10
Fig. 12 for outdoor temperature/indoor humidity relationship in
auto humidification mode.
Humidification Off — The humidification function can be
turned off completely. This does not require changing existing
set points.
To Select Humidification — Press the softkey below the hu-
midification icon to bring up humidity select screen. Humidifi-
cation options are only available when in Heating mode. When
system is in AUTO mode, humidification options are available
if the last system operation was a call for heat.
The humidifier is actually turned on when humidity is 1%
below set point and turned off when it reaches 4% above set
point. This built-in hysteresis prevents humidification output
from toggling on and off when humidity level is near the set
point.
DEHUMIDIFICATION — Dehumidification is done only
during cooling. Depending on type of equipment used, com-
pressor speed, fan speed, set point adjustment, and equipment
cycling are modified to provide added dehumidification. A de-
humidification set point (separate from humidification set
point) is available to the user. It can range from 46% to 98%
relative humidity.
When actual humidity is higher than the set point, a dehu-
midification demand exists. The thermostat responds by acti-
vating the dry contacts (D1/D2 when enabled in Option 19).
The thermostat may also control the compressor and fan, de-
pending on equipment type and dehumidification selection
choice. The 3 available selections are described below. A man-
datory 30-second fan off delay will be enforced if there has
been a call for dehumidification during a cooling call. The
amount of extra dehumidification available is very dependent
on the type of equipment. Without a variable-speed fan, the
system’s ability to adjust dehumidification is very limited.
Normal Dehumidification Operation — When normal dehu-
midification is selected, the compressor will not turn on with-
out a cooling demand. If dehumidification demand exists while
cooling, dry contact will also be active. This output commands
variable-speed fans to reduce their airflow, which improves
water removal from the cooled air.
Cool to Dehumidification — The cool to dehumidification se-
lection tells the system to operate the compressor, within limits,
when there is a dehumidification demand even if there is no
cooling demand. The limits are that the system may overcool
up to 3 F, but no more, while attempting to satisfy a dehumidi-
fication demand. Within this 3 F range, there is an additional
balance between overcooling and humidity satisfaction.
When overcooling must occur, the dehumidification set
point is adjusted upward by 2% per degree of overcooling. For
example, a cooling set point of 76 F and a dehumidification set
point of 60% is equivalent to a cooling set point of 75 F and a
dehumidification set point of 62%. This dehumidification set
point change is internal to the thermostat and is not shown on
the display. See Fig. 12.
Fig. 12 —
Auto Humidification
Dehumidification Off — Dehumidification can be turned off
completely. This can be done without changing existing set
points.
To Select Dehumidification — Press the softkey below the
dehumidification icon button to bring up dehumidification se-
lections. Dehumidification options are only available when in
Cooling mode. When system is in AUTO mode, dehumidifica-
tion options are available if the last system operation was a call
for cooling.
If FAN is set for continuous operation (Fan On icon dis-
played), then the G output is turned off for 30 seconds at the
end of each cooling cycle as long as dehumidification demand
exists. Like humidification, dehumidification actions are initi-
ated when humidity is 1% above set point and are terminated
when humidity drops to 4% below set point. This prevents un-
necessary toggling of dehumidification actions when humidity
is near the set point.
Holiday —
A holiday selection is available specifically for
times when the space will not be occupied for an extended peri-
od. Holiday mode has an automatic hold, meaning that set
points are not affected by the programmed schedule. Holiday
mode is active for a specified period of time. While in Holiday
mode, the system provides temperature and humidity protec-
tion for the space in the selected mode, but not comfort. When
Holiday mode is active, an arrow will be displayed beside
“HOLIDAY” in the upper left corner of the display.
HOLIDAY SET POINTS — A special set of temperature and
humidity set points are active in Holiday mode. They are ad-
justable by the user and are used exclusively for Holiday mode.
They are remembered from one holiday selection to the next.
See Table 4 for default holiday values.
Table 4 – Holiday Default Values
HOLIDAY HUMIDIFICATION — Normal humidification
is available using holiday set points. Auto humidification is
available, adjusting its set point with outdoor temperature the
same as when occupied. Holiday humidification can be turned
off independently of occupied humidification. While setting
the Holiday set points, the Holiday humidification set point is
accessible by pressing the softkey below the humidification
icon when the box is around the heating set point.
HOLIDAY DEHUMIDIFICATION — Normal Dehumidifi-
cation, Cool to Dehumidification, and Dehumidification OFF
are all available in Holiday mode. The selection of one of these
can be different from that of occupied mode. Holiday dehumid-
ification selection and set points are remembered the next time
holiday is used. While setting holiday set points, the holiday
dehumidification set point is accessible by pressing the softkey
below the dehumidification icon when the box is around the
cooling set point.
OPERATION
Timers
FIVE-MINUTE COMPRESSOR TIMEGUARD — This
timer prevents compressor from starting unless it has been off
for at least 5 minutes. It can be overridden for 1 cycle by simul-
taneously pressing the OCCUPIED
and UP buttons.
CYCLE TIMER — Based on the selection of 4, 6, or 8 cycles
per hour, this timer is set to 15, 10 or 7.5 minutes. This time
must elapse from the start of one cycle before another cycle can
start. It serves to impose the cycles per hour limits. It can be
OUT
S
IDE TEMPERATURE (F)
-20 -15 -10 -5 0 5 10 15 20 25
3
0
3
5 40 45 50
45%
40%
3
5%
3
0%
25%
20%
15%
10%
5%
0%
T
ARGET HUMIDITY
9
8
7
6
5
4
3
2 1
a33-9173
MODE
AUTO SET POINTS
Fan
Follows setting of Option 37
Heat Set Point
55 F
Cool Set Point
85 F
Humidification Set Point
20
%
Dehumidification Set Point
98
%
