UL 1400-1 Ed. 1-2022

Outline of Investigation for Fault-Managed Power Systems - Part 1: Safety Requirements - Published Date: April 10, 2020

1.1 This Outline of Investigation specifies requirements for Fault-Managed Power Systems (FMPS), also referred to in the National Electrical Code, ANSI/NFPA 70 as “Class 4 Power Systems”. These systems are characterized by sophisticated monitoring and control systems that monitor the circuit for faults and control the power transmitted to ensure that the energy delivered into a fault is limited. Class 4 power systems differ from Class 2, and Class 3 systems. Class 4 power systems are not power limited at the source but are power limited with respect to risk of electric shock and fire hazards between the output of the Class 4 Transmitter and input of the Class 4 Receiver.  NOTE: The term “Class 4” and “FMPS” are used interchangeably throughout this Outline.  1.2 This Outline of Investigation is applicable to Class 4 equipment and circuits designed to be installed and used in accordance with Article 726 of the National Electrical Code, ANSI/NFPA 70.  1.3 In addition to the requirements in this Outline, a Fault Managed Power System shall comply with the relevant requirements of the Standard for Audio/Video, Information and Communication Technology Equipment – Part 1: Safety Requirements, UL 62368-1. Wherever there is a conflict between the requirements of this Outline and UL 62368-1, the requirements of this Outline shall apply.  1.4 This Outline is also applicable to Class 4 receivers that are integrated into other utilization equipment. This equipment shall also comply with the corresponding applicable Standard for the utilization equipment in question.  NOTE: Annex E documents decisions made by the developers of this Outline for Edition 1. This is intended to provide an understanding and background for future revisions as the technology for FMPS evolves.