Honeywell THM5421C1008 Benutzerhandbuch

21

68-0287—1

DEHUMIDIFICATION DROOP CONTROL
In extremely high humidity conditions, the thermostat keeps 

the air conditioner running (energizing Y/Y2 and G) for up to 

3°F below the temperature setpoint. It does this while trying to 

achieve the desired humidity setpoint and balancing that with 

the temperature setpoint. The thermostat controls up to 3° F 

below the temperature setting until either the humidity setpoint 

is satisfied or conditions change.

Controls humidity levels in the house by dehumidifying without 

the use of the air conditioner. This setting requires a dedicated 

unit for dehumidification. Dehumidification with a whole house 

dehumidifier will take place when the thermostat is in the Cool, 

Off, Auto, Heat or Em.Heat modes. If the system is installed 

with a whole house humidifier, dehumidification with a whole 

house dehumidifier will only take place when the thermostat is 

in Cool, Off or Auto modes (Auto only if the previous call was a 

call for cooling).

When controlling a whole-house dehumidifier the user can 

toggle between auto (dehumidify when needed based on 

setpoint and current humidity level) and off (see Fig. 29).

1. Press the More key until the inside humidity percent and 

dehumidification setpoint are shown.

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

dehumidifier setpoint, to set desired humidity level for 

dehumidification in the summer.

3. Press Done key.

Ventilation setup options include ISUs 400, 401, 402, 403, and 

404. Combined, these will determine a percentage of 

maximum ventilation limit. The thermostat will calculate 

whether or not this level of ventilation meets ASHRAE 

standard 62.2. If ASHRAE 62.2 is met a P will appear in the 

display above the setup number. If ASHRAE 62.2 is not met an 

F will appear in the display above the setup number.

Passing ASHRAE 62.2 is only applicable when vent is running. 

For example, if installer has set to not vent during sleep period, 

ASHRAE 62.2 would be met at all times except during sleep 

period.

Ventilation occurs two ways:

AUTOMATIC
Uses installer setup to determine amount of ventilation 

required based on house and equipment size. To disable 

automatic ventilation, switch the ventilation setting to Off. The 

user can still use the timer to request ventilation.

ON DEMAND
User can also set a vent timer that will circulate fresh air into 

the home for a set period of time from 20 to 180 minutes in 20-

minute increments. The vent timer is enabled whether 

ventilation is set to “Auto” or “Off.”

VENTILATION IN HIGH HUMIDITY CONDITIONS (SETUP FUNCTION 0406)
If Ventilation Control is available (setup function 0400 set to 1 

or 2), this allows the ventilation equipment to turn on if the 

humidity rises approximately 10% above the RH setting in 

heating mode to exhaust the extra humidity.

A red LED indication is located in the upper right corner of the 

thermostat. It is only visible when lighted.

When the L terminal is wired to an equipment monitor, the LED 

signals when a check or fail signal is sent to the thermostat 

from the system. This is operational in the Heat, Off, Cool or 

Auto positions.

MORE

DONE

CANCEL

DEHUMIDIFIER

M23515

DONE

M23520

MORE

DONE

CANCEL

VENT

M23519