photocells

[sparkadaddy]

I always considered a photocell just another switch. When its dark its on and when its light its off. I just got done changing a half dozen outdoor wallpacks with their own photocell in each fixture.
The circuit that was running the old fixtures was run off of one photocell mounted on the building.
I kept the old circuit with the building photocell to run my 6 fixtures and they all come on sporaticly. When I bypass the building photocell they come on just fine. I called the new fixtures company rep and he told me I had to buy his building photocell because the old one was not compatible. What am I missing here? Is a photocell not just a switch? Or am I being bamboosilled?

 

[hbiss]

Re: photocells

I don't know why either, could be it uses a solid state switch (like a dimmer full on) and the waveform causes problems for the others. I've never see a photocontrol like that though, they always use a relay. Could also be that the photocontrols in the wall packs like to be powered up all the time.

But I also don't know why, if each wallpack has its own photocontrol, you are using an additional photocontrol to control the whole bunch. Are there other fixtures on the circuit? Easiest thing to do then is to disconnect the photocontrols in the fixtures, they are not needed. If not, ditch the main one, it's not needed.

-Hal

 

[charlie b]

Re: photocells

This may sound like I am merely splitting hairs, and I don?t know if this will help, but you may simply have a case of miscommunication. To start with, a photoCELL is not a ?switch.? It?s a generator! It generates a DC current when light hits it, and it generates no DC current when it is in the dark. The device that you called a photocell consists of a photoelectric sensor and some amount of electronics. This is what Hal just called a ?photocontrol.? Somewhere within the electronics there will be a switch.

So I would surmise that what the manufacturer is telling you is that the electronic package (with its photoelectric sensor) ? the one that came from the older wallpacks ? is not compatible with his new fixtures. To me, that is not an unreasonable statement.

 

[bennie]

Re: photocells

The start up time delay in the unit photocells is making them operate at different times.

A photo cell needs a short period of time to begin operation when first energized.

 

[hbiss]

Re: photocells

That's what I was alluding to above. Most of these things are not exactly state of the art. The ones I have actually looked at used a thermal relay that had to heat up to operate (or open the contacts). This is why there should be power to them all the time, or at least for some time before they activate.

-Hal

 

[electricman2]

Re: photocells

Photocontrols are designed to have line voltage applied continuously in order to work properly. I believe I would just disable the building control.

 

[a.wayne3@verizon.net]

Re: photocells

position would make a world of difference,guess it could be a light show

 

[sparkadaddy]

Re: photocells

Thanks again for the response. I have to leave the building control because the energy saving engineer says so.

 

[hbiss]

Re: photocells

I have to leave the building control because the energy saving engineer says so.

If there is nothing else on the circuit how does it save energy? :roll:

Why don't you suggest this to him, something I do all the time. Many times a photocontrol will come on too early even when you have it oriented properly. This might not be a problem at dusk but if it gets dark during the day because of a storm you don't need them coming on. Replace the building control with a time clock. Set it so the lights cannot come on during the day. You can also have it turn them off at a certain time. This works for something like an office building where it will be unoccupied after a certain hour.

-Hal

 

[pwhite]

Re: photocells

i would check with the compatibility of the existing photocell with the new ones. draw out the two photo cell circuits, and see if their specifications agree with each other.

 

[oneelectron]

Re: photocells

I know the packs are up on the wall now but if you just disabled the photo cells on the packs, you bypass the double photo-cell problem (compatibility), and remove the possibility of a faulty pack being the fault of a photo-cell, my usual suspect.