Honeywell THM5421C1008 Benutzerhandbuch

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The System key selections vary based on your heating and/or 

cooling system type.

Heat — Thermostat controls the heating system.

Off — Both heating and cooling systems are off.

Cool — Thermostat controls the cooling system.

Auto — Thermostat automatically changes between heating 

and cooling operation, depending on indoor temperature.

Em. Heat — Emergency heat cycles to maintain temperature. 

Compressor is locked out and auxiliary heat turns on as 

needed.

The Fan key selections vary based on the heating and/or 

cooling system type.

On — Fan runs continuously. Use this setting for improved air 

circulation or for more efficient central air cleaning.

Auto — fan follows the fan program schedule.

Circ — fan runs randomly approximately 35% of the time. Use 

this setting for improved air circulation or for more efficient 

central air cleaning when you do not want the fan running 

continuously.

The VisionPRO

®

 IAQ Touchscreen Thermostat reads the 

inside humidity level and allows for a humidification setting with 

or without frost protection. Humidification will only take place 

when the thermostat is in Heat mode or in Auto mode when the 

previous call was a call for heating.

WITH FROST PROTECTION
Controlling humidification with frost protection requires an 

outdoor temperature sensor. The Frost Index (scale 1–10) will 

limit the amount of humidity added to the air based on outdoor 

temperature, with 1=most dry and 10=most humid. This 

prevents frost from accumulating on windows.

WITHOUT FROST PROTECTION
The frost setpoint is not displayed, but a humidity setpoint can 

still be set.

1. Press the More key until the inside humidity level set-

point is shown.

2. Use Up and Down arrow keys, located to the right of the 

humidity setpoint, to set desired humidity level.

3. Press Done key.

The VisionPRO

®

 IAQ Touchscreen Thermostat reads the 

inside humidity level and allows for a dehumidification setting, 

and can be set to dehumidify using the air conditioner or a 

whole house dehumidifier.

The set range for dehumidification is 40 to 80%, and can be set 

in 5% increments. The thermostat must be in Cool mode or 

Auto mode when the previous call was a call for cooling.

Dehumidifying in this manner runs the air conditioner longer 

than simply cooling the house would require, and can be set to 

run 1, 2, or 3°F below the temperature setpoint. This feature is 

called Dehumidification Droop Control.

NOTE: You must use this setting if:

—

No powered, whole house dehumidifier is present, 

and

—

The system uses the air conditioner as the

dehumidifier.

MORE

DONE

Inside

 

Humidity

M23518

HUMIDIFIER

CANCEL

MORE

DONE

CANCEL

DEHUMIDIFIER

M23496

DONE

CANCEL

DEHUMIDIFIER

M23514