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Page Title: Ground Fault Circuit Interrupters (GFCIs) and ARC Fault Circuit Interrupters (AFCIs)
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DOE-HDBK-1092-2004
4. American Society for Testing and Materials (ASTM)
5. National Fire Protection Association (NFPA)
6. Underwriters Laboratory, Inc. (UL)
7. Factory Mutual Engineering Corporation (FMEC)
8. Other NRTLs recognized by OSHA on a limited basis.
Where no clear applicable code or standard provides adequate guidance or when questions
regarding workmanship, judgment, or conflicting criteria arise, personnel safety protection shall
be the primary consideration. Therefore, where there are conflicts between the mandatory
requirements of the above codes, standards, and regulations, the requirements that address the
particular hazard and provide the greater safety shall govern.
2.7  GROUND FAULT CIRCUIT INTERRUPTERS (GFCIs) AND ARC
FAULT CIRCUIT INTERRUPTERS (AFCIs)
There are two classes of GFCIs, each with a distinct function. A Class A GFCI trips when the
current to ground has a value in the range of 4 through 6 milliamperes and is used for personnel
protection. A Class A GFCI is suitable for use in branch circuits. A Class B GFCI (commonly
used as ground fault protection for equipment) trips when the current to ground exceeds 20
milliamperes. A Class B GFCI is not suitable for employee protection.
Ground-fault circuit protection can be used in any location, circuit, or occupancy to provide
additional protection from line-to-ground shock hazards because of the use of electric hand
tools. There are four types of GFCIs used in the industry:
1. Circuit breaker type
2. Receptacle type
3. Portable type
4. Permanently mounted type
The condition of use determines the type of GFCI selected. For example, if an electrician or
maintenance person plugs an extension cord into a nonprotected GFCI receptacle, the easiest
way to provide GFCI protection is to utilize a portable-type GFCI.
2.7.1
HOW A GFCI WORKS
See Section 4.14 for ground-fault protection of equipment. GFCIs are devices that sense when
current--even a small amount--passes to ground through any path other than the proper
conductor. When this condition exists, the GFCI quickly opens the circuit, stopping all current
flow to the circuit and to a person receiving the ground-fault shock.
Figure 2-1 shows a typical circuit arrangement of a GFCI designed to protect personnel. The
incoming two-wire circuit is connected to a two-pole, shunt-trip overload circuit breaker. The
load-side conductors pass through a differential coil onto the outgoing circuit. As long as the
2-5


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