National Electrical Code Tips: Article 750, Energy Management Systems
At about 1.5 pages long, this is one of the shortest NEC Articles. It was new with the 2014 NEC (as was the also short Article 728, which precedes it in Code order).
- Typically, a Code Article will expound on the installation requirements for whatever it covers. For example, Article 430 really goes into depth about motors. This Article does not go into depth about energy management systems. It merely provides a few restrictions on their installation and application.
- The expectation is that you, as the designer or installer, are a qualified person using the relevant industry standards. Other codes may provide more restrictions or prescriptions than Article 750 [Informational Note, 750.1]. That is, Article 750 doesn't replace other codes or standards. It simply adds the voice of the NEC to them.
- The systems covered by this Article are those that monitor/and or control loads or power sources [750.2].
- Both "control" and "monitor" are specifically defined in this Article. What's key in both definitions is the involvement of electric power.
- An energy management system cannot override any control necesssary to ensrue the continuity of alternate power sources for fire pumps, health care facilities, emergency systems, legally required systems, or critical operations power systems [750.20].
- The system can monitor the loads just described [750.30], and it can control these to a limited extent [750.30(A)].
- The system cannot disconnect the power to elevators (or escalators, moving walks, or stairway lift chairs), positive mechanical ventilation for hazardous locations, ventilation used to exhaust hazardous gas or reclassify an area, emergency lighting, or essential systems in health care facilities [750.30(B)].
- Be careful in how the energy management system adds loads. It isn't permitted to overload a branch circuit, feeder, or service [750.20(C)]. This could happen in any number of ways. Also, don't make the mistake of adding too many loads to these circuits and then relying on the energy management system to keep things sorted out. Do the sorting out in your design. Use the energy management system to reduce total energy consumption, not to add phantom capacity to branch circuits, feeders, and services.
- Protect those first responders. On the enclosure of the controller, disconnect, or branch-circuit OCPD, post a directory showing which devices and circuits the system controls [750.50].