NEC 700.3(f) Code Change

In 2017, the NFPA’s National Electric Code® (NEC®) introduced a new provision, 700.3(f), which legally mandates the ability to connect a temporary power source to an emergency system. This provision requires that the emergency system rely on a single alternate power source, which can be disabled for servicing or maintenance. The most common method of meeting this requirement is through the installation of a Tap Box. The permanent switching means for connecting a portable or temporary power source must comply with the following:

• The connection to the portable or temporary power source must not require any modification to the permanent system wiring.
• The transfer of power between the normal and emergency sources must not exceed 10 seconds (as per NEC 700.12).
• Mechanical or electrical interlocking must prevent inadvertent interconnection of power sources.
• The switching means must include a contact point that signals, at a remote location from the generator or another facility monitoring system, that the permanent emergency source has been disconnected from the emergency system.

Manual switching is permissible for transitioning from the permanent power source to the portable power source and for connecting a load bank. Applications subject to this code include hospitals, healthcare facilities, public communications centers, places of large assembly (such as hotels, theaters, sports arenas), and industrial processes where power interruption could create serious health hazards.