Taking 120v from a 3 phase breaker? - Page 3
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  1. #27
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    Sep 2001
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    East Stroudsburg, PA
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    13,215
    Originally posted by jrc2905
    I will not connect the new 120/208-240 cooler until a dedicated 240 breaker for this cooler is put in the panel by a licensed electrician.


    That's a very good idea. Someone else should take responsibility for the next fire.

  2. #28
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    Sep 2001
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    East Stroudsburg, PA
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    13,215
    Originally posted by condenseddave
    Originally posted by bodab20
    i would post but now i'm scared of condenseddave.(i hope its speled right). Seems he's the only expert on here so the rest of us just sit back and listen..He'll teach us how to spel better and about electrical stuff!
    You are a very gay guy, but thanks for posting nothing at all. You're a grand help, and a tribute to your sexual preference.
    So, Bobo, you happy now that we got that out of the way???

    It was the best I could do without asking you to post something that made sense, and enduring the agony of watching you struggle to come up with something useful.

    You were fun cannon fodder for a minute, though.

  3. #29
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    Aug 2002
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    manitowoc wisconsin
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    Dave,sometime you are so full of hot air I have almost mispelled your name as uncondensabledave myself...hahahaha
    Take your time & do it right!

  4. #30
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    Sep 2001
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    East Stroudsburg, PA
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    Originally posted by markwolf
    Dave,sometime you are so full of hot air I have almost mispelled your name as uncondensabledave myself...hahahaha
    Some of you goofballs do it intentionally, I know.

    I just wish these new guys would learn which hills were worth dying on before they wander into the firefights.

  5. #31
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    Dec 2004
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    441
    Dave, everything I put up on this thread I learned with a voltmeter and by asking questions, I have a short fuse too.
    this was one topic that would light it off if I had any concern for life and property.

  6. #32
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    Aug 2002
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    391
    To condenseddave; YES.
    The obvious is obvious

  7. #33
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    Nov 2004
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    Anchorage Alaska / Seattle WA
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    sounds like there needs to be a small distrubution panel set. HOwever, pulling a 120 circuit off of a 3 phase Bkr is ok if you have a dedicated neurtal and a equipment ground for the 120 ckt and live up to the tap rules in the Code. As far as the other compressor failures I would see if they were 240 volt single phase compressors. If you have a 208Y 3 phase circuit and try to run compressors rated for 240 you are starting out behind the 8 ball on voltage drop. The result will be a slow burn down on the compressors.

  8. #34
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    Nov 2004
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    Anchorage Alaska / Seattle WA
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    203
    Originally posted by indian
    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.
    When you find crap like this look at the service and see if there are two or three transformers on the pole. Some utilities use a two transformer lashup - it sucks bigtime. What you are looking at is a delta that is grounded in the middle of one winding. Wish i could draw on this it would make it much simpler. You should never get a reading to ground from an ungrounded conductor of 0 volts unless you have a ground fault. The grounded delta should be 120/120/208+-... Just try and keep all the controls off the high leg. The location of the high or wild leg seems to be different depending on what part of the country you are in and when the service was installed. I have seen them on the right and in the center. NEVER trust a service like this - be sure and check everyhting you do. Otherwise you WILL let the smoke out of something.

  9. #35
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    Nov 2004
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    Anchorage Alaska / Seattle WA
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    Originally posted by indian
    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!

    THis must be a very odd lashup. What is the high leg voltage to another leg. If this is a 480v Y configeration you better be very carefull. Looks like a ground fault on one leg. If you get a high resistnace ground fault on one leg of a 480v Y system you will get a rise in the ungrounded phases. The harder the ground fault the higher the ungrounded phases will go. If the facilities you are working in have a high resistance ground grid you will not trip a breaker with a 480 v ground fault - We use this type of system all the time in processes where you do not want to have a sudden interruption of power - in other words there needs to be an orderly shutdown for saftey's sake. The grounding resistor will limit the ground fault to 5 amps or less and sound a GF alarm. Then the electricial boys can sort out where the ground is. A single ground fault is not a problem in the short term - but man when you get that second fault there is going to be some breaker tripping. The main thing about working with systems like I am describing is your safety when working on a faulted system like you are describing. If for some reason you get yourself in a position where you are the ground path instead of the resistor you will find yourself passing 277 v to ground. That will not be a pleasant situtation and I have a friend that is no longer able to work because of just that kind of accident. If I were you I would ask some very pointed questions before I worked on a 480 system that showed 0 volts to ground on ANY phase... Please take this warning. I have many many years of industrial electrical experence.
    John

  10. #36
    Join Date
    Nov 2001
    Posts
    33
    I don't know if it is still done or not, but at one time they used in wet locations a "hot ground" (my term) one leg of the three phase, was ran to the "grounded or neutral wire" would be normally, this was done in theory to make a wet location safer with the use of the three phase, as if there were any faults the theory was it would trip the breaker quicker, and be safer in wet environments. or at least that was waht I was told.

    I first ran into it in the water plant and the sewage treatment plant on a military base, that was built in the late 50's early 60's, (it was on 208 Y three phase) there was no 110 in this situation and in the office the one 110 was produced by a buck transformer,

    all I know is it is a head scratcher until you figure out what your working with,

    It would have been very simular to the CORNER-GROUNDED DELTA in the web site below but in this location I rember it as a 208 volt "Y" set up but may have been a 240 delta. hey it was 25 years ago.

    http://www.bmillerengineering.com/elecsys.htm

    the web site above gives you the normal connections of most Electrical Supply Configurations that are in use to day.





    [Edited by BHD on 12-22-2004 at 10:44 PM]

  11. #37
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    Sep 2001
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    East Stroudsburg, PA
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    Originally posted by indian
    Dave, everything I put up on this thread I learned with a voltmeter and by asking questions, I have a short fuse too.
    this was one topic that would light it off if I had any concern for life and property.
    Dude, you have me right confused.

    I often forget who I offended in the past ten minutes, becasue there are so very many, but I went back through this thread, and checked, and I think I must've missed you.

    I never questioned your advice, as far as I can see.

    Am I missing something????

  12. #38
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    Sep 2004
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    3,157





    Electrical Supply Configurations
    Following are the typical transformer configurations that are used to supply 60 Hz power
    at 600 volts or less in the United States. While these generally describe the utility supply, large industrial facilities may receive power at higher distribution voltage levels and
    derive the lower voltages internally. The voltages in the chart are the standard nominal supply values.

    Several of the systems are rarely used for new installations, although they are still found
    in existing facilities. Other arrangements exist that are used only occasionally or for
    special purposes, and these have not been included at this time.

    The colors green, green/yellow, white, natural gray, orange, brown & yellow are reserved for specific conductors as defined by the NEC. All other conductors may be any color
    except these. While the chart shows typical color usage, some installations will differ.


    SINGLE-PHASE
    THREE-WIRE

    Nominal Voltages
    Phase-Phase Phase-Neutral
    240 120

    This is the most common supply for residences and small commercial facilities. It is also used for the offices in industrial facilities, where it may be derived from a higher available voltage by means of a local transformer.

    TWO-WIRE

    Nominal Voltages
    Phase-Phase Phase-Neutral
    - 120
    - 277

    Used infrequently for residential service or industrial single-phase loads.

    TWO-WIRE ISOLATED

    Nominal Voltages
    Phase-Phase Phase-Neutral
    120 -
    240 -

    Used to prevent ground fault arcs in hazardous atmosphere areas in hospitals and other similar applications. It may also be used as part of a power quality solution for sensitive loads. Isolated sources are generally derived locally near the point of use.

    THREE-PHASE, THREE-WIRE
    CORNER-GROUNDED DELTA

    Nominal Voltages
    Phase-Phase Phase-Neutral
    240 -
    480 -
    600 -

    Used occasionally in industrial facilities with only three-phase loads. No neutral is available.

    UNGROUNDED DELTA

    Nominal Voltages
    Phase-Phase Phase-Neutral
    240
    -
    480 -
    600 -

    Used occasionally in industrial facilities with only three-phase loads, or where isolation is required. No neutral is available.

    OPEN DELTA

    Nominal Voltages
    Phase-Phase Phase-Neutral
    240 -
    480 -
    600 -

    Similar to full delta, but used less frequently, for smaller three-phase loads.

    UNGROUNDED WYE

    Nominal Voltages
    Phase-Phase Phase-Neutral
    480 -
    600 -

    Used occasionally in industrial facilities with only three-phase loads, or where isolation is required. The center point may be grounded through a high impedance, but no neutral is available.

    THREE-PHASE, FOUR-WIRE
    GROUNDED WYE

    Nominal Voltages
    Phase-Phase Phase-Neutral
    208 120
    480 277
    600 347

    This is the most common system for large commercial office buildings at 208 volts, or industrial facilities at 480 volts with 277 volt lighting. All three phases can supply phase-to-neutral loads.

    CENTER-TAP GROUNDED DELTA

    Nominal Voltages
    Phase-Phase Phase-Neutral
    240 120 (phases A & C)
    208 (phase B)

    Used for commercial or industrial facilities with primarily three-phase loads. The high leg (phase B) must be identified, and is not usable for phase-to-neutral loads.

    CENTER-TAP GROUNDED OPEN DELTA

    Nominal Voltages
    Phase-Phase Phase-Neutral
    240 120 (phases A & C)
    208 (phase B)

    Similar to full delta, but used for smaller systems with minimal three-phase loads.




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  13. #39
    Join Date
    Dec 2004
    Posts
    441
    Originally posted by condenseddave
    Originally posted by indian
    Dave, everything I put up on this thread I learned with a voltmeter and by asking questions, I have a short fuse too.
    this was one topic that would light it off if I had any concern for life and property.
    Dude, you have me right confused.

    I often forget who I offended in the past ten minutes, becasue there are so very many, but I went back through this thread, and checked, and I think I must've missed you.

    I never questioned your advice, as far as I can see.

    Am I missing something????
    Don't try to read me too deep, guess I'm tired of being in between residential and commercial and dealing with the chiefs and the cowboys!

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