Lennox L7742U Programming And Application Manual page 22

Dehumidification
(continued)
ComfortSenset Model L7742U thermostat operation
with Humiditrol enabled
Cooling only Dehumidification will only occur if:
S
a dehumidification demand is present,
S
a cooling demand is not present,
S
outdoor temperature is less than 95ºF,
S
indoor temperature is not cooler than 65ºF or cooler than the heat-
ing setpoint + 2ºF (IF the difference between cooling and heating
setpoints is greater than the deadband).
In this case, 24 VAC is removed from the D" terminal and Y1 & Y2"
terminal (if available) becomes activated with 24VAC. This will cycle the
indoor variable speed motor to the dehumidification speed and cycle Y2
ON" to the outdoor unit. Cooling calls have priority over Humiditrol
calls.
Heating only Thermostat will cycle heating ON" and OFF to main-
tain heating setpoint. Dehumidification functions are disabled.
Autochangeover Dehumidification will only occur if a dehumidifica-
tion demand is present, a cooling demand is not present, outdoor tem-
perature is less than 95°F, indoor temperature is above 65°F and the
indoor temperature is not cooler than 2ºF above heating setpoint.
In this case, the 24 VAC is removed from the D" terminal and the Y1 &
506061−01 06/08
Y2" terminal (if available) becomes activated with 24VAC. This will
cycle the indoor variable speed motor to the dehumidification speed
and cycle Y2 ON" to the outdoor unit. Cooling calls have priority over
®
Humiditrol calls. Humiditrol® mode is allowed to overcool up to 2°F
above the heating setpoint.
Note: If the last thermostat demand was a heating demand, the thermo-
stat does not require a cooling demand before Humiditrol
Humidification Sensor Fault
If the humidification sensor fault occurs, then the H terminal becomes
inactive, and the D terminal goes to 24V.
NOTE − Dew point adjust is only available when an outdoor sensor is
attached.
®
Other Humiditrol EDA Notes:
If the outdoor sensor is disconnected while HUMIDITROL is enabled,
®
the thermostat will not allow operation in dehumidification mode.
Set point range: 45 to 60% Relative Humidity (RH). Factory default −
50%.
Relative Humidity controls to within 2% on either side of RH set point.
When the D" terminal is activated with 24VAC, dehumidification is in-
active.
BASIC, PRECISION and HUMIDITROL modes are deactivated by de-
fault from the factory.
As a precaution, regardless of how low the heating setpoint has been
®
set, Humiditrol dehumidification is inhibited below 65ºF indoor temper-
ature.
Page 22
®
operation.