A properly grounded system ties each device, appliance, and fixture back to the service panel with a separate grounding conductor (the bare copper or green insulated copper wire). It’s unrealistic to attempt this with an old electrical system unless you’re replacing it (in which case, the grounding would be part of replacing the system). You also could install a GFCI in place of an existing, two-wire receptacle. The National Electrical Code allows an ungrounded, two-wire receptacle to be replaced with a GFCI. A GFCI can even protect any receptacles downstream (away from the panel or power source). A GFCI used in this manner will only protect you from ground faults; it will not act as a ground for any equipment plugged into the receptacle(s). As a rule, it’s best for GFCIs to protect only a single box, not multiple receptacles. If you try to use one GFCI to cover multiple receptacles, you might experience nuisance tripping due to the greater sensitivity to current fluctuations. A GFCI installed to replace a twowire receptacle should be marked “No Equipment Ground.” A GFCI must be wired according to stamped terminals on the back of the receptacle. They will be marked “Load” and “Line” as well as “Hot” and “White.” The hot wire (which runs from the panel or fuse box) is the line conductor; anything going off to another load or receptacle is the load conductor. How do you know which is which? You’ll need your voltage tester.
With the power off and the old receptacle removed, separate all the wires in the box so they’re not in contact with each other (or with the box if it’s metal). Turn the power back on, and put one end of your probe on one hot wire and one on the neutral that is paired with the hot you are testing. If the bulb doesn’t light up, try the other black wire and neutral. The one that lights up the tester’s bulb is the line conductor. It’s the one receiving power from the current you switched back on at the service panel or fuse box. Connect this to the “Line,” “Hot” side of the GFCI. It is very important that the line side hot and neutral conductors or wires be connected to the “Line” side of the GFCI; otherwise, the GFCI will trip or will not work at all. If the line and loads are reversed, the GFCI will still have power if it is tripped, producing a hazardous situation.
As an alternative to installing a GFCI to replace an ungrounded receptacle, it is permissible to install a grounding conductor to an ungrounded circuit by using an individual No.12 insulated green copper conductor to connect each receptacle being grounded to the closest cold-water pipe. The grounding conductor will then have to be secured to the pipe using an approved clamping device. It also can be run directly back to the panel and installed in the grounding/ neutral bar.
