Lennox ComfortSense L7742U, Programming And Application Manual, Page: 2 / 44

506228−01 05/09
Page 2
Table of Contents
ComfortSense
®
Model L7742U Thermostat 3 . . . . . . . . . . . . .
Features 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Touch Screen Display 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Home ScreenCurrent Conditions & Temp. Settings 5 . . . . .
Controlling the Heat/Cool Modes of Operation 6 . . . . . . . . . . .
Controlling the Fan Operation 7 . . . . . . . . . . . . . . . . . . . . . . . . .
Controlling the Schedule 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Schedule TabProgramming 8 . . . . . . . . . . . . . . . . . . . . . . . . .
Options TabReminders & User Settings 10 . . . . . . . . . . . . . . .
Options TabInstaller Settings 13 . . . . . . . . . . . . . . . . . . . . . . . .
Resetting Program to Factory Conditions 16 . . . . . . . . . . . . . . .
EPA ENERGY STAR
®
Recommended Setpoints 17 . . . . . . . . .
Humidification 19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dehumidification 21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Humiditrol
®
Enhanced Dehumidification Accessory (EDA) 22 .
Stage Delay and Differential Settings 24 . . . . . . . . . . . . . . . . . . .
Temporary Temperature Change (Pausing the Schedule) 31 . .
Optional Remote Outdoor Sensor 32 . . . . . . . . . . . . . . . . . . . . . .
Service Reminders 33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unit Part and Serial Numbers 33 . . . . . . . . . . . . . . . . . . . . . . . . .
Memory Protection 33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Appendix A. Flow Diagrams & Wiring Diagrams 34 . . . . . . . . . .
Appendix B. Diagnostic Info. & Available System Settings 39 .
NOTE − This thermostat is equipped with automatic compressor
protection to prevent potential damage due to short cycling or extended
power outages. The short cycle protection provides a 5−minute delay
between heating or cooling cycles to prevent the compressor from be-
ing damaged.
CAUTION
This is a 24VAC low−voltage thermostat. Do not install on volt-
ages higher than 30VAC.
Do not short (jumper) across terminals on the gas valve or at the
system control to test installation. This will damage the thermo-
stat and void the warranty.
WARNING
Always turn off power at the main power source by switching
the circuit breaker to the OFF position before installing or re-
moving this thermostat.
All wiring must conform to local and national building and elec-
trical codes and ordinances.
Do not switch system to cool if the outdoor temperature is be-
low 45°F (7°C). This can damage the cooling system.
These instructions are intended as a general guide and do not super-
sede local codes in any way. Consult authorities having jurisdiction be-
fore installation.
Check thermostat for shipping damage. If you find any damage, imme-
diately contact the last carrier.