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System Installation Guide
Basic and Advanced Temperature Control Options (ISU 3010)
Basic Options: The Installer Setup displays basic temperature control options
which include Backup Heat Differential, Backup Heat Upstage Timer and Outdoor
Temperature Lockouts. Note: Outdoor Temperature Lockouts only apply to Heat
Pump applications.
Advanced Options: The Installer Setup displays both Basic and Advanced Options.
Advanced temperature control options include Finish With High Cool Stage, Finish
With High Heat Stage, Temperature Differential settings between all stages and
Cycle Rate settings per stage.
Finish With High Heat or Cool Stage - When a multi-stage heating or cooling system is used, this feature keeps the high stage
of the heating or cooling equipment running until the desired setpoint is reached.
Backup heat differential and upstage timer
A backup heat differential and backup heat upstage timer can be set on heat pump
systems with backup heat. See installer setup options (ISU 3090-3110).
Normal operation
When the Backup Heat Differential is set to Comfort, the thermostat uses backup
heat as needed to keep the indoor temperature within 1° F (0.5° C) of the setpoint.
When the Backup Heat Differential is set to 2° F or higher, backup heat is not used
unless the indoor temperature drops to the Backup Heat Differential setting or the
Backup Heat Upstage Timer expires, whichever occurs first. The upstage timer starts
when the highest stage of the previous equipment type turns on.
Manual temperature change
When the Backup Heat Differential is set to Comfort, the thermostat uses backup
heat as needed to keep the indoor temperature within 1° F (0.5° C) of the setpoint.
When the Backup Heat Differential is set to 2° F or higher, if the heat pump is mak-
ing progress as expected, backup heat will not be used to reach the new setpoint.
Set to a higher number to use less backup heat (a greater difference between the
current indoor temperature and the new setpoint is required to turn on backup heat).
See notes below.
Programmed recovery
If the heat pump is making progress as expected, backup heat will not be used to
reach the setpoint of the next program period. Backup heat is always restricted dur-
ing a programmed recovery when the Adaptive Intelligent Recovery feature is used.
See note below.
During a programmed recovery (or when the temperature setpoint is changed by the user), the thermostat waits to turn on the
backup heat depending on system performance, load conditions and how many degrees the temperature setpoint is changed.
Backup heat will be used ONLY when the temperature is not rising quickly enough to reach the setpoint in a reasonable time.
If the backup heat was used in the last 2 hours because the heat pump was not able to maintain the setpoint, the thermostat
may turn on the backup heat earlier when the user raises the setpoint.
69-2688—11 I/O-CHTSTAT03
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