Stop mounting motion sensors right above the thermostat

I see this at least once a week on service calls. A motion sensor 2 feet from a heat vent or right above a thermostat cycles false alarms every time the HVAC kicks on. That warm air blast triggers the PIR element. I pulled one down yesterday in Phoenix, moved it 6 feet away to a wall, and the homeowner's been false alarm free for 24 hours. How many of you are still leaving sensors within 4 feet of a vent on new builds?

3 comments

3 Comments

hayden7098d ago

Yeah, "that warm air blast triggers the PIR element" is exactly the problem people don't think about. I've seen so many installs where they stick the sensor right in line with a ceiling vent or on a wall above a baseboard heater, and then they wonder why the alarm goes off at 2 AM when the furnace kicks on. The warm air hitting that plastic cover changes the temperature just enough to fool the sensor into thinking something moved. It's not even about being 4 feet away half the time, it's about the direction of the airflow. If the vent blows straight down onto the sensor, you could be 10 feet away and still get issues. I always test with a hair dryer on low for 30 seconds before I finalize a sensor location, just to see if the heat sets it off. Most people skip that step and pay for it later with nuisance alerts.

mary7768d ago

I heard a guy say he uses a hair dryer to test sensor spots, seems smart.

derekward8d ago

Saw a guy once mount a sensor directly above a space heater and wondered why it tripped every 15 minutes.

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