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Photocell switch - Unwanted behavior

JohnPJackson's picture

I just bought an inexpensive photocell switch, an Intermatic KC4121C.  I was frustrated to discover that when you energize the device, it begins operating by first supplying power to its connected load (an outdoor lamp) for a minute or so, then it goes into a normal operation mode and either switched the load off if it registers enough daylight, or leaves the load switched on if it's dark.

I was trying to obtain a photocell switch that would only supply power to its load device if it was dark out, and never when it's daylight.  I have an outdoor light that I want to have turn on when the sun goes down, and turn off at 7:00pm, every day.  My plan was to use a timer and the photocell switch together to accomplish this.  I wanted to use the timer to turn on power to the photocell switch at noon each day, and then cut power to it at 7:00pm.  What I want to avoid is having the photocell switch turn on the outdoor lamp at noon for that first minute or so, every day, before going into normal operation mode and shutting the lamp off again, until sunset or 7:00pm, whichever comes first (depending on the length of daylight for the time of year it is).

Does anyone know of a photocell switch that doesn't have this unwanted initial power up routine built into it?  I just want one that can be energized during daylight hours, that does nothing at that point but then be ready to switch on its load when the sun goes down.

Thanks for any ideas or feedback anyone has to share :)


Easy to find. (post #216565, reply #1 of 4)

This switch should be easy to find. You can even get one that screws into a medium base bulb socket. Just out of curiosity what's wrong with the light going on for a minute or so at noon? Wasted electricity?  For 100w conventional bulb at a very high rate this would cost about 30 cents a year. For a LED close to nothing. I have a LED light in a cabinet that costs less to run 24/7 than a timer would cost. Why not a motion sensor light with a photo cell?

My biggest concern about the (post #216565, reply #2 of 4)

My biggest concern about the extra on/off cycle of the lamp every day is that I want to maximize the life of the lamp.  On/off cycles are part of the wear and tear on electronics.  The lamp in this case is an LED array, 350W.  It's an inexpensive Chinese made unit that's sold as 500W, 50K Lumens.  I've run it through a watt meter and found it's only drawing 350W.  Either way, it's plenty bright for the parking area I'm going to use it for and I'm just trying to get the most out of it by designing and installing it as well as I can, from the start.  I'm not concerned about the extra electricity use.  And I want the light to come on at dusk, and go off soon after closing time at the business where the parking area is - my wife's vet clinic.  There's already an ordinary PAR38 motion light out in front but it's not enough.  Customers like to be able to see their surroundings as they approach and before they head out the door.  The motion lights don't come on soon enough for that.

I called Intermatic today and they confirmed the unit I have can not be reconfigured to not power up its load when it's initially energized.  They also said they didn't know of anyone else who made a photocell switch that didn't also do the same thing.  The support person I spoke to though sounded particularly devoid of any hint whatsoever of trying to really consider if there was any other way he could think of to deal with this, or to try and find a solution I'd be happy with.  I was pretty disappointed with that.

LED lamps probably have the (post #216565, reply #3 of 4)

LED lamps probably have the least "cost", in terms of lost lamp lifetime per power on/off cycle, of any type of lamp sold.  It's not worth worrying about.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Get a timer with separate  (post #216565, reply #4 of 4)

Get a timer with separate  inputs for the timing power and switched loads. 

Wire both the photocell and timer to be ON all the time. 

Run the photocell load wire to the timers switched load input.