Who This Checklist Is For (and When to Use It)
If you're in the middle of specifying a lighting retrofit for a commercial or industrial facility, you've probably hit this wall: motion sensor or occupancy sensor? It looks like a small detail in the spec sheet, but I've seen it derail projects—costing time, money, and trust with the client.
This checklist is for project managers, electrical contractors, and facility engineers who need to make this call quickly and correctly. It's based on reviewing roughly 200+ lighting control specs annually in my role as a quality manager, and catching about 12% of first deliveries for re-spec in 2024 alone due to sensor mismatches. This is one of the top three recurring issues I flag.
There are three steps. Don't skip the third one—it's the one most people get wrong.
Step 1: Define the Space Behavior (The 15-Minute Rule)
Don't start with the sensor spec sheet. Start with how the space is actually used. This sounds obvious, but I've rejected batches where the vendor assumed 'open office' meant one thing, and the client's actual usage was completely different.
Answer two questions:
- How long is a person typically stationary in the primary task area? If it's under 15 minutes (warehouse aisle, corridor, restroom), you want a motion sensor (PIR or microwave). These detect small movements—head turns, hand gestures, even breathing—and keep lights on. If the person stops moving for 15 seconds, the sensor might assume the space is empty. That leads to lights going out while someone is still working.
- Is the space ever intentionally unoccupied but active? Think server rooms, electrical closets, or storage areas with automated equipment. Here, an occupancy sensor (using ultrasonic or dual-tech) is better. It detects larger movements and sometimes background noise, but it's less likely to false-trigger to be left on. The key difference: an occupancy sensor waits longer before declaring the space 'vacant'—usually 5 to 15 minutes of no detection. A motion sensor is much quicker to shut off.
Checkpoint: If you can't answer both questions with certainty in 15 minutes, you need a site visit before ordering. Don't guess. Guessing on this step was the reason for a $22,000 redo on a project I reviewed in Q1 2024.
Step 2: Match the Sensor to the ABB Lighting Controller
This is where the technical spec matters. ABB's lighting control ecosystem—particularly through the ABB Ability platform—offers different integration points. You can't just pick any sensor off the shelf.
- For IoT-enabled retrofits (ABB Ability connected): Use ABB's occupancy sensors with digital output (e.g., the OCC-S series). These communicate directly with the lighting controller via DALI or BACnet. A standard PIR motion sensor with a relay output won't integrate cleanly. You'll end up with a 'dumb' on/off circuit that doesn't report data back to the platform. That defeats the purpose of the IoT upgrade.
- For standalone emergency lighting: Emergency lighting circuits often need a separate sensor or a contactor override. I've seen specs where a single occupancy sensor was supposed to control both general and emergency lighting. That's a code violation in most jurisdictions. You need a lighting contactor (ABB's E-line series works well here) to isolate emergency circuits from occupancy sensing.
- For retrofit packages: If you're using a pre-engineered ABB retrofit kit, check the compatibility matrix. The kit may come with a specific sensor. I've rejected deliveries where the contractor ordered a 'universal' sensor and it didn't physically fit the housing or the wiring layout. The retrofit kit documentation usually lists this clearly.
Checkpoint: List the exact ABB controller model (e.g., ABB Ekip, ABB Ability Edge) and verify the sensor is listed in its compatible accessories document. This step takes 10 minutes now and saves weeks later.
Step 3: The Hidden Variable You Must Check (Most People Skip This)
Here's the one that causes the most headaches: timeout duration on the sensor itself.
Most sensors come with a factory default timeout—commonly 5 minutes for motion sensors, 15 minutes for occupancy sensors. But this default is almost never right for the application. I had a project in 2023 for a warehouse where the occupancy sensors were set to 5 minutes (the motion sensor default). The lights kept going off while forklifts were loading. The contractor blamed the sensor, the vendor blamed the wiring, and the client was furious. The fix was a 5-second DIP switch change to set the timeout to 20 minutes.
Most people think the difference between motion and occupancy is just technology (PIR vs. ultrasonic). The real difference in practice is the timeout behavior. If you don't specify the timeout in your order, you'll get the factory default. And the factory default is almost never right for your project.
On a recent 50,000-unit order for a university dormitory complex, I specified a 12-minute timeout on all occupancy sensors for common areas and a 2-minute timeout on motion sensors for restrooms. The vendor missed the note on the restroom sensors. We caught it during pre-install inspection—avoiding a site-wide retrofit headache.
Checkpoint: In your purchase order or spec document, explicitly state the required timeout duration for each sensor type. If you're unsure, test it: set the timeout to double what you think you need. You can always reduce it later in software; you can't easily fix it after installation.
Common Mistakes and Final Notes
Here are the three mistakes I see most often in my quality audits:
- Using motion sensors in open offices. People shift in their chairs; a PIR sensor will see that as movement. If the timeout is too short, lights flicker. But the bigger issue is that an open office with 20 people doesn't need a sensor—it needs a photocell or a schedule. A motion sensor in a high-occupancy space is just an expensive on/off switch that cycles unnecessarily.
- Assuming 'occupancy' means the same thing to every vendor. One project used an ABB OCC-S sensor alongside a non-ABB sensor. The non-ABB sensor had a different detection pattern. The result: zones overlapped, some areas were over-lit, others were dark. Stick to one sensor family for the entire project if possible.
- Not documenting the photo sensor behavior. Many occupancy sensors have a built-in photo sensor that prevents lights from turning on if ambient light is sufficient. In a retrofit with a skylight or window-rich space, this can cause lights to stay off even when someone enters. We had to rewrite the spec on an $18,000 project because the sensor was 'blind' during the day. We should have specified a model with a daylight override.
I don't have hard data on industry-wide defect rates for sensor misspecification, but based on our five years of orders, my sense is that about 8-12% of first deliveries have a sensor compatibility or configuration issue. On a 1,000-unit retrofit, that's 80-120 units that need to be swapped after installation. The cost of rework is far higher than the cost of getting the spec right upfront.
Prices for ABB sensors vary—range roughly from $30 to $120 per unit depending on technology and integration level (based on distributor quotes, early 2025; verify current pricing). The cost of a re-spec or re-install can easily be ten times that per fixture. The time you spend on this checklist will pay for itself many times over.