Bath Fan/Light replacement - 3 3-wire at fan

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Old 11-29-18, 10:45 PM
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Question Bath Fan/Light replacement - 3 3-wire at fan

I'm helping my friend replace her bath fan/light unit. The fan and light are controlled by separate switches in the bathroom. The old one worked but was on it's last legs, so she bought a new unit and tried to do it herself, but stopped once she realized "wires are involved". I've replaced a bath fan before, simple! And I've done a number of other basic upgrades like this.

We did not label the connections when removing the old unit, unfortunately. I recall the whites were all tied together, the blacks were connected separately to the unit, but I don't recall if one had two blacks and one had one black or what.

Where I'm stumped: At the fan in the ceiling/attic, there are three 3-wire conduits, all similar in appearance with a bare copper ground, a black wire and a white wire. With the circuit breaker on, one of these is hot, and I labelled it such. The others are dead regardless of the switch settings.

We tried wiring the fan with all the whites linked together and the hot black and one of the "dead" blacks to the fan. Switched on the circuit breaker, nothing. Turned on the fan switch in the bathroom and the circuit breaker blew. What did I do wrong?

Any suggestions? I'm stumped. I can't figure out how the switch works with the hot at the fan anyway.

Thanks for any help you can offer.
 
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Old 11-29-18, 11:47 PM
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Typically youll have 12-3 (ground is not counted) for this kind of setup. You'll have a white a red and a black. Your commons, white, are wired together and one hot goes to the fan and the other goes to the light. The fan and the light both were working prior to starting? Pics would help.
 
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Old 11-30-18, 09:46 AM
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Thanks Taylorhudson. Both the fan and the light were working (although the fan was running very poorly) before. Fan switch and light switch are separate. There is no red wire. My friend snapped a pic this morning.

There are three sets of black, white, and bare copper (ground) wires.
 
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Old 11-30-18, 11:15 AM
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There are three sets of black, white, and bare copper (ground) wires.

Where are the three conduits? Regardless, what you have is one power source cable and two switch loop cables, they each go to a wall switch. The white in the power source cable gets connected to the light white wire and the fan white wire. The black in the power source cable gets connected to the two switch loop white wires. Now you should have two black wires remaining, these are both switched hot wires. One of the black wires is connected to the light black wire and the other gets connected to the fan black wire. The bare ground wires should all be connected together and then connected to the fan/light metal box.
 
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Old 11-30-18, 12:42 PM
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Thanks Joe! I would not have figured this out myself. Your description is clear. I will try that tonight when my friend gets off work.

I think I used the term "conduit" incorrectly. I meant the bundle of wires in the white sheath.
 
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Old 12-02-18, 01:33 PM
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Thanks @CasualJoe! Your instructions worked perfectly. My friend and her hubby love the new quiet fan and light in the bathroom.
 
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Old 12-03-18, 09:25 AM
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Thumbs up

No problem, glad I could help out.
 
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