NEC Section 700.3(F): Connecting Portable Generators During Emergencies

When electrical systems are critical to life safety, it is essential that backup power remains available even when the primary backup system fails. National Electric Code (NEC) Section 700.3(F) addresses this concern by providing guidelines for connecting portable generators as a temporary power source, thus ensuring uninterrupted power during emergency situations. This article takes a quick look at the core requirements of this specific provision of the NEC.

NEC Section 700.3(F): Key Provisions
  1. Temporary Connection of Portable Generators: 700.3(F) outlines the requirement for a means to connect a portable generator, or another temporary source of power, when an emergency generator (acting as single source of alternate power) is out of service for maintenance or repairs. This connection capability is crucial for facilities where the emergency system needs to remain functional even during maintenance of the sole alternate power source.
  2. Transfer Equipment Capabilities: The Code requires that transfer equipment be available to allow the switch-over from the permanent source of backup power to a portable or temporary source. This ensures that, should there be a power outage while the permanent generator is undergoing repairs, power won’t be lost to crucial systems and equipment.
  3. Safety Protocols: When connecting a portable generator, safety is paramount. The connection should be in a manner that ensures protection against back-feed, maintains the integrity of the grounding system, and adheres to all other relevant NEC guidelines.
  4. Connection Interface: To facilitate a seamless connection of the portable generator, an external means such as a receptacle, connection cabinet, or a plug must be permanently installed. Having a predetermined procedure and connection point allows for the quick and safe connection of a temporary power source. It is important to note that the Code requires the connection point for the portable generator to be located outdoors.
  5. Rating and Labeling: The means of connection for the portable generator, such as a receptacle or connection cabinet, must have a rating not less than the largest portable generator anticipated for the facility. The connection means should also be labeled to identify it as the designated point for portable generator connections.
  6. Instructions for Safe Operations: The NEC mandates that written instructions on safe operating procedures be provided and readily accessible to facility personnel. This includes procedures for transferring between the normal power source, permanent generator, and the portable generator.
Load Bank Testing of Permanent Generators

In many facilities, it is also essential to ensure that the primary backup system (the permanent generator), functions optimally when called upon. One of the best methods of assessing the performance and health of a generator, whether after repairs or during routing testing, is by the use of a test load bank.

NEC 700 recognizes the reality of long-duration maintenance and testing events, and permits the use of switching equipment to connect a test load bank to the permanent generator while a portable generator is actively supplying power to the building loads. A “dual purpose” connection cabinet with interlocked switches is one tool allowing facility managers to perform real-time, thorough testing of the permanent generator, while minimizing potential disruptions to the building’s critical systems.

Safety is critical when connecting a load bank during the time a portable generator is in use. Proper precautions and procedures must be in place to ensure that there are no risks of back-feed, that the load bank connection doesn’t interfere with the operation of the portable generator, and that all power transitions occur smoothly and without incident. Proper interlocks, transfer switches, labeling, and well-trained personnel can ensure that both operations – powering the facility and testing the permanent generator – happen simultaneously and safely.

Importance of Section 700.3(F)

Whether it’s a health-care facility, a critical manufacturing facility, or a residential building, the need for a consistent power supply is obviously important. Through the implementation of the guidelines provided by NEC 700.3(F), buildings and facilities can also develop confidence in their emergency response plan, ensuring that crucial systems will remain in safe operation during planned or unforeseen maintenance activities.

For additional support:

On-Site Power Advisor can assist engineering firms in specifying safe means for connection of temporary power systems. For further design support, please contact here.

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