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  1. RonShap

    Underground Duct Bank Ampacity Calculation

    ETap takes care of the conductor info for you, just tell it the size. The more important info is the installation characteristics. rho of the surroundings, spacing between cables/ducts, load factor, current
  2. RonShap

    IBC CODE - FIRE DETECTION IN SCHOOL.

    What code did you use to decide to put detectors in the corridors, electrical rooms, communication rooms? You need to refer to a code for all minimums, then you can always go over an above if you want. Minimums are generally in your adopted building code. If it happens to be the un-amended...
  3. RonShap

    Neher McGrath Calc UG Ductbanks

    For underground ductbank calculations for ampacities, we typically use a rho of 55 for concrete and 90 for soil. We concrete encase our ductbanks, then cover with soil up to grade. We have the contractor send a submittal with lab tested sample / typical material that will be used around the...
  4. RonShap

    Jockey Pump for Fire Pump system

    It is convenient since the feeder is already there, but not required...
  5. RonShap

    Transformer Differential for Arc Flash Mitigation on Unit Substations

    In both cases, the clearing time will be detection plus the clearing time of the primary protection device opening. The diff protection detection time should be the same as it seems the position of the secondary CT's are just either on the line side or load side of the 480V main. The...
  6. RonShap

    Let Thru Curves

    Not a lot of use for them anymore since UL and the NEC require series rated testing of assemblies for determining the adequacy of an under-rated device downstream. I don't have that model in my library. Some still use them for control panel withstands. Is that your application?
  7. RonShap

    Close transfer of load between two power transformers

    Do a voltage check from Phase A of one transformer secondary to the other and you should measure ~0. Same for B and C, and if it is true, then parallel at will.
  8. RonShap

    short circuit current and soft loading - for equipment evaluation analysis.

    Any closed transition (milli-seccond or multi-second) should include both source contributions for short circuit calculations and arc flash if it creates worst case. Generally worst case for arc flash will be one source (lowest fault current).
  9. RonShap

    NEC code requirement

    To add the jreaf, if you have multiple generator set output breakers due to different load types (NEC Article 700, 701 and 702), 700 & 701 will have a different requirement for GF than 702. Also depends on the size of the generator and voltage. Check out 700.6(D), 700.27, 701.6(D), 701.26 and...
  10. RonShap

    Estimating Connected and Demand Loads

    I'm trying to find a comprehensive reference for estimating connected and demand loads very early on in a new project based on VA/sf (or W/sf) I've used the very abbreviated list in IEEE 241 (old Gray Book) Table 15, but would like to find something more comprehensive and if nothing else, more...
  11. RonShap

    Credentials that young EIT's can acquire?

    LEED and NICET
  12. RonShap

    Fire detector sensor in sewage pump room

    Fire detection is typically placed per the locally adopted building code. If the adopted Building Code is based on the International Building Code, you will find the requirements in Section 907
  13. RonShap

    Double Bus Bar switch gear

    Faults due to mice reduce based on voltage, since spacing between energized conductors are further apart.
  14. RonShap

    Emergency Power Off Requirement for IT Systems?

    For clarity, the US standards do NOT require an EPO for this application, as well as most IT applications. NEC Article 645 allows for leniencies that are not worth taking, even in a data center if you provide an EPO, all of which for sure do not apply to this classroom application.
  15. RonShap

    Cast resin transformers

    I like this side by side comparison from Schneider http://www2.schneider-electric.com/resources/sites/SCHNEIDER_ELECTRIC/content/live/FAQS/275000/FA275901/en_US/7300DB0401.pdf Keep in mind they make cast coil, so it may be a little biased.
  16. RonShap

    Disadvantage of Electronic Soft Starter

    Depending on the motor size, and reliability needs, it is often cheaper just to get a VFD and use it as a soft starter.
  17. RonShap

    Does a raised floor need to be grounded?

    Are there metallic stringers / pedestals that make up the grid to support the tiles? Then NEC Section 250.4(A)(4) may require you to bond the floor and trench covers, and depending on if there are metal stringers, in more than one location.
  18. RonShap

    LV phase rotation

    You can change only at the transformer, and you can reverse all at the same time. It will be a little rough because you have a lot more wire at the main.
  19. RonShap

    UPS battery low

    What voltage is the battery typically floating at? Usually a 480V UPS will have the battery float at 480V+ to be able to recreate the 480V sinwave. Is this a large system? What does the user manual indicate regarding battery voltage?
  20. RonShap

    Electrical Power PE Exam study material

    You might have already seen this but https://cdn.ncees.org/wp-content/uploads/2012/11/PE-Ele-POW-Apr-2009-21.pdf

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