This Orbit programmable thermostat uses an internal disposable battery for its primary power. A "C" wire is not required. It will work with a 2 wire system. There is no home/away feature on this model. There is no vacation feature on this model.
The Orbit Clear Comfort 83521 is part of the Thermostat
test program at Consumer Reports. In our lab tests, Thermostat
models like the Clear Comfort 83521 are rated on multiple criteria, such as those listed below.
Manual operation: The ease of manually controlling the thermostat's temperature set-point, heating/cooling schedule, home/away and vacation features - when they are available.
Programming: The ease of creating a heating and cooling schedule considering, navigational, contextual and informational elements that make programming easier, and the number of steps.
Display: The ease of reading the display considering, character size, spacing, layout and contrast.
Touch screenWhether the display is a touchscreen or not.
Events per day
Events per dayIndicates the maximum events-per-day that can be added to a heating or cooling schedule.
Early recoveryIndicates whether or not the thermostat can trigger the heating or cooling process earlier than a scheduled time, in order to get the house to temperature by the scheduled time.
Auto changeoverIndicates whether or not the thermostat can automatically switch from a heating system to a cooling system mode.
Auto daylight savings
Auto daylight savingsIndicates whether or not the thermostat can automatically adjust its clock based on daylight savings time.
Air filter reminder
Air filter reminderIndicates whether or not an air-filter reminder is present.
Password protectionIndicates whether or not the thermostat provides some sort of password protection or lockout - a code, key sequence or setting - which limits the ability to change the thermostat's settings.
Primary powerThe primary power source.
an internal disposable battery
Backup powerThe backup power source.
Two wire compatible
Two wire compatibleIndicates whether or not the thermostat can be used in a 2 wire system.
C wire required
C wire requiredIndicates whether a "C" wire is required to power the thermostat.
Power sharingIndicates that when using a 2-wire setup, whether the thermostat draws power through the wires to charge a battery. This may cause some HVAC systems to operate unpredictably or erratically.
Warranty (yrs.)The length of time the thermostat is covered by its manufacturer for defects or repairs.