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  • Basic breaker panel anatomy

    This started in another thread, but at the request of a senior member I'm asking it in it's own thread:

    If you put a 110v circuit in a typical single phase panel, you run the black wire to the lug on the breaker feeding off of one of the center busses. You run the white neutral to a neutral bar and the green ground to a ground bar that's typically tied to the neutral bar if they are not one and the same to start with.

    If you put a 220v circuit in, the breaker snaps over two of the meshing busses in the center of the panel and the black wire goes to one lug and the white goes to the other breaker lug leaving the white and the black both going to a center buss. That leaves the bare (or green) copper wire going to the ground buss.

    I'm trying to grasp this. Is the black and the white completing the circuit between each other with the green just being there for safety but not actually being used? I wired the 220v plugs with 6/2 Romex with a black a white and a skinny bare copper. the also had 6/3 Romex with a black, a white, a red and a bare copper. I'm hoping I got the right stuff because there's no place to put the red on the three-pin twist-lock Hubble outlets I got. How does a circuit work without a neutral? I'm hoping the bare isn't a neutral because that skinny wire would be scary if it was continually carrying the same load as the black and white.

    Yes, I know this makes me look stupid. I know how to chase schematics on an 18-wheeler and solder wires, I did it constantly for over 20 years and actually enjoyed it. Residential and commercial electricity is still new to me when it gets beyond replacing the GFI in the bathroom or something simple as that.

    Also, I have the 3" conduit from the transformer to the meter base, then conduit into the shop to a box, then split to two side-by-side 200A panels. I have the ground rod by where the conduit comes out by the shop. I don't see a place to snug-down the bare ground rod wire in the meter base. Does that mean I need to run the copper to one or both panels? I'm in southern Tennessee and the inspector said there is no codes book for my county, just the same basic national codes the other counties use. Electricians from other counties say they have over half a dozen different sets of codes for each county they work so they don't know what he's talking about.

    Inspector said since it wasn't a commercial application I was able to run all plastic conduit in the shop as long as everything is enclosed, which it is.

  • #2
    Hot wires that go to breaker lugs should really both be black--or almost any color other than green or white or bare.

    Ed
    For just a little more, you can do it yourself!

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    • #3
      The Romex comes that way.

      Comment


      • #4
        Usually for 220 VAC one hot conductor is black and the other is red, but it is allowed to use the white wire for the other hot leg as long as it is painted or taped with red or black on both ends where it is connected. Some electrical wiring has just red and black, plus ground, but in larger sizes like #8/2:

        https://www.homedepot.com/p/Southwir...8801/300502957

        While searching I found an interesting article on old wiring:

        https://inspectapedia.com/electric/O...cal_Wiring.php

        This is also interesting:
        https://www.doityourself.com/stry/typesofwireandcable

        More info:
        https://www.thespruce.com/electrical...coding-1152863

        https://www.doityourself.com/stry/22...interpretation
        http://pauleschoen.com/pix/PM08_P76_P54.png

        Paul: www.peschoen.com
        P S Technology, Inc. www.pstech-inc.com
        and Muttley www.muttleydog.com

        Comment


        • #5
          Re: load carrying in the conductors - in a 120v circuit, the current flows through the breaker, out the black wire and returns through the white wire to the neutral bar. In 240v, the current flows out the black wire and returns through the white (or red) wire & through the other breaker. There is no neutral current. The ground wire only carries current if there is a fault that connects the black or white wire to the equipment case. The 2nd breaker in a 240v circuit protects that (white or red) wire in case it is shorted to ground.
          Last edited by Bob Engelhardt; 11-16-2018, 08:34 AM.

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          • #6
            No neutral for US 240V wring, both wires are hot. The circuit is completed from black to red. The ground wire never carries current except in case of a fault.

            The standard service box is where the ground rod wire goes, to the ground bar in the box. From the pole, the three wires are the two hot wires, plus a grounded neutral/ground. THAT wire comes to the service box, and also goes to the ground bar. The first box that has breakers in it, which in some places is on a pole in the yard, is the "service" box, and the ground rod goes to that.

            The meter box does not, in any situation I have seen, get a ground wire to it from the rod, unless it also has breakers in it.



            Originally posted by ed_h View Post
            Hot wires that go to breaker lugs should really both be black--or almost any color other than green or white or bare.

            Ed
            It's MUCH WORSE than that...

            YOU NEVER USE WHITE FOR ANYTHING BUT A NEUTRAL, IT'S IN THE CODE FOR A GOOD REASON. *

            It is said that the white wire kills more people than the hot wires.... That s because there are many ways, including using it as a hot wire without marking it with a different color, for the white wire to be "hot". Everyone is predisposed to assume the white wire has no voltage on it. Do not add to the problem by using it as a hot wire. Use the black and red "romex" instead.

            * yes I know about "switch whips", but let that alone for the moment.
            1601

            Keep eye on ball.
            Hashim Khan

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            • #7
              Think of it this way - In your 240 V circuit, each of the two lines in the center buss is 120 relative to the neutral if there is a neutral. However, , this is alternating current, and one side is at max when the other is at min, thus, between side one and side two you have 120V + 120V == 240V.

              Your 120 V circuits are using only one of those one-side-to-neutral circuits. "Neutral" is a bit of a misnomer. It is really only "neutral" relative to those two lines, not to only one of them. When you are using only one of the 120 V lines the neutral is the "return" side of the circuit and is closer to (but not identical with) ground.

              For a 240V device such as a welder or the elements on an electric kitchen range, no current would flow through the neutral, and it is omitted. "Ground", and safety, are another issue.
              "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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              • #8
                The 3-wire cable is for single phase power. The 4-wire cable is either for three phase power or for special outlets that require both a neutral and ground lead. A good example is an electric clothes dryer.

                metalmagpie

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                • #9
                  If you DO use 4 wire cable having a white wire for 3 phase, you need to re-mark the white wire with colored tape or other permanent means so that it is not confused with the system that wires many 120V outlets from one "240 plus neutral" cable.



                  Newer kitchen ranges DO use a neutral.

                  It used to be that there was an exception for units that used a 120V clock, that they could use the grounding wire for the 120V, so it was a "combined use". That has been eliminated now for several code versions, and even a 240V kitchen range uses a neutral.
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    Originally posted by mickeyf View Post
                    Think of it this way - In your 240 V circuit, each of the two lines in the center buss is 120 relative to the neutral if there is a neutral. However, , this is alternating current, and one side is at max when the other is at min, thus, between side one and side two you have 120V + 120V == 240V.

                    Your 120 V circuits are using only one of those one-side-to-neutral circuits. "Neutral" is a bit of a misnomer. It is really only "neutral" relative to those two lines, not to only one of them. When you are using only one of the 120 V lines the neutral is the "return" side of the circuit and is closer to (but not identical with) ground.

                    For a 240V device such as a welder or the elements on an electric kitchen range, no current would flow through the neutral, and it is omitted. "Ground", and safety, are another issue.
                    Just to clarify a bit. A 240V circuit does not need a neutral...ever. Any device using only 240V only needs two hots and a ground.
                    By adding a neutral you enable the use of one of the hots plus the neutral to create a 120V circuit but the 240V part of the device
                    never uses the neutral. In the case of a kitchen range, for example, the neutral wire allows for a 110V circuit for control purposes
                    but the 240V (for the heating elements) functions independently of the neutral.

                    Originally posted by metalmagpie View Post
                    ...The 4-wire cable is either for three phase power or for special outlets that require both a neutral and ground lead...
                    Three-phase power will work fine with any 4-conductor wire but a cable designed specifically for 3-phase normally doesn't have a
                    white wire. As has been pointed out previously a white wire should only be used as a neutral where 120V power is required...

                    Edit...J. Tiers types faster than I do...
                    Keith
                    __________________________
                    Just one project too many--that's what finally got him...

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                    • #11
                      You should always work as if all the conductors (except bare or green ground wires) are hot. The white wire going back to the service box is "safe", but if you have an electrical box that has two circuits in it, with neutrals tied together, when you disconnect the common connections, the neutral to one of the circuits may be hot, if the load is still connected. It may not be up to code to have a shared neutral, but I have seen this and I may even be guilty of having done this at some time. It is obviously a problem if both circuits are on the same leg (phase), as the load currents will add and can overload the neutral. But in cases where opposite phases are present, the common neutral will carry only the difference in load currents.
                      http://pauleschoen.com/pix/PM08_P76_P54.png

                      Paul: www.peschoen.com
                      P S Technology, Inc. www.pstech-inc.com
                      and Muttley www.muttleydog.com

                      Comment


                      • #12
                        Buy a book like Wiring simplified(Richter/Schwan/Hartwell) and read a bit before doing something really wrong. If you have any sense at all the book will be a very good general guide on how to wire things correctly and why. Mike

                        Comment


                        • #13
                          Originally posted by Fear View Post
                          Yes, I know this makes me look stupid. I know how to chase schematics on an 18-wheeler and solder wires, I did it constantly for over 20 years and actually enjoyed it. Residential and commercial electricity is still new to me when it gets beyond replacing the GFI in the bathroom or something simple as that.
                          When it comes to safety, the only stupid question is the one that wasn't asked. You are asking the right questions.

                          BTW, welcome to the forum.

                          It is perfectly acceptable to use ##/2 romex (white, black, bare) from the big box stores for 220/240 circuits. You will meet most codes by marking both ends of the white wire some other color. Red Heat shrink tubing (you mentioned wiring in 18 wheelers) works great.

                          Comment


                          • #14
                            Another thing to consider is the level of current you're expecting to use from the outlet. You may need to be using a thicker gauge of wire- in which case you might as well use the proper wire -black, red, white, green- or black, red, green if no 110 will ever be derived from it. In many cases it would be a 20 amp circuit instead of a 15 amp, and the standard 14/2 or 14/3 is not rated for it.
                            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                            Comment


                            • #15
                              The confusing point here is the use of the different colors. In the original theory:

                              Green or bare wire is for a safety ground.

                              White is for Neutral. Gray is also generally used for Neutral but I am not sure how official that is.

                              All other colors are for hot conductors. "Hot" means that they have a potential (Voltage) that is not at the ground level - 115V, 230v, 208V, 440V, etc. are all considered hot.

                              Then the confusion comes from the fact that the most common cable, BY FAR, is the one which is INTENDED for use on a 115V circuit. This is the most common type of circuit in all installations in the US. This, most common cable will have three colors: Black, White, and Green or bare. Cables ARE made for 230V and three phase circuits, but your local hardware may not stock them. And they may not be on every electrician's truck when he/she arrives to a job. These cables will have different color combinations like Red, Black, Green (230V type) or Red, Black, Yellow, Green (three phase type), etc.

                              So, it has been allowed to use the most common, Black-White-Green/bare cable (as well as others) to substitute for a cable with the theoretically correct colors. BUT, the Code specifies that the conductors should be either painted or taped with an appropriate color at BOTH ends where they are connected. So, a White wire becomes a Red one if Red paint or tape is applied to both ends. This is legal and it probably saves tons of gas when electricians do not have to go back to the shop on every other job to get the correct cable.

                              When I wired my garage-shop I used the standard 12 gauge, Black-White-bare cable for both 115V and 230V circuits. All were 15 or 20 Amps so that size worked for all of them. For the 230V circuits for my mill and air conditioner, I wrapped the ends of the white wire with red tape for about 2" from the strip point. This is what the code calls for. This single cable is available at almost every local hardware and home supply and by using just one type I probably saved some dollars.

                              I don't think any cable that is made for electric wiring ever has two conductors that are the same color. Even when they make cables with dozens or a hundred or more conductors, they find ways to color them differently, like a base color and a stripe or two stripes of another color. So two blacks, one being taped black, would not be good practice and it is probably not according to code. You should use DIFFERENT colors when taping the ends of the wires. You can find small assortments of several colors of electrical tape in most hardware stores and electric supply houses. You can also buy large size rolls in almost any color you want. I have five color assortments and a large roll of red tape in addition to several rolls of black electrical tape.

                              PS: I also find those assorted colors of tape handy for color coding tools that I purchased for use at specific machines. I use one color for mill tools, another for lathe tools, a third for the drill press, etc.
                              Paul A.

                              Make it fit.
                              You can't win and there is a penalty for trying!

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