I had a Honeywell CM67 thermostat which gave a temperature reading about 3 deg C lower than when measured with my IR Thermometer (ie by pointing it at the thermostat case and display as well as the wall around it).
I've just replaced the thermostat because of a (different) fault with a new Honeywell CM907 (the new version of the CM67) and I'm getting the same thing. I know that I can change the calibration / temperature offset, but I wondering why it's happening at all. Is it something to do with the way I'm using the IR thermometer?
Thanks,
Michael