NEMA 280 : 1990

Foreword
Scope
1 Referenced standards and definitions
     Referenced standards
     Definitions
2 Characteristics of ground fault circuit interrupters
     General
     Principles of operation
     Double grounded neutral protection
     Test means
     GFCI tripping characteristics
     Types of GFCIs
       Basic GFCI
       Blank face type GFCI
       Permanently mounted type
       Circuit breaker type
       Receptacle type
       Portable type
       Cord connected type
3 Ratings
     Rating information
       Class
       Rated voltage
       Rated frequency
       Rated continuous current
       Rated withstand current
       Rated withstand current
       Rated interrupting current
4 Markings
     General
     Types which are permanently connected into current
       Class A devices
       Class B devices
     Portables and cord connected types
5 GFCI application considerations
     GFCI application considerations
6 Installation guidelines for electrical systems with
   GFCI
     Location of GFCI on system
       At load center or panelboard, or a permanently
        mounted type after panelboard
       At outlet box
     Wiring considerations
       At load
       Portable units
       Branch circuits
         120V 2W - with equipment grounding conductor
         120V 2W - older branch circuits without
          grounding conductor
         120/240V 3W - with equipment grounding
          conductor
         120/240V 3W - dedicated to an appliance
7 Field test devices
     Integral test devices
     Supplemental GFCI testers
       Possible improper indications when using
        supplemental test devices
         Supplemental test device on circuits containing
          leakage
         Supplemental test device on circuit with open
          grounding conductor
         Supplemental test device on circuit with
          reversed polarity
         Supplemental test device on circuit with
          grounded and equipment grounding and equipment
          grounding conductors interchanged
         Supplemental test device on circuit without
          leakage
         Supplemental test device on circuit with
          reversal of line and load wires
     Other test devices and test instruments
     Periodic verification checks
8 Field troubleshooting
     Line side of GFCI
     At the GFCI
     Load side of GFCI
       Load side of neutral ground
       Equipment ground and neutral connected together
        on load side
       Excessive leakage to ground
       Multi-wired branch circuits (shared neutral)
       High moisture conditions
       Inability to reset tripped GFCI
       Circuit breaker type
       "Supplemental tester does not trip GFCI, but test
        button does"
Appendix
A GFCI cross references to National Electrical Code -
   1990 edition

Covers ground fault circuit interrupters (GFCI) that provide electrical shock hazard protection from line-to-ground fault currents on grounded circuit of 120, 120/240, and 208Y/120 volt two-, three-, and four-wire supplies. Covered in this guide are characteristics of the various types of GFCIs, construction details, marking data, installation guidelines, field testing recommendations, and field troubleshooting information.