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Original Request
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Request ID:
8476
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Date Submitted:
November 08, 2020
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Requested By: Jason Szumlanski
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Code:
National Electrical Code
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Edition:
2017
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Chapter:
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Section:
705.12
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Topic:
Photovoltaic System Interconnection on Feeders With Meter/Main Combination Devices
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Question:
How is NEC 705.12(D)(2)(3)(c) applied when an inverter output connection is made on feeder conductors fed from a primary source via feed-through lugs in a meter/main combination service entrance device? Does the inverter output overcurrent protection device (OCPD) count toward the sum of the OCPD devices "on" the primarily supply panelboard as described in this section and allow up to the busbar rating for the sum of the load and supply overcurrent devices, regardless of additional loads at the end of the feeder? This question applies equally to NEC 2014 currently in effect and 2017 which is imminently to be in effect.
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Comments:
It is my interpretation that the attached drawing is code compliant with this section. The sum of the inverter output connection plus all load OCPD devices "on" the panelboard as described in this section does not exceed the rating of the meter/main combination service entrance device busbar. The main breaker in the subpanel on the load side of the inverter connection adequately protects the subpanel busbar and complies with NEC 705.12(D)(2)(1)(b). There is no segment of the main panel busbar nor the feeder where the ampacity can be exceeded under any scenario without the primary supply OCPD tripping. The subpanel load is not relevant to the calculation in 705.12(D)(2)(3)(c) because that portion of the circuit is protected via the provisions of 705.12(D)(2)(1)(b). Interestingly, NEC 2020 addresses feeder conductors fed via feed-through lugs in 705.12(B)(3)(6) and appears to support this interpretation.
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Attachment 1: Download
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