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  1. #1
    Join Date
    Oct 2009
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    Default wiring Bath fan/GFCI on existing light circuit

    Moving into a house built in 1950, with a switched vanity light and no outlets in the master bath (previous owners had the oh-so-classy outlet-in-a-light-socket doohickey behind one of the vanity globes).

    I'd like to put in an exhaust fan/heat lamp combo in the ceiling and a GFCI outlet at the switch plate. I'm picturing a 4-gang box with a lightswitch, 2 timers (heat lamp and fan), and the outlet.

    My question concerns the wiring, and what is appropriate/safe/legal. I'm planning to run 12-3 straight up the wall from the box to the attic so the red and black control 2 streams of switched power to the light and fan with a common neutral (per the mfr. wiring diagram).

    Does the neutral going to the existing vanity light need to be in series with the new neutral at the fixture, or can the existing and new neutrals be hooked together in the wall box at the pigtail connection?

  2. #2
    Join Date
    Aug 2007
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    Default Re: wiring Bath fan/GFCI on existing light circuit

    In houses of the vintage such as yours it's common to find that existing bathroom light will be part of another circuit in other parts of the home ....... also unless the wiring had been updated it's also likely the wiring is only 2 conductor without the safety equipment ground ( bare or green ) conductor.

    Those fan/heat lamp combo units draw a minimum of 2 amps ..... depending .... could be more. Now 2 amps may not sound like much .... but ..... if the circuit is also feeding other parts of the home this may be enough to trip breakers / fuses. This is a reason I wouldn't recommend tying into the existing light circuit.

    Instead ..... It would be best to run your 12/3 from the service panel to your switch box and onward up to the attic for the fan / lamp combo.

    Or ......... and only if this allowed by code in your area .........

    Since a dedicated 20 amp feed to a GFCI is required in the bathroom then run 12/2 from the service panel to the line side of the GFCI ...... you need to do this anyway.

    *** only if this allowed in your area *** ..... from the load side of the GFCI wire the hot ( black ) to the 2 switches / timers that will feed the fan / lamp combo.
    From the 2 switches ............ the red ( of the 12/3 ) will attach to one switch and the black ( of the 12/3 ) to the other switch of the cable running into the attic.

    The neutral ( white ) from the 12/3 will attach to the load side of the GFCI.


    Does the neutral going to the existing vanity light need to be in series with the new neutral at the fixture, or can the existing and new neutrals be hooked together in the wall box at the pigtail connection?
    Wiring is mostly done in parllel. the conductors are connected at a common point at a junction .... like a pigtail.
    One exception would be a switch ..... these would be wired in series of the hot controlling a device.

    Mounting the fan/lamp unit will reuire special considerations for properly sealing and ducting if this unit will be inside the attic space .... that's another topic.


    Hopefully this helps.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
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    Fayette County, Ohio
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    5,797

    Default Re: wiring Bath fan/GFCI on existing light circuit

    I have to agree with Canuk. Chances are you have a 15 amp circuit (14 ga. wire)feeding the light and probably other circuits in the house. I would run a new 20 amp circuit (12ga. wire) from the panel.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  4. #4
    Join Date
    Oct 2009
    Location
    Philly
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    Default Re: wiring Bath fan/GFCI on existing light circuit

    Thanks for the advice. I was hoping not to have to fish wire between multiple floors, but if I have to, I have to.

    Quote Originally Posted by canuk View Post
    Instead ..... It would be best to run your 12/3 from the service panel to your switch box and onward up to the attic for the fan / lamp combo.
    Why would I run the 12/3 all the way from the panel? Wouldn't I run 12/2 to the box and then 12/3 from the 2 switches to the fan?

    Quote Originally Posted by canuk View Post
    Or ......... and only if this allowed by code in your area .........
    The municipality website lists the 2006 ICC Electrical Code as the code they enforce - any insights as to whether this is allowed?

  5. #5
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    Default Re: wiring Bath fan/GFCI on existing light circuit

    Quote Originally Posted by jackbird View Post


    Wouldn't I run 12/2 to the box and then 12/3 from the 2 switches to the fan?
    Yep .... you are correct


    The municipality website lists the 2006 ICC Electrical Code as the code they enforce - any insights as to whether this is allowed?
    Can't help you there .... we don't use the ICC or NEC up here.
    I'm sure that answer would be provided when you pickup your permit for doing the electrical work.
    Last edited by canuk; 10-18-2009 at 11:09 PM.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  6. #6
    Join Date
    Sep 2009
    Location
    jersey
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    174

    Default Re: wiring Bath fan/GFCI on existing light circuit

    Assuming the fan isnt in the tub zone and the gfi not load protecting the light it should be fine on the same circuit considering your uprading to any gfi at all. Draw it out and submit it with your permit application and let the ahj decide.

    I also agree that a 20 amp dedicated circuit is the best practice here, particularly with 50+ year old wiring and no EGC. Dont be afraid to put an extra box in and locate the gfi near the sink where it belongs intead of next to the switch, you may appreciate it later.
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