# Thread: MASTER OVERRIDE SWITCH

1. gar
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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.

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Originally Posted by JFletcher
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. 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!

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

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Sorry I left out alot of information. Lighting controls clearly are not my specialty. All the circuits are 120v/15a. The way I have wired it is that the 3 ccts share a common neutral. The client would like a time clock to turn on/off the lights in the building at programmed times. However, they would like an override switch in order to turn on the lights in the case that somebody is in early/ keep them off in the case that it is a holiday etc and nobody is in. I am not familiar with time clocks or contactors. I understand that I am able to use a 3 pole contactor for this purpose.. do I need a separate cct to power the coil? And would the time clock be single pole/ single throw? I love the i put but still struggling with the best way to accomplish this

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All of the lights in the building are controlled by occupancy sensors and/or manual switches. All they wish to do is have them turn off at night and on in the morning. Except the given example exceptions I listed. So basically everything powered or everything off. But while keeping the power to the time clock.

7. gar
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Casualsparky:

Your new information is useful, but still not adequate.

About electromechanical relays (a contactor is just a relay). A relay consists of an isolated coil to create a controlled magnetic field to actuate an electrical contact. The coil voltage does not need to have any particular relationship to the voltage of the switched circuit. Quite often both voltages will be the same. These do not need to originate from the same source.

Your present system has a multitude of motion sensors and manual switches.

Based on a part of the description of what you want the following could be done:

1. After your breaker panel install a 3 pole contactor with normally open contacts to switch the 3 hot lines of your 3 circuits.

When this contactor is energized all your circuits will work like they do now.

When this contactor is de-energized, then there will be no available lights.

Control the contactor from a simple timer. This will always do the same thing every day.

To over-ride the timer connect a SPST manual switch in parallel with the timer contact. When this switch is closed the contactor is energized and your system will work like it does now. Under this closed condition the timer has no effect on the operation of the lighting system.

This has some disadvantages, but may be adequate.

.

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There is something to be said for constructing the override system using latching contactors and momentary pushbuttons:

If you use two static switches as in the most recent suggestion, then leaving one of the switches in the wrong position will override the time clock action indefinitely.

If instead you use the time clock to generate on and off pulses to a single latching contactor any override, either on or off, can be reversed at any point using the opposite button and in any case the next time clock set point activation will return to the normal schedule until the next override.
The disadvantage is that you cannot preset the on-override to prevent the time clock from turning off the lights but must instead turn the lights back on after the clock has turned them off.
Nor would it work for setting the lights to override off in advance of a long weekend. (You would also have to use a 7-day time clock to handle normal weekends properly.)

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Originally Posted by Casualsparky
Sorry I left out alot of information. Lighting controls clearly are not my specialty. All the circuits are 120v/15a. The way I have wired it is that the 3 ccts share a common neutral. The client would like a time clock to turn on/off the lights in the building at programmed times. However, they would like an override switch in order to turn on the lights in the case that somebody is in early/ keep them off in the case that it is a holiday etc and nobody is in. I am not familiar with time clocks or contactors. I understand that I am able to use a 3 pole contactor for this purpose.. do I need a separate cct to power the coil? And would the time clock be single pole/ single throw? I love the i put but still struggling with the best way to accomplish this
Just parallel the contacts from this across the contacts of the time clock.

Simple to use, operator friendly, and the user sets the amount of override time he/she so chooses. It's even fail safe and restores control to the time clock after it times out.

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Originally Posted by Jamesco
Just parallel the contacts from this across the contacts of the time clock.

Simple to use, operator friendly, and the user sets the amount of override time he/she so chooses. It's even fail safe and restores control to the time clock after it times out.
That gives you override ON, but the OP also wants override OFF for off schedule days/times the building is not in use.
Add a second such timer with NC instead of NO and put it in series with the time clock contacts?

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