Honeywell Prestige THX9321 System Installation Manual page 21

Humidification
THX9321/9421 Prestige ® IAQ and RF ElM
The thermostat can be set to control humidification in all modes (Heat, Off, Cool
[ISU 8060]). A discharge air sensor is required to humidify in the cool mode. If
both humidification and dehumidification are set up to be controlled in the same
mode (Heat, Off, Cool), the thermostat maintains a 15% deadband between
humidification and dehumidification setpoints. The thermostat automatically
switches between humidification and dehumidification to maintain the desired
humidity level.
Humidification Control Options: (ISU 8070)
• Humidify Only When Heat is On
• Humidify Only When Fan is On
Humidify on Demand: Thermostat Controls Fan
• Humidify on Demand: Humidifier Controls Fan
To see all humidificationoptions, press Menu> InstallerOptions> View/EditCurrent Setup> Humidification.
Residential dehumidification
Dehumidification Equipment Options: (ISU 9000)
• A/C with Low Speed Fan
• A/C with High Speed Fan
• Whole House Dehumidifier
When set for A/C with Low Speed Fan or A/C with High Speed Fan, an overcool-
ing limit can be set from 0 ° to 3 ° F (iSU 9070). The thermostat uses the cooling
system to reduce humidity by lowering the temperature up to 3 ° F below the
current cool setpoint until the the desired humidity level is reached. If set for
A/C with Low Speed Fan, configure U1, U2 or U3 as normally open or normally
closed (ISU 9050) and wire the terminal to the Low Speed Fan terminal on the
equipment. During a calt for dehumidification, the thermostat opens or closes the
universal relay (U1, U2 or U3) to lower the fan speed.
Note; The thermostat will not lower the fan speed when the second stage of
cooling is on.
The Whole House Dehumidifier option requires a dedicated unit for dehumidifica-
tion. The thermostat can be set to control dehumidification in all modes (Heat,
Off, Cool [ISU 9120]).
if both humidification and dehumidification are set to be controlled in the same
mode (Heat, Off, Cool), the thermostat maintains a 15% deadband between
humidification and dehumidification setpoints. The thermostat automatically
switches between humidification and dehumidification to maintain the desired
humidity level.
To see all dehumidificationoptions,press MENU> INSTALLEROPTIONS> VIEW/EDITCURRENT SETUP>
DEHUMIDIFICATION.
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