• SCCR with control panels fed in series

    I am trying to interpret correctly the logic of the SCCR method suggested in NEC 409.110 (4).b  which is the UL508A SCCR Calculation. According to this method, all the components in the feeder circuit would defin...
    last modified by zeno
  • SJ/SO cord conductor color use

    I have a heating unit that is supplied 3 phase (with ground) power via an SJ/SO type of cord (it may be either 230 or 460).  The question is about conductor colors within manufactured cables: do I have to re-iden...
    last modified by kgilpin@adcomfg.com
  • NFPA 79 Wording/meaning

    I am just making sure I am reading this properly.  Could use an outside opinion.   In NFPA 79 Where color is used for identification, the color shall be used throughout the length of the conductor...
    last modified by jlassiter
  • LV control  panel primary and secondary  fusing

    In low voltage control panels ( typically 120 VAC PLC panels )  how can the code be correctly applied for fusing from a control transformer to loads such as electronic modules.  One main fuse from the line s...
    last modified by jz2018
  • Can I use 20 AWG multiple conductor cable in a raceway for control/signal circuits?

    I have a light tower and emergency stop button mounted 50 ft from the system enclosure.  The current for the light tower is 300mA at 24VDC.  I want to use a 20 AWG multiple conductor cable in a raceway to co...
    last modified by kkelly
  • Does a 24VDC enclosure light circuit need dedicated circuit protrection?

    There is a 24VDC LED light bar and a door switch in my enclosure which turns the light on/off depending if the door is open or closed respectively.  My question is does the light need its own ...
    last modified by kkelly
  • NFPA-79 Wire Color Code

    The NFPA-79 Wire Color Code is important for any person to quickly identify Circuits.  Consequences of using the wrong Wire Color could be lethal.   The NEC calls out (3) Colors:      * ...
    last modified by rcramereleceng
  • Electrical Panel Lexan Covering Exposed 480VAC

    I worked for 24 years at General Motors and it was common to see exposed 480VAC in electrical panels covered with Lexan glass to prevent accidental contact. We performed arc flash studies and all of our panels were la...
    last modified by zz3l4b
  • Does the NEC allow for the use of nonmetallic electric conduits in plenum of a confined space in a building?

    The NEC don't allow for the use of nonmetalic electric conduits in plenum (open space above false ceiling used for return air) in order avoid the convey of smoke and/or fire to other parts of the building. Is this ap...
    last modified by abdulazizabuali
  • 480vac 3ph Power Distribution

    I have a system where we are supplying a skid with 3 VFD/motors. The VFD/motors are each wired to there own fused safety disconnect.  The skid also has a fused disconnect for power supply to a 480/120 transformer...
    last modified by marc.gelinas
  • Single motor protection with VFD per Article 430.130

    Looking for interpretation of Article 430.130(A)(1) and (2) with respect to Branch-Circuit Short-Circuit and Ground Fault Protective device rating for single motor applications when a VFD is installed. The article ref...
    last modified by tom.brenner
  • NFPA 79 Inspector needed

    I'm looking for a 3rd party inspector to inspect a machine to NFPA 79 standard in the Wisconsin area.   Any suggestions.
    last modified by mwessel
  • Instrumentation Enclosure Component Fill Volume Requirement?

    Instrumentation Enclosure Component Fill Volume Requirement?   Hello,  I work for what amounts to an industrial supplier and we produce instruments that are composed of various electrical/other components....
    last modified by jtmiller
  • Knowledgeable Person

    Is there a industry excepted definition of a Knowledgeable Person.  I am working on updating my EEWP and we are looking into the approval portion and would like to have a knowledgeable person in this pr...
    last modified by jmerati
  • Surge Protection

    NFPA 79, 7.8.1 States that " SPD's (surge protective device) shall be provided for industrial machinery w/ safety interlock circuits to protect against the effects of overvoltages sue to lightning and switching surges...
    last modified by jeremy.bello@emerson.com
  • Wire Color for Remain Energized 24VDC Conductors.

    NFPA79 specifies: The use of other colors for the following applications shall be as follows: (1) WHITE with BLUE stripe for grounded (current-carrying) dc circuit conductor (2) WHITE with ORANGE stripe ...
    last modified by borisg
  • Electric Griddle info.

    Hello, my company is promoting a function and we have 4 electric griddles similar to the George foreman type.  I was trying to find information on what gage extension cords are needed spanning a length of 75-100 ...
    last modified by troy.cornett
  • 300va transformer, must the core be grounded

    I have equipment using a 300va custom wound transformer.   The core is lacquered and I have to grind off the coating to ground the frame.     Is it mandatory that the core be grounded and...
  • Door Interlock as par NFPA 79 Clause 6.2.4.

    Hello,   We have separate enclosure where enclosure which contains the supply disconnecting means has mechanical interlock that door can not be open without  making switch OFF. We also have second enclosur...
    last modified by vishal_g_patel
  • HOA hand switch leg direct to motor starter

       There has been some debate among my coworkers lately about the "Hand" switch leg of a rotary HOA selector switch going directly to the coil of a motor starter. I have been making the case that this i...
    last modified by jfosterjrod58