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Thread: 3-way, dual timer switch wiring

  1. #1
    In the Trades mtcummins's Avatar
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    Default 3-way, dual timer switch wiring

    One of my investment properties has an existing single pole backfed (no neutral in box) switch powering the basement lights. I want to have it turned into a 3-way with the existing switch location at the top of the basement stairs, and add an additional switch at the back door leading out to the garage. I want both of these to be timer switches, so the tenants don't leave my lights on all the time.

    I was thinking of the old school mechanical timers, the ones you twist to set the time. Reason for that is, I was thinking I can get away having this all wired with 12-2 wire of that unmentionable brand, rather than having to rerun the line to the switch to get a neutral up there. All that would need to be added is a single 12-2 leg over to the new switch. Also something nice about keeping it simple - less things to break/go wrong.

    I have no need for a constant on function, only timed use, and want that timed functionality at both switch locations. In fact, not having the option of a constant on is actually desirable in this circumstance.

    See my attached sketch of a wiring diagram to see if I'm thinking correctly. I think it would work. My main concern is that in the circumstance of both timers being in the "on" state, you'd get a weird power loop kind of situation between the switches. Would that be a problem since its all being fed the same power from the same circuit? One switch would probably be about double the distance from the Jct box as the other - maybe 20 feet for one, and 35 or so feet for the other, if that makes a difference. I've been told there could be some issue with power being in a different waveform or something, but that side of things is a bit over my head. I just want to know if it would work, and work safely.

    If this doesn't work, are there any ways to do 2 countdown timers on the same set of lights? I can't seem to find any...


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    -mike-

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    Electrical Contractor/Instructor jwelectric's Avatar
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    you are going to have the stairs on a timer?????????????????

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    Jack of all trades DonL's Avatar
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    Quote Originally Posted by jwelectric View Post
    you are going to have the stairs on a timer?????????????????

    Sounds a bit unsafe.

    I guess the emergency lighting and Exit signs will be working.
    Theory only works perfect in a vacuum.

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    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by DonL View Post
    Sounds a bit unsafe.
    And non-compliant

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    Moderator & Master Plumber hj's Avatar
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    You do NOT have a "three way" setup. You have two switches in parallel, and as long as they both feed from the same "hot" lead it will work. The light will go on when either timer is activated and stay on until both "time out".
    Licensed residential and commercial plumber

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    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by hj View Post
    You do NOT have a "three way" setup. You have two switches in parallel, and as long as they both feed from the same "hot" lead it will work. The light will go on when either timer is activated and stay on until both "time out".
    Does it light the stairwell? If so then the timers would not be compliant

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    Electrical Contractor/Instructor jwelectric's Avatar
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    (c) Where one or more lighting outlet(s) are installed for interior stairways, there shall be a wall switch at each floor level, and landing level that includes an entryway, to control the lighting outlet(s) where the stairway between floor levels has six risers or more.


    Exception to (A)(2)(a), (A)(2)(b), and (A)(2)(c): In hallways, in stairways, and at outdoor entrances, remote, central, or automatic control of lighting shall be permitted.

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Possibly a motion sensor also in parallel so it would override the timers?
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    In the Trades mtcummins's Avatar
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    Thanks for the clarification on my terminology. Yes, I'm looking for 2 switches in parallel, to sort of function like a 3-way switch setup due to the switches being timers, but it is technically speaking wired in parallel.

    Quote Originally Posted by hj View Post
    Possibly a motion sensor also in parallel so it would override the timers?
    Hmm, that could be a good additional measure. I had thought about trying to do just occupancy sensors, but it didn't seem feasible as a primary method with the setup of the space. It would probably be a good fail-safe though in parallel with timers, to ensure lights don't go off on your way up the stairs or something. Hadn't thought about combining the two methods...

    Here's the building situation. Its a converted single family house, with apartments on 1st and 2nd floors. The main hallway/stairwell has independent lighting controls for each unit, so they may turn their own hall lighting on and off at their will. The basement has a door that leads outside to the detached garage, and a stairwell up to the main hallway, with laundry in between the two. This area would be used primarily for tenants coming down to do laundry, but some tenants might choose to enter the building through the basement and go up to their units from there, rather than the front door.

    Currently, there is a standard 2 pole toggle switch at the top of the basement stairs that lights the stairs and the laundry area. There is no way to turn on the basement lights from the rear door. I'm trying to fix that last problem - give lighting control from that entrance - while also keeping the lighting from being left on constantly.

    By timer, I mean a countdown timer, not one that turns lights on and off on a schedule. Tenants can turn the lights on when going through, but they'd turn off after an hour (or whatever setting they put it to) automatically.

    Not sure if that meets the letter of the code or not, but it does seem to meet the spirit of it, especially with the added occupancy sensor. And it solves a bad compliance issue, of not having any lighting available at the entry door.

    What I'm most interested in is the theoretical side. An EE friend had a concern that a wiring setup like this could allow the power to reach opposite sides of both timer switches in a different waveform (I think that was the word he used) from each other, potentially causing some sort of problems in the event of both timers being on and these different waveforms meeting each other at each timer's contact point. As I said, I don't understand that level of electrical theory, so just wanted to put it out there to you guys who know way more about it than I do.
    -mike-

  10. #10
    Electrical Contractor/Instructor jwelectric's Avatar
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    Your EE friend has lost his mind or done to many drugs as this is bull about the wave or the forum.

    If this is rental property then the building and fire code will force you to install a three way switch at the top and bottom of the stairs even if you put automatic means in place.
    Should someone have an accident on those stairs you will no longer have a rental property as the property is what the law suit will end up costing you

  11. #11
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by mtcummins View Post
    What I'm most interested in is the theoretical side. An EE friend had a concern that a wiring setup like this could allow the power to reach opposite sides of both timer switches in a different waveform (I think that was the word he used) from each other, potentially causing some sort of problems in the event of both timers being on and these different waveforms meeting each other at each timer's contact point. As I said, I don't understand that level of electrical theory, so just wanted to put it out there to you guys who know way more about it than I do.

    Your EE friend was most likely talking about If it is wired wrong, and you have two sources of opposite phase. Then you have 240V.

    It may be easier to add a alarm that indicates the light has been left on.


    Being other people live there, It will need to meet fed and local code.
    Theory only works perfect in a vacuum.

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    In the Trades mtcummins's Avatar
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    So am I having a fundamental misunderstanding of the code? I have to provide wall switched lighting to all habitable rooms (not the case for any of this lighting area), and the required lighting in all hallways, stairways, and outdoor entrances can be remote, automatic, or central. I've provided wall switches at the required locations and lighting for the stairs and door, with automatic controls. Is there some nuance to the way its written, or somewhere the code defines a wall switch as a toggle switch only, that I'm missing? I only have the 2006 IRC handy, so couldn't look at full electrical code, just their summary, and I can't seem to find anything that would suggest that this setup doesn't meet code, but I could be missing something as the IRC is sort of the electrical code cliff's notes. Just trying to understand what's expected.

    Good to know about the waveform thing... I was just chatting with him briefly online, didn't get much detail. It sounded like a typical engineer's overprotectionary measure to me. I know you can't put 2 separate sources into the same switch, certainly not if they're opposite phases. I don't think that was what he was referring to, but not sure. It seemed like the wiring diagram would work to me, and I've seen setups before that I'm pretty sure were wired basically like this that worked fine.
    -mike-

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    Moderator & Master Plumber hj's Avatar
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    He was either trying to dazzle you with his brilliance or baffle you with his B.S., but either way you would be wise to not listen to him about anything else either, if that is his level of incompetence.
    Licensed residential and commercial plumber

  14. #14
    Moderator & Master Plumber hj's Avatar
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    A "3 way switch" installation allows you to turn the light on at either location and turn it off from the either one. YOUR "two switches" in parallel allows you to turn on the light from either switch, BUT you have to turn it off from the same one. The timer allows it to turn off without the person going back physically and turning it off, but it is still just a number, and it can be any number, of single poles switches operating the light.
    Licensed residential and commercial plumber

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    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by mtcummins View Post
    So am I having a fundamental misunderstanding of the code?
    Yes


    210.70 Lighting Outlets Required. Lighting outlets shall be installed where specified in 210.70(A), (B), and (C).


    (A) Dwelling Units. In dwelling units, lighting outlets shall be installed in accordance with 210.70(A)(1), (A)(2), and (A)(3).

    (1) Habitable Rooms. At least one wall switch–controlled lighting outlet shall be installed in every habitable room and bathroom.


    Exception No. 1: In other than kitchens and bathrooms, one or more receptacles controlled by a wall switch shall be permitted in lieu of lighting outlets.


    Exception No. 2: Lighting outlets shall be permitted to be controlled by occupancy sensors that are (1) in addition to wall switches or (2) located at a customary wall switch location and equipped with a manual override that will allow the sensor to function as a wall switch.


    (2) Additional Locations. Additional lighting outlets shall be installed in accordance with (A)(2)(a), (A)(2)(b), and (A)(2)(c).


    (a) At least one wall switch–controlled lighting outlet shall be installed in hallways, stairways, attached garages, and detached garages with electric power.


    (b) For dwelling units, attached garages, and detached garages with electric power, at least one wall switch–controlled lighting outlet shall be installed to provide illumination on the exterior side of outdoor entrances or exits with grade level access. A vehicle door in a garage shall not be considered as an outdoor entrance or exit.


    (c) Where one or more lighting outlet(s) are installed for interior stairways, there shall be a wall switch at each floor level, and landing level that includes an entryway, to control the lighting outlet(s) where the stairway between floor levels has six risers or more.


    Exception to (A)(2)(a), (A)(2)(b), and (A)(2)(c): In hallways, in stairways, and at outdoor entrances, remote, central, or automatic control of lighting shall be permitted.


    (3) Storage or Equipment Spaces. For attics, underfloor spaces, utility rooms, and basements, at least one lighting outlet containing a switch or controlled by a wall switch shall be installed where these spaces are used for storage or contain equipment requiring servicing. At least one point of control shall be at the usual point of entry to these spaces. The lighting outlet shall be provided at or near the equipment requiring servicing.


    When you read the underlined part be sure to look carefully at the word controlled. By saying controlled it is saying that it must be able to turn the light off or on at both locations. The building and fire codes will not allow a timer on a light in a stairwell. One could be somewhere on the stairs when time runs out and stranded in the dark.
    Every staircase that has six risers or more must have a light that is controlled by a set of three way switches and no timers at all. Even if automatic switches were installed the set of three way switches are still required.

    Make the installation your purpose and someone (renter) get hurt and they may very well become the landlord.

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