In this episode of “EC&M Tech Talk,” Randy Barnett, a journeyman electrician, inspector, author, trainer, and electrical safety expert, provides an overview of the NFPA 79, Electrical Standard for Industrial Machinery.
The NFPA 79 standard addresses the electrical requirements to protect people and property for industrial machines that operate at 1,000V or less. The requirements begin at the source of supply to the machine and apply to items such as the disconnecting means, control circuits/devices, interlocks, permissives, and emergency stops. There are 19 chapters and several informative annexes in the standard. Chapter 3 provides numerous definitions for terms found in the standard, including a definition for “Industrial Machinery (Machine).” Always refer to standard definitions for correct terminology.
Disconnecting means must be capable of opening all phase conductors to the machine. Interlocks prevent enclosure doors from being opened when power is applied to the industrial machine. Control power is generally required to be supplied from a control power transformer within the machine and be fed from the source of supply to the machine. Operator stations, control pushbuttons, and switches must be located to prevent inadvertent operation. Protection against short circuits, ground faults, overvoltage, high temperature, and overspeed are examples of the types of equipment protection discussed.
This Tech Talk identifies some of the more common topics concerning NFPA 79. Additional items found in the standard address wiring, lighting, servo drives, and motors. Care must always be taken to refer to the complete standard as necessary to determine compliance.
