Automatic Lighting: Steps to Follow for Adding Photocells to Outdoor Lights

Automating Commercial Exterior Lighting

In commercial facility management, automating exterior lighting is a critical step for both security and operational efficiency. Photocells (dusk-to-dawn sensors) ensure that perimeter lights, wall packs, and parking lot fixtures are active only when natural light levels fall below a specific threshold. This transition to automated controls reduces energy waste and ensures that your facility is never left in the dark.

What is a Photocell?

A photocell, or photoelectric sensor, is a light-sensitive resistor that controls an electrical circuit based on ambient light intensity. In a commercial application, these sensors are typically integrated into the wiring of LED wall packs or pole lights to provide autonomous operation. This eliminates the need for manual switching or complex digital timers that require adjustment for seasonal daylight changes.

Installation Guide for Commercial Photocells

Step 1: Specification and Materials

Ensure your photocell is rated for the voltage of your commercial circuit (typically 120V or 277V). For industrial use, "stem-mount" or "button" photocells are common. You will need:

• UL-Listed Photocell Sensor
• Non-contact voltage tester
• Wire strippers and commercial-grade wire nuts
• Silicone sealant (for weatherproof mounting)
• Screwdriver set

Step 2: Power Isolation

Locate the appropriate circuit breaker in your facility's electrical panel. De-energize the circuit and utilize a lockout/tagout procedure. Use a voltage tester at the fixture to confirm that no current is present before proceeding with the installation.

Step 3: Accessing the Fixture Wiring

Open the junction box or the access panel of the exterior lighting fixture (such as a commercial LED wall pack). Identify the three primary wires: Line (Black), Neutral (White), and Ground (Green/Copper).

Step 4: Wiring the Photocell

Commercial photocells typically feature three wires: Black (Line), White (Neutral), and Red (Load). Follow this professional wiring configuration:

• Neutral Connection: Connect the White wire from the photocell to the White Neutral wires from both the power source and the light fixture.
• Line Connection: Connect the Black wire from the photocell to the Black "Hot" wire coming from the power source.
• Load Connection: Connect the Red wire from the photocell to the Black "Hot" wire of the light fixture. This allows the sensor to act as the gatekeeper for power.

Step 5: Mounting and Weatherproofing

Mount the photocell through a knockout in the fixture or junction box. Ensure the sensor eye is facing North or away from direct artificial light sources to prevent "cycling" (where the light turns itself off). Apply a bead of professional-grade silicone sealant around the mounting point to prevent moisture ingress into the electrical housing.

Step 6: Commissioning and Testing

Restore power to the circuit. Since it is likely daylight during installation, the fixture should remain off. To test, place the black protective cap (included with most sensors) or your hand over the photocell lens for 30–60 seconds. The fixture should illuminate. Remove the cover to confirm the light deactivates when exposed to ambient light.

Step 7: Sensitivity and Aiming

If your commercial photocell includes a sliding cover or sensitivity dial, adjust it to ensure the light activates at the desired level of dusk. Proper aiming ensures the sensor is not triggered by passing vehicle headlights or the light emitted by the fixture itself.

Conclusion

Integrating photocells into your commercial outdoor lighting system is a high-impact upgrade for any facility. It provides a reliable layer of security while significantly reducing the man-hours required for lighting management. For more information on optimizing your facility's exterior, refer to our Outdoor Lights FAQs.