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How do I tell if a ground is really grounded?

15992 Views 4 Replies 4 Participants Last post by  AllanJ
I need to replace the 4 speed wall switch for my fan. When I removed the old one I discovered it was not grounded. The ground (uninsulated) wire was coiled in the back of the box. I checked a wall light switch box and found the same thing. I want to ground the new fan switch but how do I test the ground wire to be sure it's really grounded?
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Inside your electrical boxes, do you have a ground wire that is part of the building wiring? If the wiring is "romex" cable you would have a black, a white, and a bare ground in each cable entering the box. If it is wired using conduit, the conduit may be the ground.
What else can you tell use about your house. How old is it? Do you have circuit breakers or fuses?
The house was built in '85. The cable going thru the box and the cable from the fan are 3 wire. The black wire from the fan goes thru the switch and then spliced into the black wire going thru the box. The white wire and the ground wire from the fan are spliced into the white and ground wire going thru the box. Based on this can I assume the ground wire is really grounded?
If the house was built in '85, everything should be grounded. If you want to be sure, use a multimeter set to measure AC voltage. With the power on (be careful), there should be about 120 volts between hot and ground. Or, with the power off and the multimeter set to measure resistance, there should be close to zero ohms between ground and neutral.
Not foolproof but here are two steps.

1. Using wires with alligator clips on the ends or other similar means connect a fixture with 200 watts of incandescent light between the hot wire and the ground. The lights should come on with full brightness.

2. Inspect your main breaker panel to see that all the ground wires in the various cables are attached to a terminal strip that in turn makes metal to metal contact with the panel frame (box; can) and there is a fat ground wire from the main panel to a ground rod or to the cold water pipe where the latter enters the house.
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