Ground Fault Circuit Interrupters
Electrical code requires the installation of ground fault circuit interrupters (GFCIs) in
residential dwellings to protect against shock. Receptacles in bathrooms, garages,
outdoors, crawl spaces, unfinished basements, kitchens and near wet bar sinks require
protection.
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A GFCI is a receptacle with a built in circuit to detect leakage current to ground on the
load side of the device. When the GFCI detects leakage current to ground, it will
interrupt power to the load side of the device, preventing a hazardous ground fault
condition.
These devices should be tested regularly, because they rely on mechanical connections
that will degrade over time. According to a recent study performed by the Leviton
Institute on average 15% of GFCIs were inoperative when tested. “Voltage surges from
lightning, utility switching and other sources all take their toll on the devices, which is
why Underwriters Laboratories (UL) requires that GFCIs be tested monthly.”
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Using proper grounding techniques, testing and maintaining a good electrical ground
and installing protection devices are the best ways to protect people and equipment from
electrical shock.
Equipment Failure
When sensitive electronic equipment fails, the initial reaction is to throw our hands up
and blame it on poor power quality. This makes the problem seem unmanageable and
out of our control. Most of these problems are actually under our control, because 80%
of all power quality problems are found in the electrical distribution and grounding
system.
In addition to preventing the possibility of fire, a good low impedance electrical system
will protect electronic equipment. A high resistance connection, like a loose wire, will
cause the voltage to fluctuate, or drop, when a large load is applied. If the voltage drops
low enough, it can cause electronic equipment to lock up, reset or shut down completely.
Grounding is another concern for electronic equipment. While ground impedance of one
Ohm or less may protect people from electric shock, it may not be adequate protection
for electronic equipment. IEEE recommends a ground impedance to be less than 0.25
Ohms for proper protection.
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NEC code Article {210-8 (a)}
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Study Identifies potential GFCI weaknesses,
Electrical Marketing, August 18, 2000
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