Photocell under this type of roof?

A

Akten

Member
Location
New York
Occupation
Engineer
Hi, I was wondering if photocell lighting (to replace the light shown in photo) would work on the location shown here? I am not sure if the shade from roof would affect the performance / operation of a photocell wall pack type lighting.

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You''re more likely to have problems with the photocell picking up the light, leading to flickering.
 
LarryFine said:
You''re more likely to have problems with the photocell picking up the light, leading to flickering.
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Do you mean that the fixture turning OFF could be an issue? What type of control would you recommend for outdoor light in this situation?
 
Akten said:
Do you mean that the fixture turning OFF could be an issue?
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I mean it gets just dark enough, the light comes on, the added light turns the photocell, back off, the drop in light triggers it on again, and you have oscillating light, a.k.a. flicker.

Akten said:
What type of control would you recommend for outdoor light in this situation?
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Ideally, remote location for the photocell, where it can't see its own light.

If there's a wall switch, replace it with an astronomical timer.
 
Many photocells come with a hood so you can block the light from one side. Make it so it sees out away from the light fixture.

I also had some lights where I used dusk to dawn light bulbs. I don't know where the light sensor is on those, but they would obviously see a significant portion of the light bulb light. I'm wondering if they have made these now so they don't see the light from LEDs by perhaps looking at the UV spectrum or some wavelength missing from LED sources.
 
The shade from the overhang would cause the lights to come on earlier and go off later than if the photocontrol were placed in the open, depending on the ambient illumination at that spot. Factors such as the photocontrol facing East, for example would allow it to be exposed to morning sunlight, even if under an eve, and turn off prematurely on sunny days. This is why photocontrols should ideally always have and open unobstructed view of the North sky.

I think that if your photocontrol were located at the top of the cluster near the soffit, I don't think that light from the reflector floods aimed down and out would create enough illumination on the underside of the soffit to cause an oscillation problem. If anything, the small increase in ambient would bias the photocontrol to turn off sooner.

EDIT: I just noticed that you mentioned replacing the floods with a wall pack having a built-in dusk to dawn photocontrol. My experience is that there should be no problem as the manufacturer has taken the photocontrol location on the fixture into account.

-Hal
 
hbiss said:
The shade from the overhang would cause the lights to come on earlier and go off later than if the photocontrol were placed in the open, depending on the ambient illumination at that spot. Factors such as the photocontrol facing East, for example would allow it to be exposed to morning sunlight, even if under an eve, and turn off prematurely on sunny days. This is why photocontrols should ideally always have and open unobstructed view of the North sky.

I think that if your photocontrol were located at the top of the cluster near the soffit, I don't think that light from the reflector floods aimed down and out would create enough illumination on the underside of the soffit to cause an oscillation problem. If anything, the small increase in ambient would bias the photocontrol to turn off sooner.

EDIT: I just noticed that you mentioned replacing the floods with a wall pack having a built-in dusk to dawn photocontrol. My experience is that there should be no problem as the manufacturer has taken the photocontrol location on the fixture into account.

-Hal
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Usually the photocell on wall packs are on the side, so you are correct, unless it is mounted close to an adjacent wall were light might be reflected back towards the photo cell.
 
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