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Design considerations for generator distribution switchboards

NFPA 70: National Electrical Code Article 700 specifies the requirements to install emergency power systems such as lighting when power from the normal source is interrupted. But while properly configuring the distribution switchboards of the generators in emergency systems is crucial, it is often a source of anxiety and confusion for installers. Electrical contractors and consultants need to understand all the applicable codes so they can arrive at a solution that complies with NEC 2020 requirements. This session discusses some of the traditional areas of confusion surrounding generator distribution switchboard design. For instance, the presenters will go into how to properly segregate 701 and 702 loads. 701 loads consist of “legally required standby” loads which include elevators, ventilation, and fire-detection equipment. 702 loads are considered “optional standby,” covering areas such as heating, refrigeration, and data processing. One of the questions that often comes up is whether wiring for optional standby loads can share the raceway, box, and cabinets with legally required wiring. The reason for confusion is that more than one interpretation of the code is possible, requiring the owner and AHJ to decide on a preference.