Announcement

Collapse
No announcement yet.

"Smart" light switches and correct wiring...

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    "Smart" light switches and correct wiring...

    I've been looking at these "Smart" switches that connect to your WiFi network and can be controlled by software / Alexa etc. They are meant to replace the standard light switches in a building.

    Almost all of them boldly state that a "neutral wire is required" in order for the switch to work properly. And apparently in older buildings, it was not normal to bring the neutral wire to each switch in the building. So here are my questions:

    1) Why would neutral be required in the first place? I mean they have power from the main, so what could possibly exist in these circuits that they won't work without a neutral wire connected?

    2) Couldn't earth ground be substituted in this case where a neutral wire does not exist?

    Thank you,

    #2
    Re: "Smart" light switches and correct wiring...

    I just found the answer to number 1. Apparently, the point of the neutral wire is to ensure that the WiFi circuit remains powered even when the switch is in the off position.

    Comment


      #3
      Re: "Smart" light switches and correct wiring...

      you cannot use ground .

      Comment


        #4
        Re: "Smart" light switches and correct wiring...

        lol this reminds me of the old X10 wireless stuff and how it deals with the lack of neutral - and hence why it was so unreliable... I guess we do have progress now at expensive of needing to wire in neutral (hoping that some idiot electrician didn't wire hot to the target and switched the neutral line... that's a NEC violation...)

        Comment


          #5
          Re: "Smart" light switches and correct wiring...

          Originally posted by EasyGoing1 View Post
          And apparently in older buildings, it was not normal to bring the neutral wire to each switch in the building.
          Correct, a neutral in a switch box wasn't required until the 2011 revision of the NEC (national electric code), so it is common for "end of circuit" switches (switches where "hot" power runs into the fixture box not the switch box, and then a single wire (with neutral recoded as hot) is run to a switch prior to that to not have a neutral in the switch box. Post 2011 NEC (note: individual states adopt NEC revisions at different rates, so the 2011 code wasn't adopted by every state in 2011, I believe some states are still on the 2008 code even today) an "end of circuit" switch would need to use 3 conductor wire with an incoming and outgoing hot (black/red), neutral (capped with a wire nut if the switch doesn't need it), and ground vs. 2 conductor wire (with neutral recoded as hot) commonly previously used.

          The "old" way of doing an end of circuit switch:


          The post-2011 NEC way of doing an end of circuit switch:



          Originally posted by petehall347 View Post
          you cannot use ground .
          Correct, that would be a code violation (which will be a big issue with insurance if anyone is shocked or there is a fire), the correct thing to do would be to bring a neutral to the switch box (generally replacing the existing 2 conductor wire with 3 conductor in the case of an end of circuit switch, though if it is from the original build and not a previous rewire or circuit added after initial construction the wire will be generally stapled to the stud and ceiling joists/trusses, so it may not be as simple as ting a new wire to the old and pulling it through.
          Attached Files
          Last edited by dmill89; 06-15-2021, 09:35 PM.

          Comment


            #6
            Re: "Smart" light switches and correct wiring...

            electronic switches - do you really want to go trying to remove them in the dark to do a recap in a few years??

            Comment


              #7
              Re: "Smart" light switches and correct wiring...

              Originally posted by stj View Post
              electronic switches - do you really want to go trying to remove them in the dark to do a recap in a few years??
              Remove them in the dark? Perish the thought!

              Comment


                #8
                Re: "Smart" light switches and correct wiring...

                Originally posted by petehall347 View Post
                you cannot use ground .
                So as it turns out ... even though this building is rather old ... the gang boxes have neutrals in them ... they aren't connected to anything they are just all wire nutted together, but they're there!

                :-)

                Comment


                  #9
                  Re: "Smart" light switches and correct wiring...

                  Originally posted by EasyGoing1 View Post
                  So as it turns out ... even though this building is rather old ... the gang boxes have neutrals in them ... they aren't connected to anything they are just all wire nutted together, but they're there!

                  :-)
                  That is standard if the circuit runs through the switch box (since the neutrals still have to go the the fixture after the switch, I assume by nutted together you mean neutral wire coming into and going out of the box), it is only cases where the power (and neutral) come to the fixture first and then a switch is "tacked on at the end" with a loop of the hot wire going from the fixture, to the switch and back that there is commonly no neutral in the switch box prior to the 2011 code update.

                  My house built in 1988 has a mix of switches where the circuit passes through the switch box (which have a neutral in the box), and "end of circuit" switches where power goes to the fixture first and the switch box only has a single 2 conductor piece of romex (with the white wire recoded as hot) with power coming in and going out on the same romex and thus no neutral (like the diagram in my previous post). In my case it looks like the original electrician just did whatever required less wire based on where the switches and fixtures were in the run (common, since "professional" electricians will often do things the cheapest way possible that meets code).

                  Comment

                  Working...
                  X