My heating and cooling system has a terminal labeled "COM". What is a COM terminal and what do I do with it?
A COM terminal is often used as another name for the C terminal and issued to provide power to your thermostat. COM can also refer to a communication circuit and will not provide power to the thermostat. If you have both a C and COM terminal on your heating and cooling system the thermostat should be wired to the C terminal. Please refer to the Quick Start Guide for more information.