Lennox ComfortSense L7742U User manual

06/08 506062−01
*2P0608* *P506062-01*
E2008 Lennox Industries Inc.
Dallas, Texas, USA
COOLING
TUE OCT 23 1:15PM
STabbed user interface with
touch screen interaction
SHumidification measurement
and control
SWhite backlighted screen
with adjustable brightness
SProgrammable or
non−programmable options
SEquipment maintenance
reminders
SAutomatically changes
between heating cooling
HOMEOWNER’S MANUAL
ComfortSenset7000 Series
Model L7742U Touch Screen Programmable Thermostat
CONTROLS
506062−01
06/08
Supersedes 05/08
Table of Contents
ComfortSensetModel L7742U Thermostat 2. . . . . . . . . . . . .
Display Fields & Touch Screen Points 3. . . . . . . . . . . . . . . . . .
Home ScreenCurrent Conditions & Temperature Settings 4
Controlling the Heat/Cool Modes of Operation 5. . . . . . . . . . .
Controlling the Fan Operation 6. . . . . . . . . . . . . . . . . . . . . . . . .
Controlling the Schedule 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Schedule ScreenProgramming 8. . . . . . . . . . . . . . . . . . . . . .
Options screenReminders & User Settings 9. . . . . . . . . . . .
Humidification 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dehumidification 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Humiditrol
®EDA Accessory 12. . . . . . . . . . . . . . . . . . . . . . . . . .
Temporary Temperature ChangePause the Schedule 13. . .
Remote Outdoor Sensor 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Memory Protection 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Litho U.S.A.

506062−01 06/08 Page 2
ComfortSense Model L7742U Thermostat
The ComfortSensetModel L7742U thermostat is an electronic 7−day,
universal, multi−stage, programmable, touch screen thermostat. It also
offers enhanced capabilities including humidification / dehumidification
/ dewpoint measurement and control, Humiditrol®EDA (Enhanced De-
humidification Accessory) control, and equipment maintenance re-
minders.
SLarge, clear display with backlight shows the current and set tem-
perature, day/date/time, indoor relative humidity and outdoor tem-
perature (if optional outdoor sensor is used).
SDehumidification measurement and control
SHumiditrol
®EDA capability
SDew point adjustment control
SMenu−driven programming guides user through the scheduling
process showing only necessary information on each screen.
SErgonomic design.
SSmooth Setback Recovery starts system early to achieve set-
point at start of program period.
SCompressor short−cycle protection (5 minutes).
SReal−time clock keeps time during power failures and automati-
cally adjusts for daylight savings time and leap year.
SMaintenancereminders let user know when to service or replace
filters, humidifier pads, ultraviolet lamps, plus two user or installer
defined custom reminders.
SProgram Hold options allow user to override the program sched-
ule as desired by time and date.
SSelect individual days or groups of days to set programming.
SProgrammable fan offers increased air quality when combined
with a whole house air indoor air quality product.
SOutdoor temperature display (with optional outdoor sensor)
shows current outdoor temperature.
Your installer has set up your thermostat based on the type of heating
and cooling system and accessories that you thermostat connects to.
This booklet details user settings available to you that will give you as
much or little functionality and control as you want.

ComfortSensetModel L7742U Touch Screen 7−Day Programmable Thermostat
Page 3
Display Fields & Touch Screen Points
A Selection Tab touch screen points − Press to select HOME screen
(normal display). Press SCHEDULE for programming. Press OP-
TIONS to set alerts, service reminders, and other settings.
B
C
DH
J
I
G
F
E
F
A
Figure 1. Display fields and touch screen points
B MODE. Press to cycle through HEAT, COOL, AUTO
(autochangeover), OFF, EM HEAT (emergency heat) system
operations.
CFAN. Press to cycle through ON, CIRC (circulate), AUTO fan op-
erations.
D SCHED (schedule) controls whether or not the schedule is being
used. Press to change between ON and OFF.
EDisplay field shows the room temperature.
FDisplays the current operation’s SET AT point; if in AUTOchange-
over, both HEAT and COOL SET AT points are shown.
GUp/down arrow touch points. Press to adjust temperature up or
down; if in AUTOchangeover mode, 2 sets of up down arrows.
HDisplays different information depending on the tab selected:
DHOME tab: displays outdoor temperature (if outdoor sen-
sor is installed), indoor humidity (RH), which equipment is
running, hold settings information, service reminders, etc.
(see Page 4).
DSCHEDULE tab: displays the event being programmed
(see Page 7);
DOPTIONS tab: displays a scrolling list of adjustable pa-
rameters, including filter and service reminder periods,
etc. (see Page 9).
IUp/down arrow touch points for scheduling adjustments and for
making setting adjustments on the OPTION screens:
DHOME screen: only accessible except when executing a
HOLD SETTING.
DSCHEDULE and OPTION screens: used to adjust sched-
ule and option settings.
JDynamic touch points − not visible in HOME screen unless execut-
ing a HOLD SETTING. For SCHEDULE and OPTIONS settings,
these boxes appear and change depending on the selection. See
the schedule (Page 7) and options (Page 9) sections for de-
tails.

506062−01 06/08 Page 4
Home ScreenCurrent Conditions & Temperature Settings
OUTDOOR TEMP 95F
TUE OCT 23 1:15PM
INFORMATION
DISPLAY AREA
Figure 2. Home Screen
The HOME screen (figure 2) displays indoor temperature and outdoor
temperature (if outdoor sensor is installed and if turned on in user set-
tings). Other system operational information, such as indoor relative
humidity (if turned on in user settings), dehumidifying, cooling or heat-
ing, will alternately be displayed in the information display.
The home screen displays temperature and the temperature settings in
large fonts. The INFORMATION DISPLAY shows the present day,
time, and operational information in a smaller font.
The menu tabs along the top of the screen are used to access the
SCHEDULE screen (for program setup) and the OPTIONS screen (to
access user/installer settings including, change to 24 hour clock,
change Fahrenheit to Celsius, set filter and service reminders, and
many other settings.
Equipment operation information appears in the boxes along the left
side of the home screen to indicate fan operation setting, cooling or
heating equipment operation setting, and whether or not scheduled pro-
gramming is ON or OFF. From these boxes, users can change the unit’s
mode to HEAT, COOL, AUTO (autochangeover − default), EM HEAT
(emergency heat − for heat pump applications including dual fuel and
HP with Electric Heat), or OFF.
Also, the user can change the fan between ON (fan runs continuously
whether or not cool or heat equipment is running), AUTO (fan runs ac-
cording to the schedule), or CIRC (circulate − user sets percentage of
fan run time).
The user can also decide whether or not to operate the unit per the pro-
grammable schedule, or in a manual mode using the SCHED box.

ComfortSensetModel L7742U Touch Screen 7−Day Programmable Thermostat
Page 5
Controlling the Heat/Cool Modes of Operation
Press the screen anywhere − the first press turns on the backlight.
While in the HOME screen, press MODE field; repeated
presses scroll through all the modes. AUTO
(autochangeover) mode allows the thermostat to switch
between Heating and Cooling, whichever mode is dictated by
the indoor temperature. EM HEAT (emergency heat)
bypasses the first stage of heating (any stage[s] of heat pump
heating) and goes directly to the heat stage used for
maximum heating to more quickly warm a very cold house.
When the indoor temperature decreases or increases, the HEATING or
COOLING cycle will turn on based on the displayed mode. When the
HVAC system is on, the information display (shown in figure 3) will dis-
play one or several operational messages (listed in the table below). If
the outdoor sensor is connected, and is turned on in both installer and
user settings, outdoor temperature will be included in the displays. The
table below summarizes the information messages.
When the faults, errors, and service information displays appear, action
boxes will appear under the second line entries, REMIND, CLEAR,
SERVICE, or RESET. Press the box to perform the action.
Figure 3. Selecting Mode of Operation
Information Displays:
Faults, Errors and Service Information Operating Information
TEMP SENSOR ERROR, MEMORY ERROR
CALL FOR SERVICE
Top line: fault./error
Bot. line: action
SET DATE/TIME
Default DATE/TIME (MON JAN 1 12:00 PM) [First time start up message]
NO OUTDOOR SENSOR
REMIND CLEAR SERVICE
Top line: fault./error
Bot. line: action
HEATING, COOLING, HUMIDIFYING, DEHUMIDIFYING,
SYSTEM OFF, OUTDOOR TEMP xxF, INDOOR RH xx%,
MON SEP 24 3:OO PM
Top line: operation messages
Bottom line: date and time
REPLACE: MEDIA FILTER; UV LAMP; HUM PAD; METAL INSERT
REMIND RESET
Top line: serv. req’d
Bot. line: action
SCHEDULE ON, SCHEDULE OFF, WAIT,
FAN ON, FAN CIRC
MON SEP 24 3:OO PM
Top line: add’l operation msgs
Bottom line: date and time
ROUTINE SYS CHECK−UP
REMIND RESET
Top line: serv. req’d
Bot. line: action
HOLD SETTING UNTIL PRESS SCHED TO
MON SEP 24 3:OO PM RESUME PROGRAM
[Alternating messages during
a held schedule]
NO OUTDOOR SENSOR, HUM SENSOR ERROR, HVAC ERROR DETECTED
REMIND SERVICE
Top line: fault./error
Bot. line: action

506062−01 06/08 Page 6
Controlling the Fan Operation
Press the screen anywhere − the first press turns on the backlight.
From the HOME screen press the FAN field;
repeated presses scroll through all the modes,
AUTO, ON, and CIRCulate.
Fan Modes
Fan Modes (ON, AUTO and CIRC) can be changed either from HOME
screen or from the SCHEDULE screen when programming the thermo-
stat. The three settings work like this:
SIf FAN mode displays AUTO on the HOME screen, this means
that the FAN is following the schedule.
SIf FAN mode displays ON on the HOME screen, this means that
the fan is NOT following the schedule and that the fan will run con-
tinuously until it is changed from the HOME screen.
SIf FAN mode displays CIRC (circulate) on the HOME screen, this
means that the fan is NOT following the schedule and that the fan
will cycle during periods of equipment inactivity. The cycle time is
dependant on user settings FAN CIRCULATE (Page 10).
If FAN mode displays AUTO (HOME) and ON or CIRC was selected
during scheduling for the current period, the thermostat will indicate the
current fan mode in the information display (FAN ON or FAN CIRC).
In the CIRC mode, the user can cycle the fan for a programmed
percentage of active time per hour, during periods of equipment
inactivity (i.e., heating or cooling equipment not running). The fan is ON
for 5 minutes at a time. The user may change the percentage of ON time
that the fan is on (see FAN CIRCULATE [Page 10]):
Fan Program
The user can program the fan to be ON, AUTO, or CIRC during a
program event period. While scheduling the event, if the fan is set to
ON, it will remain on during the entire event. If it is set to CIRC, it will
circulate during equipment inactivity per user programmable cycles
(see FAN CIRCULATE, Page 10). If set to AUTO, the fan will come with
the equipment to serve the heating/cooling demand and go off
accordingly. Using the fan continuously or circulating the fan during the
occupied times may better improve the indoor air quality.
NOTE − When the HOME screen FAN mode is changed to ON or CIRC,
whatever was scheduled is ignored − the fan will either be ON or it will
CIRCULATE per the user−programmed intervals (USER SETTINGS −
FAN CIRCULATE [Page 10]). When FAN − AUTO is selected in the
HOME screen, the schedule IS followed.

ComfortSensetModel L7742U Touch Screen 7−Day Programmable Thermostat
Page 7
Controlling the Schedule
Turn schedule on and off
Press the screen anywhere − the first press turns on the backlight.
From the HOME screen press SCHED; repeated
presses toggle the schedule ON and OFF. If ON,
the system follows the program developed by the
user (Page 7). If OFF, the system operates as a
non−programmable thermostatthe user must
make changes when desired. The
autochangeover feature will continue to operate
based on the manual user inputs.
Schedule screen
Press the SCHEDULE tab along the top of the screen. The display
changes to programming mode (figure 4) and shows the current set-
tings. The thermostat may be programmed for two or four (default)
events per day. The names for the events are: WAKE, LEAVE, RE-
TURN, and SLEEP. The selected time for an event to occur is based on
when you want the event to begin. Four events are common for work-
ing households.
Programming may be performed in groups of days or individual days,
as follows:
AMON TO SUN − allows every day to be set the same.
BMON TO FRI (weekday programming) and
SAT TO SUN (weekend programming).
CMONDAY through SUNDAY allows individual days of the
week to be programmed separately.
NOTE − After using one of the groups of days described above, the
program does allow you to subsequently change individual days to
suit your needs.
To select the groupings or individual days, scroll through the selections
pressing NEXT.
Programming Complexity
The programming process for groups of days or individual days is the
same, except in the amount of times required to go through the process.
Full WeekThe least complex program is the full week MON TO
SUN" program, wherein the events for every day of the week are the
same. This requires one time through the event programming process.
Work WeekNext in complexity to the full week program is the work
week program wherein the events are set for a typical work week (MON
TO FRI) and different events are set for the weekend (SAT TO SUN).
This requires two times through the events.
Day by DayMost complex because this requires going through the
programming process 7 times.
WAKE PERIOD BEGINS
5:OOAM
Figure 4. Schedule Screen

506062−01 06/08 Page 8
Schedule ScreenProgramming
Days & Events Programming process
Action Display shows...
1 Press SCHEDULE tab SCHEDULE screen
2 Press EDIT UP/DOWN arrows on right−hand
side of screen; EDIT changes to
CANCEL
3 Press NEXT to highlight the de-
sired grouping of days
Days change to match selected
group, e.g. MON TUE WED THU FRI
4 Press an event: WAKE (default),
LEAVE, RETURN, & SLEEP to
select for programming
Filled triangle above event
indicates which event is selected
for change
5 Press UP/DOWN arrows to
select desired temperature
After change is made, SAVE
appears in the bottom right−hand
of the screen
6 Press FAN repeatedly to select
desired fan mode
Fan indicator displays selection
(ON, AUTO, or CIRC)
7 Press UP/DOWN arrows to
adjust start time for
selected event
Information area displays start
time
8 Repeat steps 4 − 7 for all remaining events.
(If you selected other than MON TUE WED THU FRI SAT SUN), continue;
otherwise, skip to step 11.
9 Press NEXT for the next group
or the next day
Days change to match selected
group, e.g. SAT SUN
10 Repeat steps 3 through 8 for the remaining days, if necessary.
11 Press SAVE when all events and
days are programmed as desired
The changes are made and the
schedule screen reappears.
24
6
1
7
5
WAKE PERIOD BEGINS
5:OOAM
911
3
Figure 5. Programming days and events

ComfortSensetModel L7742U Touch Screen 7−Day Programmable Thermostat
Page 9
Options ScreenReminders & User Settings
CLEAN button
When you select the OPTIONS tab, two buttons appear near the bot-
tom of the screen labeled CLEAN and ENTER. Press the CLEAN but-
ton to deactivate the touch" points for 30 seconds. Clean the screen
with a soft cloth moistened with a mild glass cleaning solution.
The Options screen provides user and installer access to the various
features for setup and access to the reminders. Installer settings
MUST BE SET BY A QUALIFIED PERSON.
REMINDERS
USER SETTINGS
Reminders [OPTIONS TAB > REMINDERS > [ENTER] ]
Set timers from 1 to 24 months in either calendar time or system run
time. Reminders appear when it is time to service the following (for
more details on REMINDERS, see Page 14):
REPLACE MEDIA FILTER
DUE THU APR 1O O8
REPLACE METAL INSERT
DUE SUN MAR 16 O8
REPLACE HUM PAD
DUE THU APR 1O O8
REPLACE UV LAMP
DUE SUN MAR 16 O8
ROUTINE SYS CHECK−UP
DUE IN 216O HOURS
CUSTOM REMINDERS
DUE SUN MAR 16 O8
User Settings [OPTIONS TAB > USER SETTINGS > [ENTER] ]
Press the OPTIONS tab; use the arrows to select USER SETTINGS.
Press ENTER.
USER SETTINGS
INSTALLER SETTINGS
The following items are available for modifying. Follow the instructions
for each parameter.
DATE/TIMESet month, day, year, hour, and minute using DATE/
TIME option. Select DATE/TIME; press ENTER. Small, filled up-arrow
is selected column; use up/down arrows to adjust; press box below
each small up-arrow to select each column. Adjust; press SAVE.
FEB 11 2OO8 12PM 49
MON DAY YR HR MIN
CANCEL||||||SAVE|
F/Cdefault is Fahrenheit; to change to Celsius, scroll to F/C; press
ENTER. Use arrows to change to C; press SAVE.
F OR C
DEFAULT(F) F
12 OR 24 HOUR clockdefault is 12H; to change, scroll to 12 OR 24
HOUR; press ENTER. Use arrows to change to 24H; press SAVE.
12 OR 24 HOUR
DEFAULT(12HR) 12H

506062−01 06/08 Page 10
Options ScreenReminders & User Settings (continued)
EVENTS DAILY 2 OR 4default is 4; to change, scroll to EVENTS
DAILY 2 OR 4; press ENTER. Use arrows to change to 2; press SAVE.
EVENTS DAILY 2 OR 4
DEFAULT(4) 2
DISPLAY INFOcontrols some of what is displayed in the field below
the temperature and above the time on the HOME screen; it may dis-
play OUTDOOR TEMP, INDOOR RH (relative humidity), or neither if
TEMP and RH are turned OFF. Scroll to DISPLAY INFO; press EN-
TER. Use arrows to select TEMP or RH; press ENTER.
DISPLAY INFO
OUTDOOR TEMP
INDOOR RH
NOTE − When accessing the OUTDOOR TEMP option OUTDOOR
SENSOR REQUIRED" will display if not turned ON by the installer.
Also, the home screen will display NO OUTDOOR SENSOR" if the
physical sensor was not installed.
For INDOOR RH, use arrows to select ON or OFF; then press SAVE.
INDOOR RH
DEFAULT(OFF) ON
For OUTDOOR TEMP, select ON or OFF; then press SAVE.
OUTDOOR TEMP
DEFAULT(OFF) ON
HUMIDITROL ADJUSTSee Humidification − Humiditrol®EDA sec-
tion (appears only when Humiditrol setup in installer settings).
FAN CIRCULATEAs an option to running the fan all the time, CIRCu-
late allows the user to decide how much the fan will run during periods of
equipment inactivity. The fan ON time is always set to 5 minutes. This
option will cause the fan to come on more or less frequently. The default
is 35%; to change, scroll to FAN CIRCULATE; press ENTER. Use ar-
rows to change to 15, 25, or 45%; press SAVE.
FAN CIRCULATE
DEFAULT(35%) 25%
15% (9 minutes fan runtime per hour)
25% (15 minutes fan runtime per hour)
35% (21 minutes fan runtime per hour)
45% (27 minutes fan runtime per hour).
COOLING LIMITdefault is 45º; to change to any degree between
45ºF and 99ºF, scroll to COOLING LIMIT; press ENTER. Use arrows to
change to desired temperature; press SAVE.
COOLING LIMIT
DEFAULT(45°F) 55°F
HEATING LIMITdefault is 90º; to change to any degree between
45ºF and 90ºF, scroll to HEATING LIMIT; press ENTER. Use arrows to
change to desired temperature; press SAVE.
HEATING LIMIT
DEFAULT(9O°F) 85°F
SECURITY LOCKdefault − no locks at all − this provides two methods
of locking the thermostat − NO prevents others from making any
changes at all or YES prevents others from making changes other than
temperature setpoints. Scroll to SECURITY LOCK and press ENTER;
ALLOW TEMP ADJUST screen appears; press box below YES or NO.
The ENTER LOCK CODE screen appears.
ALLOW TEMP ADJUST
YES NO
ENTER LOCK CODE
OO O
|| |||
To enter lock code, press box below each small up-arrow to select each
column. Use up/down arrows to enter a number, then press the box be-
low the next number and repeat to enter a 3-digit lock code; write down
the number for future reference; press SAVE.
NOTE − If the user settings security code is forgotten or misplaced for
some reason, the universal code 864" may be used to unlock.