Spec Sheet

Table Of Contents
THX9321 PRESTIGE
®
2.0 AND THX9421 PRESTIGE
®
IAQ WITH EIM
103 68-0311—07
If Window Protection is turned Off, the thermostat controls
the humidity level to the user's desired humidity setting.
Frost or condensation may appear on windows.
Set up Humidification
1. Select the Humidifier Type at ISU 8000. See Fig. 211.
NOTE: Based on the humidifier type you select, the
thermostat defaults to the most commonly
used settings for that humidifier type.
For example, a Bypass or Fan Powered
humidifier will default ISU 8070 to “Humid-
ify Only when Fan is On.
A Steam humidifier will default ISU 8070 to
“Humidify on Demand: Thermostat Controls
Fan.
Fig. 211.
2. If optional remote wireless indoor sensors are
installed, you can choose which sensor you want to
use for humidification control. You can use a differ-
ent sensor for dehumidification. See “Wireless
Indoor Sensor” beginning on page 132 for more
information.
Fig. 212.
3. Select the terminals wired to the humidifier. See Fig.
213.
NOTE: U1, U2, and U3 are Normally Open Dry Con-
tacts that require power from the system
transformer or a separate transformer. See
Wiring IAQ Equipment or a Heat/Cool
Stage to the Universal Terminals” beginning
on page 152.
Fig. 213.
4. Set Window Protection settings. See Fig. 214.
NOTE: Outdoor sensor is required for Window Pro-
tection.
Fig. 214.
5. Select the system mode(s) to allow humidification.
See Fig. 215.
NOTE: Heat includes Heat, Emergency Heat and
Auto. If the system is in Auto mode, the ther-
mostat will allow humidification if the last
call was for heat.
Cool includes Cool and Auto. If the system is
in Auto mode, the thermostat will allow
humidification if the last call was for cool.
A discharge sensor is required to humidify
in the Cool mode. The thermostat prevents
condensation in the duct work by not allow-
ing the humidifier to run when the dis-
charge temperature goes below the dew
point temperature. The humidifier is
allowed to run again after the discharge
temperature rises above the dew point tem-
perature.