MAGM 225

Mr. Conrado

Ground-Fault Circuit Interrupters

GFCI’s• GFCI’s are inexpensive, easy to install,

and readily available and could possibly save your life.

• Just as overcurrent (breakers) devices protect circuits. GFCI’s protect lives.

How they work• First it must be understood that current

in a circuit enters the load through the black wire and exits the load on the white wire.

• The black disk between the black and white wires compares the current leaving the load to the current entering the load. If the currents are not the same the disk will break the circuit.

• The current could be as low as .006 amps.

How they work• GFCI’s do not require a ground leg to

operate properly.• The GFCI will open the circuit in 1/30th

of a second or 30 times faster than a heartbeat.

• As good as they are they are not perfect. If the person becomes the load and is insulated from ground the GFCI will not sense any current loss and the person will be severely shocked.

Types of GFCI’s• Receptacle and Circuit Breaker types

– Receptacle • Fit into standard receptacle box• Protect any receptacle down stream of

the GFCI

– Breaker• Fit into service panel just as a standard

breaker and if wired correctly will protect all receptacle in the circuit.

• Are more expensive and less convenient to use than receptacle type but tend to last longer.

– Both are available in 15 – 20 amp and 120 or 240 volt configurations.

Where Ground-Fault Protection is Required

• GFCI’s are very sensitive and so must not be wired where life or property will be in jeopardy if the power is cut off.

• The NEC does require GFCI’s in a few locations.

– Kitchens

– Bathrooms

– Garages

– Crawl spaces

– Unfinished basements

– Decks / Porches

– Outbuildings

– Outside receptacles

Where Ground-Fault Protection is Required

• A few exceptions– Corded non-mobile appliances in a

garage or basement that a power loss would damage.

• Ie: freezer, fridge, etc.

Wiring a GFCI• In order to save lives GFCI’s must be

wired correctly.• GFCI’s use separate load and line

connections plus a ground wire.• Often it is difficult to tell the load from

the line connections without reading the GFCI receptacle itself.

• Find the line wires (from the panel) and connect to the line terminals of the receptacle.

• Connect the load wires to the load terminals.

• Tuck and attach receptacle into box.

Testing GFCI’s• GFCI’s should be tested once every

month using the internal test button• For more accurate testing a

commercial GFCI tester can be purchased.