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  1. #1
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    Default Start - Stop Push Button Wiring

    Hey all,
    long time reader, first time poster.
    I'm having a difficult time figuring out how to wire an old GE start - stop push button switch to a 3-phase motor. This is for a friend of mine who has a wood jointer across the street. I usually don't touch jointers, as they are how I became nineandtwothirds, but this is a favor!
    I found this drawing of what is essentially an identical switch, but the wires on the diagram are marked 1, 2, and 3. I cannot find anywhere that will tell me where these are coming from/going to. Can anybody give me a sense of this?
    Any help would be appreciated, especially in the form of in-depth descriptions. I'm not terribly proficient at reading wiring diagrams, obviously.
    Thanks,
    9 2/3wiring-example.jpg

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    They are used with a contactor (relay)

    Are you trying to use them to directly control the motor load ?

  3. #3
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    That was the plan. Is that... a bad plan?

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    Quote Originally Posted by nineandtwothirds View Post
    That was the plan. Is that... a bad plan?

    Yes. The buttons are normally momentary.

    There ARE "manual motor starters" which look similar. Those are usually essentially switches, in which case the buttons are obviously the type that stay down when pressed.

    With the momentary, they are wired for the start button, which is "normally open", to send control power to the contactor coil, and when the contactor closes, an auxiliary contact on it closes to maintain control power to the coil after the button is released.
    The stop button is "normally closed" and is wired in series with the control power, so that when it is pressed, control power is removed from the coil and the contactor opens.

    For motors over 1 HP, an overload detector is used, which has a normally closed contact that is put in series with the stop button. In case of an overload, that opens the contactor. (motors at or under 1 HP can have an internal overload protector, in which case the external one is not needed).

    With the contactor, if the power fails, the machine will not restart when power comes back on, because the contactor will be opened when power fails, and cannot close until "start" is pressed.


    Y

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    Default

    As JST stated, that diagram looks like the switch input circuit to a motor latching contractor, so you are missing part of the diagram/information/picture that includes the contactor. In general, those three wires would be connected to the "normally open", "normally-closed", and "common" on the contactor(relay). ("1" would be the normally-closed, "3" normally open, and 1 "common" in that diagram). The contactor itself will also contain the single-phase input to the contactor coil, and the actual relay contacts that supply power to the motor. There are lots of variations of contactors so you'd need to post more specifics.

    I do have a couple of OLD tools (old delta lathe with 1/2 hp 3phase motor for example) with 1Hp and less motors that have the old mechanical non-momentary switch, the buttons on those are not "momentary", and not per the diagram above.

    120V+ is very dangerous, get some help if not familiar with working on it.

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    The rest of the story, so someone else does not become 9.5....

    sqd-motorstarterdrawing.jpg

    uglys-motorstarterdia.jpg

    SAF Ω

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    A final comment: GOOD versions of the switch you show have a "guard" on the start switch, to reduce the risk of someone or something inadvertently starting the machine. Usually this is a ring around the switch, so that something falling against the assembly is unlikely to push the button.

    The stop switch is NEVER guarded, to allow even a somewhat mis-aimed slap to hit the stop switch if there is a problem. Modern E-stop switches actually stick up for easy access, and also latch off, so the machine must be intentionally started by an action that is different from the normal one, after an e-stop has been made. E-stop, depending on the degree of safety needed, as well as power involved, may be simply wired in series with the regular stop button, or may even be a special type in series with the actual power wires, for a positive cutoff.

  9. #8
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    Quote Originally Posted by SAF View Post

    uglys-motorstarterdia.jpg

    SAF Ω
    Something like this, only you need a contactor made for 3 phase

    See the middle leg where it says (NOT USED) ?
    You need to use that one also

  10. #9
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    Excellent. Thank you everyone!


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