Energy management is becoming commonplace in today’s electrical infrastructures through the control of utilization equipment, energy storage and power production. Yet, limited consideration is found in electrical installation standards to actively manage these systems. These systems are intended to reduce energy cost or support peak power needs in relation to a broader electrical infrastructure demand. Energy management has two basic aspects, monitoring the system and controlling some portions of the system, both of which must be separated to permit an energy management system to monitor and possibly restrict control that would adversely affect the electrical system or personal safety. The most important aspect is to ensure that an overall energy management system does not override essential systems.
The increasing energy management focus and smart grid initiatives in this country are often voluntary; still others are mandatory because they are driven by regulations in adopted energy codes. So how does energy management work affect building electrical safety? And, what rules ensure that energy management systems do not affect minimum requirements for building systems that must remain operational? These challenges are more common among designers and engineering teams engaged in providing energy management services for existing buildings and achieving energy efficiency in new construction. However, new energy management system rules in the National Electrical Code must be applied to electrical system designs.
In all the efforts to reduce energy consumption in buildings, various continuous duty loads, such as lighting, must be carefully analyzed during energy audits to determine which loads can be controlled. The energy audit is one of the most important steps in achieving effective energy reduction and management. The auditor must be experienced in building electrical safety systems requirements and understand which loads energy management systems can and cannot control. Controlling or switching essential electrical safety systems loads could compromise safety for building occupants.
Energy management will grow significantly in the coming years and will affect electrical systems in all occupancies. The NEC is being equipped with requirements that address energy management and that support the safe and sound growth of this important feature and functionality in many building electrical systems. There will be abundant opportunities for qualified contractors that offer energy management and smart grid services in addition to traditional electrical construction.
Any energy management or energy-efficiency project or service must be performed in a fashion that does not compromise any emergency or essential electrical system loads from being operational when needed. Examples of loads that should not be controlled by energy management are pressurization fans for egress stairwells, lighting systems in the egress path to exits, and ventilation systems that run to achieve lower hazardous area classification.
The NEC contains the prescriptive electrical requirements that are widely adopted as law in the North American electrical safety system. New Article 750, “Energy Management Systems,” resulted from work of a specifically assigned NFPA Smart Grid Task Force responsible for identifying needs in the NEC related to energy management. There are other energy codes being adopted and applied in various jurisdictions across the country. These energy codes include performance requirements that directly affect the electrical installation. In other words, the performance requirements in adopted energy codes will drive the applicable prescriptive NEC requirements that apply to the installation or system.
The new article includes important definitions, information about essential alternate power systems loads that cannot be controlled, and a section that permits load shedding and power disconnection. The rules are necessary to prohibit energy management control from disabling them. The new article also prohibits energy management systems from causing any branch circuit, feeder or service to be overloaded. Another interesting requirement applies to energy management systems that remotely control building systems. The Code requires a directory of the controlled device(s) and circuits(s) to be posted on the enclosure for the controller, disconnect or branch-circuit overcurrent device.
In addition, Section 220.12 requires lighting load calculations for specified occupancies in accordance with Table 220.12. A new exception relaxes these requirements for a building that is designed and constructed to comply with an adopted energy code under the following conditions:
• A power-management system is installed that provides continuous information regarding the total general lighting load.
• The monitoring system is equipped with alarms to alert the building owner or manager that the lighting load exceeds the energy code allowance.
• The demand factors in 220.42 are not applied to the general lighting load.
Electrical systems controlled by energy management systems must meet all adopted regulations. Refer to the new Article 750 for such requirements.