If the Y1, W1, or W2 (W2 in electric heat systems only) outputs are energized 
when the mode is set to HEAT, EHEAT, or AUTO, operating in Heat, then the 
heating equipment is on. When all of these outputs are off, the heating 
equipment is off. 
 
 
Inputs 
Power supply 
Class II transformer secondary voltage supplied to the thermostat is 18.0 to 30.0 Vac, 50/60 Hz. Voltage is 
applied between R and C connector. 
 
Space air temperature 
The space air temperature measurement is supplied by an NTC "J" curve (type II) thermistor. The resistance of the 
thermistor is 10K ohm nominal at +25°C with an accuracy of ±0.20°C from +15.6°C to +32.2°C (approximately 
0.5°F accuracy from 60°F to 90°F). 
If the thermistor reading is invalid, the space temperature is measured by the Sensirion SHT21 humidity and 
temperature sensor.    
 
Remote temperature sensor 
The remote temperature measurement is supplied by a NTC "J" curve (type II) thermistor connected between T and 
C. This thermistor is supplied by the installer to use for Space, Outdoor, Supply Air, or an average with the space 
air temperature. When used for the space temperature sensor, up to 9 remote space sensors can be averaged (1, 
or multiples of 4, or 9). The T input allows for remote occupancy override with T55 style sensor.  
•  If the Occupancy Input installer setting is set to OCCUPIED, when a short in the circuit from 2 up to 5 seconds 
in duration is sensed, a change is made from the unoccupied heating and cooling setpoints to the occupied 
heating and cooling setpoints for the current time period, for the configured allowable time.  
•  If the Occupancy Input installer setting is set to UNOCCUPIED, when a short in the circuits sensed for more 
than 2 seconds, the occupied heating and cooling setpoints change to the unoccupied heating and cooling 
setpoints for the current time period.  
•  Alternatively, you can use the remote temperature sensor input as a remote occupied/unoccupied selection 
as well as an indicator of economizer fault or Filter Reminder. 
•  Alternatively, Wi-Fi outdoor temperature is available by GPS location services – determined when the 
thermostat is installed and registered through a Wi-Fi connection.