Sensing in the return air of an indoor unit is not always ideal, especially when fresh air is being introduced. All of the Mitsubishi Electric wired wall controllers now have the ability to sense the room ambient via the inbuilt thermostat. This means you are sensing the actual space temperature where the end user is. If the wall controller is not located in an appropriate location for sensing the space condition, a PAC-SE41 remote sensor could also be installed.