Heat Pump And Backup Heat Operation; Heat Pump With Outdoor Temperature Lockouts; Geothermal Radiant Heat; Heat Mode - Honeywell THX9321 Prestige 2.0 Product Data

®
THX9321 PRESTIGE 2.0 AND THX9421 PRESTIGE

HEAT PUMP AND BACKUP HEAT OPERATION

Heat pump with outdoor temperature lockouts

Outdoor temperature lockouts are optional. See Installer Setup options (ISU 3120).
Backup heat allowed to run with heat pump
Heat pump with backup heat as needed *
* No backup heat unless indoor temperature drops to selected Backup Heat Differential setting, or Backup Heat
Upstage Timer expires. Heat pump stays ON when backup heat turns on.
Backup heat NOT allowed to run with heat pump
* No backup heat unless indoor temperature drops to selected Backup Heat Differential setting, or Backup
Heat Upstage Timer expires. Heat pump turns OFF when backup heat turns on.
Backup Heat Type
Electric forced air
Gas or oil forced air
Hot water radiant heat
Hot water fan coil
Other

Geothermal Radiant Heat

The thermostat can be setup to control Geothermal Radiant
Heat, Geothermal Forced Air Heat and Backup Heat, all from
one thermostat. The thermostat stages the equipment starting
with the Geothermal Radiant Heat followed by Geothermal
Forced Air Heat and then Backup Heat as needed to maintain
the desired temperature. The thermostat allows you to set
differential temperature settings between each stage if you
want the equipment to stage a certain way (see ISU 3030 to
ISU 3090, page 31). For additional wiring diagrams, see
page 141.
NOTE: To turn off Radiant Heat during the shoulder sea-
sons, install an outdoor reset control and connect
to the Radiant Heat or switch the thermostat to
Emergency Heat mode.
68-0311—02
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Heat pump only
Backup heat only
Heat pump only
Heat pump or backup heat operates *
Backup heat only
Table 8. Heat Pump and Backup Heat Operation.
Backup Heat Operation
Allowed to run with heat pump
NOT allowed to run with heat pump
Allowed to run with heat pump
Selectable in installer setup
Selectable in installer setup
IAQ WITH EIM
(see table below)
(see table below)
Electric Backup Heat (Backup Heat Allowed
to Run with Heat Pump)

HEAT MODE

The thermostat turns on Backup Heat only when the indoor
temperature drops to the selected Backup Heat Differential
setting or the Backup Heat Upstage Timer expires (whichever
occurs first). Geothermal Radiant Heat and Geothermal Forced
Air Heat stay on when the Backup Heat turns on.
EMERGENCY HEAT MODE
The thermostat turns on the Backup Heat to maintain the
desired temperature setting. Geothermal Radiant Heat and
Geothermal Forced Air Heat are not used.
100
Backup heat lockout
Compressor lockout
Backup heat lockout
Compressor lockout
Backup Heat Fan Operation
Thermostat controls fan
Equipment controls fan
[n/a]
Thermostat controls fan
Selectable in installer setup