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  1. #1
    Join Date
    Aug 2009
    Posts
    2

    Default 99 y/o House with Unusual 3-Way Switch Wiring - HELP

    Looking at a duplex house, 2up/2down, built 1910, armored cable. Stuff is so old, it's often hard to see what the wire colors are.

    Trying to figure why roof light is not lighting. It's controlled by two switches. Circuit is powered, bulb is good.

    So I thought I'd just replace the switches. When I looked at them to make sure I was wiring the travelers correctly, I couldn't make sense of them. So I buzzed them out. Found very non-standard 3-way switch setup.

    One roof light wire connected to COMMON on first switch.
    Travelers on first switch are HOT and NEUTRAL. (YES!!)

    Other roof light wire connected to COMMON on second switch.
    Travelers on second switch are HOT AND NEUTRAL (YES!!!)

    The HOT & NEUTRAL from the first switch feed the second switch in the same 3-conductor cable. (The HOT & NEUTRAL in the second switch go elsewhere, so I presume it's powering another light or outlet.)

    Here's a diagram (Forgive background backtics-Can't format otherwise. A cleaner copy is attached.)

    H`--+------------------+```````````````
    ````|``````````````````|```````````````
    ````|`````````````+---`|`----------->`L
    ````|`````````````|````|```````````````
    ````|```#######```|````|```#######`````
    ````+---#```C`#---+````+---#```C`#-->`L
    ````````#`````#````````````#`````#`````
    ````````#`````#````````````#`````#`````
    ````+---#`````#````````+---#`````#`````
    ````|```#######````````|```#######`````
    ````|`````SW1``````````|`````SW2```````
    ````|``````````````````|```````````````
    N`--+------------------+```````````````


    Now, this would probably work since you would have the combinations of H/H, H/N, N/H and N/N. Two would turn on the light and two wouldn't.

    One problem, of course, you'd also have the potential for having H/H at the light!

    Another problem: if the switch briefly connects both travelers while switching, you'd short hot to neutral. Ouch.


    1. Have you ever seen anything like this? It's been here forever. Switches seem to work, but they're old and I was intending to replace them. Just nervous about this whole arrangement.

    2. Is this OK?

    3. Was this acceptable 80 years ago?

    4. If not OK, what should I do about this? I want the lights to work.
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  2. #2
    Join Date
    Aug 2009
    Posts
    2

    Default Re: 99 y/o House with Unusual 3-Way Switch Wiring - HELP

    Got some good responses from doityourself.com forum here

    Result: This is a "Carter" 3-way configuration. Banned in NEC in 1923.

    Question: How best to "fix" this?

  3. #3
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    6,023

    Default Re: 99 y/o House with Unusual 3-Way Switch Wiring - HELP

    I'm guessing you have K &T wiring. If the light and the switches are the only things on the circuit the wires can be moved around to a standard configuration. However, with out tracing out all the wiring you don't know if something else is taped into one of the hot or neutral runs. I would recommend a rewire but ifnothing else is on the circuit see modified drawing drawing.
    Jack
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