THX9321 PRESTIGE
®
2.0 AND THX9421 PRESTIGE
®
IAQ WITH EIM
105
68-0311—02
Dehumidification - Residential
The thermostat reads the indoor humidity level and allows the
user to set a dehumidification setting. The thermostat controls
the humidity level using the cooling system or a whole house
dehumidifier.
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.
Dehumidification using the Cooling System
When set for A/C with Low Speed Fan or A/C with High Speed
Fan, an overcooling limit can be set from 0 °F 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 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 to the
Low Speed Fan terminal on the equipment. For example, if the
U1, U2, or U3 terminal is normally closed, it will open when the
thermostat calls for dehumidification.See “Wiring IAQ
Equipment or a Heat/Cool Stage to the Universal Terminals”
NOTE: The thermostat will not lower the fan speed when
the second stage of cooling is on.
Set up Dehumidification With Cooling
System
Some screens shown in this section may not appear on the
thermostat, depending on how you set up dehumidification.
1.
Select the Dehumidification Equipment in ISU 9000. See
Fig. 216.
2.
If optional remote wireless indoor sensors are installed,
you can choose which sensor you want to use for dehu-
midification control. For example, you can use one sen-
sor for humidification control, and another for
dehumidification. See “Wireless Indoor Sensor” begin-
ning on page 130 for more information.
Fig. 217.
3.
If you are sensing humidity from two separate locations
(one for humidification and another for dehumidification),
you can select which humidity reading to display on the
home screen. See “Wireless Indoor Sensor” beginning
on page 130 for more information.
Fig. 218.
4.
Select the terminals wired to the A/C with Low Speed
Fan. See Fig. 219.
Fig. 219.
