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I finally get why the old timer said never mount the panel near a vent
Earlier this month I did a swap in a finished basement in Naperville. Customer wanted the keypad next to the HVAC return because it looked clean. My mentor Bob told me years ago that airflow kills false alarms when dust gets pulled into the motion sensor. I figured he was just being old school. Two days after I left, they call about the system going off at 3 AM every night. Turned out the return vent was blowing straight onto the PIR sensor and the filter was filthy. Moved the panel six feet over and ran a new wire, no trouble since. Bob retired in 2019 but he still answers my texts. Anyone else get burned ignoring a veteran's warning about sensor placement? What else do they say that actually holds up?
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logan5611mo ago
Try aiming the sensor away from windows too, sun glare sets them off worse than dust.
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riverdavis1mo ago
Actually most optical smoke detectors are looking for scattered light, so they're more about the particles floating in the air than direct sunlight. I mean, direct sun can heat up the sensor housing and cause false alarms in some cheap models, but it's usually the dust buildup inside that's the real culprit. I've seen units mounted right next to big south facing windows work fine for years. The bigger issue is placement near kitchens or bathrooms where steam and cooking grease get in. Not trying to argue, just saying the sun thing is more of a minor factor compared to regular cleaning.
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