National Fire protection Association (NFPA) 70B (Recommended Practice for Electrical Equipment Maintenance) contains the requirements to perform frequency inspections and evaluate components of equipment for safe operation. Understanding the basics of the most-used annexes in 70B is useful to maintenance personnel.
An asterisk by a section number in NFPA 70B refers to the Annex A explanatory material that further describes a particular requirement. For example, Annex A, Section A.3.2.1 explains the term “approved” in greater detail.
This annex is presented as a guide for the preparation of a walkthrough inspection checklist that will be more applicable to a particular facility. Annex B suggestions are directed toward minimizing electrical hazards that may occur where maintenance is performed on a day-by-day basis.
This annex is used as a training aid for changing the behavior of employees and teaches them to follow the company’s safety manual. Behavioral changes will only take place with the introduction of new techniques that reshape attitudes and replace old skills with new knowledge. Annex C is equipped with the training information that, when properly instructed, makes learning quicker and more effective.
This annex contains symbols that have been standardized to aid those who are responsible for reading electrical diagrams and schematics and for ensuring the accurate inspection of electrical equipment for safe operation. Personnel should learn material identification in order to properly associate symbols with installed electrical wiring and equipment that they have been assigned to troubleshoot or maintain. For example, Figure D.1 contains some typical symbols that are used on electrical power and control schematic drawings that can serve in maintaining equipment.
In conjunction with symbols, this annex forms a single-line power diagram as well as other diagrams and serves as an aid to ensure other power sources won’t back-feed equipment that is supposed to be isolated and safe to maintain. To ensure safety, single-line diagrams should be kept up-to-date and should always be reviewed. For example, Figure E.1 includes symbols to represent a single-line power distribution system with switching and overcurrent devices.
This annex has forms that can be used for setting up a testing and maintenance program that, if applied appropriately, will provide optimum benefits. For such a program to work efficiently, testing data and maintenance actions should be recorded on comprehensive test-circuit diagrams and forms. It’s useful, sometimes, to record both test data and maintenance information on the same form. A dependable filing system should be set up for these forms, which will provide an efficient and rapid retrieval of information regarding previous testing data and maintenance pertaining to various types of equipment. Note that a well-designed form also serves as a guide or checklist of inspection requirements related to the safe operation of equipment. For example, Figure F.1 contains a checklist for a typical work order request form, which can be filled and presented to management.
Annex G provides tables of receptacle configurations from the National Electrical Manufacturers Association (NEMA) for users to select the correct mating receptacle for matching the attachment plug in order to cord-and-plug connect the equipment. For example, Figure G.1 shows the typical NEMA configurations for general-purpose nonlocking plugs and receptacles that are used for easy insertion and removal. However, Figure G.2 applies when locking-type plugs and receptacles are used and when they are inserted and twisted in the locked position. They cannot be removed until this process is undone.
This annex covers requirements that deal with the maintenance of equipment and components that necessitate long time intervals between repair shutdown procedures. Note that environmental and operating conditions of equipment may require adjustments to the interval checks recommended in the annex. For example, Table H.4 covers interval checks for low-voltage equipment.
This annex provides interval checks for the most commonly used equipment in commercial and industrial facilities. The interval checks and references to sections can aid in setting up a reliable maintenance program.
NFPA 70E and 70B are companions in safety. The National Electrical Code is an installation code, NFPA 70E is an electrical safety document, and 70B is a reference for evaluating components for safe operation and for performing interval inspections of related wiring and equipment.
STALLCUP is the CEO of Grayboy Inc., which develops and authors publications for the electrical industry and specializes in classroom training on the National Electrical Code and other standards, including those from OSHA. Contact him at 817.581.2206.