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  • 220 Volt Wiring Question

    I've grown tired of dragging around power cords to my various machines so I'm in the process of running a separate 220 line to a wall close to where my lathe and mill are. Looking at my diagram I have an existing 110v line in conduit with a couple 4" boxes at either end. I have a 220v disconnect box mounted on that wall also, that was originally for the welder which found another spot in the shop. I'm going to pull 2 #12's and a ground from the main panel off a breaker to the disconnect box and fuse it at 20 amps. I'm going to run the 220 wires through the existing conduit that houses the 110v wires and drop a box off that conduit for the 220 outlets. No problem doing that as it's not a code violation. This saves me the trouble of running a separate conduit. What I want to do from there is run a 4 conductor extension cord to my lathe with a 220v receptacle and a 110v receptacle for the light and DRO's. Now....... there is a couple ways to do this. the first way is just to take one leg of the 220 line and ground and you have your 110. Done with 3 wires. Altough not reccomended and not to code we have all seen it done before. Technically there should be a nuetral wire there for the 110v outlet.
    So what I want to do is just grab a neutral from the 110v line that is right there and use it. An electrician friend said no.... I should run the nuetral back to the main box. So that means I have to run 80 feet of nuetral just for one 110v outlet. What is the reasoning??? The only thing I can think of is that if the 220v device faults it could send 220 through the 110v neutral. Thoughts ???

    JL..................


  • #2
    Why not just come off of your existing 110V outlets and add a couple 110V outlets to that circuit, then run your new 220V circuit as you were planning on.

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    • #3
      You sure your lot got a man on the moon ?

      I mean you struggle to get 3 wires across America
      .

      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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      • #4
        won't work - you also need neutral to get your 110 - ie one L + neutral = 110. You'd need to do 4 wires (or three + metal conduit) assuming its legal to go that route. I'd just go in steel conduit one run for 220 and one 110, its nice keeping everything separate and the materials aren't that expensive

        Now....... there is a couple ways to do this. the first way is just to take one leg of the 220 line and ground and you have your 110. Done with 3 wires. Although not recommended and not to code we have all seen it done before. Technically there should be a neutral wire there for the 110v outlet.
        my initial response was based on the diagram...but reading this, wow, run the other way from that idea. While a closed circuit, there's a much potential and current flow in the neutral line as there is L1 or L2....if this is routed through ground, doesn't that make every box, machine, motor frame, stick of conduit live while its a closed circuit? I don't think I've ever seen that done and it sounds like a death trap...maybe i',m having a brain cramp and missing something but that just seems crazy to me
        Last edited by Mcgyver; 02-28-2011, 03:43 PM.
        .

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        • #5
          Its not allowed and not a good idea for a few reasons:

          Plug too much into the 120v outlet, and the other circuit that uses that neutral, And you could overload the neutral with the combined current. (If you don't use opposing phases)

          And what if someone turns that circuits breaker off, And then starts mucking with the circuit, disconnects the neutral only to find.. ZAP, its still live via some other circuits load!

          Or maybe at some point someone switchs the phases at the breaker box. Yaknow, Just changes the breaker/disconnect and reconnects em however is convienant.

          Sharing neutrals with unrelated circuits stoped when we gave up knob and tube. For good reason.
          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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          • #6
            You will need nuetral conductor from the main panel to the disconnect box for the 120v to work properly, you cannot use the ground wire per code...your electricain freind is 100% correct.

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            • #7
              Use the existing wires to pull a red and black #8 and a white #8 and a green wire through the existing conduit. Now put a breaker box where you would put the disconnect and work your circuits out of the breaker box. You will have to change the breaker in the main box to a 220 double breaker.

              If the conduit is to small use a surface mount conduit of the needed size.
              It's only ink and paper

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              • #8
                Originally posted by Mcgyver
                won't work - you also need neutral to get your 110 - ie one L + neutral = 110. You'd need to do 4 wires (or three + metal conduit) assuming its legal to go that route. I'd just go in steel conduit one run for 220 and one 110, its nice keeping everything separate and the materials aren't that expensive



                my initial response was based on the diagram...but reading this, wow, run the other way from that idea. While a closed circuit, there's a much potential and current flow in the neutral line as there is L1 or L2....if this is routed through ground, doesn't that make every box, machine, motor frame, stick of conduit live while its a closed circuit? I don't think I've ever seen that done and it sounds like a death trap...maybe i',m having a brain cramp and missing something but that just seems crazy to me
                My diagram is for the most part correct. The first way I described taking a 110v was to grab one of the lines and use the ground...... that is not a real safe way to do it altough I've seen it done all over the place. A 220 device only needs the two lines to run, the ground is just there for safety reasons. useing that ground as a nuetral could cause the conduit to become hot if the 220 device faults. I on't do it that way myself. My question in wondering was if I could just grab the nuetral from the existing 110 box rather than run a nuetral all the way back to the main box.

                JL.............................

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                • #9
                  I believe the NEC allows you to share neutrals...BUT, you have to have a means to kill power to all circuits sharing that neutral simultaniously...like by using a 2 pole breaker or a tie bar between all the single pole breakers using that neutral..., such that you can't shut off only one and have a "live" neutral on the other. As far as sizing goes, the neutral doesn't carry as much current as the hot, so 2 circuits shouldn't be a problem...if it was, the NEC wouldn't allow it.
                  Last edited by lbhsbz; 02-28-2011, 06:30 PM.

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                  • #10
                    Originally posted by JoeLee
                    A 220 device only needs the two lines to run, the ground is just there for safety reasons. useing that ground as a nuetral could cause the conduit to become hot if the 220 device faults..
                    I don't think that's the case; if you go L1 to ground to create a 110 circuit, both are hot when the 110 circuit is closed - you would not need a 220 fault to make it hot. It'll work as in the power will flow, but everything connected to ground will be hot when the circuit is closed.

                    using neutral from the other 110 line is safer, although by no means legal or good - as the other guys have pointed out you could have current from more than one breaker going through the neutral potentially in excess of it rated current plus someone in the future could turn off the breaker only to get electrocuted as neutral in the circuit he thought i turned off was live from the second circuit using it. Not worth it imo.
                    .

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                    • #11
                      Originally posted by Mcgyver
                      I don't think that's the case; if you go L1 to ground to create a 110 circuit, both are hot when the 110 circuit is closed - you would not need a 220 fault to make it hot. It'll work as in the power will flow, but everything connected to ground will be hot when the circuit is closed.

                      using neutral from the other 110 line is safer, although by no means legal or good - as the other guys have pointed out you could have current from more than one breaker going through the neutral potentially in excess of it rated current plus someone in the future could turn off the breaker only to get electrocuted as neutral in the circuit he thought i turned off was live from the second circuit using it. Not worth it imo.
                      Your correct, when the 110v device is on the return or nuetral / ground becomes hot because it's now the return path. I wonder if it's OK to share grounds?? between the 220 and the 110 ?? or should the ground also be brought from the main panel along with the nuetral??

                      JL....................

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                      • #12
                        Seems to be some confusion here. Neutral and Ground are not the same and not interchangeable. This has killed/injured many. The NEC, like many rule books is at least partially written in blood.
                        It seems to me , with your limited understanding, an electrician would be a good investment.

                        Comment


                        • #13
                          Isolating the 220 and the 110 from each other is good.
                          People have done what you suggest, but if you ever have a fire and the insurance company finds out.........

                          The correct way to do this is to use a stepdown transformer.
                          Go to a scrap dealer. any old industrial machine will have one ( control Transformer)and then you wire it for 220 input and have a isolated 110 output..much safer

                          Rich

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                          • #14
                            What is it with some people? Why gamble with your life or your home or shop? Is it because you're cheap? Is it just too hard to do maybe? This is by every means cutting too many corners. Will you get bit? Maybe. Maybe not.

                            If you want to know how to install this circuitry correctly, you should ask for help. I would be happy to assist (assuming you are in the US). But if you are trying to get away with something (which your drawing on almost every level indicates), you will get no reinforcement from me; and I hope very little from anyone else.

                            Am I giving you hell? You betcha. I work with low, medium and high voltage power in an industrial setting every day. That's my career. I absolutely know, and have seen what can happen when people cut corners or simply make a mistake. I even lost a friend to electrical dumb ass many years ago.

                            Do it right. Live.

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                            • #15
                              Originally posted by garagemark
                              What is it with some people? Why gamble with your life or your home or shop? Is it because you're cheap? Is it just too hard to do maybe? This is by every means cutting too many corners. Will you get bit? Maybe. Maybe not.

                              If you want to know how to install this circuitry correctly, you should ask for help. I would be happy to assist (assuming you are in the US). But if you are trying to get away with something (which your drawing on almost every level indicates), you will get no reinforcement from me; and I hope very little from anyone else.

                              Am I giving you hell? You betcha. I work with low, medium and high voltage power in an industrial setting every day. That's my career. I absolutely know, and have seen what can happen when people cut corners or simply make a mistake. I even lost a friend to electrical dumb ass many years ago.

                              Do it right. Live.
                              For the most part my drawing is correct. There is no code violation in the USA running 220 in the same conduit as 110 as long as there is no low voltage wires in that same conduit such as phone or tv. One of the methods I stated ( using L1 and Gnd) was not something I had planned on using, I only stated that I have seen it many times and know it's an incorrect shortcut.
                              I was just inquiring as to why I couldn't take a nuetral from a nearby line in the same conduit as opposed to having to run a dedicated one from the main panel. I'm not trying to do this becaus I'm cheap, It's just because the conduit is there. I wired my whole shop 25 years ago both 110 and 220 and had it all inspected. Asking for help here was what I was doing but I think there is some confusion between my drawing and my question.

                              JL.............................

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