Our plant site has an on hand stock of Starline busway for rated at 250A (T5 series), and the (city submitted) electrical plan for a new project calls out the (on hand) 250A busway to be fed by a 100A feeder with 100A OCPD.
The city plan checker had an issue with the fact that we are suppling a Starline 250A rated bus way with only a 100A circuit and provided a NEC code citation to support their position (NEC 368.17(A).
Below is the code citation that the city provided.
Response to the electrical designer is in red is mine.
NEC 368.17 Overcurrent Protection
Overcurrent protection shall be provided in accordance with 368.17(A) through (D).
(A) Rating of Overcurrent Protection — Feeders
A busway shall be protected against overcurrent in accordance with the current rating of the busway (Not to exceed current rating capacity of the busway). A 100A OCPD protects the 250A rated busway…”In accordance with the current rating of the busway” against overcurrent.
Exception No. 1: The applicable provisions of 240.4 shall be permitted.
Exception No. 2: Where used as transformer secondary ties, 450.6(A)(3) shall be permitted.
(B) Reduction in Ampacity Size of Busway
Overcurrent protection shall be required where busways are reduced in ampacity. The 250A busway current derating capacity in this case begins at the at the panelboard with the (New proposed) 100A OCPD and properly sized feeder conductors.
Is the plan checker's comment a correct application? Are my (in red) responses correct?
The city plan checker had an issue with the fact that we are suppling a Starline 250A rated bus way with only a 100A circuit and provided a NEC code citation to support their position (NEC 368.17(A).
Below is the code citation that the city provided.
Response to the electrical designer is in red is mine.
NEC 368.17 Overcurrent Protection
Overcurrent protection shall be provided in accordance with 368.17(A) through (D).
(A) Rating of Overcurrent Protection — Feeders
A busway shall be protected against overcurrent in accordance with the current rating of the busway (Not to exceed current rating capacity of the busway). A 100A OCPD protects the 250A rated busway…”In accordance with the current rating of the busway” against overcurrent.
Exception No. 1: The applicable provisions of 240.4 shall be permitted.
Exception No. 2: Where used as transformer secondary ties, 450.6(A)(3) shall be permitted.
(B) Reduction in Ampacity Size of Busway
Overcurrent protection shall be required where busways are reduced in ampacity. The 250A busway current derating capacity in this case begins at the at the panelboard with the (New proposed) 100A OCPD and properly sized feeder conductors.
Is the plan checker's comment a correct application? Are my (in red) responses correct?
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