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  1. 240.87 - setting the instantaneous to less than the available arcing current

    how does one exploit this option. Is arcing current a function of available fault current and in any event, how does one assure at the design stage that the main breaker on a 1200A, 480V...
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    brand new

    good to know Ron.

    This is only a few years old so shouldn't be by any particularily old codes. And definitely field wired so...

    Thank you gentlemen!
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    75 vs 90 degrees

    What is it that governs our using the 75 degree column in 110.15(B)16 for over 100 and up? And under what circumstance could you use the 90 degree column?

    The reason I ask is that I recently ran...
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    relationship between tons of cooling and kW

    I'm looking at a Filtrine water cooled chiller with Cooling Capacity of 265,000 BTU/Hr's and looking to find the electrical load.

    The FLA is 75A. Ok - so 75A x 480 x 1.73 gives 62kW.

    But...
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    480V and a clarification on which feeder we're talking about

    That's my suspicion as well on the #6 conductor. The voltage is 480V and this, it bears clarifying, is on the generator side not the utility. So utility feeder has an OCPD that is 6 times FLA. On...
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    How about if...

    What if there were lets say a small load on the neutral load (lets say it's feeding a mostly 3 phase load DP but with single pole breaker load).

    Does 215.2(A)2 still apply. Can I size the...
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    Fire Pump Feeder

    To a 100HP fire pump, is an MI feeder emergency feeder (i.e. run from the generator) comprised of 3#1 &1#6.

    Per 310.15(B)17 in the 75 deg column, #1's and #6's are rated for 195A and 95A...
  8. Thanks

    That makes a lot of sense
  9. Low temp rise dry type transformers - OCPD selection

    If you've got a 112.5kVA transformer with 115deg rise, it has an overload capability of I believe 12%. Therefore it's essentially rated for 126kVA

    Assuming you will have primary and secondary...
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    GE Busway - Pre-spectra

    Does anyone have in their archives, an old GE Buylog or copy of those Gray Engineering binders they used to distribute, showing non-sandwiched type, pre-spectra busway. If so and its not too much of...
  11. thank you

    I kinda thought so. Good to KNOW SO!
  12. Ground conductor for multiple circuits in single pipe

    Typically, I wouldn't run more than 3 single phase, 20A circuits in a conduit. I always run dedicated neutrals and a single ground conductor. So if I were feeding three lighting circuits via one...
  13. I suppose its a structure

    I suppose it's a structure. It's a very typical pre-case, open on the sides 3 story "structure".

    Where does the code define what would make it a structure vs a garage exactly? Building types...
  14. fire sealing in an open garage electrical room

    Working on an open 3 story garage. The only enclosed space is the electrical and a storage room on the first floor. Walls are CMU. Do penetrations through these walls need to be fire sealed or...
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    your input

    they do all use DC lights with drivers outside the room. The DC protects against the lights interfering with image. The concern I've run into with DC lights is the magnet interfering with the...
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    flickering ligthts in MRI rooms

    Some vendors of luminaires made for MRI rooms indicate that the wiring method must be aluminum conduit. In your experience, is MC Cable provided its in accordance with the NEC; i.e. fine for normal...
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    Robroy

    Just checked them out and sent them an e-mail. Good lead - thanks
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    wiring of an outdoor garage

    have been tasked with specifying the re-wiring of an existing concrete pre-cast garage (3 stories - maybe 60K square feet total). The exercise is owed to the fact that it was originally done with...
  19. thank you gentlemen

    much appreciated!
  20. Fire Doors and Auto Doors in Hospitals - smoke detectors

    I realize that it can vary from state to state, but per NFPA 72, NFPA 101 and or the IBC, what is the general rule for smoke detectors relevant to fire doors. I believe that you need them within 6...
  21. Hard conduit for LS and Crit and Hospital Grade AC cable (and now MC)

    Does anyone know when the NEC first strated requiring hard conduit for LS and Crit and the additional ground in AC cable for hospitals? Even if roughly?
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    ISO 7 Cleanroom - Electrical Requirements

    I'm designing the electrical for an ISO 7 clean room. the conduit and wire unlike many such rooms will not be exposed on the walls but run in a wall cavity. I believe I can just use typical NEC...
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    Thank you gentlemen

    As to why! As it turns out, he's just running through a couple of nipples from main to ATS to panel. He said the 4/0 will be easier to terminate.
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    parallel conductors in the same conduit

    I was recently asked by a contractor if they could run parallel 4/0 instead of a single set of 500kcmil (for a 400A feeder). And he wants to put them all in the same pipe.

    Assuming we can do that...
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    but definitely NOT an NEC requirement correct

    see title line

    And thanks very much for the input!
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