700.12(H) DC Microgrid Systems.
Code Change Summary: A new code section allows DC microgrid systems to be used as a source of power for an emergency system.
Emergency Systems are those systems legally required and designated as emergency by municipal, state, federal, or other codes, or by any governmental agency having jurisdiction.
Emergency systems are intended to automatically supply emergency lighting, power, or both, to designated areas and equipment in the event of failure of the normal power supply or in the event of accident to elements of a system intended to supply, distribute, and control power and illumination essential for safety to human life.
When an emergency happens that takes out the normal utility power to a building required to have an emergency system, a reliable back up source is critical. DC microgrids have proven to be a reliable source of power and in the 2020 NEC®, were added to Section 700.12.
Part III of Article 700 specifies all types of equipment permitted to be used as a source of power for an emergency system. This includes:
- Storage batteries
- Generators
- Uninterruptible Power Supplies (UPS)
- Separate electrical service
- Fuel cell systems
- Unit equipment
- DC Microgrid Systems
A DC microgrid is a power distribution system consisting of two or more interconnected dc power sources that supply dc-dc converters, dc loads, and/or ac loads powered by dc-ac inverters. A dc microgrid is typically not directly connected to an ac primary source of electricity, but some dc microgrids interconnect via one or more dc-ac bidirectional converters or dc-ac inverters.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC® edition of NFPA 70.
2017 Code Language:
This code section did not exist.
2020 Code Language:
N 700.12(H) DC Microgrid Systems. Sources connected to a dc microgrid system shall be permitted where the system is capable of being isolated from all non-emergency sources.
DC microgrid systems used as a source of power for emergency systems shall be of suitable rating and capacity to supply and maintain the total emergency load for not less than 2 hours of full-demand operation.
Where a dc microgrid system source serves as the normal supply for the building or group of buildings concerned, it shall not serve as the sole source of power for the emergency standby system.