Wiring in a GFCI to an existing circuit
There’s no such thing as too careful when you’re working around wiring. (I know this because I once cut through a 240-volt line after my father, an electrical engineer, told me the line was dead. It wasn’t.)
Start at the main panel by turning off the power to the outlet you want to upgrade. Then use a circuit tester to make sure the receptacle you’re about to dismantle is really dead.
Disconnect the wires from the back of the old receptacle and wire in the new GFCI — black wire to the gold colored screw, white to the silver screw. There are test buttons on the front of the receptacle to make sure it works.
The process is about that simple.
Many old houses have antiquated wiring systems with no separate ground — that’s the bare wire you’ll find in modern cable along with the white and black wires.
A GFCI works just fine without that ground and will still protect you against shock.
Protect the whole run of receptacles
One other thing to remember. Branch circuits usually include a number of receptacles, one wired to the next. You can give all of them GFCI protection by wiring in a single GFCI receptacle at the start of the branch circuit.
In the outlet box, connect the black and white wires that come from the main panel to the screws marked “line” on the back of the GFCI receptacle. Then feed the next outlet from the screws marked “load.”
Downstream receptacles will now behave just like GFCIs. If you get “line” and “load” mixed up, this will not be the case.
You can also use a GFCI circuit breaker to protect all of the receptacles on a branch circuit. It replaces a standard breaker in the main panel. Of course if you’re electrical system has never been upgraded from fuses to circuit breakers you’re out of luck.
AFCIs work differently
When current jumps across a gap it’s called an electrical arc. That can produce very high temperatures and result in a fire.
An AFCI is designed to sense an arc and turn off the power before it can cause any harm. It replaces a conventional breaker in the main panel, so if you’ve got an old fuse panel you’re not a candidate for this upgrade.
Some electricians think that AFCIs have limited value in ungrounded wiring systems — knob and tube, for instance, or non-metallic cable without an integral ground.
If you’re really interested in adding AFCI protection, get some guidance from a licensed electrician first.
Call Pacific Coast Electric Heating and Air, Inc. at 408-212-0230