220v and 110v wiring question
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  1. #1
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    Default 220v and 110v wiring question

    Im almost done restoring my 1959 Bridgeport. I have a dedicated 220v line for it but I really don't want to have to run a separate 110v line to power the DRO and power feed. Can I just branch off one lead and make a separate receptacle on the mill to power the DRO and X power feed?

    There is already a shortage of 110v outlets around this place lol

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    You need a neutral wire to have 120v, I have most of my machines to 50 amp 4 prong plugs because I like to unplug machines when not in use. Having outlets on the machine is super convenient, I like to have a couple switched for lighting, coolant or a vacuum. What I've done is add a small (5-15amp depending on need) fuse on the 120v hot line then to a gfci. If you don't want to trip the GFCI and blank your dro get a small UPS battery backup. And use that just for the dro. Or connect the dro before the GFCI, which is mostly safe as long as you don't take your dro into the shower.

    Back when I did complex stuff on my bridgeport the UPS was a must.

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    Yes, if you run a nut. and add a 20 amp fuse for the 120v plug, if it is ONLY used for the dro you dont need the gfi, but if it used for power tools you need the gfi...Phil

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    I'm assuming you're talking 220 3 phase. If that's the case it depends. If it's corner grounded 3 phase the answer is no. I would be more inclined as I have on my home mill, to add a control transformer to step down from 220 to 110 and then wire the outlet(s) in there (fused of course). This makes for a tidy installation and you don't have to worry about blowing the DRO, power feed, and worklamp up if you every move the machine elsewhere.

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    it is 220v 1ph, that would suck if I have to run a whole new line, thats gonna be expensive and time consuming, I would have to rerun the whole 220v line with new wire to add a neutral? what if I just put a control transformer to reduce to 110v for the DRO?

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    Quote Originally Posted by 57buick View Post
    ...what if I just put a control transformer to reduce to 110v for the DRO?
    That is an acceptable approach and one taken by many, in the same circumstances.

    (not really a 'control' transformer but a generic step-down)

    1) fuse the output of the transformer.
    2) bond (tie one end to ground) the output of the transformer.
    3) be sure the transformer you select has an appropriate current rating.

    When in doubt talk to an electrician.

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    Quote Originally Posted by 57buick View Post
    ....transformer to reduce to 110v for the DRO?
    Preferred way, actually. 'Future proofing" route.

    Because it works the same across (any) two legs of 3-Phase as across (the only) two legs of 1-P.

    One CAN utilize a 220/230/240 VAC primary to a 110/115/120 VAC center-tapped secondary with the centre tap Earthed as well. Not uncommon for wet environment corded power tools.

    That gives you the 120 VAC you need across the "ends" but each is only 55---60 VAC above ground instead of one Earthed and the other at the full @ 120 VAC above ground.

    BEFORE. you do anything further...

    LOOK at your DRO's manual and/or PSU.

    If a "globalized" unit? It may have:

    EITHER

    - a manual selector switch for 120/240 (nominal) as AC input right on it or on its power supply..

    ELSE

    - a PSU that is automagically able to run the DRO's modest load off any incoming 50-60 Hz source from 80 or 100 minimum to 240 or 250 VAC maximum.

    No pre-selection switch required.

    See laptop 'puter "brick" with IEC cords, some fax/inkjet/laser printers..

    A DRO usually needs less power than a laptop, so flexible power might already "be there" to simplify the maker's need of stocking more than one flavour of goods, North America/Japan market, rest of the world.

    2CW

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    I'm in the control (or step down) transformer group. There's no chance of miswiring when the machine is moved, and you don't have to run extra wires.


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