Ground Fault Circuit Interrupter Safety
December 2000

We take it for granted that our ground fault circuit interrupters (GFCIs) are providing protection if we can operate a tool or other item through them. However, this may not be the case. While the device will allow current to flow through it, monitoring of the current may not be taking place.

Built into the device is a metal oxide varistor (MOV), used as a surge suppressor. The MOV absorbs the voltage surge and converts it into heat. Repeated surges can degrade the MOV, allowing current to still flow but not providing the protection required. Voltage surges such as lightning strikes in the area can cause a surge, as can a utility switching. When your GFCI trips and you reset it and power is restored, you need to go one step further and press the test button to ensure that the device trips open to stop current flow. This test button creates a difference of 5 milli-amperes between the hot and neutral through a resistor built into the device.

UL 1943 is the standard for testing GFCIs. Each manufacturer must ensure that its product meets this standard. Included in the listing and labeling of GFCIs are instructions that they be tested monthly.

Both the National Electrical Code and OSHA’s electrical standards require that equipment be used and installed in accordance with any instructions included in the listing and labeling. The purpose of this is to ensure as much as possible that the device is functioning properly. The bottom line, then, is to ensure that your GFCIs function as life-protecting devices, whether at work or home.

The following must be performed if you use GFCIs:

• Test your GFCIs monthly or as recommended.

• When a GFCI trips, reset it and then trip it using either a GFCI tester or the test button on the device, making sure this stops the current. Then reset it and use the circuit.

Not testing your GFCIs can give you a false sense of security that could result in serious injury or death!