NEC Article 702 outlines the requirements for optional standby systems, which are systems installed to provide backup power for facilities or operations during a power outage. These systems are not legally required but are often critical for the continued operation of certain business processes or for comfort. Here is a comprehensive overview of the key sections within this article:

702.1 Scope

This section covers the installation and operation of optional standby systems, which are not legally mandated but are essential for ensuring the continuity of specific operations or preventing financial loss.

702.2 Definitions

Defines key terms related to optional standby systems to ensure clarity and consistency in application. This includes definitions for “optional standby systems” and differentiation from emergency systems and legally required standby systems.

702.3 Application of Other Articles

Specifies that the requirements of other NEC articles apply to optional standby systems, except where modified by Article 702. This ensures that general electrical safety standards are maintained.

702.4 Capacity and Rating

Optional standby systems must have sufficient capacity to carry the entire load of the designated equipment. The capacity and rating must be determined based on the operational requirements and the criticality of the loads being supported.

702.5 Transfer Equipment

Transfer equipment must be suitable for the intended use and must prevent the inadvertent connection of normal and alternate sources of supply. This is essential to protect against electrical hazards and ensure reliable operation of the standby system.

702.6 Signals

Specifies that visual and audio signaling devices must be installed to indicate the status of the standby power system. These signals alert personnel to the operational status and any issues with the system.

702.7 Signs

Requires signage to be installed to identify the presence of an optional standby system and provide essential information about the system’s operation. This includes the location of transfer switches and other critical components.

702.10 Wiring Methods

Permits the wiring for optional standby systems to occupy the same raceways, cables, boxes, and cabinets as other general wiring. This integration simplifies installation and maintenance while ensuring safety.

702.11 Grounding

Outlines the grounding requirements for optional standby systems. Depending on whether the generator is a separately derived source, grounding methods differ:

• 702.11(A) Separately Derived Systems: Grounding involves connecting to a grounding electrode system.
• 702.11(B) Non-Separately Derived Systems: Bonding to the equipment grounding conductor is required.

702.12 Outdoor Generators

Specifies requirements for outdoor generators used in optional standby systems:

• 702.12(A) Generators Over 15 kW: Requires a disconnecting means within sight of the building if the generator is not cord-and-plug connected.
• 702.12(B) Generators Under 15 kW: Allows for a simplified disconnecting means if the generator is cord-and-plug connected.

Optional standby systems play a crucial role in maintaining operational continuity and preventing financial losses during power outages. While not legally required, they are often vital for specific business operations and residential applications. For more detailed information and specific requirements, consulting the NEC Handbook and additional resources provided by the NFPA is highly recommended.

Sources:

• Codebook City: National Electrical Code Tips on Optional Standby Systems
• JADE Learning: NEC Articles 701 and 702 Overview
• NEC 2023