I measured 62 degrees on a supply register and by the time I brought my phone out to take a picture of the reading the temperature began rising slowly to 68 degrees. I continued to hold the thermometer steady on the register and a few minutes later the temperature started coming down again to 62 degrees. This has happened a few times to me in inspections before. Its not a thermometer issue as it has worked fine in between these inspections. I’m thinking this may be caused by a range of issues and I know its not our job as inspectors to locate the issue but just report what we see. But I would like to give my client more information as what is likely causing this. Anyone else ever see this before?
It’s most likely operator error, as the infrared thermometer is reading the grill or duct behind the grill, it isn’t reading the air temp at all.
Minor movement of your device changes the focal point of that scanner’s field of view (which is quite narrow and has nothing to do with the laser dot), resulting in a temp change. Even slight variations in the distance or angle between the tool and scanned area will have that effect.
Try measuring the temp at the plenum with a different tool (or at the register with a different tool), and you’ll get completely different results.
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You should not use. those to check air temperature at all. They do not measure air at all only surfaces. If the surface is shiny it is even more off. Get you some digital thermometers and measure at air handler (is most accurate) or in registers.