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Type: Posts; User: Carultch

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  1. Replies
    9$$
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    1,076

    Not necessarily. On feeders and branch...

    Not necessarily.

    On feeders and branch circuits, and anything else behind the main service disconnect, you have control over shutting off the circuit, and would likely do so as standard procedure....
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    11$$
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    287

    The rule on 60C terminals is usually more...

    The rule on 60C terminals is usually more academic than practical. It is a rule that applies in theory, for when equipment/terminals are not specifically listed for any temperature (which is rare). ...
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    11$$
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    287

    90C rated wire does not necessarily mean you need...

    90C rated wire does not necessarily mean you need 90C terminals/equipment. It just means that 60C or 75C rated terminals become the "weak link" in the terminal-wire-terminal assembly. Most...
  4. That's not even remotely close to what the unit...

    That's not even remotely close to what the unit horsepower means at all. It makes no mention of how high the horse lifts the load, and 746 is really the number for the conversion factor of HP to...
  5. Draw out the equilateral triangle, and the "Y"...

    Draw out the equilateral triangle, and the "Y" within it, representing the phase voltages on the complex plane. Put the origin at the center of the "Y". The projection of each leg of the "Y" onto...
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    7$$
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    529

    Taps are governed by 240.21(B). Conductors...

    Taps are governed by 240.21(B). Conductors governed by 240.21(C) are no longer called taps, they are called transformer secondary conductors. The rules are very similar to rules for taps, but the...
  7. Replies
    7$$
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    727

    The reason that works out that way, is as...

    The reason that works out that way, is as follows. When you combine the formula after the f-factor and M-multiplier intermediate steps of the fault current across transformers calculation, you get...
  8. Replies
    7$$
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    727

    Here's how to calculate fault current across a...

    Here's how to calculate fault current across a transformer:
    https://forums.mikeholt.com/showthread.php?t=171709
  9. Replies
    29$$
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    2,722

    The MPPT range published on the datasheet, is the...

    The MPPT range published on the datasheet, is the range where performance can achieve the published CEC weighted efficiency. It may operate lower than the MPPT range and still seek the array's...
  10. Replies
    29$$
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    2,722

    That topology is atypical, and is subject to the...

    That topology is atypical, and is subject to the risk that the installer makes an oversight when ordering, and gets it backwards. So you are looking at a somewhat custom transformer, rather than the...
  11. Replies
    7$$
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    1,090

    NEC2017/690.15 now requires the AC disconnect...

    NEC2017/690.15 now requires the AC disconnect within 10 ft of the inverter, or a remote means to shutoff a more distant disconnect, that can be reached within 10 ft. I think this is overkill in...
  12. In the OP's situation, I would anticipate a small...

    In the OP's situation, I would anticipate a small stub of raceway sleeveing the cable as it exits the building envelope and enters the disconnect enclosure. Would that small stub of raceway also...
  13. It is not the rating of the transformer that...

    It is not the rating of the transformer that governs the sizing of this OCPD, it is the rating of the load connected to its load side. This OCPD has the purpose of protecting the transformer...
  14. Replies
    4$$
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    696

    220.5(B) allows you to round OCPD calculations to...

    220.5(B) allows you to round OCPD calculations to the nearest ampere, if after you apply your safety factors, your number ends up being no greater than 0.5A from the OCPD size you use. That would...
  15. Replies
    29$$
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    2,722

    A light commercial application will likely be...

    A light commercial application will likely be built with a 120/208V service, and this is the default service voltage unless there's an advantage to having 277/480V. Even larger commercial/industrial...
  16. Replies
    19$$
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    1,238

    What that section of the NEC is saying, is that...

    What that section of the NEC is saying, is that in certain topologies of transformers, the primary OCPD can effectively protect the secondary conductors too, as if they are a direct extension of the...
  17. Replies
    10$$
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    1,424

    Erickson is a manufacturer of conduit fittings. ...

    Erickson is a manufacturer of conduit fittings. Their brand was the original manufacturer of the three-piece coupling (aka Erickson coupling), which allows you to independently rotate two pieces of...
  18. Replies
    10$$
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    1,424

    There are ways you can cut the conduit, without...

    There are ways you can cut the conduit, without re-pulling the cable. Such as using a chain cutter for the conduit and taking extra care to avoid cutting thru the wiring. You will need to plan on...
  19. Replies
    35$$
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    4,400

    Inside a building, if it is not otherwise inside...

    Inside a building, if it is not otherwise inside a raceway, yes. DC circuits from solar arrays, have to be in metal, in some form or another. This would either mean using metal clad or armored...
  20. Replies
    18$$
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    1,284

    A 2" nipple of EMT is no longer than the...

    A 2" nipple of EMT is no longer than the back-to-back bodies of the setscrew connectors. I would think the nipple would need to at least have a plain cylindrical section long enough to even fit a...
  21. Thread: 75*C vs 90*C

    by Carultch
    Replies
    50$$
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    4,263

    The terminal ampacity would be based on the 75C...

    The terminal ampacity would be based on the 75C column, regardless of how many wires are terminated in the group. It has to do with the whole equipment (i.e. everything inside the factory-assembled...
  22. Replies
    3$$
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    840

    Keep in mind that inverter current does not...

    Keep in mind that inverter current does not necessarily scale directly with nominal power. Some inverters may have a larger current limit, to account for non-unity power factor or...
  23. Replies
    2$$
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    737

    1 ft from the array, it has to be brought down to...

    1 ft from the array, it has to be brought down to 30V and below. Essentially 24Vdc power for the power electronics, and communication/control circuitry.
    Within this boundary of the array, it has to...
  24. Thread: Upsized EGC

    by Carultch
    Replies
    22$$
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    965

    Not in 2014 and later. Prior to 2014, it didn't...

    Not in 2014 and later. Prior to 2014, it didn't specify, but now it specifies "the minimum size that has sufficient ampacity for the intended installation". That tells me, that you account for...
  25. Replies
    56$$
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    2,321

    What exactly is the advantage of CCA as opposed...

    What exactly is the advantage of CCA as opposed to standard aluminum? I would guess that in concept, the copper would give it a performance advantage, but the NEC doesn't model how you can take...
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