general illumination shall not be less than that calculated in 220.14(A) through (L) the loads shown being based on nominal branch-circuit voltages."

              So if I have a branch-circuit that has only gereral-use receptacles that have no specific loads I must calculate the branch-circuit load in accordance with 220.14(I) which states that each receptacle outlet be caluclated at not less than 180 volt-amperes.

              Chris
              Last edited by raider1; 01-10-07, 03:04 PM.

              Comment


                #8
                I know that is the logic, Chris. But I am not prepared to endorse it. As I implied earlier, this is a matter of some debate. And I don't want to rehash the debate here, for fear of taking over the original topic.

                If you wish to use some part of 220 as the basis for designing (i.e., calculating the load on) a branch circuit, you are welcome to do so. But I see no direct connection between 210 and 220. For example, 210.19(A)(1) does not say that you MUST use the methods of 220 to calculate the load on the branch circuit you are now designing. You may certainly do so, but nothing commands you to do so, and nothing forbids me from doing it some other way.
                Charles E. Beck, P.E., Seattle
                Comments based on 2017 NEC unless otherwise noted.

                Comment


                  #9
                  And I don't want to rehash the debate here, for fear of taking over the original topic.
                  Agreed, this topic has been hashed and rehashed before. I doubt that either one of us will change the others mind with a new debate.

                  Chris

                  Comment


                    #10
                    Ok now Im wondering. So you calculate or are calculateing to a get a general load calculation right? So in keeping with what your saying your calculating for a circuit amount, lets say you come up with 5 cir's. Then when you wire it you dont have to adhear to any constants as far as amount of general recp's on thoses cir's. So the amount of circuits calc'd are lets say 5. Then on those 5 cir's you can put umpteen recp as long as there general. I guess I can see that because your not knowing what loads are going to be put on each recp. Correct?

                    Comment


                      #11
                      Originally posted by charlie b
                      And I don't want to rehash the debate here, for fear of taking over the original topic.
                      "fear of taking over the original topic"
                      I think you're talking about the original topic.

                      I'm familiar with the last sentence of 220.14(J) "No additional load calculations shall be required for such outlets" so the 3va per sq foot of Dwelling units on Table220.12 works out to 600sq' for 15a and 800sq' for 20a but 220.14(J) is titled "Dwelling Occupancies".

                      For commercial buildings you have to look back to the main paragraph of 220.14. . No matter what the requirements of 210 are, 220.14 states, "In all occupancies, the minimum load for each outlet for general-use receptacles and outlets not used for general illumination shall not be less than that calculated in 220.14(A) through (L)"

                      Since 220.14 says "shall not be" and 220 is just as much a part of the code as 210, why wouldn't the 180va limit of 220.14(I) or (L) apply ?

                      David
                      David
                      I get paid for doing stuff in Ohio

                      Comment


                        #12
                        Originally posted by rasmithircgov
                        Ok now Im wondering. So you calculate or are calculateing to a get a general load calculation right? So in keeping with what your saying your calculating for a circuit amount, lets say you come up with 5 cir's. Then when you wire it you dont have to adhear to any constants as far as amount of general recp's on thoses cir's. So the amount of circuits calc'd are lets say 5. Then on those 5 cir's you can put umpteen recp as long as there general. I guess I can see that because your not knowing what loads are going to be put on each recp. Correct?
                        If you are calculating for a dwelling unit using section 220.14(J), I would say that you are correct.

                        But 220.14(I) is in section II for Branch-circuit Load Calculations, and as such this is dealing with the load for a single branch-circuit and each receptacle "Shall be calculated at not less than 180 volt-amperes".

                        Chris

                        Comment


                          #13
                          I don’t recall being a participant in the earlier debate(s) on this issue. Let me just give a vague notion of my view, and leave it there. Feel free to disagree, but I don’t intend to disagree back or to cite any supporting NEC articles.

                          My general notion is that 220 is fiction, and 210 is reality.

                          By that I mean that 220 is all about making sure the facility has enough power available from the utility (and at lower-level feeders and branch circuits) to handle the loads that the NEC authors consider to be the minimum required for a safe installation. 220 has nothing to do with the ACTUAL equipment being installed. Specifically, it does not account for the current that will be drawn by any installed component at any point in time. We are allowed, for example, to presume that all ten residents in a ten-unit apartment building will not all be running their electric ranges at high power at the same time. But in reality it might happen, especially during certain holidays. If everyone does, and if the main trips, then the residents won’t be happy. But the NEC tells us that it does not promise to make everyone happy. We don’t have to supply enough electricity to power every item in the building at the same time. That is the essence of 220.

                          By contrast, 210 tells us, in explicit terms, what circuits must be present, what circuits can serve only one purpose, what circuits must have GFCI or AFCI, what locations must have receptacles, and gives a host of other real life requirements. It is real stuff.

                          Let me address this specifically:
                          Originally posted by raider1
                          210.19(A)(1) states "Branch-circuit conductors shall have an ampacity not less than the maximum load TO BE SERVED." (My emphasis)

                          This does not talk about the calculated load. The load “to be served” is the real, actual, physical stuff that gets built. So if I put in a receptacle, what load will be served? A table lamp, perhaps, rated at 60 watts (not 180 VA)? A portable space heater, perhaps, rated at 1200 watts (not 180 VA)? A stereo that draws 1.5 amps (OK, that one is 180 VA)? We don’t know, and we can’t know, unless we are the owners of the house being built, and we have complete plans showing what will get plugged into each receptacle.

                          And that brings me to,
                          Originally posted by raider1
                          How do we figure the "maximum load to be served"?

                          It’s a good question and a fair question. If YOU choose to use 180 VA per receptacle, I think you will have made a good choice. But the “load to be served” is not the same as the “calculated load.” 210.19(A)(1) never points you to 220. I say again, nothing commands me to use that method. The method makes some sense, but there are no words that explicitly or implicitly require it.

                          If I designed my new mansion (still pending notification of having won a big lottery prize), and if I wanted a long hallway with 60 watt floor lamps on both sides every 6 feet or so, and if this hallway wound up with 24 receptacles, so that the total “load to be served” is 12 amps, I can put all 24 receptacles on the same 20 amp circuit, and you cannot tell me it violates 210.19(A)(1).

                          I guess that my bottom line is that if you wish to convince me that the limit is 13, then I must ask you to either show me where 210 tells me to use 220, or compose your argument without the use of 220.
                          Charles E. Beck, P.E., Seattle
                          Comments based on 2017 NEC unless otherwise noted.

                          Comment


                            #14
                            Your new mansion will be a 1 family dwelling most likely so the 13 on a 20 wouldn't apply anyway. My new mansion will be a mud hut out in the wilderness with no utilities; I'll wire it your way anyway.
                            Bob on the left coast.

                            Comment


                              #15
                              Originally posted by sarsenault
                              T...what is the maximum number of 120V/20A GFCI receptacels that can be put on a 20A circuit?
                              Don't some manufac. have a limit on this?


                              I have some cloudy recollection of a similar post/question....anyone remember that?

                              Comment

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