Lennox Furnace Thermostat Manual

The Lennox Furnace Thermostat is a precision temperature control device designed for Lennox heating systems, featuring programmable settings, temperature scheduling, system mode selection, fan control, temperature hold functions, and advanced diagnostics. Compatible with Lennox single-stage and multi-stage furnaces, this thermostat offers intuitive operation with backlit display, filter change reminders, and system status indicators. Below are key sections for installation, programming, operation, troubleshooting, and maintenance.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting to Furnace System 7. Programming and Scheduling 8. Advanced Features 9. Care & Maintenance 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: Digital display with backlight, mode selection buttons, temperature adjustment, programming interface, system status indicators, wiring terminals.

Feature	Description
Digital Display	Backlit LCD showing temperature and system status
Programmable Settings	7-day programming with multiple temperature periods
System Mode Selection	Heat, Cool, Auto, Off modes
Fan Control	Auto and On settings for furnace fan
Temperature Hold	Temporary override of programmed schedule
Filter Change Reminder	Programmable alert for furnace filter replacement
System Status Indicators	LED indicators for heating, cooling, fan operation
Wiring Terminals	Standard thermostat terminals (R, W, Y, G, C)
Battery Backup	Maintains settings during power outages
Diagnostic Mode	System error codes and troubleshooting information

Installation

Turn off power to furnace before installation. Mount thermostat on interior wall away from direct sunlight and drafts.

Remove old thermostat: Turn off furnace power, remove cover, label wires.
Mount new base: Level and secure mounting plate to wall.
Connect wires: Match labeled wires to corresponding terminals (R, W, Y, G, C).
Attach thermostat: Snap onto mounting plate.
Restore power: Turn furnace power back on.

WARNING! Always turn off furnace power before installation to prevent electrical shock. Ensure proper wire connections.

First-Time Setup

After installation, configure basic settings for optimal operation.

Set date and time: Access time settings in programming menu.
Configure temperature units: Select Fahrenheit or Celsius.
Set filter change interval: Program reminder for 1-12 months.
Calibrate temperature: Adjust if needed for accuracy.
Test system: Verify heating and fan operation.

CAUTION! Ensure furnace power is restored before testing. Follow manufacturer wiring diagrams.

Specifications

Power Requirements: 24VAC from furnace or battery backup
Temperature Range: 40°F to 90°F (4°C to 32°C)
Display: Backlit LCD with temperature and status icons
Programming: 7-day, 4 periods per day
Compatibility: Lennox single-stage and multi-stage furnaces
Wiring: Standard 5-wire terminal block
Battery Backup: 2 AA alkaline batteries (not included)
Operating Environment: 32°F to 122°F (0°C to 50°C)
Dimensions: 4.5" W x 3.25" H x 1" D

Controls and Settings

Front panel controls: MODE button, FAN button, UP/DOWN temperature arrows, HOLD button, MENU button.

Display Icons: Heating flame, cooling snowflake, fan, battery low, filter change reminder.

Basic Settings: Temperature setpoint, system mode (Heat/Cool/Auto/Off), fan mode (Auto/On). Advanced Settings: Program schedule, temperature differential, filter timer, display brightness, temperature calibration, system test mode.

Connecting to Furnace System

Standard 5-wire connection: R (24V power), W (heat), Y (cool), G (fan), C (common).

Turn off furnace power at circuit breaker.
Remove old thermostat and label all wires.
Connect wires to matching terminals on new thermostat base.
Secure thermostat to mounting plate.
Restore furnace power and test operation.

Tip: Take photo of old thermostat wiring before disconnecting for reference.

Programming and Scheduling

Create custom temperature schedules for energy efficiency.

Access programming: Press MENU, select PROGRAM.
Set wake time: Morning temperature for each day.
Set leave time: Temperature when home is unoccupied.
Set return time: Evening temperature when home.
Set sleep time: Night temperature setting.
Copy schedule: Apply same schedule to multiple days.
Temperature hold: Press HOLD for temporary override.
Cancel hold: Press HOLD again to resume schedule.

WARNING! Do not set temperature below 55°F in winter to prevent pipe freezing.

Advanced Features

Filter Change Reminder: Program interval (1-12 months) in maintenance menu. System Diagnostics: Error codes display for furnace issues. Adaptive Recovery: Learns system timing for temperature reach. Temperature Differential: Adjust minimum temperature variation before system activates.

Care & Maintenance

Clean display with soft, dry cloth. Replace batteries annually. Keep area around thermostat clear for proper temperature sensing.

CAUTION! Do not use liquids or cleaners on display. Turn off power before any maintenance.

Regulatory Information

UL Listed: Complies with UL 873 standards for temperature indicating and regulating equipment. FCC Part 15: Class B digital device compliant. Manufactured to Lennox quality standards. For technical support, contact Lennox Customer Service at 1-800-9-LENNOX or visit www.lennox.com.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Blank display	Power loss/dead batteries	Check furnace power; replace batteries; verify wiring.
Furnace not heating	Thermostat settings/system issue	Set to HEAT mode; check temperature setting; verify furnace power.
Incorrect temperature	Location/calibration issue	Relocate away from heat sources; calibrate temperature sensor.
Fan not operating	Settings/furnace issue	Set fan to ON; check furnace filter; verify G wire connection.
Error codes displayed	System fault	Note error code; consult furnace manual; contact service technician.

Reset: Remove batteries and disconnect power for 30 seconds to reset.

Service: 1-800-9-LENNOX; www.lennox.com