Commonly Asked Questions Regarding GFCI's


What is a ground fault?
Normally, line current to an electrically-operated device flows to the device through the hot conductor and returns from the device through the neutral conductor. It is common for the hot current to be slightly greater than the neutral current, with the difference being referred to as leakage current to ground. If the leakage becomes large enough to present a shock hazard to a user of the device it is described as a ground fault. A ground falult can result from a defective device, such as a metal case tool with deteriorated insulation, or misuse, such as dropping the device into water.
What is a GFCI and how does it work?
The Ground Fault Circuit Interrupter's (GFCI's) circuitry senses an imbalance between the hot and neutral circuits (ie the electrical current going through the tool to the operator and to the ground). If the difference between the circuits exceeds a pre-determined level, the GFCI disconnects (interrupts) both the hot and the neutral lines. Class A (portable) GFCI's are designed to trip when the ground fault circuit current exceeds between 4-6 milliamps (mA).
Portable GFCI's must also protect against an open neutral condition. In other words, if the neutral line is cut or not connected, the unit must cut off all power. If the hot were still live, the chance exists for power to go directly through the operator to ground. A relay or electronic circuitry is required to protect against open neutral. If someone were to attempt to make their own portable GFCI, without using a relay, the resulting device would not be OSHA compliant. OSHA inspectors are aware of this and they often ask for proof of open neutral protection.
Will a GFCI work with a double-insulated (non-grounded) tool?
Yes. As stated above, the GFCI senses an imbalance in the power circuits, not a flow of current in the ground circuit.
Should the GFCI be used at the power tool end or the power source?
It is recommended by the manufacturers that the GFCI be used at the power source so that the entire extension cord is protected. Some inspectors like to see a GFCI in use at the operator end.
Will a GFCI function like a circuit breaker and "trip" with too much amperage draw?
No. A GFCI will be damaged if it is overloaded for a prolonged period. However, most portable units will take temporary surges caused by the start-up of power tool motors.
Why are the portable GFCI units more complicated and more costly than permanent, wall-mounted units?
The portable, outdoor units must protect against an open neutral condition which is accomplished either by the use of a relay or more complicated electronic circuitry.
Do GFCI units need to be tested with an external tester?
No. The test button, which should be used daily, actually puts an imbalance between the hot and neutral circuits and self-tests the unit. If the test button fails to trip the GFCI, the unit should not be used. If an inspector does test a GFCI with an external tester, the GFCI should trip between 4 and 6 milliamperes, according to UL standards.
Are GFCI's required on job sites?
Yes, the use of GFCI's is described in the following publications:
OSHA's code of Federal Regulations 29CFR 1926.404
National Electric Code (NEC) 305-6
The OSHA regulation clearly states that users have a choice between (1) the Assured Grounding Program or (2) the use of Ground Fault Circuit Interrupters. As of January, 1996, the National Electric Code allows the use of Assured Grounding in industrial plants only.
For some of the following reasons, the use of GFCI's is preferred by contractors and OSHA inspectors over the Assured Grounding Program:
  • Assured Grounding Program requires a written procedure to be continuously enforced at each construction site and applies to each cord set and receptacle which are not part of the permanent wiring and to all electrical equipment.
  • Assured Grounding Program requires tests as outlined in the aforementioned publications. The tests must be documented. The cords and equipment require some form of identification, such as colored tape, to identify that the quarterly tests have been performed. With the myriad of power tools and extension cords on most job sites, this createa a documentation nightmare.
  • Even if all equipment and cords are properly tested and documented, there is still a chance for grounding failure during any work day. Therefore, some inspectors require GFCI's even if an Assured Grounding Program is in effect. Hence, GFCI's are the safest form of personal protection from electrical shock hazards.


Did You Know?
  • People are most susceptible to electrocution when the electrical frequency is from 50 to 60 Hz. The standard frequency for household current in the United States is 60 Hz.
  • One in ten construction deaths is caused by electrocution.*
  • Sixty percent of the electrocution deaths (on construction sites) are caused by factors other than workers coming into contact with overhead power lines.*  

SAFETY FIRST! Select the right cord for the job.


The charts below shows the recommended wire gauge and length for various horsepower and amperage ratings at 125 volts. The lengths indicated are the maximum length which should be used.



Ratings of Tool/Applications
HP of Motor
1/3 and 1/4
1 1/2


Ratings of Cord Gauge Size
Up to 50 ft. long
50 ft. to 100 ft.



Why Choose  Polar/Solar™

Coleman Cable manufacturers our GFCI units using our toughest, most rugged cord: Polar/Solar™ (Type SJEOW). These cords offer the following benefits over ordinary SJT cords and SAVE YOU MONEY BECAUSE THEY LAST LONGER:

  • Resistance to oils, grease, chemicals
  • 2 1/2 times greater abrasion resistance
  • Tear and puncture resistance
  • Wide temperature range (flexible at -67F)
  • Flame retardant
  • Superior flex endurance