Warning: Had a motion sensor fail on a 3rd floor condo job because of a hidden HVAC vent.

I was finishing up a job in a high rise downtown last month. The place had those fancy ceiling vents that blow straight down. I mounted a PIR in what looked like a perfect corner, away from windows. Did the walk test, it worked fine. Came back two days later because the customer said it kept going off at night. Turns out, the building's AC kicks on hard around 2 AM, and that vent was blowing a column of cold air right across the sensor's field of view from about 15 feet away. The temp difference was enough to trip it. I had to remount it on a different wall entirely, which meant running a new wire channel. Has anyone else run into HVAC drafts causing false alarms from a distance like that? What's your go-to fix besides just moving the sensor?

3 comments

3 Comments

the_sam8d ago

Adjusting the sensitivity? Man, I was so focused on the mounting bracket I probably would have tried to recalibrate the building's AC first. My first move is always the most complicated one possible. You ever try to solve a simple math problem by reinventing numbers? That's me with a screwdriver.

james_kim16d agoMost Upvoted

Did you try adjusting the sensor's sensitivity first?

the_dylan16d ago

Honestly that's the first step everyone skips and it drives me nuts. It's like people would rather take something apart than just turn a dial. I see it with everything now, phones, cars, even coffee makers. We're so trained to look for the hard fix that we miss the simple setting right in front of us. Makes you wonder what else we're overcomplicating.