Honeywell THX9321 Prestige 2.0 System Installation Manual page 21

Humidification
The thermostat reads the indoor humidity level and allows the user to set a
humidification setting with or without window protection. The thermostat can be
setup to control a humidifier in any system mode (Heat, Off, Cool [ISU 8060]). A
discharge air sensor is required to humidify in the cool mode.
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
Residential dehumidification
The thermostat reads the indoor humidity level and allows the user to set a dehu-
midification setting. The thermostat controls the humidity level using the cooling
system or a whole house dehumidifier.
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 equip-
ment. For example, if the U1, U2 or U3 terminal is normally closed, it will open
when the thermostat calls for dehumidification.
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 setup to control dehumidification in all modes (Heat,
Off, Cool [ISU 9120]).
If humidification and dehumidification are setup to operate in the same system mode (Heat, Cool, Off), and you
are sensing humidity from one location, the thermostat will automatically enforce a 15% deadband between the
humidification and dehumidification settings. The thermostat will automatically switch between humidification and
dehumidification to maintain the desired humidity level.
If humidification and dehumidification are setup to operate in the same system mode (Heat, Cool, Off), and you are sensing
humidity from two different locations using a remote wireless indoor sensor (for example, main level and crawl space), the
thermostat will allow humidification and dehumidification to operate at the same time, and there is no deadband between
humidification and dehumidification settings.
THX9321/9421 Prestige
21
IAQ and RF EIM
®
69-2490—05