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  1. Replies
    2$$
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    71

    You said the 4160V gear is already in the room...

    You said the 4160V gear is already in the room with the (2) chillers. Why would the addition of a transformer make the replacement of one of the chillers make it a problem?
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    8$$
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    159

    23168 I suspect the L-G fault current is 2X...

    23168
    I suspect the L-G fault current is 2X because you are dealing with only half the split phase winding, and only half of the impedance, but still all of the primary fault current as the primary...
  3. Are these actually 700 or 701 loads? Actually...

    Are these actually 700 or 701 loads? Actually Emergency or Legally required?

    Actually even if 702 loads, the code requires the transfer to be suitable for the indented use and designated and...
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    8$$
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    541

    As additional info, I have found that when the...

    As additional info, I have found that when the AHJ makes a code reference for egress lighting levels, it is usually to the adopted building code first and if it doesn't have a reference, then they go...
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    8$$
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    541

    Exit signs...

    Exit signs
    https://forums.mikeholt.com/showthread.php?t=184338

    For exit lights, it is based on the design of the light fixture and having the code required amount of FC on the floor.
  6. Thread: Battery Cables

    by ron
    Replies
    4$$
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    272

    Use DLO that is also RHH insulation rated. RHH...

    Use DLO that is also RHH insulation rated.
    RHH is a recognized insulation type and can be found
  7. Thread: duct bank

    by ron
    Replies
    4$$
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    388

    The layout of the 6-4" or 2-4" is important to...

    The layout of the 6-4" or 2-4" is important to how the ampacity of the conductors work out.

    For example, if the ampacity is based on Detail 3 from Annex B, then that would tell you the spacing of...
  8. Thread: Jacket Damage

    by ron
    Replies
    4$$
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    449

    A document from Southwire...

    A document from Southwire
    https://img1.wsimg.com/blobby/go/ebc3fdf8-949a-405c-9795-92e4372b83b8/downloads/1c6659pdp_152172.pdf

    from UL...
  9. Replies
    9$$
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    650

    If the utility transformer neutral point (XO) is...

    If the utility transformer neutral point (XO) is grounded, then the utility is considered solidly grounded.
    Is there no neutral brought to the MCC from the transfer switch or no neutral brought out...
  10. According to this link...

    According to this link https://www.ecmag.com/section/codes-standards/seeking-clarity-understanding-arcing-current-versus-bolted-fault-current
    The Doughty Neal Paper states, for a 480V system, the...
  11. Thread: Wireway Sizing

    by ron
    Replies
    6$$
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    534

    I've seen that done, run along the top of the...

    I've seen that done, run along the top of the server racks. The wireway conductor fill count is then done via typical methods.
  12. Thread: Wireway Sizing

    by ron
    Replies
    6$$
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    534

    I know that UL has a listing for Metallic outlet...

    I know that UL has a listing for Metallic outlet boxes (QCIT) http://productspec.ul.com/details.php?ccn=QCIT

    406.5 says that a receptacle has to be installed in an identified box or assembly. I...
  13. Replies
    16$$
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    982

    Presumably you have done a load calculation per...

    Presumably you have done a load calculation per Article 220.

    What is the load at the house and how does that equate to the feeder size that you would run at 120/240V single phase or 120/208V 3...
  14. Thread: Wireway Sizing

    by ron
    Replies
    6$$
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    534

    Sort of like this? ...

    Sort of like this?


    https://www.legrand.us/wiremold/raceway/steel-raceway/multi-channel-raceway/4000-large-raceway/4000-large-raceway.aspx
  15. Replies
    5$$
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    481

    Due to grid switching and the "smart grid", power...

    Due to grid switching and the "smart grid", power can come from lots of directions with changes / development making it hard to keep track, so they often just defer to unlimited primary calculations...
  16. Replies
    5$$
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    491

    This was one of the long answer questions on my...

    This was one of the long answer questions on my PE exam a while back.

    This link has some good bullet points.
    http://www.50hz60hz.com/60hz-motor-running-on-50hz-power-supply.html
  17. Thread: %IZ vs %Z

    by ron
    Replies
    3$$
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    371

    IZ% Percent impedance. Voltage drop due to...

    IZ% Percent impedance. Voltage drop due to impedance at rated current expressed in percent of rated voltage.
    The formula to convert to short circuit impedance .... I will look for it
  18. Replies
    22$$
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    930

    Depending on how much THD the generator is...

    Depending on how much THD the generator is putting out, the UPS may not recognize it as a valid source and then limit the furnace runtime to the amp-hour rating of the battery (15 minutes or whatever...
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    15$$
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    799

    Rumor is that the next NEC will required SPDs for...

    Rumor is that the next NEC will required SPDs for every service.

    UL 1449 Standard for Surge Protective Devices 4th Edition is the standard to be sure the product is listed to.
  20. Replies
    3$$
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    337

    You are quotable

    You are quotable
  21. Replies
    3$$
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    337

    The Dorm room is likely not a Dwelling unit, but...

    The Dorm room is likely not a Dwelling unit, but the Building probably is a Dwelling unit.

    Interesting issue that has been discussed.

    https://forums.mikeholt.com/showthread.php?t=52807
    ...
  22. Thread: Feeder Disconnect

    by ron
    Replies
    3$$
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    250

    You don't have to land in a 800A OCPD on the roof...

    You don't have to land in a 800A OCPD on the roof if you can comply with the tap rules in 240. You originate in an 800A OCPD, right?
  23. Thread: 75 vs 90 degrees

    by ron
    Replies
    4$$
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    436

    Even 1558 SWGR is tested at 75 deg terminations. ...

    Even 1558 SWGR is tested at 75 deg terminations. Without an intermediary termination box at either end, you are stuck at 75 deg ampacities.
  24. Thread: Conductor Size

    by ron
    Replies
    5$$
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    512

    Yes, unless there is some type of future growth...

    Yes, unless there is some type of future growth planned.
  25. Thread: Grounding a Genset

    by ron
    Replies
    2$$
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    528

    Sounds like only 3 wire loads, so you plan to use...

    Sounds like only 3 wire loads, so you plan to use the generator as a separately derived source is good. No need to pull a neutral conductor downstream.

    Review references in Article 250 for...
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