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Thread: MASTER OVERRIDE SWITCH

  1. #11
    Join Date
    Apr 2008
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    Ann Arbor, Michigan
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    6,573
    180201-1107 EST

    We have no clear definition of what is the desired logic.

    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?
    What does the following mean?
    My client would like all of their lighting controlled via a time clock and contactors.
    Suppose this is a building with many rooms and halls. Are the halls on the time clock? Do the halls have individual switches that can turn lights on, that is, override the time clock in the ON direction? Same for individual rooms, but possibly different criteria.

    What is to happen if the override switch is not turned off? In a pulsed system the time clock could turn off the lights at its timed off time. But suppose a person is in a totally enclosed room, pulsed the lights on, but while the person is in the room the time clock pulses off the lights. The person is in the dark.

    However, they would like to have a master switch to override the timeclock.
    Override to ON or to OFF. Are there individual switches on different legs of the contactors?

    How can I accomplish this without killing power to the timeclock and messing it up?
    I think this was already answered. But it is simple. Just power the time clock from an independent always on power source, and use the time clock output contacts as an isolated contact set.

    A precise definition of the desired logic of the system must be created, only then it is possible to design a circuit to accomplish the desired objective. So far there is not an accurate definition of what the system is to do, or what the system looks like.

    .

  2. #12
    Join Date
    Apr 2017
    Location
    New England
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    86
    Quote Originally Posted by JFletcher View Post
    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.
    I was thinking that he would feed the switch from the line side of the clock thus it would energize the lights even if the clock was not calling for the lights to be on. I did not think about turning the lights off, I like the points that were brought up.

  3. #13
    Join Date
    Dec 2010
    Location
    Tennessee NEC:2008
    Posts
    4,403
    I'm not seeing why we need to build a nuclear sub when all we need is a life boat!
    Most timers have an override/manual switch!
    If you aim at nothing, you will hit it every time!

  4. #14
    Join Date
    Apr 2008
    Location
    Ann Arbor, Michigan
    Posts
    6,573
    180213-1048 EST

    Until the desired logic is defined you can not design the circuit. So far the logic has not been defined.

    .

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