neutral wire, and a green grounding wire. From the service panel, the black hot wire is connected to a black or brass hot line terminal. The white wire is connected to the white or silver line terminal. The green wire is connected to the green grounding terminal.
One aspect of GFCI protection to consider is placement.
That is because the GFCI’s location along the circuit determines whether or not it also protects other receptacles along the circuit. See Figure 3 on GFCI placement.
If the GFCI is placed in position A, it will also provide protection to the load side, or receptacles B, C and D. If instead, the GFCI is in position D, it will not provide protection to receptacles A, B, and C.
When replacing an old receptacle, the situation can get complicated. For example, the existing receptacle may also be connected to another receptacle, and it’s important to identify its position in the series.
Remove the old receptacle from the electrical box. If there is only one cable consisting of 2 to 3 wires, the receptacle is probably in position D or else it is the sole receptacle for the circuit. See the graphic for GFCI placement.
On the other hand, when the old receptacle has been removed and there are two cables for a total of 4 to 6 wires, the receptacle is in position A, B, or C. Don’t assume that the old receptacle was correctly wired.
One common installation mistake that workers and even electricians make is what is called line load reversal. Current standards for GFCI devices make it so that if the line and load cables are acci- dently reversed, the device simply will not work. In older devices, however, it was possible to reverse the line and load connections.
In the case of some of the older GFCIs where the line and load cables are reversed, the outlet will continue to provide electricity, even when the test button has been pressed. Generally, people test their GFCIs by pressing the test button. This makes the reset button pop out, a signal that the outlet is now dead, and the GFCI has done its job. But with GFCIs where the line and load are reversed, that indicative pop still occurs, but the outlet is still live-a false positive. Furthermore, all outlets that are connected downstream of this outlet, presumed to be GFCI protected from the upstream GFCI, are also still live. It is common to find this mistake, and there are GFCI three-light testers that are available at most hardware stores that can diagnose this and other potentially dangerous situations.
Another installation mistake is called reversed polarity, where the hot wire is connected to the neutral terminal, while the neutral wire is connected to the hot terminal. See Figure 4. Appliances plugged into outlets whose polarity was reversed will still work, but they are dangerous. That’s because most appliances are wired to have the hot side of the circuit, not the neutral, controlled by their on/off switches.They present a shock hazard because even when they are off, if they are still plugged into an outlet and the hot and neutral wires were reversed, they are still getting electricity. People touching the outside metal of light bulbs and other appliances have been known to get shocked.