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Re: CQD answer published Wednesday, March 27, 2019 -Large equipment
1) Charlie, Thanks for all work that you put into CQD, I look forward to it every day! My understanding is that busway is a wiring method and that 110.26(C)(3) is intended to apply to the equipment that houses switches or breakers. 110.26(C)(3) states “equipment rated 800 A or more that contains overcurrent devices, switching devices, or control devices…” The 1200 Amp busway itself does not include the overcurrent device, the 400 Amp bus-plug is the equipment containing the OCPD. For an 800 Amp bus-plug I would agree with the response given, but for a 400 Amp plug in unit the answer provided is not the typical understanding I’ve had about how to apply the rule in 110.26(C)(3). I wonder if the answer would have been the same if we had a 1000A riser with cable and conduit to a tap box that is close coupled to a 200A safety switch? Thanks again. Rod West
Hey Rod and Rodney thanks for your comments and kind words - we are all constantly learning. As both of you mention, the 1200 ampere busway in the original question does not contain overcurrent devices or switching devices, the circuit breaker or fusible switch (bus plug) rated at 400 amperes does. You both have great points, because the equipment containing the overcurrent protective device (bus plug) is less than 800 amperes, the rule literally does not apply to it. Seems interesting that if this was a panelboard rated 800 amperes or more, with lower rated circuit breakers or fusible switches, the rule would apply to the panelboard, even though the cabinet the panelboard was in doesn't actually have an ampere rating.
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ABOUT CHARLIE: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.
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