Circuit Planning Basics

Discussion in 'Electrical Forum discussion & Blog' started by cakins, Nov 5, 2007.

  1. cakins

    cakins New Member

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    About to take on rewiring my house in preparation for a panel upgrade which an electrician will do. Local code allows me to do the wiring for the circuits.

    Been reading a bunch, with a book titled "Wiring a House" as one well referenced book. It's by Rex Cauldwell, a master electrician, published by Taunton. I like a lot of his info, but am unclear on part of the basic circuit planning.

    In talking about the guages of wire he uses, he says he usually reserves 14-3 for one circuit which would have the hard-wired smoke alarms on it and any 3-wire switching items. Ok, that sounds easy. But then he also mentions that all hard-wired smoke alarms must be wired together so that when one goes off, they all go off. Again, no problem, except ...

    He then mentions that it's best to put smoke alarms in the bedrooms, rather than just outside them as code allows. His mapped 2 bedroom circuits, which require AFCI protection, appear to be individual circuits, though.

    Of course, individual houses require individual design of circuit maps. But how can all the smoke alarms be wired together and have the bedrooms be on isolated circuits - not to mention also have the other 3-way switched items on the same circuit?

    My house is small, just 2 BR, 1 bath. If I put the smoke alarms, BR lights for both BR's and other 3-way items on one 14-3 circuit, then I have to make that entire circuit AFCI protected, right? Then, if I do the receptacle circuits for the BR's as two separate circuits, each of these must be AFCI also. Am I thinking of this correctly?

    I guess my confusion is that it seems like on one hand he's showing everything in each BR on it's own AFCI circuit, yet if that includes a smoke detector, then those have to be on the same circuit as the other smoke detectors in the house, which means they can't be on the individual BR circuits.

    Any insight is appreciated.
  2. Chris75

    Chris75 Electrician

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    Location:
    Litchfield, CT
    Bedrooms do not have to be on an individual circuit, but they must be AFCI protected, and I usually install my smokes on an individual circuit... FYI, smokes are a building code, so make you check your local requirements...
  3. cakins

    cakins New Member

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    So - to clarify what you're saying - your smokes are then also on an AFCI if they are in the BR?
  4. Alectrician

    Alectrician DIY Senior Member

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    689
    1. One smokie in each BR and one outside the entrance to the bedroom(s). This is USUALLY the hallway.

    2. I don't think the author meant that the 3ways and smmokies should be onthe same circuit but they would use the same wire (14/3)

    3. I THINK they made a changes in 2008 and anything in the BR's must be AFCI. Before it was just recepticals. Not sure.

    4. Forget the notion of a 14/3 circuit. You will have one circuit for both bedrooms including smokies. The 14/3 just runs between the smokies to give them poer (black) and to interconnect them (red). You feed the first smokie with 14/2 and run 14/3 to the others.

    If you WANT to put both bedrooms on seperate circuits fine, but all the smokies have to be on one or the other.
  5. cakins

    cakins New Member

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    12
    Thanks for the input so far. I think I kind of like the notion of doing the lighting and smokes for the BR's all on one circuit, but possibly doing the BR receptacles on separate circuit(s) to allow the possibility of using at least one of the BR's for an office with enough capacity for computer/pro audio equipment. I'd use 12-2 on those circuits.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Location:
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    I know copper is expensive, but consider running heavier gauge wire to the outlets in case you decide you need the extra amperage. An alternative is to run multiple runs to a room. If you don't have central air, also consider a dedicated 20A circuit for a room a/c unit(s).
  7. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Location:
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    Don't use AFCI or GFCI circuit for fire alarms

    2005 NEC 760.21 says non-power-limited fire alarm circuits shall not be supplied through GFCI or AFCI. Don't know what 2008 says.

    Also, Firex (an alarm manufacturer) recommends you use a "single dedicated AC branch circuit", which would preclude including lighting on the same circuit. Rules and recommendations for new construction are more stringent than for old work.
    Last edited: Nov 6, 2007
  8. cakins

    cakins New Member

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    12
    Are you saying heavier than 12 guage to the receptacles? That's not common is it? I had considered maybe a dedicated circuit for sensitive electronics, though I'm not sure I'll do that just due to cost. This isn't my dream home by any stretch. My first house and first refurb. A very small house overall.
  9. cakins

    cakins New Member

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    I'm guessing "non-power-limited fire alarm" = hard wired smoke alarm? :)

    So, how can one live up to both parts of the code? My understanding is that everything in a BR must be on an AFCI. Which rule does a person follow when the code seems to be saying 2 conflicting things?

    I probably need to recheck the local codes to make sure.
  10. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Basically, yes. As I understand it, "Non-power-limited" means the kind you and I might install, hard-wired to building power. "Power-limited" means a much fancier version that a pro fire-alarm guy would install, with a transformer or other intervening device between building power and the device. At least, that's what I infer from the Code (760.41). Maybe one of those pros can enlighten me.

    And yes, I think you've figured out how to resolve the conflict -- ask your local guy. The Code clearly says all "outlets" in bedrooms must be AFCI protected, and an "outlet" is any point from which power is taken, so the box on which you mount the alarm would seem to be an outlet. Given the history of AFCIs, if I installed an AFCI on my alarm circuit, I would replace it with a standard breaker as the inspector drove away.
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
    North Carolina
    What you are installing in your dwelling unit are “smoke” alarms.

    Each and every “outlet” in bedrooms are required to be Arc-Fault protected.
    Don’t confuse the word “outlet” and think that it means a receptacle outlet only. In the bedroom you will have receptacle outlets, lighting outlets as well as smoke alarm outlets and they all have to have arc-fault protection.
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    22,143
    Location:
    New England
    No, instead of running 14-2 for the outlets, consider maybe using 12-2 in case you decide you need some more current...you could go with a 20A breaker instead of a 15A one. It's easier to do now than redo it later. Course, sometimes having a second 15A circuit is sufficient. A home office can be an energy hog...laser printer, maybe a small frig, computers, shreader, coffee pot, etc.
  13. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    2,718
    Location:
    Central Florida
    Yeah, but... my Firex Smoke/CO installation instructions say they're governed by 760. Maybe they've got delusions of grandeur?
  14. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
    North Carolina

    Could you post these installation instructions

    I couldn't find anything about the "FIRE" alarm in their installations found here nor did they say anything about 760 in this one either.

    EDIT

    Change the word Fire above to Smoke
    Last edited: Nov 6, 2007
  15. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,718
    Location:
    Central Florida
    Here you go... page 4, under "Warning" toward the bottom.

    http://www.firexsafety.com/NR/rdonl...-9BE7-7B47F44EEDF6/0/1101124DEnglish12000.pdf

    Quote: "Smoke alarm wiring to be used shall be in accordance with the provisions of Article 210 and 760 of the National Electrical Code..."


    The promo pub (dated 2005) doesn't mention 760, as you pointed out. The installation instructions (which do reference 760) are dated 2006. Whether it's called a "fire alarm" or "smoke alarm" it's clear to me they want it wired i/a/w 760. I just talked with a nice lady in Firex Tech Support, who says that "NFPA is requesting" that they follow 760 in the installation of their smoke/co alarms, which (I assume) is why the instructions were updated and are so worded.

    When all is said and done, I'm not sure how else you would install it, anyway.
    Last edited: Nov 6, 2007
  16. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,540
    Location:
    North Carolina
  17. b.c. sparky

    b.c. sparky New Member

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    3
    I'm not familiar w/ american code, but in Canada smokies aren't permissible on a dedicated cct. Sounds like the house is so small you can get away w/ max. 3 smokes. Generally the infeed should come off a lighting cct. (or a cct w/ common lights on it) and the other smokes interconnected w/ a 3-wire. Point being, if you have a smokie that's nuisance tripping you can't just kill the cct. and have no f.a. protection. If buddy's coming to do the service change anyway, pay him a bit more to coach you along.
  18. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT
    Connecticut has an amendment, so I don't have to have my smokes AFCI protected...
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