Memory Protection; Date Code & Serial Number - Lennox ComfortSense L7742U Programming Manual

In many applications, the ComfortSenset Model L7742U
thermostat will display the temperature sensed by the
remote outdoor sensor. With the heat pump system, the
remote outdoor sensor helps determine when to turn on
the second stage of heating for optimal comfort.
When the outdoor sensor is connected, the temperature
displays in the information display area (below the indoor
temperature display).
Installing Remote Outdoor Sensor
Install the remote outdoor sensor on a northern wall of the
home, away from direct sunlight or other heat sources that
may affect its sensitivity.
IMPORTANT
The outdoor sensor must be connected to operate
a system with a Humiditrol

Memory Protection

The thermostat stores all the information concerning its
programming (state, mode, program information, last tem-
perature measured) in a nonvolatile memory.
This function avoids the loss of the state of the thermostat
when a power−down occurs. The only thing that might be
lost is the clock, however, a lithium battery will remember
clock information for as long as it has charge (approxi-
mately 30 days). When power down occurs (due to a pow-
er outage) the thermostat is able to switch off all relays.
The O and B relay will maintain their last state.
Service Reminders
The user may turn on and turn off the following service re-
minders (all of which default to OFF) in either chronological
time and/or run time and may be reset (to default) or
delayed (snooze) at any time:
®
accessory.
Replace Media Filter
Routine Sys (System) Check−up
Replace Hum (Humidifier) Pad
Replace UV Lamp
Replace Metal Insert for Pure Air
NOTE − When chronological time is selected, the timer
runs based on the calendar. When time is selected in run
time, the timer runs based on the time the specific output is
ON (e.g. Fan output for Media Filter).
When the reminder time (either calendar time or run time)
has elapsed, the system displays a screen from which the
user can either RESET or DELAY the reminder.
The user can reset the timer either before is has expired
(i.e. reminder is set to 6 months and user decides to reset it
to 6 months or change it to different value at the end of 4th
month) or when the time has expired and a reminder mes-
sages has been displayed.
When a reminder is turned off, the indicator will not be acti-
vated even if the timer is expired. Note that setting filter re-
minder to 0 (OFF) will not reset the timers, but will deacti-
vate the filter indicator.
In the case of a power interruption:
S
lithium battery has charge the total accumulated
time is maintained (i.e. the counter does not recycle to
zero).
S
lithium battery has NO charge the due date of re-
minders is maintained.
Unit Part (Catalog) & Serial Numbers
A label on the back of the thermostat is visible through an
opening in the back of baseplate. This identifies the Len-
nox Catalog Number, Part Number and Serial Number.
Separate the baseplate from the thermostat to see addi-
tional manufacturing information.
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ComfortSenset Model L7742U Touch Screen
7−Day Programmable Thermostat