Circuits National Electric Code

In the United States, this new interest was recognized, and in 1956, the National Electrical Code (NEC) introduced the use of intrinsically safe electrical circuits. 

These enclosures are designed to meet the applicable requirements of the National Electrical Code (NFPA 70) for Class I Groups A, B, C, or D hazardous locations that may be in effect. In this type of equipment, the circuit interruption occurs in air. 

Acceptable protection techniques for electrical and electronic valve accessories used in specific class and division locations include explosion-proof enclosures intrinsically safe circuits nonincendive circuits, equipment, and components dust-ignition-proof enclosures dusttight enclosures purged and pressurized enclosures oil immersion for current-interrupting contacts and hermetically sealed equipment. Details of these techniques can be found in the National Electrical Code Handbook, available from the National Fire Protection Association. 

Ground fault circuit indicator (GFCI)-protected electrical receptacles, approved by National Electrical Code... 

Electricity Equipment, switches, breakers, fuses, switch boxes, junctions, special fixtures, circuits, insulation, extensions, tools, motors, grounding, national electric code compliance. 

A single motor branch circuit is to be used to serve three motors rated at 1/3HP, 1/2HP, and 1/4HP. The motors are operating on a 115 volt, 60 hertz, single phase circuit. Using the given table, the calculated full load amps (A) that will be used to size the feeder for this branch circuit according to the National Electric Code is most nearly ... 

The first section Installation of Electrical Systems, 1910.302 to. 308, for the most part, covers installation of electrical equipment. Its use is very similar to the National Electrical Code electrical equipment installation. However, there are some sections of the installation requirements that do cover electrical safety. The primary example is providing appropriate working space for equipment likely to require examination, adjustment, servicing, or maintenance while energized. That working space is generally built-in when electrical equipment is installed. The requirements for ground-fault circuit interrupters are another example. 

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