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Ground Fault Circuit Interrupters

Introduction

According to OSHA 1910.399, a ground fault circuit interrupter, or GFCI, is defined as “. . . a device whose function is to interrupt the electric circuit to load when a fault current to ground exceeds some predetermined value, that is less than that required to operate the over current protective device of the supply circuit.”

GFCIs are designed to shut off electric power within as little as 1 /40 of a second. It works by comparing the amount of current going into the electric equipment to the amount of current returning from the equipment along the circuit conductors. If the current exceeds six milliamperes, the GFCI interrupts the current enough to prevent electrocution.

GFCI’s can be incorporated into a special outlet, part of a power cord or put in-line and continually monitor the current passing through the receptacle. When a difference is sensed, indicating a leakage of current that could cause an injury, the GFCI quickly breaks the circuit.

GFCIs are intended to protect people similar to the way breakers and fuses protect wiring in a home or business. For example: electricity follows the path/route of least resistance. So if someone were to touch an electrical system with a leak, the person touching the system may be a better route of ground for the electricity to pass through since the individual offers very little resistance.

Where are they used?

GFCIs are used in wet or humid environments, high-risk areas and places where people could come into contact with ground or ground equipment. Typically in home use, GFCIs can be found in kitchens and bathrooms. Other applications include outdoor outlets, spas and pools. Occupations that use GFCI’s include dairy farms, breweries, steam plants and construction sites.

The following are GFCI regulations according to the OSHA Construction Standard 1926.404 ~ Wiring Design and Protection for Construction Sub part K of the 29 Code of Federal Regulations (CFR):

1926.404 (b)(l)(ii)

Ground fault circuit interrupters–All 120V, single-phase 15A and 20A receptacle outlets on construction sites, which are not a part of the permanent wiring of the building or structure and which are in use by employees, shall have approved ground fault circuit interrupters for personal protection. Receptacles on a two-wire, single-phase portable or vehicle mounted generator, rated not more than 5KW, where the circuit conductors of the generator are insulated from the generator frame and all other ground surfaces need not be protected with ground fault circuit interrupters.

1926.404 (b)(l)(iii)

Assured equipment grounding conductor program–The employer shall establish and implement an assured equipment grounding conductor pro-gram on construction sites covering all cord sets, receptacles which are not a part of the building or structure and equipment connected by cord and plug which are available for use or used by employees. The program shall comply with the following minimum requirements:

1926.404 (b)(l)(iii)(A) A written description of the program, including the specific procedures adopted by the employer, shall be available at the job site for inspection and copying by the Assistant Secretary and any affected employee. 

1926.404 (b)(l)(iii)(B) The employer shall designate one or more competent persons (as designed in 1926.32(f)) to implement the program. 

1926.404 (b)(l)(iii)(C) Each cord set, attachment cap, plug and receptacle of cord sets, and any equipment connected by cord and plug, except cord sets and receptacles which are fixed and not exposed to damage, shall be visually inspected before each day’s use for external defects such as: deformed or missing pins, insulation damage, or indications of possible internal damage. Equipment found damaged or defective shall not be used until repaired.

GFCI Program Requirements

Employer must provide:

• Written description of program 
• Competent person to implement the program 
• Inspection and testing 
• Records of test results

Inspections/Tests

Visual inspection of the following equipment is required:

• Cord sets 
• Cap, plug and receptacle of cord sets 
• Equipment connected by cord and plug

Exceptions:

• Receptacles and cord sets that are fixed and not exposed to damage.

Frequency of tests:

• Before first use 
• After repair and before placing back in service 
• Before use after suspected damage 
• Every 3 months—however, cord sets and receptacles exposed to damage must be tested at regular intervals not to exceed 6 months

Conduct tests for:

• Continuity of equipment of grounding conductor 
• Proper terminal connection of equipment grounding conductor

Note: For additional information please see 29 CFR 1926.404

Other Sources

• 29 CFR 1926.404 
• 29 CFR 1910.399 
• N.E.C. National Electric Code 
• OSHA booklet: Controlling Electrical Hazards at:
  www.osha-slc.gov/OshDoc/Additional.html

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