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Thread: Adding a Bath Electrical Circuit

  1. #1
    DIY Member diydude's Avatar
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    Default Adding a Bath Electrical Circuit

    Hi,

    I'm new here, but I've fished around for info on occasion. I'm remodeling a small bathroom (about 5' x 10'), which includes adding a recessed light in the shower and radiant heat for the floor (considering 10 sq ft of SunTouch mat: 1-amp draw). My house is 36 years old, and the wiring is a bit funky. There's one 15-amp circuit powering the bathroom that has the following loads:

    Lights fixtures:
    - kitchen (2)
    - chandelier (1)
    - downstairs bathroom (1)
    - deck (1)
    - downstairs bedroom (2)

    Outlets:
    - downstairs bathroom GFCI (1)
    - downstairs bedroom (1)
    - upstairs bathroom GFCI (1) - probably not necessary that it be GFCI, since it feeds off the downstairs GFCI. Anyway.
    - living room (1)

    Other:
    - downstairs bathroom fan
    - kitchen range hood

    Phew!

    Through my investigation of this circuit, I also found that one of the receptacles has a 12/3 wire from a 20-amp circuit running to it that feeds a kitchen receptacle a few feet away. This second receptacle has 14/2 wiring feeding off the 12/3 wire; seems dangerous, but that's another story and something I'll address while I have the wall open by upgrading from 14/2 to 12/2.

    (1) So, I'm trying to think through the best way to deal with the bathroom circuit. My thought was to add a 20-amp circuit for the bathroom that would power the following:

    - GFCI outlet
    - A switch for the shower's recessed light: As a matter of design, are shower recessed lights usually on a separate switch from vanity lights?
    - Radiant floor heater
    - I thought about moving the fan to the new 20-amp circuit - not sure.

    (2) Since the GFCI upstairs is fed off the one downstairs, I was going to swap the 1-gang box downstairs out for a 2-gang to give myself more space to keep the 15-amp wiring as-is in the box. The GFCI upstairs would pigtail directly off the 15-amp circuit in the new 2-gang box and I'd run the 20-amp wiring to the downstairs GFCI in the same 2-gang box.



    Does this make sense? Something better?

    Thanks.
    Last edited by diydude; 07-30-2012 at 11:55 PM.

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    In stalll a new 20 amp circuit for nothing but the two bath recptacles.
    Read the installation insturctions for the mat heater as it may call for a circuit for it.

    All the lights can remain on the 15 amp circuit

  3. #3
    Moderator & Master Plumber hj's Avatar
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    IF your analysis of the bathroom circuit is correct and you really do have all those items connected to it, then it must have been installed by a very incompetent electrician, a handyman, or a DIY homeowner. At the very least you MUST run a new circuit for the items you are installing. A 1 amp draw for the floor mat is about a tenth of what a toaster uses, so I would not expect too much heat from it.
    Licensed residential and commercial plumber

  4. #4
    DIY Member diydude's Avatar
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    Quote Originally Posted by hj View Post
    IF your analysis of the bathroom circuit is correct and you really do have all those items connected to it, then it must have been installed by a very incompetent electrician, a handyman, or a DIY homeowner. At the very least you MUST run a new circuit for the items you are installing. A 1 amp draw for the floor mat is about a tenth of what a toaster uses, so I would not expect too much heat from it.
    I believe that's how the electrical was originally installed. The baths had/have their original fixtures. I also have a garage circuit that is wired to a living room receptacle; breaker trips when I'm using the miter saw or the table saw and the plasma tv is turned on. I wired a 20-amp circuit in the garage last year.

    Moving the upstairs GFCI to a new 20-amp circuit as jwelectric suggested would probably mean opening a wall, which I'm not sure I want to do. I was going to run a separate 20-amp circuit for the upstairs bathroom later.

    Edit: I could just fish the 12-amp wiring to the GFCI upstairs without tearing into the drywall, but I was worried about the 12" stapling requirement. Is that still a concern?
    Last edited by diydude; 07-31-2012 at 09:22 PM.

  5. #5
    DIY Senior Member Homeownerinburb's Avatar
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    Regarding the SunTouch mat, absolutely find the manufacturer's installation instructions on that stuff.

    If I did not KNOW for a fact that the mat was correctly installed, I'd certainly not ever use it.

    I would be very reluctant to install that sort of stuff without a GFI to protect people walking over it.

  6. #6
    DIY Member diydude's Avatar
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    Quote Originally Posted by Homeownerinburb View Post
    Regarding the SunTouch mat, absolutely find the manufacturer's installation instructions on that stuff.

    If I did not KNOW for a fact that the mat was correctly installed, I'd certainly not ever use it.

    I would be very reluctant to install that sort of stuff without a GFI to protect people walking over it.
    The instructions I saw mentioned a 20-amp circuit with GFCI. The SunStat therm apparently has GFCI. I'll review the instructions included with the actual mat I end up buying to make sure.
    Last edited by diydude; 07-31-2012 at 09:22 PM.

  7. #7
    DIY Member diydude's Avatar
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    Quote Originally Posted by diydude View Post
    I could just fish the 12-amp wiring to the GFCI upstairs without tearing into the drywall, but I was worried about the 12" stapling requirement. Is that still a concern?
    Never mind, I got my answer about the stapling. My understanding is that since the upstairs GFCI is housed in a finished space, I don't need to staple the new wires running to that outlet to the framing.

    My current plan is to run two 20-amp circuits: One for the two GFCI outlets in the bathrooms and a second circuit that runs lights and floor heat in the downstairs bathroom. I want to get the downstairs bathroom off the messy 15-amp branch circuit.

    Thanks to everyone for the responses.

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    DIY Senior Member kreemoweet's Avatar
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    You may well come to regret putting both bath GFCI's on the same circuit. It's been my experience that two blow dryers operating at the
    same time will frequently trip a 20A breaker.

  9. #9
    DIY Member diydude's Avatar
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    Quote Originally Posted by kreemoweet View Post
    You may well come to regret putting both bath GFCI's on the same circuit. It's been my experience that two blow dryers operating at the
    same time will frequently trip a 20A breaker.
    There's only one hair dryer in the house, with no plans for others, so it should be ok.

  10. #10
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by diydude View Post
    My current plan is to run two 20-amp circuits: One for the two GFCI outlets in the bathrooms and a second circuit that runs lights and floor heat in the downstairs bathroom. I want to get the downstairs bathroom off the messy 15-amp branch circuit.

    Thanks to everyone for the responses.
    You meant to say one for the receptacles and one for the heat and put the lights on a 15 amp circuit, right?

  11. #11
    DIY Member diydude's Avatar
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    Quote Originally Posted by jwelectric View Post
    You meant to say one for the receptacles and one for the heat and put the lights on a 15 amp circuit, right?
    Ok, please educate me. With the assorted loads on the current 15-amp circuit, I was thinking that I could put the lights and the floor mat on a 20-amp circuit of their own. I didn't read anywhere that the mat needed to be on a dedicated circuit, so I figured this was ok.

  12. #12
    Electrical Contractor/Instructor jwelectric's Avatar
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    The lights are okay like they are. It has been working for a while now so no need to mess with them.

    I typed one thing thinking something different above. Although it is hardly legal I would install one 20 amp circuit for one bath receptacle then install one 20 amp circuit for the other baths receptacle. I would then install from the load side of the receptacle to the thermostat for the heat. This way the heat is GFCI protected.

    In most cases it would be okay to figure the heat at 15 watts per square foot. 25 times 15 equals 375 watts. Now 125% will bring this to 468.17 now divide by 120 volts and we have 3.9 amps.

    Once the heat fails then simply disconnect it from the line side of the receptacle.

  13. #13
    DIY Member diydude's Avatar
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    Quote Originally Posted by jwelectric View Post
    The lights are okay like they are. It has been working for a while now so no need to mess with them.

    I typed one thing thinking something different above. Although it is hardly legal I would install one 20 amp circuit for one bath receptacle then install one 20 amp circuit for the other baths receptacle. I would then install from the load side of the receptacle to the thermostat for the heat. This way the heat is GFCI protected.

    In most cases it would be okay to figure the heat at 15 watts per square foot. 25 times 15 equals 375 watts. Now 125% will bring this to 468.17 now divide by 120 volts and we have 3.9 amps.

    Once the heat fails then simply disconnect it from the line side of the receptacle.
    One thing I forgot to mention is that I'm going to be moving from an overhead vanity to two wall sconces, in addition to the recessed light I'm installing. I believe the draw by the two wall sconces will be equivalent to the current vanity lighting, so I'm thinking it shouldn't be a concern; just need to install two new boxes in place of the vanity box. The radiant floor supposedly only draws 1 amp (I'm only installing 10 sq ft), which is why I was thinking to move the lights to the 20-amp circuit with the floor mat and put both GFCIs on the other 20-amp circuit to make things legal. Also, the thermostat I'm buying for the floor mat has built-in GFCI protection.

    We'll be remodeling the kitchen later, and we have receptacles and switches for the kitchen on the current 15-amp bath circuit, so I wanted to move all the bath items off that 15-amp circuit. A 20-amp circuit does exist for the kitchen in case I need to tap into it for the kitchen additions as an option (most likely recessed lights and maybe a couple other upgrades).
    Last edited by diydude; 08-01-2012 at 09:39 PM.

  14. #14
    Electrical Contractor/Instructor jwelectric's Avatar
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    Could you post a link to that thermostat and heat pad?

  15. #15
    DIY Member diydude's Avatar
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    Quote Originally Posted by jwelectric View Post
    Could you post a link to that thermostat and heat pad?
    Sure.

    Here's the owner's manual for the thermostat. I read the instructions a little closer, and they call for a 15-amp breaker max. at the panel to connect the thermostat for the size mat I'm using (10 sq ft). The mat instructions mention a 20-amp circuit - I'm guessing this is for headroom considerations: http://www.warmyourfloor.com/media/t..._500670-EN.pdf

    SunTouch 4' x 30" mat I plan on installing: http://www.warmwire.com/products/sun...-12000430.html
    Last edited by diydude; 08-02-2012 at 08:48 AM.

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