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Thread: MASTER OVERRIDE SWITCH

  1. #1
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    MASTER OVERRIDE SWITCH

    Hi,

    I am having trouble figuring this out, or if its even doable. Maybe there is an all in one device I havent come across. My client would like all of their lighting controlled via a time clock and contactors. Simple enough. However, they would like to have a master switch to override the timeclock. How can I accomplish this without killing power to the timeclock and messing it up?

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    I am assuming you are using a line voltage timer. All you need to do is use a single pole switch (single phase) that energizes the load side of the time clock. It must be on the same circuit as the time clock feed. If you are using other than 120v you may need to use a double pole or triple pole switch respectively.

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    Quote Originally Posted by Casualsparky View Post
    Hi,

    I am having trouble figuring this out, or if its even doable. Maybe there is an all in one device I havent come across. My client would like all of their lighting controlled via a time clock and contactors. Simple enough. However, they would like to have a master switch to override the timeclock. How can I accomplish this without killing power to the timeclock and messing it up?
    A 3-way switch will work for you. Use the common screw to your contactor, then connect the load side of your timers to one of the switch legs and 120V to the other

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    Casualsparky did not say whether the override was to turn lights on, turn them off, or both (three position switch required for the latter.)

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    180131-2149 EST

    More of the desired logic needs to be defined.

    Suppose you have a light that is normally controlled by some timer or other source, and in addition you want manual control.

    You can use a GE RR relay or some other pulse controlled mechanically bi-stable relay.

    Thr RR relay has two coils, one is SET and the other is RESET. After setting or resetting the relay it remains in its last state.

    Any number of manual switches, or other sources can control the RR relay. Basically there are two wire ORed logic circuits. One is set and the other is reset.

    Whatever was the last source to trigger the RR trlay defines the state of the light.

    .

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    180131-2350 EST

    To add to my logic discussion.

    This system could be setup to always allow manual control of ON and OFF. So if the time clock turned on the light, then any time after that time clock on time the manual switches could turn off and on the light as desired.

    What to do when the time clock gets to its off time? It could turn the light off whether or not set by the time clock or manually, or it could be inhibited from turning off the light if the ON had been manually generated.

    If the time clock turned on the light, then the manual switch could turn off the light. Or if the time clock turned on the light, then this could inhibit manual turn off during the on period of the time clock.

    You could have some, but not all, of the manual switches have more or less complete control of the on-off function.

    More complex functions can be added such as occupancy sensing, and/or amount of exterior light.

    .

  7. #7
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    Quote Originally Posted by GoldDigger View Post
    Casualsparky did not say whether the override was to turn lights on, turn them off, or both (three position switch required for the latter.)
    Override should be in both logic sets and all possible settings: time clock controlled on and off, and desired on and off. Matt87 and crispysonofa, a single snap switch will not turn on the lights if the clock calls for them to be off, and a 3-way will not turn off the lights if the time clock calls for them to be on.

    Simplest, cheapest way to achieve all 4 possible outcomes or choices that I see would be to use a 3 position switch like you mentioned or 2 regular switches, one from load side of the clock, and one from a permanent power source. They may need to be 2 pole if 208 or 240V like crispy brought up.
    Electricians do it until it Hertz!

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    I think the simplest setup would be to combine the ideas mentioned using a 3-way and a single-pole switch like this:

    Time clock always hot to maintain time setting. Connect load to terminal common of 3-way. One traveler terminal to clock output, other traveler terminal to one terminal of SP switch. Other terminal of SP switch to always-hot terminal feeding clock. 3-way switch marked Auto/Manual, SP switch marked Manual On/Off.

    Another option is a center-off switch, connected as 3-way above without SP switch, common to load, second terminal to clock, third terminal to hot.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

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    We always use ASCO 917's mechanically held lighting contactors with momentary time clocks and momentary override switches.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

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    HOA to contactor coil.
    What is he looking to do ?

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