Quick Hits

Episode 7: Overcurrent Protection & Selective Coordination (700.30 - 700.32)

Selective coordination is non-negotiable (700.32). In an emergency, we want the branch circuit fuse to blow, NOT the main generator breaker. If a fault occurs in one room, the rest of the building must remain illuminated.

Selective Coordination Analysis

• Mandate:  Coordination must be achieved with all supply-side and load-side OCPDs.

• Documentation:  This must be performed and documented by a licensed professional engineer .

• Maintenance:  You must re-evaluate coordination every time you modify the system or replace an OCPD with a different model.

The "So What?" Layer

Compare the  Ground Fault requirements (700.31). In standard systems, ground faults trigger an automatic disconnect. In Article 700,  automatic disconnection for ground faults is PROHIBITED  for the emergency source. Instead, you provide "Indication" (700.7(D)). We prioritize keeping the lights on over protecting the equipment from a ground fault during an emergency.

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