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The bathroom exhaust fan motor housing is connected to the housing that vents to outside. In that housing is 120V wiring for the fan. There is a black wire, a white wire,and a ground/bare wire. I have connected the black and white wires to what they needed to be connected. Do I absolutely have to hook the ground as well?

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    Do you have to? No, it's your house, your life. Should you? Yes, absolutely.
    – FreeMan
    Commented May 8, 2023 at 16:45
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    Is there some reason you don't want to? Is it tripping GFCI when you do? Commented May 8, 2023 at 20:46

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Yes, you need to connect ground. If your wiring to the switch is in metal conduit, then the fan should ground automatically. If your wiring is in non-metal conduit then you need to run a ground wire and connect it to the fan and to ground in the switch box. If your wiring is non-metallic cable (a.k.a., Romex) then it should include a ground wire and you need to connect it to the fan ground wire.

There is one big exception: Old houses may legitimately not have had ground wires to the fixtures when built. If that is the case and you are replacing an existing fixture and your cabling does not have ground then you don't need to do anything with the ground wire from the fan. But that is relatively rare - most houses from the 1950s on, and most older houses that have had electrical upgrades over the years, will have grounds available.

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  • Are you saying that conduit itself is a ground? That would be new to me. Most conduit I see is galvanized steel (?) which would make a poor grounding material. My old house has Romex routed through conduit, but the conduit itself is not connected to the ground. For a very cheap price you can find a ground tester at the home center, which I recommend to the OP as an easy way to address his question. If the fan is ungrounded, the fixture absolutely needs to be grounded. Home inspectors can't even be bothered to sniff at issues like this any more!
    – AdamO
    Commented May 8, 2023 at 16:14
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    @AdamO Rigid metal conduit (which is a specific type, but by which I mean here as opposed to the flexible stuff (armored cable) which may or may not be a valid ground depending on the type) is a very good ground! With metal conduit and metal boxes you don't need ground wires. That is true even though those metal conduits and boxes are mostly steel and not the much better conductors copper or aluminum - steel is plenty good enough for the intended use of ground, which is to conduct electricity in a fault situation. You wouldn't use steel as an ordinary conductor (in residential use anyway). Commented May 8, 2023 at 16:17
  • +1 thanks, I will check into my code or other to learn more on this. Super interesting!
    – AdamO
    Commented May 8, 2023 at 16:28
  • @AdamO Outside New York and Chicago, most houses in the US have non-metallic cable (Romex) and little to no conduit. But actually plenty of houses have metal boxes, and with a metal box you are supposed to actually connect the ground wires to the box, and if you have a switch (any with a metal yoke) or a good quality "self-grounding" receptacle then you connect the ground from the incoming cable to the metal box and you don't connect a ground wire to the switch or receptacle. All with steel boxes - grounding works that way and it works well. Commented May 8, 2023 at 16:32
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    Grounding is really important because it helps both for lightning (via ground rods and/or copper pipe) and electric system faults (ground back to main panel and bonded to neutral). Starting point is to see what, if any, grounding is in your main panel Commented May 8, 2023 at 17:03

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