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  1. #1
    Join Date
    Aug 2002
    Posts
    391
    I had a service call to put a new outlet plug on a cooler that ran on 120/240. The maintenance guy cut it off because it would not fit on the 240 outlet. After putting a new put and outlet in I did not have proper voltage, I opened the panel and saw that they were taking one 120 line from one leg of a 3 phase breaker that used to run a 120v cooler.

    There were bunch of other code violations in the panel also, I told the owner my job was done but he needed a lic. Electrician to fix the mess in the panel. This is a small meat packing plant.

    My question is what effect on equipment does this have when you take a 120v line off a breaker that supplies 3 hase equipment.
    The obvious is obvious

  2. #2
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    None, if done properly.

    What voltage did you have at the outlet? High, like 180 VAC? If so, and the phase-to-phase voltage was really 240, and not 208, you might've been on the bastard leg of a Delta circuit.

    To correct it, simply measure the phase to neutral voltages at the breaker, then choose one of two phases that read 120 to neutral, and avoid the one reading high.

  3. #3
    Join Date
    Sep 2004
    Posts
    3,157
    If you are referring to 208 3 phase
    like condensate dave said it will be fine but remember you wont have three phase power avalible in that circuit.

    I worked in a shop that manufactured Duct work, They made that kind of stuff a habit. I had to work on a piece of equipment and after turning off the breaker for that circuit I opened the panel up and tested for power and sure enough , power was still there on one leg.

    They had used 1 leg from a different breaker, and the other two from a double pole breaker

    doing that kinda stuff is just inviting trouble

  4. #4
    Join Date
    Dec 2004
    Posts
    509
    the greatest threat i see in doing something like that is where your neutarl is being picked up from, if they are running neutral to ground then you are taking a chance of charging everything grounded if theres a short to ground condition, so its possible a motor housing or a door panel could become hot. i hope im explaining it correctly. in order to do what your describing that 110 vlt circuit needs its own ground, or its a safety hazard.

  5. #5
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Originally posted by ct2
    If you are referring to 208 3 phase
    like condensate dave said it will be fine but remember you wont have three phase power avalible in that circuit.

    They had used 1 leg from a different breaker, and the other two from a double pole breaker

    doing that kinda stuff is just inviting trouble
    There is absolutely NOTHING wrong with carrying a neutral and using one leg of a three pole breaker to obtain a 120V circuit. It MUST be done properly, and you MUST use 5 wires for this circuit. Then you WILL have three phase, and the 120V, and, if your little heart so desires, a single pole 240V circuit as well, all from one breaker. But it MUST be done properly.

    If you wire things like you spell my name, please don't wire anything anymore, for the sake of all. Electricity in the hands of someone who doesn't fully understand it is a very dangerous item.

    Originally posted by gas_n_go
    the greatest threat i see in doing something like that is where your neutarl is being picked up from, if they are running neutral to ground then you are taking a chance of charging everything grounded if theres a short to ground condition, so its possible a motor housing or a door panel could become hot. i hope im explaining it correctly. in order to do what your describing that 110 vlt circuit needs its own ground, or its a safety hazard.


    Again, for clarification, there must be FIVE wires in this three phase circuit, from the panel.

    Three "HOTS", One NEUTRAL, and One Earth ground. EVEN if the "neutral" originates form the same lugbar as the "ground".

    Really, consult a local electrician if you have any questions.

    This stuff is really "commercial electrical 101".

  6. #6
    Join Date
    Dec 2004
    Posts
    509
    damn dave! thats what i was trying to say, that you had to use your earth ground for your neutral. im sorry i missspelled your name, please dont yell at me again. i got feelings you know, and im just a dumb tech, if i was smart enough to spell dont you think i woulda choosen a better career then this one, geez!

  7. #7
    Join Date
    Dec 2004
    Posts
    441
    Still better be damn careful. Anyone else deal with 3 phase with a wild leg? I think electricians and power companies call it 3 phase delta. Instead of 120v to ground across all three you may pull two 240v to ground and one that shows 0v. Its that third one that will kill ya or burn something into the ground. Have seen one case where the wild leg was into something like 360v, yet pahse to phase all came up 208/230.

  8. #8
    Join Date
    Dec 2004
    Posts
    441
    Oh yea, we also have a few with 460v 3 phase with wild leg. Talk about something dead serious, 460v one leg to ground, really makes you pay attention though!

  9. #9
    Hey Dave .... I guess all those times I mis spelled your name are begining to pay off...

    Now others are carrying on the "tradition"....



  10. #10
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Originally posted by gas_n_go
    damn dave! thats what i was trying to say, that you had to use your earth ground for your neutral. im sorry i missspelled your name, please dont yell at me again. i got feelings you know, and im just a dumb tech, if i was smart enough to spell dont you think i woulda choosen a better career then this one, geez!
    Uh, Spanky? YOU didn't misspell it, and I wasn't yelling at YOU, until now.

    YOU were simply confused, and apparently remain that way.

    There is going to be a quiz at the end of next week, so you best start paying attention.




    Bob, I'd like to think that your misspellings were intentional. At least on some level.

  11. #11
    Join Date
    Aug 2002
    Posts
    391
    Thanks for the replies, you say that this is ok but would it pass muster with the local inspector, and what about a mismatch in the amperes rating on the circuits.
    The obvious is obvious

  12. #12
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    There is absolutely nothing wrong with doing it, if it's done properly. In fact, it's a very frequently used technique. Unless a locazl regualtion exists forbidding it, thed inspector should have no problem ith the theory, but maybe the application.

    Bear in mind that residential cooktops and clothes driers use this type of circuit, just from a single phase source.

    As far as current imbalance, it would have to be severe to cause a problem. Other circuits in the panel should even out the draw.

    The real problem with doing this would be the possibility of having a convenience recepetacle on a 70 amp breaker. But, then, that would be an improper use.




  13. #13
    Join Date
    Dec 2004
    Posts
    441
    Originally posted by R12rules
    Hey Dave .... I guess all those times I mis spelled your name are begining to pay off...

    Now others are carrying on the "tradition"....


    Just what were you calling me when you were misspelling my name?

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