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Thread: So where does neutral go?

  1. #1
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    Default 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. #2
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    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

  3. #3
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    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.
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  4. #4
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    Quote 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

  5. #5
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    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 at 03:25 PM.
    Len

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

    Quote 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!

    Quote 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!

  7. #7
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    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.

  8. #8
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    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 at 07:09 PM.
    It's only ink and paper

  9. #9
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    Default 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 at 06:46 AM.

  10. #10
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    Default

    Quote 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

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