Installing New Bathroom Fan on Existing 40A Circuit


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Old 06-14-18, 06:13 PM
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Installing New Bathroom Fan on Existing 40A Circuit

Hello,

I originally posted this incorrectly in "Electrical, AC & DC.

I'm working with a buddy on his home built in the mid-50's that only has 6 breakers to it's electrical system. There is 1 @ 15A, 2 @ 20A, 2 @ 30A (coupled together), and 1 @ 40A. His bathroom light and outlet are run off of the 40A circuit, along with the central AC. I'd like to install a bathroom fan in the ceiling that will vent through the gable in the attic.

The wiring from the bathroom light switch comes up through the top plate of the wall that it's on, travels over the ceiling joists, and then down into the top plate of the wall where the vanity lights are installed. It's cased in flexible steel conduit. We want the fan to run whenever the vanity lights are turned on.

Can I (carefully, with the power off) cut the conduit back between the switch and the vanity lights, cut the wiring, and splice in some 12-2 romex to run to the new ceiling fan? I would use the appropriately sized wire nuts, and make the connection inside a junction box that I would nail to the top side of a ceiling joist. It seems pretty straight forward to me, which I've learned is a sign that I should consult with some more experienced people. I'd greatly appreciate any thoughts you all might have.

Thanks in advance!
 
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Old 06-14-18, 06:39 PM
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NO. None of this should be run off a 40 amp circuit. This is unsafe and should be corrected ASAP. General purpose circuits may only be 20 amps max and should not be tied into the A/C circuit. .
 
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Old 06-14-18, 06:47 PM
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His system needs to be replace. The 120v bathroom connections need to be moved to the 15 or 20 amp breakers NOW to prevent a possible fire.. The panel you describe sounds like a 60 amp panel. They haven't been code for many years. 100 amp is now minimum. What he really needs is a whole new service.
 
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Old 06-15-18, 07:50 PM
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Thank you both for your advice. He's called an electrician and is getting the bathroom and the furnace (I guess that was on the 40A circuit, too) each on their own dedicated 20A circuits. The electrician is also adding a tie-in for the new fan, too, so it's just a matter of connecting it. It's been wired that way for at least 13 years. Glad it's getting fixed.
 
 

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