gfci install, replacing an ungrounded plug in a basement
I have un ungrounded outlet along a basement wall that I want to replace with a GFCI outlet. There are two wires visible in the box, a white and a black in each one, no grounds. The existing two prong plug has the top screws connected with the white from one wire to silver and the black lead from the other wire opposite on the brass screw. The bottom screws are connected white from wire one to silver and black from wire 2 opposite it. I’m not used to seeing the white and black from one wire criss crossing opposite each other (tab on plug isn’t broken, I don’t believe). If I disconnect either set of wires that circuit goes dead (obviously) but so does another plug a few feet down the wall and also the overhead lights go out so clearly the box sneds current on to other sites. When I put in the GFCI and connect it up as I normally would with white and black on the same “line” plane and the other black and white on the same “load” plane, nothing works. I doubt that I should mix up the load line configuration to mimic what was there previously with the two prong plug but I still would like to have a GFCI at that spot. Can anyone explain please what’s the correct way to proceed?
Replies
The circuit feeds through the box to other boxes farther along. When you do this it's necessary for the black wire coming into the box to be connected to the black wire leaving the box, and for the white wire coming in to similarly connect to the white leaving. This produces the appearance of a continuous unbroken wire to the boxes farther along in the circuit.
In your case you would simply remove the old receptacle and install the new, connecting the two black wires to the brass colored side and the two white wires to the silver colored side. But you have to pay attention as to which are the "entering" vs "leaving" wires -- the "entering" wires (from the breaker/fuse) should be connected to the "line" terminals, and the "leaving" wires (to "downstream" receptacles) should be connected to the "load" terminals.
Finally, GCFI receptacles are usually delivered in "tripped" condition, and you must first turn on the power at the breaker/fuse and then press the reset button before the receptacle and everything on the "load" side becomes energized.
If you get the line and load sides confused the unit will not work. And the unit will not reset unless it's receiving power from the breaker panel.
OK, I did connect blacks to brass screws and white to silver screws the standard for receptacles feeding other circuits. With your advice I'll next try reversing the line and load connection as you advise that the GFCI won't work if lines are reversed. By the way what's the easiest way to discover which is the line vs load wire when dealing with a box with multiple wires in it?
You need an electrical tester. Turn the circuit off. Disconnect all the wires. Make sure none are touching anything. Turn the circuit on. Put the tester on the black wires until you find the hot one. Remember which one it is. Turn the circuit back off. The white wire in the same cable or conduit as the hot wire and the hot wire consitute the line side. Everything else is the load. If your circuit is in conduit rather than cable, it could possibly be grounded. In some installations condiut can serve as the ground.
again thanks- that was easy enough