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Thread: 120/208, 1Ph, 3 Wire

  1. #21
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    Quote Originally Posted by Besoeker View Post
    And, sorry, we don't have two phase over here that I know of.
    Not being argumentative. Just trying to be straight with the facts. I'm sure you understand.
    Did the UK never have 2-phase? It was pretty popular at one time over here. I forget how that came to be exactly but I would think y'all would have had a similar development.
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  2. #22
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    Quote Originally Posted by Sean.Day72 View Post
    I have a scenario where there is a existing transformer in the field (no data on the existing transformer) and an adjacent Eaton Panel. The nameplate on the panel reads 120/208, 1Ph, 3W. Correct me if I'm wrong but the only way to get this voltage is to pull one phase off of a 3 phase transformer? If that is the case isn't technically split phase? I'm adding some small loads out their and was hoping to add a 40 amp 2 pole breaker to the Eaton board.

    The other solution is to contact the utility and get info on the existing transformer, but that usually takes weeks...
    Sounds like 208 is available. You have two 120 volt busses so a 2-pole breaker will get the 208 you want.
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  3. #23
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    Quote Originally Posted by Sean.Day72 View Post
    The existing transformer has no name plate on it, just a serial number for the utility. What I think happened is that this transformer has been sitting out in the yard for some time (it looks old) and they recently built a access control gate close by. They installed a rack with a service disconnect, meter, and the eaton panel and tapped into the old transformer. Since the gate only has some cameras and a small motor, 3 phase power was not required so they only pulled 1 phase off of it. I'm adding some small loads close by so the plan is to put a 2 pole 40 amp breaker into this existing eaton panel to feed a small panel to power up some street lighting. I just want to confirm I'm not loosing it

    And I misspoke this is not split phase, it appears to be line-line
    You are not losing it. You should be able to get the 40A, 208V you need.
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  4. #24
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    Quote Originally Posted by Sean.Day72 View Post
    I'm not sure until the utility gets back to me. My guess is the 208V is line-line with Y connection on the secondary of the existing transformer. The only other way I know how to get 208 is if the existing transformer is a delta with high leg configuration, which I never seen used with this particular client.
    The high leg system would not be labeled 120/208 so you must have a wye secondary. The high-leg system would be 240/120 if three phase or 120/240 if single-phase.
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  5. #25
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    Quote Originally Posted by Sean.Day72 View Post
    The nameplate on the panel reads 120/208, 1Ph, 3W. Correct me if I'm wrong but the only way to get this voltage is to pull one phase off of a 3 phase transformer?
    It uses 2 phases when fed wye-wye using two transformers instead of three. When fed delta-wye it uses 3 phases but still only needs two transformers.

    The 3W 120/208 is called a network system but is also commonly referred to as a single-phase system because it serves single-phase loads.
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  6. #26
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    Quote Originally Posted by mivey View Post
    Did the UK never have 2-phase? It was pretty popular at one time over here. I forget how that came to be exactly but I would think y'all would have had a similar development.
    I can't say it never had but not that I recall. But I'm only ten years old...............
    Si hoc legere scis nimium eruditionis habes.

  7. #27
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    Quote Originally Posted by Besoeker View Post
    I can't say it never had but not that I recall. But I'm only ten years old...............
    Sure.....using the canine unit system for age, so that makes you about seventy.
    "Electricity is really just organized lightning." George Carlin


    Derek

  8. #28
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    Quote Originally Posted by jumper View Post
    Sure.....using the canine unit system for age, so that makes you about seventy.
    Close............
    And my ca nine unit just patted me gently on the knee. Food, out, or attention.
    He got all three.
    Si hoc legere scis nimium eruditionis habes.

  9. #29
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    Do you have a voltmeter? It will answer your question.

    .

  10. #30
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    Obviously (for those of us in the states) 120/208 single phase is real common in apartment and multi tenant buildings. Once though I was doing a resi service on a resi street, just assumed it was split phase like I always do. Got a call later from the utility guy, said I needed to add a fifth jaw clip because it was 120/208. I looked later and they had "stolen" two phases off a three phase bank feeding some commercial stuff and run it down the alley to pick up half the block.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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