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leftisright 09-17-2009 07:38 PM

Wiring a new bathroom vent fan, circuit keeps blowing, what am I doing wrong?
Circuit supply (black, white, ground) goes into junction box, which supplies to hall light and bathroom light. I've spliced B/W/G to fan box, then spliced B/W/G to B/W/G of wall switch. The fan runs, but when I flick the switch, it blows the circuit. What am I doing wrong? Please help!


jbfan 09-17-2009 10:27 PM

In the fan box, take the black from the incoming power and connect it to the white wire going to the switch. Remark this wire with a piece of black tape.
Take the black wire from the switch and connect to the black wire of the fan.
Take the white wire of the fan, and connect it to the white wire of the incoming power cable.

220/221 09-17-2009 10:35 PM

Make the corrections in the JUNCTION box, not the fan box

petey_c 09-17-2009 10:41 PM

leftisright, Your description of your situation is confusing. Does one switch control both the hall and bathroom lights? Did you install a fan/light combo where there was once just a light? If that's the case and there's only one set of "B/W/Gs" in the box, then the fan and light will be on at the same time. Power off first. Ideally you should have three sets of "B/W/Gs". One set is power to the switch box and two "switch legs." One set for the hall lighting and another for the bath lighting. The "Gs" get spliced together with a "tail" long enough to attach to the switches (using a green wire nut). The "Ws" get wire nutted together and tucked in the box. The hot "B" gets attached to the bottom of each of the single pole switches. That should leave you with two "switch legs" (the other 2 "Bs"). They get attached to the top of the switches. At the fan; (usually) a small junction box/area with two sets of "Bs", two "Ws" and one "G". The "Gs" wire nut together and tuck away, then the "Ws", then the "Bs". Plug in the fan and light fixture. With the switches in the off position, power the circuit back on. Lemme know if this was any help.

jbfan 09-17-2009 10:41 PM


Originally Posted by 220/221 (Post 329108)
Make the corrections in the JUNCTION box, not the fan box

Thanks, missed that part.

220/221 09-17-2009 10:43 PM

We know exactly what you did but I can't tell you exactly what to do because I'm not 100% sure of your existing wiring.

Explain in detail and it will be easy.

You created a dead B/W short when you hooked the "switch loop" up to B/W power supply.

White is power TO the switch. Black is the switch leg back to the fixture/fan. This is the only case where you tie black to white. We call it a suicide switch :jester:

leftisright 09-18-2009 03:00 PM

Sorry I wasn't clearer... here's what I've got. Circuit power to junction box, which supplies hall light with separate switch, bathroom light with separate switch. Spliced from circuit power B/W/G to fan box B/W/G, ran wire from fan box to separate switch B/W/G. Circuit still trips.

If there is any way I can explain it better, let me know,

Thanks for all the help!

bob22 09-18-2009 07:36 PM

You essentially have to create a continuous loop with your wiring. So, from your supply, all grounds (bare wire) always are connected and only to a ground (and any metal boxes in which they are in). Black supply is typically interrupted by the switch and then continues onwards to the device being controlled (your fan in this case).
So, your supply's black goes to one switch screw, a new black wire to other switch screw; that wire continues to the fan's black wire. The white from the supply continues uninterrupted (usually in the switch box you splice the white supply wire to the white wire in the cable with the black wire going to the fan so it really isn't interupted but spliced so it is continuous) to the fan's white wire. The ground from your supply is used to ground the metal box of the switch, the switch (if it has a green grounding screw), and the fan.
So, the black wire brings electricity to the switch, the switch is closed, the electricity goes out the screw with the black wire to the fan's black wire, through the fan motor, out the fan's white wire, to the white wire back to the CB bus bar; you've a loop. I can't tell from your description too well where you went wrong.
PLEASE make sure the circuit breaker is off or the fuse is removed on the circuit you are working on so you don't kill yourself.

I hope this helps. I think it would be helpful to get a book or two on basic wiring at any book store or big box store. Wiring Simplified is a good one.
Sites have some info:

Thurman 09-19-2009 11:39 AM

"Spliced from circuit power B/W/G to fan box B/W/G, ran wire from fan box to separate switch B/W/G. Circuit still trips." NOTE: where you stated "ran wire from fan box to separate switch B/W/G. You still are not describing the colors of wiring from "fan box to to separate switch", and which colored wires you are connecting to what. This is important! I like jbfan's instructions with 220/221's slight correction, this is the way I am used to doing it. Take a minute, make a drawing of what you have and compare it to jb's instructions. Take a deep breath, and start over. We all do at times. Good Luck, David

GetYourShineBox 09-20-2009 01:38 AM

are you wiring neutral (white) directly to any of the switches? never wire neutral to a switch.

leftisright 09-21-2009 04:18 PM

Thanks, jbfan, 220/221 (Mr. Mom ref?), peteyc, Thurman, bob22. Followed jbfan's instructions (with 220/221's addition, I now have a working bathroom fan! No more fogged up mirrors for me!:thumbup:

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