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  1. #11
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    Default Re: Adding 3-way switch

    Here's another thought that should meet code requirement. However it does require opening the light j-box that has the branch supply feed.

    It appears the branch supply feed is in the light j-box -- which likely means there are black and white conductors at the existing switch box ( lets call it A ).

    Since the gauge of wire -- 12awg or 14awg is unknown -- lets call it X

    Run X/2 drop from the existing light j-box to the new 3 way switch ( lets call it B )
    From switch B a run of X/2 to switch A

    The white of the existing X/2 from switch A gets moved and connected to the neutrals at the light j-box --- the other end of this white is capped with a wire nut if not used at the switch box.

    The black of the existing X/2 from switch A is connected to the switched feed to the lights. ( at the light j-box ). The other end of this black at the switch box is connected to the *common* screw of the new 3 way switch.

    The black and white from the *new* X/2 drop between switches A&B are connected to the *traveller* screws at both switch A&B.

    The black of the X/2 from the light j-box is connected to the constant supply feed at the light j-box . The other end of this black will connect to the *common* screw of switch B.

    The white will have the end at the light j-box connected to the neutral bundle with the other end capped with a wire nut in the switch B box if not used.

    This way you are suppying the required neutral to the switch locations ---- using more commonly available and cost effective cabling ---- and depending on switch box sizing likely not be concerend with over stuffing.

    The exception will at the light j-box ( branch junction ) which likely requires a change to a larger one or an additional j-box to accomodate the extra connections.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  2. #12
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    Default Re: Adding 3-way switch

    To add to the confusion no neutral may be required in individual cases.

    404.2(C) exception 2
    (2) Cable assemblies for switches enter the box through a framing cavity thatís open at the top or bottom on the same floor level or through a wall, floor, or ceiling thatís unfinished on one side.

    This means in a single floor plan house where the cable from the switch goes up a wall cavity into an unfinished attic, no neutral is required. The question is if the switch is updated later to an occupancy switch that requires neutral, can you run a single conductor neutral wire down to the switch in the wall cavity or would the cable need to be replaced with a cable which includes neutral?
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  3. #13
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    Default Re: Adding 3-way switch

    This raises a question for your NEC requirement --- retrofit box and cable run.
    Can you simply install a retrofit box -- say on a wall in the middle of a stud bay and run the cable through the stud bay without securing to a stud?
    "" an ounce of perception -- a pound of obscure "
    - Rush

  4. #14
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    Default Re: Adding 3-way switch

    m_albertson, if you can go back in time to before the adoption of the 2011 NEC, you can do it the way I first posted.

    IF by some chance your local AHD (Authority Having Jurisdiction) has not yet adopted the 2011 National Electrical Code, your job is easier. Otherwise, you'll have to replace the cable from the light fixture to the existing switch with 12/3 (or 14/3) and run 12/4 (or 14/4) cable from the existing switch to the new switch. In this case, which color is connected where will be different than in my first post.

    The best thing to do is contact your local electrical inspector and ask what he will approve, in writing if possible. Then when you get your inspection, request that particular inspector do the inspection. Or you could just hire an electrician and let them deal with the bureaucracy.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  5. #15
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    Default Re: Adding 3-way switch

    Quote Originally Posted by Fencepost View Post
    m_albertson, if you can go back in time to before the adoption of the 2011 NEC, you can do it the way I first posted.

    IF by some chance your local AHD (Authority Having Jurisdiction) has not yet adopted the 2011 National Electrical Code, your job is easier. Otherwise, you'll have to replace the cable from the light fixture to the existing switch with 12/3 (or 14/3) and run 12/4 (or 14/4) cable from the existing switch to the new switch. In this case, which color is connected where will be different than in my first post.

    The best thing to do is contact your local electrical inspector and ask what he will approve, in writing if possible. Then when you get your inspection, request that particular inspector do the inspection. Or you could just hire an electrician and let them deal with the bureaucracy.
    Why not run the neutrals into the switch boxes anyway ? It's not going to hurt anything -- besides someday in the future it maybe needed and if you're running cables anyway might as well run it while you're doing the cabling. Inspectors love it when you go beyond code.

    Depending on price and availability there's no need for X/4 cable -- you just need 4 conductors.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  6. #16
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    Default Re: Adding 3-way switch

    Without knowing the particulars for the installation, is the wiring going up or down in a wall cavity to an unfinished space above or below the installation or some other route, it is not possible to say if neutral is needed or not under NEC 2011. The safest bet would be to install the wiring with the neutral, needed or not.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  7. #17
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    Default Re: Adding 3-way switch

    Quote Originally Posted by canuk View Post
    Why not run the neutrals into the switch boxes anyway ? It's not going to hurt anything -- besides someday in the future it maybe needed and if you're running cables anyway might as well run it while you're doing the cabling. Inspectors love it when you go beyond code.

    Depending on price and availability there's no need for X/4 cable -- you just need 4 conductors.
    I'm speaking to the difficulty of adding or replacing wire between the fixture and the existing switch location. It may not be possible without tearing into the walls.

    I'm not so sure about just adding a conductor (or using two X/2 in place of one X/4). If it doesn't already, I wouldn't be surprised if future versions of the code prohibit running parallel romexes on a single circuit like this -- the requirement would be that all conductors be in the same raceway (conduit) or jacket. The reason would be to prevent confusion.

    As for running X/4 between the two switch locations if you do not have a neutral from the fixture to the existing switch, you now have an unused conductor; someone in the future may assume that the white conductor is a neutral and hooked up properly at the other end. This could be worse than not having it at all.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  8. #18
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    Default Re: Adding 3-way switch

    To answer my question, no you can not run a single conductor wire, the only single conductor wire NEC allows you to run in walls is a ground wire.

    Yes you can use 2 X/2 cables in place of a 4 conductor cable at this point, however, I believe the re-designation of white wires will eventually be removed from code.

    The big problem right now is that there is entirely to much ambiguity in the new code section 404.2 with the current exceptions. According to the code if you are running the cable up through a wall into an unfinished attic you are not required to include the neutral. The idea that it can easily be replaced if an occupancy, digital, or motion switch is used later and needs the neutral. But suppose the cable is going up through a wall cavity into an unfinished attic area then across the attic to a finished area to a fixture box for a first floor ceiling light. Do you need neutral or not. If you read the code one way you do not but the cable would not be easily accessed in the finished area.

    As far as I can see the best path of action right now is to always include the neutral wire.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  9. #19
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    Default Re: Adding 3-way switch

    Quote Originally Posted by Fencepost View Post
    I'm speaking to the difficulty of adding or replacing wire between the fixture and the existing switch location. It may not be possible without tearing into the walls.
    Considering there is no provision already in place to convert this particular situation to a 3 way switch circuit it will require -- A) an additional switch box located and installed --- B) traveller conductors run between the existing switch and new switch locations --- so , there will be some tearing into walls and difficulty fishing lines anyway --- even with the method you posted

    I'm not so sure about just adding a conductor (or using two X/2 in place of one X/4). If it doesn't already, I wouldn't be surprised if future versions of the code prohibit running parallel romexes on a single circuit like this -- the requirement would be that all conductors be in the same raceway (conduit) or jacket. The reason would be to prevent confusion.

    Perhaps yes --- perhaps no
    That's in the hands of your NEC.

    I'd be surprised you cannot use two different cables to accomplish the same result. If it is then it's not a problem and if in futrue revisions to theNEC where it will no longer be allowed --- it won't matter here since it would grandfathered in place.

    Usually the confusion is from someone that doesn't know what they are doing , perhaps they shouldn't be messing around with electrical wiring.

    As for running X/4 between the two switch locations if you do not have a neutral from the fixture to the existing switch, you now have an unused conductor; someone in the future may assume that the white conductor is a neutral and hooked up properly at the other end. This could be worse than not having it at all.

    Are you saying the "unused conductor " is the white?
    How and why would it " be worse than not having it at all "?
    If the neutral wasn't connected then it would be like not having it all. --- there would be no completed circuit or potential current without the neutral connected.
    Fensepost --- we can beat this thread to death.
    I suggested a method that I suspect is code compliant ( even with the questionable neutral requirement ). It was an alternative method using commonly available 2 conductor cable that some homeowners may even have a spool kicking around the house ---- rather than running out to source and buy more expensive cable.

    It doesn't matter to me which method is used or using 2,3,4 or 10 conductor cable .

    And for what's it's worth --- if the current code requires new wiring to include the neutral at switch locations --- I say great and why not do it here ?
    "" an ounce of perception -- a pound of obscure "
    - Rush

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