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Electrical amperage question

  1. Apr 25, 2015 #1
    Im looking into getting an electrician.... but it drives me crazy when I dont know why something is done a certain way.

    I bought a Bendpak 10000 lb automotive lift. the motor supplied is 220 single phase or 3 phase (i am using single phase)
    the motor for 220 single phase is supplied with a white, a black, and a green wire. The instructions call for 10 gauge wire up to this point with a 25 amp circuit breaker (double throw of course)
    The wiring calls for 2 wires to be run approximately 14 feet with 14 (fourteen) gauge wire to a switch that is supposedly good for 15 amp.
    The only way that i can see this working is with each leg grounding the other lead, that it is actually only considered 15 amp for each wave length (being out of phase for each other)
    1. Is this correct in theory?
    2. Also, being called 220 single phase.... shouldnt this actually be called 2 phase?
    I have man more questions.. but this is a good start
     
  2. jcsd
  3. Apr 26, 2015 #2

    Averagesupernova

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    Your terminology is a bit off. Why are you bringing wavelengths into this? Without knowing what the 15 amp switch is controlling no one can give much of a comment. It is in fact single phase. This sort of thing has been discussed many times here on PF. A search should turn up something.
     
  4. Apr 26, 2015 #3

    wirenut

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    Is the switch actuated by a bar across the lift legs, so it will stop the motor if the top of the car hits it?
    If so it is a safety switch to prevent lifting the car too high.
    The reason for 10 awg wire up to the connection point is for inrush current. If you look at the nameplate of the motor,
    the full load amps is probably around 18 to 20 amps.
    As for why the switch is rated for 15 amps ? Are you sure it is 15 amps and not 20amps?
    A model number or some specs would help.
    Also it is a two POLE breaker, not two throw.
     
  5. Apr 26, 2015 #4
    So far you both are right on. (I should not post things online when I am totally exhausted and ready to go to bed, I apologize)

    Yes, the switch is for a cuttoff switch to make sure the lift doesnt damage the lift or the vehicle.
    my understanding is that is cuts off supply to one of the leads and cuts off the ground to the other lead.
    I had done a few searches online to try and find out, but nothing really fit (although I did not search this forum directly like I should have)
    Actually, one discussion was on exactly this subject and same model even... but the answers given seemed to contradict each other.

    The motor is 18 amp.
    Model number xpr-10a

    Thank you both for your answers.
    Hope this helps...

    utf-8BSU1BRzAwNTIuanBn.jpg
     
  6. Apr 26, 2015 #5
  7. Apr 26, 2015 #6

    jim hardy

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    that discussion includes a basic mistake.
    Uplift said
    which is dead-*** wrong.

    Current goes into the motor via one L wire and every bit of it comes back through the other L wire.
    Everything should be sized so it's protected by the breaker. Switches included.

    Caspian got it right a couple posts later on.
     
  8. Apr 26, 2015 #7
    Thank you very much... after that thread in particular, I was very confused...
     
  9. Apr 26, 2015 #8

    wirenut

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    The safety switch(normally closed) goes in series with 1 leg of the power and 1 side of the motor.
    The other leg of power goes to the push button. Nothing cuts off the ground!
     
  10. Apr 26, 2015 #9

    wirenut

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    @jimhardy I work with 1st-3rd year apprentices(who know everything" 'cuz they just learned it.") who don't believe
    that 2 hot legs on a single phase service are still single phase (shouldn't it be 2 phase?). Then try to explain what 2 phase really is, and
    watch their eyes glaze over.
    After 25 yrs as an electrician I have so many stories.
     
  11. Apr 26, 2015 #10
    thinking back I guess maybe I should just use what I know from 2 car batteries in parallel or series knowing that you're either going to combine voltage or amperage but not both. Same theory?
     
  12. Apr 26, 2015 #11

    jim hardy

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    I hope you'll use them here. I've always enjoyed your insightful posts.

    old jim
     
  13. Apr 26, 2015 #12

    jim hardy

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    ps i'm of the opinion that he should run both wires together , not separating them, to both switches.
    something in NEC 300 about running wires together to avoid magnetic fields ?
     
  14. Apr 26, 2015 #13
    clarification of my above post. this is like having two batteries in series. voltage is combined amperage stays the same. correct theory?
     
  15. Apr 26, 2015 #14
    jim hardy... I dont know enough about the theory to understand your post.... what would a magnetic field of that type do in that situation?
     
  16. Apr 26, 2015 #15
    by the way.. its all wired up and seems be doing well.. 220 volts and no problems...

    Thank you all for your help... Now just want to understand better....
     
  17. Apr 26, 2015 #16

    jim hardy

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    nothing drastic, probably.
    Separating the wires makes a loop that'll act like an antenna. It makes a magnetic field that might perturb sensitive electronics nearby , particularly when starting or stopping that big motor.

    i have such a loop in my house that i'll fix when i re-panel the room .
    There's one outlet controlled by a three way switch.
    I noticed that the touch-dimmer lamps in my living room turn themselves off whenever i switch a capacitive load ( like a computer ) that's plugged into that outlet. Even those fluorescent curly bulbs in an ordinary lamp that's plugged into in that socket will do it. Incandescents and dimmable LED bulbs are okay though.



    http://www.mikeholt.com/technical.php?id=powerquality/unformatted/EMIKarl&type=u&title=Power Quality Article

    I dont think it's dangerous to separate them but it might give you some strange symptoms.
     
    Last edited: Apr 26, 2015
  18. Apr 27, 2015 #17

    wirenut

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    @jimhardy The safety switch is just a SO type cord (switch leg) from the point of power connection to the
    switch and back. The power to the motor actually comes from the main connection point.
     
  19. Apr 27, 2015 #18

    wirenut

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    @jimhardy I think in your situation , unless they are on the same circuit, they won't be able to do this very much longer.
    I believe they are going to require arc-fault breakers in family/living rooms soon. If it is a neutral from a different circuit
    the breaker will trip immediately.
    BTW the stories I could tell about "experienced" electricians wiring 3 way switches would make your hair stand up.
     
  20. Apr 27, 2015 #19

    Averagesupernova

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    Arc faults are already required just about everywhere. Used to be just bedrooms. Then everywhere except the kitchen and bathrooms. Now bathrooms are about the only thing that don't require them. Any finished living space. The rules are getting stricter all the time. Even the garbage disposal/dishwasher require it. The sump pump outlet in the basement even requires a GFCI outlet. It used to be that it was exempt if there was only one outlet and not a duplex plugin. This way nothing except the pump could be plugged in. Now that is out the window. The claim is that nuisance trips are next to non-existent so there is no danger of the sump pump outlet tripping and ending up flooding the basement.
     
  21. Apr 27, 2015 #20

    wirenut

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    @Averagesupernova I realize the current code calls for them, but in Buffalo NY, they are enforcing the 2008 code.
    Most towns around here are using '08 (or '11 codes if you're lucky).
    I have a high water alarm on my sump. It texts me if it goes off.
     
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