running 120 equipt on 3 phase

Discussion in 'Homework Help' started by Goodies, Mar 10, 2015.

  1. Goodies

    Thread Starter New Member

    Mar 10, 2015
    3
    0
    I've got an existing 208 circuit L1 L2 G voltage on L1 to L2 is 208 voltage on L1 to G is 120 voltage on L2 to G is 88. shouldn't it be 208 120 120? I want to split the circuit into 2 120 lines.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,505
    2,367
    You need to explain the source. Is it a 3phase Star (wye) supply? A centre tapped supply etc, etc?
    3ph star if 208 between phases is 120v from phase to star neutral.
    Max.
     
  3. Goodies

    Thread Starter New Member

    Mar 10, 2015
    3
    0
    Don't know the supply, just that it's 2 legs of 3phase. I think wye. The cables are marked L1, L2, and Ground. If there was no center tap would this cause these readings running with just a ground?
    If not what scenarios would cause these readings?
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,505
    2,367
    There is such a thing as 'Wild Leg Delta' where a phase is split and the split is taken to ground as a neutral?
    But you would have to confirm the type of supply you have, the norm is 208 3ph Wye with the 120v to star point grounded neutral.
    In this case you should have 120v to neutral (or ground).
    Max.
     
    Last edited: Mar 10, 2015
  5. n1ist

    Active Member

    Mar 8, 2009
    171
    16
    You can't, legally or safely. If you had a neutral, then you could use L1 and N (or L2 and N), but you can NOT use a ground as a return. The only exceptions are grandfathered in for 3-wire ranges and dryers. To do this correctly, you will need a 208v - 120v transformer.
    /mike
     
  6. Goodies

    Thread Starter New Member

    Mar 10, 2015
    3
    0
    So what I'm hearing is no way should I be getting an 88 volt reading. That there must be something wrong .
     
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