Honeywell Home Prestige TH9321 System Installation Manual page 20

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. Recommended setting for Geothermal Heat
Pumps to allow the loop to rest.
Backup heat differential and upstage timer
A backup heat differential and backup heat upstage timer can be set on any
system that has more than one type of heating equipment. See installer setup
options (ISU 3070-3110).
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 primary heat
is making 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 primary heat 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 during 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 primary heat was not able to maintain the setpoint, the thermostat
may turn on the backup heat earlier when the user raises the setpoint. This does NOT apply to heat pumps with fossil fuel
backup heat.
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