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Thread: Updating Bathroom Circuits to 20 amp

  1. #1
    DIY Junior Member rick15752's Avatar
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    Default Updating Bathroom Circuits to 20 amp

    Hi everyone,
    I'm remodeling my two story home and would like to run 20 amp circuits to the three bathrooms. This is a tract home built in 1985 and all the bathroom outlets are on one 15 amp circuit. From the breaker panel the circuit first goes to the master bath and branches off to feed the master bedroom outlets. The master bathroom outlet is protected by a GFCI and the load side of that feeds the remaining two bathrooms and one outdoor outlet. Many times the wife and daughter managed to trip this circuit when using their hair dryers.

    My proposal is to run a 12-3 from the breaker panel to the master bathroom, pigtail a GFCI for that bathroom, then run a 12-2 to another GFCI in the next bathroom and continue on the load side of that to the last bathroom. Nothing else would be on this circuit and I would use a 20 amp tandem at the breaker panel. This circuit would share a neutral. I've looked in my copy of the NEC for anything that may prohibit sharing a neutral.

    1. Does anyone know if this would be prohibited in the NEC?

    2. Would I have any trouble with induction when using two GFCI's on this type of circuit? Would this make the GFCI's trip by one hot leg sensing induced voltage from the other leg?

    Thanks.
    Rick

  2. #2
    Homeowner Thatguy's Avatar
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    ?
    One GFCI downstream of another is unnecessary and makes troubleshooting difficult.

    The current leaving the GFCI load hot terminal has to equal within 5 mA the current returning on the GFCI load neutral terminal.

    In principle, GFCIs only know the difference current sensed by the internal toroidal transformer [see fig. 2 below]
    http://www.national.com/ds/LM/LM1851.pdf
    and are insensitive to voltages.

    My wife's hair dryer has a GFCI built into the plug but it's always the wall GFCI that trips, after a few minutes.
    No hair dryer, no nuisance trips. They happen infrequently which makes troubleshooting almost impossible.

    One of these days I'll salvage the toroid out of the failed GFCI in my basement junkbox and use it to actually measure the differential current. This is a lot cheaper than buying Fluke's instrument that does this.

    With Romex you can typically expect a half mA of current to ground due to inter-conductor capacitance.
    Last edited by Thatguy; 12-12-2010 at 03:05 PM.

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    DIY Junior Member rick15752's Avatar
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    Hi Thatguy,
    I should have typed "current" rather than "voltage." Presently, the 15 amp circuit has one GFCI in the master bath and the other two bathroom outlets, as well as an outdoor receptacle, are on the load side of that.

    In my proposed circuit, the 12-3 to the master bath would provide just one bathroom with it's own 20 amp line, not much to troubleshoot there. Then a 12-2 from that box to the next bathroom where I'll have another GFCI. Then a 12-2 from that box will go to the 3rd bathroom. I'm rethinking whether or not I should put a third GFCI in that bathroom on the line rather than a standard receptacle on the load from the 2nd. Putting a 3rd GFCI on the line voltage should negate, I hope, any type of induction problem with the GFCI. This means that the master bathroom doesn't share a load with anything else. The remaining two bathrooms share a 20 amp circuit.

    Thanks fro the info on the GFCI.
    Rick

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Seems you are missing the point! From the panel, once you install a gfci, you only need one beyond the first one. Also, if you are going to rerun wiring, run separate 12-2 to each bathroom on its own breakers, so you can have someone running a hair dryer curler, etc. in each one without hassles. While you can daisychain bathrooms (not a great idea, but done in my opinion), it can't go to the outside outlet as I understand it, either, so that would need to be tapped off someplace else, or run a new branch for it as well. there is no real benefit to running multiple gfci devices on the same circuit. If you do, connect each of them to the line side, not tapped off the load side.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member jetlag's Avatar
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    You can share the neutral that way , its called a multiwire branch circuit 2008 NEC 210.4 . You have to be be sure you use a 220/240 double breaker, you can not use a piggy back breaker in which 2 breakers are made together to go on a single lug. If you use that , it will over load the neutral. The hot wires can not be on the same phase . Now , Bath 20 amp circuit can only serve outlets in the baths , the bedroom and outside recepts have to be removed. If a circuit goes to only one bath , like you plan to do the first one , the bath light can go with it if you want , but I would leave it on the bedroon circuit. Now the next 2 baths where you feed out to the 3 rd one, no bath lighs can go with it , only the GFCI in the last two baths can be on the other circuit . You can feed the 3 rd bath from the load side on the 2 nd or you can feed from the line on the 2 nd and add another GFCI in the 3rd

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    DIY Junior Member rick15752's Avatar
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    Hi Jim,
    Yes, the outdoor receptacle will be going on a different circuit. NEC Section 210.11(C)(3)
    I just want the bathroom circuit to feed the bathroom receptacles and nothing else, not even the bathroom lights.

    I'm hoping to use a 12-3 to save space in my breaker box. The 12-3 will give me two 20 amp circuits, one for the master bathroom and one for the two other bathrooms. The other two bathrooms, one of which is downstairs and is seldom used, would share the other hot of the 12-3. The odds of overloading the shared circuit with hair dryers and/or curlers would be low, but not impossible.

    So, are you saying that just one GFCI for the master bathroom and another for the 2nd bathroom, with a standard receptacle on the load side from the 2nd bathroom? As my first post suggested? Do you know if there would be any problems caused by current induction?
    Rick

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    DIY Member jetlag's Avatar
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    people run the multiwire brance circuit to kitchen counter GFCI all the time , with half the recepts on each hot leg . Only 2 GFCI s are used with the others fed from the load sides. There is not enough induction to trip the GFCI .

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    DIY Junior Member rick15752's Avatar
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    Hi Jetlag,
    Thanks for the info. I also found some info about the type of breaker I'll need for this circuit and your information goes along with that.

    Unfortunately, the bedroom and outdoor receptacles are wired with 14-2. So, I won't be feeding any of that from the new 20 amp 12-3 or 12-2.

    I have questions about another circuit I plan to run. I want to divide a branch circuit to lighten the load and plan to run another 14-2, 15 amp circuit from my breaker panel. I want to do this because I will be installing recessed lighting in the lower bedroom which is presently an office and I don't want the extra load of the lights, computer equipment, etc., to overload the circuit. Unfortunately, this existing circuit has branches that include other areas of the home. I calculated the load with the new lights and will be overloading this 15 amp circuit. I can separate this circuit where multiple wires meet at the bedroom light switch by taking a wire off and moving this wire to the ceiling where I need a smoke detector. I happen to have the drywall down in this ceiling and it would be easy to disconnect the wire from the other and relocate it to the ceiling. Then from the breaker panel I can run a 14-2 to the smoke detector/junction box where I can pigtail a smoke detector and feed the other branches.

    Is this an accepted practice? The alternative is to run from the breaker panel, removing more drywall, and connect at a switch box in another part of the home. Obviously more work but accomplishes the same result.

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    DIY Junior Member rick15752's Avatar
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    Well I've done more research and I'm changing my mind about running a Multi Wire Branch Circuit (MWBC) for the bathrooms. I think I'm going to run two separate 12-2 wires to a tandem 20 amp breaker. The reason for this is the breaker. If I ran a 12-3 to the breaker panel and wired it as such, I would need a double pole breaker as Jetlag points out thereby using both phases of the panel. There would need to be a pole handle to disconnect both circuits at once. So, if you need to work on one circuit you would have to disconnect both circuits. Probably not a big deal. Also, there has been conflicting info on induction affecting the GFCI's. So, the simple way to go is to run two separate cables back to the breaker panel.

  10. #10
    Moderator & Master Plumber hj's Avatar
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    I think, without trying to slog through all the above posts, that you were trying to make the installation much too complicated, so using individual feeds will simplify your thought processes.

  11. #11
    DIY Junior Member rick15752's Avatar
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    I agree. "Keep it simple" is the best way.

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