Control of a load (light) from 2 sources

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unclestoolie

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Does anyone have experience controlling a light fixture from 2 sources, both a switch and also a timeclock. The theory is to use the manual switch during the week, and then have the timeclock control a few lighting circuits on the family's sabbath, 2 days a week. If the same circuit feeds both the timeclock and switches, and I run an additional conductor in between the switch and timeclock's load side, this should work in theory, right? The switch will be totally manual, and no matter what position the switch is in when the timeclock, which is parallel to the switch, takes over, the fixture should be controlled by the timeclock Any obvious code violations?
 
unclestoolie said:
Does anyone have experience controlling a light fixture from 2 sources, both a switch and also a timeclock. The theory is to use the manual switch during the week, and then have the timeclock control a few lighting circuits on the family's sabbath, 2 days a week. If the same circuit feeds both the timeclock and switches, and I run an additional conductor in between the switch and timeclock's load side, this should work in theory, right? The switch will be totally manual, and no matter what position the switch is in when the timeclock, which is parallel to the switch, takes over, the fixture should be controlled by the timeclock Any obvious code violations?
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I don't see a problem except possibly an install that may cause unwanted emf's. I would feed one switch, for instance, and then run a 3 wire to the time clock. Just connect the load from the lights to both switch legs. Of course if the timer is on, as Buck mentioned, you cannot turn the lights off from the other switch but that does not appear to be an issue for them.
 
crossman said:
I am being totally facetious here, but if the time clock contact and the switch are both closed, it creates a 310.4 violation.
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In my install mentioned above there would not be a parallel since the wires would not be connected together at both ends- thus no parallel conductor.:grin:
 
Well, there are some here that say the closed switch contacts count as the "electrically connected" spelled out in 310.4 so with that as a prerequisite, your install does violate 310.4!:grin:

I don't think that it is a violation, but some folks do.
 
crossman said:
I am being totally facetious here, but if the time clock contact and the switch are both closed, it creates a 310.4 violation.
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310.4(a) exception 1 allows it for controll wiring or is that only LV
 
080728-1600 EST

My solution would use a GE RR series relay. I happen to like these, others do not.

You can have as many manual on-off switches control one light as you want. No NEC wiring problems on the low voltage side of the system. I have five locations for my main light in the kitchen. Four locations for my breezeway and another four switches at these locations for my garage.

For your time clock operation the leading edge would be used to turn the light on and the trailing edge to turn it off. You could do lots of other things if you wanted. During the time clock period there could be randomization of on and off times.

.
 
I don't know how anyone can even remotely think this can be related to a parallel set of wires used in a feeder scenario in any way, shape, form or fashion,,,,,,,,,,,,,,,,,gosh every stop/start motor control circuit with aholding contact would be the same thing,,,,,,

Wires run in parallel in switching and control circuits are control wires and not considered feeders in parallel.

dick
 
This is so easy, guys.

Wire a single-pole switch like a bypass, but add a 3-way switch: connect one traveler screw to the single-pole's load terminal, the other traveler to the time-clock's load terminal, and the common to the load.

The 3-way and single pole together act as an "on-off-auto" selector switch.
 
Dick, you really should take a look at the code sections before posting.



dicklaxt said:
Wires run in parallel in switching and control circuits are control wires and not considered feeders in parallel.

dick
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Take a look at 310.4 and notice the word feeder is not there.

But there is an exception for control circuits.
 
Not a direct answer to the original question, but a different approach to the stated goal. Rather than use a regular switch and a timeclock in parallel, for this _exact_ application, I use the time clock switches that take the place of a single decora switch. This is personal use in my own home, not professional use.

Basically you have a time clock with a very convenient manual override used in place of the standard switch. We use this to control our main dining room light, and a couple of sensor lights which we want to keep off during Shabbos.

I've had bad luck with the _mechanical_ Intermatic units (model SS8), but have had good luck with the electronic (SCR) based units from the same company. The mechanical units were nice in that they could run just about any load (tungsten, fluorescent, _motors_, etc.) but the mechanism has a horrible failure rate. I repeat, if it is still sold, stay away from the SS8.

Many of the electronic time clock switches can only run sub 500W tungsten loads (they operate like dimmers), however some others seem rated for more general lighting (and non-lighting) loads.

The Intermatic units have an input wire that permits a second switch to operate as a remote control, permitting 'three way' applications.

They can be programmed to operate differently on different days of the week, and to adjust the operating time based upon the calculated sunset time.

I am certain that numerous competitors offer similar devices, with different capabilities, reliability, and cost. Be especially careful about which loads the device operates.

-Jon
 
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