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  • So where does neutral go?

    I've got 2 hot legs to the main switch and they go to the VFD.

    If ground goes to the bonding screw in the switch box, where the heck does the neutral go to?

    The VFD I have has single phase input/3 phase out.
    They only want the two hot legs to the VFD. A chassis ground and the 3 feeds go to the motor which by way of attachment is grounded to the machine so....where does the neutral go?
    Len

  • #2
    If the vfd only has L1 and L2 connections then the neutral gets a wire nut and doesn't go anywhere. The neutral connection is only needed if you need 110V somewhere.

    --
    Cameron

    Comment


    • #3
      Right -- two hots and a ground for 240V. No neutral.

      If you have a neutral because you're also wanting to get 120V out of this same setup, it gets tied to the ground bar in the breaker box, along with the ground wire, and from that point on the neutral and the ground STAY SEPARATE.

      Then you can get 120V from either hot leg, and the neutral. While this works -- getting both 240V and 120V from a 3-wire setup, from a single double-pole breaker -- I'm not entirely convinced a wiring inspector would like it.
      ----------
      Try to make a living, not a killing. -- Utah Phillips
      Don't believe everything you know. -- Bumper sticker
      Everybody is ignorant, only on different subjects. -- Will Rogers
      There are lots of people who mistake their imagination for their memory. - Josh Billings
      Law of Logical Argument - Anything is possible if you don't know what you are talking about.
      Don't own anything you have to feed or paint. - Hood River Blackie

      Comment


      • #4
        Originally posted by ckelloug
        If the vfd only has L1 and L2 connections then the neutral gets a wire nut and doesn't go anywhere. The neutral connection is only needed if you need 110V somewhere.

        --
        Cameron
        LOL!.......This is where I started a few threads ago!! ROTF!

        Here's the deal.
        I have #10-3 with a ground from panel to a 220V, 3 pole outlet.

        Ground is not connected in the outlet box.

        2 hot legs and neutral go in to the mill switch, the neutral to a bond lug.
        (Should that not be neutral but ground?)

        2 hot legs and a ground wire from a bond lug in the switch box go to VFD.

        Ground wire goes to chassis ground on the VFD, 2 hot legs to L1 and L2 jumpered to L3 as per Hitachio instructions.

        Chassis ground and U,V,W go to the motor.

        I was told this was an accident waiting to happen as the whole mess wasn't grounded back to the panel.

        All because I want to take 110 off and run my table feed.

        THIS is why they invented extension cords!!
        Len

        Comment


        • #5
          SGW you type too darn fast for me!


          So I'll swap that neutral for ground and then relocate the 110 box I should have in the first place.

          I'm always concerned that something will fry and the insurance co. will forget who I am!
          Last edited by QSIMDO; 04-05-2008, 05:25 PM.
          Len

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          • #6
            An attempt to add a bit of light to the subject.

            Originally posted by SGW
            Right -- two hots and a ground for 240V. No neutral.

            If you have a neutral because you're also wanting to get 120V out of this same setup, it gets tied to the ground bar in the breaker box, along with the ground wire, and from that point on the neutral and the ground STAY SEPARATE.
            Well, it all depends. If the breaker box is also the service entrance this will be OK. However, in the case of a sub-panel, like I put in my garage/shop, the neutral (also called the GROUNDED conductor in the code) is insulated from the box and the ground bus. In the code, the ground (green) wire is referred to as the GROUNDING conductor.

            The so-called "neutral" wire (GROUNDED conductor) and the "ground wire" (GROUNDING conductor) must only be connected at the service entrance.

            Since the white wire, aka the grounded conductor, may carry current under normal conditions the code avoids the use of the term "neutral conductor." The green wire, aka the grounding conductor, only carries current during a fault condition. Or at least that's how it's supposed to be!

            Originally posted by SGW
            Then you can get 120V from either hot leg, and the neutral. While this works -- getting both 240V and 120V from a 3-wire setup, from a single double-pole breaker -- I'm not entirely convinced a wiring inspector would like it.
            I have my mill wired this way. Since it is connected to the house wiring with a plug (a 3-conductor + ground twist-lock in this case) it is considered "portable equipment" and the arrangement is kosher.

            In installed wiring this arrangement (2-120 volt circuits developed from L1 and L2 sharing a common grounded conductor is called an "Edison circuit." I believe that the grounded conductor must be of a larger wire gauge than the two associated "hot" wires. A 2-pole breaker is not required in this case, but the breakers must be connected to "opposite sides of the line."

            All this may seem like over complication, but there are valid safety reasons behind it.

            Damn! This looks like I thought I was gettin' paid by the word!

            Comment


            • #7
              It is possible when splitting 240 to have unbalanced current in each side. When that happens the mid-point is no longer mid, voltage wise. If the neutral is not well earthed but tied real well to the safety ground then you can experience surprises when you touch safety grounded machinery and real ground.

              Comment


              • #8
                QSIMDO, as I understand it you have four wires from the service panel, two hots, a white and a green, is that right?

                If so, the two hot wires go to the VFD, if the bond lug you mention is to the enclosure and not an isolated lug to the VFD then you put the green wire to that lug. The green wire should run from there to the machine frame as well. This is called a mechanical ground and is to keep from getting your butt ZAPPED. The white neutral at this point is not used and should have a wire nut on it for protection.

                NOW, you want to add a 110v duplex to your machine. As I described earlier, put a fuse or breaker protection in line mounted to the VFD enclosure. Run one of the hot wires to the breaker/fuse, run a hot from the breaker/fuse, the white neutral and a green wire through a conduit or use three conductor SO cord and run it out to the mounted duplex box. Use a GFI duplex, put the hot wire on the yellow screw, put the white wire on the white/chrome screw, put the green wire on the green screw and mount the duplex recepticle in the box and put a cover on it.

                Your work is done, now use the machine and duplex.
                Last edited by Carld; 04-05-2008, 09:09 PM.
                It's only ink and paper

                Comment


                • #9
                  Single Phase Power

                  Single phase power normally consists of 4 wires, not all of which may be required depending on the application.

                  L1 - Line 1
                  L2 - Line 2
                  Neutral
                  Ground

                  L1 & L2 come from both ends of the secondary winding of the transformer and Neutral comes from the middle of the secondary winding. Neutral is also tied to ground at some point as this keeps weird and wonderful things from happening.


                  * OOPS *
                  (If you only need 240 volts you need L1, L2 & Neutral. If you need 120 volts you need either L1 or L2 and Neutral.)

                  Should have said...

                  If you only need 240 volts you need L1, L2. If you need 120 volts you need either L1 or L2 and Neutral.

                  In any application you also need Ground.

                  In 240 Volt circuits L1 is commonly Black, L2 is Commonly Red and Neutral is commonly White, and ground is either bare or Green.

                  You can come off a 240 volt 2-pole breaker and run 3 conductor w/ground and not have to worry about overloading your neutral as 2 120V loads (L1 to neutral, L2 to Neutral) will use the neutral if only 1 load is in use, but will put very little current through the neutral if both loads are in use. (the 2 120 volt loads are in series across L1 & L2.
                  Last edited by kf2qd; 04-08-2008, 08:46 AM.

                  Comment


                  • #10
                    Originally posted by kf2qd
                    Single phase power normally consists of 4 wires, not all of which may be required depending on the application.

                    L1 - Line 1
                    L2 - Line 2
                    Neutral
                    Ground

                    L1 & L2 come from both ends of the secondary winding of the transformer and Neutral comes from the middle of the secondary winding. Neutral is also tied to ground at some point as this keeps weird and wonderful things from happening.

                    If you only need 240 volts you need L1, L2 & Neutral. If you need 120 volts you need either L1 or L2 and Neutral.

                    In any application you also need Ground.

                    In 240 Volt circuits L1 is commonly Black, L2 is Commonly Red and Neutral is commonly White, and ground is either bare or Green.

                    You can come off a 240 volt 2-pole breaker and run 3 conductor w/ground and not have to worry about overloading your neutral as 2 120V loads (L1 to neutral, L2 to Neutral) will use the neutral if only 1 load is in use, but will put very little current through the neutral if both loads are in use. (the 2 120 volt loads are in series across L1 & L2.

                    I guess I have to disagree with you some on what you say, as I read it anyway.
                    A 220 circuit does not require a neutral wire. The 220 volt circuit requires (2) 110v leads going into a 2 pole breaker in the panel box.
                    Out of the 2 pole the 2 leads run to a wall receptcle and a green ground wire is included for the chassis ground.

                    A 110v circuit requires three leads. A black, a white, and a green. one lead is taken off one of the two busbars in the main box going to a single pole receptcle. The black lead comes off the single pole breaker and goes to the wall receptacle, connecting to the gold colored screw.
                    Accompaning this lead is a white lead off the neutral busbar in the panel box that goes to the wall receptacle also. This white wire connects to the silver screw on the receptacle.
                    The green lead comes off the panel ground and goes to the receptacle/machine chassis ground.

                    Maybe that is what you said, but I understood it to say that you need a neutral to run 220, and that is not correct.
                    When you come off the 2 main busbars in the panel for any 110v breaker you want to always try to keep the number of leads off each bus equal (as you can) to prevent a possible overheating situation in the neutral wiring.....pg

                    Comment


                    • #11
                      I thik this thread started as a method of getting 110V power to a light and table feed---very small loads. It now seems to be a bit fuzzy with how to wire it both safely AND legally. Why not spring for a 200 VA 220/110v isolating transformer across the 220v ahead of the VFD. That way there are no unbalaced loads, floating neutrals or "not quite" grounds.
                      Duffy, Gatineau, Quebec

                      Comment


                      • #12
                        There are good answers here and some of them are from electricians looks like, me included. No neutral or (grounded conductor) needed for a circuit that is strictly 240v. NO neutral needed in a panel that has all 240 volt breakers ( single phase , if three phase then three pole) I have seen many panels with no neutrals. BUT they do have equipment grounds. You are wanting to make a circuit that is already existing as a 240v circuit that also has a neutral run to it. You can use the neutral (grounded conductor) with one of the phase ( hot wires) conductors to make a 120 volt circuit. You need to make sure that you are using the same size wire to the 120 volt circuit, and make sure that you are carrying the grounding conductor ( green, bare, green with yellow stripe) from the panel to the metal parts of the things you are hooking up. If you down size to #12 or #14 wire you must fuse it at the proper fuse or breaker ( 20 and 15 amp ).

                        Just a note of caution, remember the color of the wire is only useful, IF the guy who wired it wired it correctly. I have also seen many white wires hooked directly to a 2 pole breaker, and even seen green wires used as current carrying conductors. Please use a meter before you disconnect wires and turn the power off. good luck.

                        Comment


                        • #13
                          pg

                          I understand and agree with everything you have written above with the exception of this part:
                          ".....to prevent a possible overheating situation in the neutral wiring."

                          I don't understand why any part of the neutral wiring would overheat as a result of unbalanced loads.

                          Here's a typical breaker panel:



                          You can see the incoming wire connected to the neutral lug is the same size as the two hot leads.

                          Each wire from the neutral busbar to an outlet or fixture is the same size as the hot wire on that circuit, and it'll be carrying the same current.

                          The neutral busbar should be adequate for the panel it's installed in, and it's not going to be carrying more than its rated capacity.

                          What part of the neutral wiring is going to overheat? And why?

                          Roger
                          Any products mentioned in my posts have been endorsed by their manufacturer.

                          Comment


                          • #14
                            Winchman

                            If you have a 50amp 240v /120v circuit. common for a range. The 240v part runs the burners. The 120v part runs lights and maybe a fan. The neutral carries the unbalanced load. The 240v phase A & B cancel their loads out on the burners. If you use the lights which only run off of ether A or B phase. This load is carried by the neutral.

                            Now if you decided to run plugs in your shop or anywhere else, but did not want 240v in any box you could run 2 -120v / 20 amp circuits off of A phase OR B phase and only one neutral. The problem is this neutral could be carrying 40 amps as it would be carrying the load from each breaker. ( JT I am trying to keep this simple) This is one way you get electrical fires. Many people pick up a neutral somewhere in the wiring and cause the same problem.

                            Bob

                            Comment


                            • #15
                              .......You guys are screwin' with my head, right?

                              You KNOW I'm still reading this thread, right?

                              Yer freakin' me out!!

                              ARRRRRRRGHHHHH!!!!!



                              Ok, here's what I did.

                              L1, L2, neutral and ground coming to the switch.
                              L1 & L2 go off to the VFD and the VFD is grounded like nature intended.
                              L1, neutral and ground go through a breaker to the 110 outlet.

                              Therefore Bob is, as before and ever shall be, your uncle!

                              If I fry myself I've instructed my wife to post my swag for sale here CHEAP but to screw everyone on shipping.

                              Now I'm off to hang a new light!
                              Len

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