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Thread: Terminal Blocks in a NEMA 4X Enclosuree in a Class 1 Div 2 environment

  1. #1
    Join Date
    Apr 2008

    Terminal Blocks in a NEMA 4X Enclosuree in a Class 1 Div 2 environment

    Any thoughts on how I prove to an inspector and an engineer that a terminal block is not considered an incendive device, so per 501.10 (B) (4) it does not need to be in an explosion proof box? He is asking for documentation that shows nonicendive at 120 volt. I can find Phoenix Blocks with built in fuses that document they are nonincendive, but our argument is over just plain old everyday terminal strips, Curtis Industries DSWT series.

  2. #2
    Join Date
    Apr 2018
    Grantsville, MD, USA
    If you find out, let me know! That is something I have come up against a few times, my colleagues hear CL I and immediately think explosionproof, even though a Div 2 installation can save quite a bit of money over a Div 1 installation if the area is indeed Div 2.

    In the NFPA 70 handbook (2014) it has a note under 501.10 (B) (4) that says 'In Class 1, Division 2 locations, boxes, fittings, and joints are not required to be explosionproof if they contain no arcing devices; or for lighting outlets or enclosures containing non-arcing devices, if the maximum operating temperature of any exposed surface does not exceed 80% of the ignition temperature.'

  3. #3
    Join Date
    Apr 2004
    Mission Viejo, CA
    I'm usually on the other side of the "The NEC is a permissive code." argument; however, in this case, if terminals of any kind were considered to be arcing, sparking or high temperature (ASH) equipment, they would be specifically noted somewhere in Article 501, Part III (Sections 501.100 - 501.150). Note that Equipment is a very broadly defined term in Article 100.

    I suspect your inspector or engineer has been influenced IEC practices.
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

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