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120V connection from residential 240V

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  • 120V connection from residential 240V

    Recently I replaced a 240V electrical HWT to gas HWT in a house. I removed wires after upstream juction box.

    there are two 120V with bare ground wires in the box. If I need 120V, I can change one 120V wire to neutral at main panel.

    I have a qestion here.

    When I checked power at the junction box just before HWT, I got 240V with two lives or 120 with one live with ground.

    If I connect one live and ground to get 120V, what is wrong?

    I should change one live to neutral to get proper 120V but when I checked one live and neutral also get 120V.

    Is it ok or not? if not then why?

    Thank you.

  • #2
    Re: 120V connection from residential 240V

    You can not use the ground as a neutral. The ground is not meant to be a current carrying conductor (which the neutral is - return path) because it is usually undersized and the ground is an emergency return path to trip the breaker if there is a neutral issue and the box becomes hot. If it were my house I would likely switch a hot for neutral and tape each end white if it was a direct run back to the panel. There has been discussion as to the legality of this but a quick call to the local inspector will resolve that.

    Comment


    • #3
      Re: 120V connection from residential 240V

      IF I am understanding what you want to do, it should be easily doable if you hook the wire up correctly in the breaker box and wire it up correctly in the wall box,
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      • #4
        Re: 120V connection from residential 240V

        Okay, so you have a #10, red, black and bare cable right? This a common 230 volt cable arrangement. This is a 230 volt circuit only, not a 120/230 volt circuit. You are missing the neutral and all the voltage measurements are correct. The problem is you cannot remark a red to white or a black to white. You are not supposed too, that is. You have what you need for a 120 volt circuit.

        This is what I would do in my house, but not in your house.

        1) Re-mark either the red or black with white tape or paint on BOTH ends.
        2) Remove the existing 2 pole 30 amp breaker and install one 20 amp single pole breaker. You will have an open slot that must be covered. They make blanks that snap into place.
        3) Connect the re-marked (white) to the neutral bar in the panel.
        4) Connect the bare ground to the ground or neutral bar if this is your main panel. The bare should be already connected.
        5) Connect the remaining black or red to the 20 amp single pole breaker. Make sure its turned off.
        6) Install a 20 amp single receptacle and matching plate.
        7) Turn on the 20 amp breaker.

        I would use a high quality 20 amp receptacle that has pressure connections for the wires. This way I do not have to concern myself with wrapping #10 wires under the screws.

        This is a code violation. Safe, but still a violation. Re-marking wires of this size is the issue.
        Last edited by John Valdes; 03-16-2010, 11:17 AM.
        Licensed Electrician

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        • #5
          Re: 120V connection from residential 240V

          John,

          "The problem is you cannot remark a red to white or a black to white. You are not supposed too"

          Is it illigal in your code, if I wrap a black, blue or red wire with white tape or spray with white paint to use as a neutral wire?

          Comment


          • #6
            Re: 120V connection from residential 240V

            Originally posted by John Valdes View Post
            This is a code violation. Safe but still a violation. Re-marking wires of this size is the issue.
            What is the logic behind that? Any reason the size matters?

            Comment


            • #7
              Re: 120V connection from residential 240V

              I know it's a violation. Stupid rule in my opinion, but still a violation. I stated I would only do this in my house and not anyone else's house.
              I hope I made that clear, very clear.

              cpw......Only the authors of the NEC can give you the correct answer to your question. As I said above I think it is a stupid rule.
              Licensed Electrician

              Comment


              • #8
                Re: 120V connection from residential 240V

                If you do someone's house, what would you do?

                Run new line or get only neutral from close by or something else?

                Thank you very much.

                Comment


                • #9
                  Re: 120V connection from residential 240V

                  Originally posted by khlee815 View Post
                  If you do someone's house, what would you do?

                  Run new line or get only neutral from close by or something else?

                  Thank you very much.
                  Run a new 120 circuit. New cable and new breaker.

                  Picking up a neutral from another circuit is also a code violation. So you would have to replace the cable too. Good question!
                  Licensed Electrician

                  Comment


                  • #10
                    Re: 120V connection from residential 240V

                    kh. what color are the conductors in you circuit? what people have done around here is mark white wire with black tape for wh. breid.............

                    Comment


                    • #11
                      Re: 120V connection from residential 240V

                      [QUOTE=breid1903;287762]kh. what color are the conductors in you circuit? what people have done around here is mark white wire with black tape for wh. breid............[QUOTE]

                      He never did say, I put my money on red, black and bare, and he never said anything.
                      In the US, the NEC forbids the re-marking of wires smaller than #4. I am fairly certain that is where they draw the line.
                      There are exceptions. Like in a switch loop. But not in this circumstance.
                      Licensed Electrician

                      Comment


                      • #12
                        Re: 120V connection from residential 240V

                        Originally posted by John Valdes View Post
                        Run a new 120 circuit. New cable and new breaker.

                        Picking up a neutral from another circuit is also a code violation. So you would have to replace the cable too. Good question!
                        Just want to add that picking up a neutral from another circuit can easily cause that neutral to exceed its current rating. So of course, it is a code violation... but important to realize that it's a real fire hazard. Not a debatable thing like re-identifying wires...

                        Comment


                        • #13
                          Re: 120V connection from residential 240V

                          i wasn't telling him to mark it. if it was marked black or red with tape, then remove the tape. my guess is he has already done what he asked if he could do and wanted an ok. breid..............

                          Comment


                          • #14
                            Re: 120V connection from residential 240V

                            i haven't wired a new circuit for wh a long time. the ones that i see here are just 10/2wg nm cable. black, white and bare. never seen a red. breid..............

                            Comment


                            • #15
                              Re: 120V connection from residential 240V

                              Originally posted by breid1903 View Post
                              i haven't wired a new circuit for wh a long time. the ones that i see here are just 10/2wg nm cable. black, white and bare. never seen a red. breid..............
                              Thats true. Usually. But when someone tells me they have a 10/2 cable without a white I automatically knew it has to be red, black and bare. Thats all it can be.
                              Licensed Electrician

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