Lennox S40 Assembly instructions

508222-01 10/2022
Copyright 2022©Lennox Industries Inc.
Dallas, Texas, USA
Lennox®S40 Smart Thermostat
Installation and Setup Guide
Dallas Home
Temp Status My Home
Heat to Cool to
68 75
72
Feels Like
60%
Away Weather
TM
TM

2
Table of Contents
Shipping and Packing List.........................................3
Thermostat External Components............................3
External Component Locations.................................3
Reboot Button, Micro USB Connection and
Built-in Sensors.........................................................3
Lennox Smart Applications .......................................3
Lennox®Smart Thermostat App (Homeowner).........3
Lennox®Smart Technician App (Installer).................3
Downloading Lennox Smart Applications ...............4
Lennox Smart Technician App ..................................4
Lennox Smart Thermostat App .................................4
Service and Support - Service Access and
Remote In ....................................................................4
Thermostat Terminal Information .............................4
Wiring Diagrams .........................................................5
Communication Wiring Options ................................5
Minimizing Electrical Noise .......................................6
Application Specic Wiring Diagrams .......................7
Dual Fuel and Ventilation Diagrams .......................13
Installation Considerations .....................................13
Thermostat Installation............................................13
Installation...............................................................13
Installing Thermostat to Sub-Base..........................14
Commissioning using the Lennox® Smart
Technician ................................................................15
Mobile Device Operating System Requirements ....15
Establishing a Direct Wireless Connection to
the Thermostat........................................................15
Commissioning Screens .........................................16
Servicing using the Lennox Smart
Technician App .........................................................16
Multiple Thermostats - Group ID.............................17
Commissioning Using the Thermostat...................17
Dealer Information ..................................................17
General Settings .....................................................17
Equipment Found Screen .......................................18
Communicating Equipment Found ..............................18
Adding / Removing Non-Communicating Equipment ..18
Lennox Smart Zoning (Optional).............................18
Reminders...............................................................19
System Name .........................................................19
Commissioning Completion ....................................19
Helping Homeowner Connect Thermostat to
the Home Wi-Fi .........................................................19
Wi-Fi Limitations .....................................................19
Home Wi-Fi Access Point is Visible ........................19
Home Wi-Fi Access Point is Hidden .......................19
Wi-Fi Terminology ...................................................20
Received Signal Strength Indication (RSSI) ...........20
Service Center ..........................................................21
Notications ............................................................21
Equipment Settings.................................................21
Thermostat ..................................................................21
Air Handler ..................................................................32
Furnace .......................................................................33
Heat Pump ..................................................................34
Air Conditioner.............................................................36
Zoning Control.............................................................36
PureAir S .....................................................................36
Add/Remove Equipment .............................................37
Add Device ..................................................................37
Smart Devices Network...........................................37
Managing Smart Devices ........................................37
Lennox Smart Room Sensor...................................37
Lennox Smart Air Quality Monitor ...........................37
Lennox Wireless Extender ......................................38
Reset ...........................................................................38
Information..............................................................38
Tests .......................................................................38
Diagnostics .............................................................39
Installation Report...................................................39
Connect to Lennox Smart Technician App..............39
Displaying Outdoor Temperature (Sensor)
and Indoor Humidity on the Thermostat
Home Screen.............................................................39
Displaying the Outdoor Sensor Temperature
on the Home Screen...............................................39
Displaying the Indoor Humidity on the Home
Screen.....................................................................39
Specic Congurations ...........................................39
Dehumidication Settings .......................................39
Dehumidication Setting Options ................................39
Overcooling .................................................................40
Dehumidication Set Point ..........................................40
Advanced Dehumidication Descriptions ....................40
Lennox Smart Zoning..............................................41
PureAir S.................................................................41
Ventilation (ERV, HRV and Fresh Air Damper).......41
Ventilation Rates .........................................................41
Energy Recovery Ventilator (ERV)..............................41
Heat Recovery Ventilator (HRV)..................................41
Fresh Air Damper ........................................................42
Zoning Application.......................................................42
Operation of Fresh Air Dampers with
Environmental Overrides.............................................42
Ventilation Control Modes ...........................................42
Notications (Service and Alert Codes) ................44
Alert Code Priority Types and Notication
Options....................................................................44
Soft Disable.............................................................45
Possible Cause ...........................................................45
Re-Congure System ..................................................45
Service Notication Alert Codes .............................45
Alert Codes .............................................................46
Installation Checklist................................................92
Index ..........................................................................95

3
Shipping and Packing List
Table 1. Packing List
Quantity Description
1 Lennox S40 smart thermostat
1 Sub-base
4 Mounting screws (#6 x 1.25 SMS pan head Phillips)
4Wall anchors (alligator anged wall anchors)
1 Quick Start guide
1Warranty certicate
Thermostat External Components
External Component Locations
Ambient Sensor
Reboot
(Pin Hole)
Micro USB with
Cap Cover
BOTTOM VIEW
FRONT VIEW BACK VIEW
Humidity
Sensor
BA
CK
V
IE
W
Sub-Base
Figure 1. Thermostat External Components
Reboot Button, Micro USB Connection and Built-in Sensors
The following diagrams in this section illustrates the basic Lennox control
wiring for all compatible components.
• Proximity Sensor - Detects a person approaching the Thermostat. If the
Thermostat is in screen saver mode and the proximity sensor setting is set
to ON (factory default is OFF), the proximity sensor takes the Thermostat out
of screen saver mode automatically and returns to the home screen when
someone approaches. This feature can be disabled by going to Menu >
Setting > Display.
• Ambient Sensor - This sensor determines ambient light levels around
the thermostat. If screen brightness is set to AUTO, the thermostat will
automatically adjust screen brightness based on surrounding room light. To
set to AUTO, go to Menu > Settings > Display and enable Auto Brightness.
• Humidity sensor - This is the intake location for the built-in humidity sensor.
Do not block the intake location. The indoor humidity percentage is displayed
(enabled by default) on the home screen. The humidity percentage display
on the home screen can be disabled by going to Menu > Setting > Display.
• Temperature Sensor - This determines the room temperature.
• Reboot button - Using a paper clip, press and hold this button for
approximately six (6) seconds to reboot the Thermostat. No settings are lost
using this procedure.
• Micro USB connector with cover - For future use.
Lennox Smart Applications
Lennox®Smart Thermostat App (Homeowner)
• The free Thermostat app is available for use on iOS and Android™ devices.
• Control cooling/heating temperatures, fan operation, set programs and set
Away mode for multiple locations.
• Controls individual zone settings if system is equipped with the optional
Lennox Zoning Control System.
• Controls PureAir S Air Purication System
• Controls fresh air dampers and ERV/HRV when using an Equipment Interface
Module (EIM).
Lennox®Smart Technician App (Installer)
• The free Lennox Smart Technician App allows the installer to commission
and service the system on most iOS and Android™ devices.
• Remotely turn the system on and off during setup.

4
Downloading Lennox Smart Applications
Scan the QR codes listed below to download the specic application you
desire.
Lennox Smart Technician App
Google Play
(AndroidTM)
App Store
(iOS)
Lennox Smart Thermostat App
Google Play
(AndroidTM)
App Store
(iOS)
Service and Support - Service Access and Remote In
IMPORTANT
Protect homeowner investment and peace of mind with active monitoring of
system operations through the Lennox S40 Smart Thermostat. This feature is
free of charge and provides basic maintenance reminders, alerts homeowner
of potential issues, and can even allow the homeowner to remotely share
diagnostics with the Lennox dealer to troubleshoot and x problems. This
proactive care helps eliminate downtime and avoid unnecessary service
visits and repair costs, ensuring nothing short of perfect air.
Please share this information with homeowner as you ask them to accept the
Advanced Diagnostics & Remote sharing permissions.
With the homeowner’s permission, use the following procedure to enable
remote access and diagnostics.
From the thermostat home screen, go to Menu > Support Services and under
Local Lennox Dealer Info verify that all of the elds have been completed.
Then select Service Access and enable Remove View and under Remote
Control select On / Always. In addition enable Alerts and Notications.
THERMOSTAT
(SIDE VIEW)
3/4”
(18.4)
SUB-BASE
(FRONT VIEW)
1/4” (6.5
SUB-BASE
(SIDE VIEW)
THERMOSTAT (FRONT VIEW)
Inches (Millimeters)
7”
(179)
4-1/2”
5-7/8” (147)
3-1/2” (89)
Figure 2. Thermostat and Sub-Base
Thermostat Terminal Information
Table 2. Terminal Designations and Wiring Recommendations
Terminal
Designation Description Thermostat Wiring
R24VAC input 18AWG unshielded
I+ RS-BUS I+ 18 - 22AWG unshielded or shielded
NOTE: Shielded wiring may be required in some rare
situations. Use two-conductor shielded cabling.
I- RS-BUS I-
C24VAC return 18AWG unshielded

5
Wiring Diagrams
Communication Wiring Options
OPTION 1
Lennox Communicating
Outdoor Unit Lennox Communicating
Thermostat
Cut shield off at this end
Indoor Unit Communicating Control
(Using Shielded Wiring for Communication Lines)
18AWG
unshielded **
Shield (drain) wire MUST
be connected to indoor unit
common terminal.
OPTION 2
18 or 22AWG
shielded
Lennox Communicating
Outdoor Unit Lennox Communicating
Thermostat
18 or 22AWG
Standard Thermostat
Cable (4-Conductor)
Indoor Unit Communicating Control
(Using Non-Shielded Wiring)
Figure 3. Lennox Communicating System Wiring Connections using Unshielded (Option 1) or Shielded Wiring (Option 2) Cabling
There may be situations where alternate wirings methods may need to be employed. Two options are available to address an inductive voltage issue. If Alert
Code 105 (see “Table 20. Service Alert Notication Codes” on page 45) is still present after following troubleshooting Steps 1 and 2 then proceed to Step 3
wiring options 2 or 3.
• Option 2 - Using shielded 2-conductor cable between the indoor, outdoor and thermostat -i and +i terminals may be required.
• Option 3 - Using unshielded 2-conductor cable between the indoor, outdoor and thermostat -i and +i terminals may be required.
NOTE: When using multi-conductor unshielded thermostat cable, refer to “Figure 5. Minimizing Electrical Noise” on page 6.

6
Lennox
Communicating
Outdoor Unit
Lennox
Communicating
Thermostat
Indoor Unit Communicating Control
(Using 2-conductor Unshielded Cable for Communication Lines and
Separate 2-conductor Unshielded Cable for R and C)
OPTION 3
18/2 Brown Solid CU CL2 Thermostat Wire
Figure 4. Lennox Communicating System Wiring Connections using
Separate Unshielded Cable (Option 3)
Minimizing Electrical Noise
When using multi-conductor unshielded thermostat cable, to minimize electrical
noise, cap unused wires as illustrated below and run to indoor unit C terminal.
Single wire
to indoor unit
terminal “C”.
Unused
wires
Single wire directly to
C terminal or
to second bundle.
.
Indoor Unit Controller
Outdoor Unit
Thermostat
R i+ I- C
Unused
wires
Figure 5. Minimizing Electrical Noise

7
Application Specic Wiring Diagrams
24VAC 1- or 2-Stage
Heat Pump or
Air Conditioner
SETUP NOTES:
DATS (Optional)
OATS (Optional)
Thermostat
Lennox Communicating
Air Handler Unit
Heat Pump Only
Cut Y1-Y2 on-board link for 2-stage outdoor units
(Non-communicating)
Cut R-O on-board link for outdoor heat pump units
(Non-communicating)
(See Lennox
Communication
Wiring Diagram)
Figure 6. Lennox S40, Lennox Communicating Air Handler with 24VAC
(1- or 2-Stage) Heat Pump or Air Conditioner
+- AB ODT
FLOAT
Switch
DH DH
Gh Rf Cf Gs YW
HVAC EQUIP.
DH
C
G
R
NC NO
NC
NO
SPDT RELAY
཰ི
ཱ
ཱི
Thermostat
Lennox
Communicating
Indoor Unit
(See Lennox
Communication
Wiring Diagram)
Figure 7. Lennox S40, Communicating Indoor Control (Conventional
Connections), Relay and HCWHD4 Series Dehumidiers

8
DATS
(Required)
OATS (Optional)
In-Zone
Thermostats
PWR
D+
D-
C
PWR
D+
D-
C
PWR
D+
D-
C
See Smart Zoning Installation instruction for damper connection information.
INDOOR
PWR
D+
D-
C
Lennox
Communicating
Indoor Unit
TS
TS
T
T
A
A
T
T
DATS
Lennox
Communicating
Outdoor
Unit
If TSTAT terminal is present,
DO NOT use.
Up to three in-zone
thermostats are
supported
Use terminal designated “Indoor” on damper
control module to connect to the indoor unit.
Damper
Control Module
Thermostat
(See Lennox
Communication
Wiring Diagram)
(See Lennox
Communication
Wiring Diagram)
(See Lennox
Communication
Wiring Diagram)
Figure 8. Lennox S40, Lennox Communicating Indoor and Outdoor Units, Smart Zoning System (Damper Control Module) and Zone Sensors

9
LENNOX
COMMUNICATING
FURNACE
48G96 Relay
GND
IN
120VAC<-------HUMIDIFIER CONNECTIONS------> 24VAC
OPTIONAL DISCHARGE
AIR SENSOR
(SEE DAS NOTES)
OPTIONAL OUTDOOR
AIR SENSOR (SEE OAS
NOTES)
ERV / HRV
24VAC UV Light Applications: In any Lennox communicating system, the indoor unit will
NOT have adequate power to to run the 24VAC UV light application. An additional transformer
will be required. UV light wiring connections are independent of the HVAC system operation
(refer to UV light installation instruction.
Humidity Control Applications: Lennox communicating thermostats can sense humdiity and controls
both 24VAC “H” and 120VAC “H” outputs to cycle humdifier based on demand. No other
control or humidistat is required. Optional outdoor air temperature sensor for use with humidifier
(if not already in the system for other function and are typically built into all Allied communicating
outdoor units
Thermostat
Lennox
Communicating
Outdoor Unit
Lennox Communicating
Furnace or Air Handler
Thermostat
DRAIN
WIRE
CONNECTS
TO C
(See Lennox
Communication
Wiring Diagram)
(See Lennox
Communication
Wiring Diagram)
(See Lennox
Communication
Wiring Diagram)
Figure 9. Lennox S40 with Humidier Accessory

10
• Set LVCS cycle time to one hour.
• Set ventilation time to 60 minutes.
Lennox Communicating
Indoor Unit
NOTE: Pass the blower motor L1 wire through the current loop on the current sensing relay as illustrated.
When there is a heating, cooling or continous fan call, the ventilation
controller will open the outdoor air damper to ventilate if the
outdoor temperature and indoor humidity are within the limits of the
ventilation controller.
NOTE: Set the communicating thermostat fan mode operation to Circulate and adjust duration to match control ventilation time duration.
26L56
CURRENT SENSING
RELAY
120VAC COIL RELAY
24VAC LVCS
DAMPER TRANSFORMER
VENTILATION
DAMPER
OUTDOOR
TEMPERATURE
SENSOR
NEUTRAL
EAC/ACC 120VAC
Thermostat
Lennox Ventilation Control System (LVC)
(See Lennox
Communication
Wiring Diagram)
Figure 10. Lennox S40, Lennox Ventilation Control System (LVCS), Current Sensing Relay, 120VAC Coil Relay, Damper Transformer, Ventilation
Dampers and Communicating Indoor Unit (using Non-Communicating Terminals)

11
HEPA BYPASS FILTER X2680 HEPA
INTERLOCK KIT
TOR COMMON WIRE
THROUGH CURRENT LOOP.
SEE HEPA INTERLOCK KIT
FOR INSTALLAT ION DETAILS
LENNOX
COMMUNICATING
OUTDOOR UNIT
LENNOX COMMUNICATING
INDOOR UNIT
LENNOX COMMUNICATING
THERMOSTAT OR DAMPER
CONTROL MODULE
CONVENTIONAL TERMINALS
LENNOX COMMUNICATING
INDOOR UNIT
(See Lennox
Communication
Wiring Diagram)
(See Lennox
Communication
Wiring Diagram)
Figure 11. Lennox S40 and HEPA Bypass Filter Interlock Kit and Humidier

12
CUT
R-DS
W914
DS
R
LENNOX COMMUNICATING
FURNACE UNIT
(SLP99, EL296 and SL280)
FOR FLOAT SWITCH
OPERATION, CUT R-DS.
FLOAT
SWITCH
RELAY
FLOAT
SWITCH
LENNOX COMMUNICATING
INDOOR UNIT CONVENTIONAL
OUTDOOR UNIT
(1 OR 2 STAGE)
LENNOX COMMUNICATING
INDOOR CONTROL (18Y04)
THERMOSTAT
CONVENTIONAL TERMINALS
FLOAT
SW
FLOAT
SWITCH
RELAY
(See Lennox
Communication
Wiring Diagram)
Figure 12. Lennox S40, Lennox Communicating Indoor Controls and Float Switch

13
Single wire
to indoor unit
terminal “C”.
Unused
wires
Single wire directly to
C terminal or
to third bundle.
.
Indoor Unit Controller
PureAir SUnit
Thermostat
R i+ I- C
Unused
wires
Outdoor Unit
Unused
wires
Figure 13. Unshielded Thermostat Cable (Multiple Conductors) used
for Wiring Communicating Indoor Unit to PureAir S
Dual Fuel and Ventilation Diagrams
For additional wiring, please refer to the accessory installation instruction.
When using a Lennox Communicating Furnace and conventional heat pump
an equipment interface module (EIM) will be require. In addition, ventilation
(ERV/HRV and Fresh Air Damper will also required an EIM. Refer to the
EIM Installation and Setup Guide 507240-0x for detailed wiring diagrams for
specic application.
Installation Considerations
WARNING
Improper installation, adjustment, alteration, service or maintenance can
cause property damage, personal injury or loss of life.
Installation and service must be performed by a licensed professional HVAC
installer (or equivalent) or a service agency.
Before beginning installation, note the type of equipment, number of stages,
and any accessories being installed.
Do
• Read this entire document, noting which procedures pertain to your specic
equipment and system requirements.
• Conform to local and national building and electrical codes and ordinances.
• Place the thermostat on a central interior wall.
• Installed thermostat a minimum of 5 feet up from the oor.
Do Not
• Install on voltages higher than 30VAC.
• Exceed 300 feet (91 meters) total wire length when using 18AWG or 22AWG
thermostat or smaller diameter wire (see “Table 2. Terminal Designations
and Wiring Recommendations” on page 4 for further details.
• Install on outside walls or in direct sunlight
• Install near air return or discharge air vents.
• Install near replaces or other heat sources
• Install on exterior walls
• Install near windows or doors
• Install near kitchens
• Install in rarely used rooms or hallways
Thermostat Installation
Installation
Use the following procedure for installation of the thermostat wall plate where
existing thermostat wiring does not exist:
1. Unpack the thermostat and sub-base.

14
2. Detach sub-base from thermostat body.
3. Determine the best location to install wall plate. Ideal location should be
located away from outside wall, direct sunlight or discharge air vents. The
thermostat should typically be installed at least 5 feet up from the oor.
4. Cut or drill a small hole for thermostat wiring.
3/8” (10 mm)
Diameter Hole
6. Pull about three inches (75mm) of thermostat wire through the opening
and remove the outer thermostat wire jacket.
Seal wire hole in wall to prevent
cold or hot air from affecting temperature
sensor in display.
IMPORTANT
Seal wire hole in wall to prevent cold or hot air from affecting temperature
sensor in Thermostat.
8. Strip a maximum of 1/4” (6 mm) insulation from end of each wire. For best
results, only strip sufcient insulation for wire to insert into the terminals
without any wiring exposed.
1/4”
9. Use a level to align the sub-base or wall plate on wall horizontally.
10. Use sub-base as a template to mark the desired mounting hole locations
on the wall.
NOTE: Make sure the UP arrow on the sub-base is pointing up.
Use the subbase as a template to
mark the desired mounting hole
locations on the wall.
Thermostat Sub-base
(Front View)
Install subbase with arrow
pointing up.
11. Drill 3/16” (5 mm) holes at marked locations on the wall for anchors. Then
insert wall anchors into holes until ush with the wall.
12. Secure sub-base with provided #6 x 1.25” pan-head screws (4).
13. Connect thermostat wiring to sub-base screw terminals.
Installing Thermostat to Sub-Base
Install HD Display with UP arrow pointing
up when attaching to subbase.
1. Hold the thermostat by the edges, line it up with the sub-base (horizontal
position), and move the thermostat toward the sub-base.
2. Center the cavity on the back of the display over the sub-base.

15
3. Gently press on the edges of the thermostat until you hear the mounting
snaps engage. Be careful not to apply force directly on the glass.
NOTE: Once the thermostat is connected, it may take up to 45 seconds for it
to power up.
4. To remove the thermostat from the sub-base, grasp the left and right edges
of the thermostat and gently pull towards yourself.
NOTE: If the thermostat is removed from the sub-base, the thermostat will
shut down and will not be able to communicate with the system.
System can be controlled from mobile devices once registration has
been completed.
5. Do not remove the label covering the thermostat screen until after power
is applied to the system.
Commissioning using the Lennox®Smart Technician
This application tool is used by dealers to commission a S40
smart thermostat using a Wi-Fi enabled mobile device.
A temporary direct Wi-Fi connection is created between
the mobile device and thermostat using the Lennox Smart
Technician App.
NOTE: The Lennox Smart Technician App only connects locally while within
Wi-Fi range of the thermostat. The app cannot connect through the
home Wi-Fi network or Internet.
To use the Smart Technician app, the mobile device must be:
• Wi-Fi capable
• Located in the home near the thermostat
NOTE: A router with Bonjour capabilities is required for this function. Check
the router features if the thermostat does not connect. Apple Bonjour®
is an implementation of zero-conguration networking (Zeroconf),
a group of technologies that includes service discovery, address
assignment, and host name resolution.
Mobile Device Operating System Requirements
The Lennox Smart Technician App is available for both IOS 11.0 or higher
(App Store) and Android 9.0 or higher (Google Play).
Establishing a Direct Wireless Connection to the Thermostat
IMPORTANT
If the connection between the Lennox Smart Technician App and thermostat
is idle for three (3) minutes, the thermostat will auto-disconnect from the
mobile device. Repeat procedures to reconnect.
1. Apply power to the thermostat.
IMPORTANT
After applying power to the thermostat a “System Under Test” screen appears,
it could indicated either the system is under reconguration or is unable to
communicate with the indoor unit. Check wiring connections between the
thermostat wall plate and indoor unit for loose or incorrect connections.
NOTE: When Lennox controls are congured for a communicating system,
all jumpers and links setting on the controls are ignored. Jumpers and
links setting are treated as defaults and would only be active if the
system was congured as a non-communicating system.
2. A Welcome screen will appear. Select the desired language to be used.
Options are English, Franҫais and Español. Select the right arrow to
continue.
3. On the Choose Setup Route screen there are two options:
»Continue setup process through the thermostat
» Continue setup process through the mobile app
Select option 2 and select the right arrow to continue.
4. The Download Lennox Smart Technician App screen will appear on the
thermostat. On that screen you can scan the QR code with your mobile
device to download the Lennox Smart Technician App from either App
Store or Google Play. If the app has already been installed, select the right
arrow to continue and proceed to step 6.
5. Once the Lennox Smart Technician App has been downloaded and
installed on your mobile device. Return to the thermostat and select the
right arrow to continue.
6. The next screen is the Connect Thermostat with Lennox Smart
Technician App. Select the Start button to continue.
7. The next screen is the Thermostat ID broadcasting screen. Start the
Technician Service App. Follow the screens on the Lennox Smart
Technician App.

16
NOTE: See “Table 3. Lennox Smart Technician App Commissioning Screens”
on page 16 for sequence of commissioning.
Commissioning Screens
The following table describes the commissioning sequence and screens in
order of their appearance during the commissioning.
Table 3. Lennox Smart Technician App Commissioning Screens
Screen Titles Selections or Status
Not Connected
Welcome - Select
Language
English
Franҫais
Español
Connect to
device
S40-XXXXXXXXX will appear. It should match the thermostat ID
that is displayed on the thermostat. Select the ID on the app’s
screen.
Connect with
Thermostat
A DIRECT -CHXX-XXX will appear. Select Connect. A conrmation
screen will appear indicating successful connection to the
thermostat. Select the right arrow to continue.
Dealer
Information
Add the dealer ID number and phone number.
NOTE: You will not be able to proceed unless either the dealer ID
or phone number is entered.
General
Information, Time,
Date and Units
• Select Country / Region
• Time, Date, Time Zone and Daylight Savings (You will not need
to populate these elds once the thermostat is connected to the
Internet).
• Temperature Unit
• Unit System
Auto-Discovery of
Communicating
Equipment
Only communicating equipment connected to the thermostat will
appear on this screen (thermostat, smart zoning, heat pumps,
furnaces, air handlers and air conditioners
Adding non-
communicating
equipment
Options None, Fresh Air Damper, HRV, ERV,
humidier,dehumidiers and non-communicating outdoor units.
NOTE: For ventilation equipment, a Lennox Equipment Interface
Module will be required.
Zoning Control
If the system has Smart Zoning installed, this screen allows for the
renaming of each zone. Assign the specic zone to a location is also
available. A custom location is also allowed.
The next screen allows adjustments of CFM settings per each zone.
Reminders
Reminders can be set for lters humidier, UV bulb replacement,
maintenance and PureAir maintenances.
Additional screens allow for setting lter reminders based on
calender time or runtime.
System Name On this screen the system name can be changed.
Table 3. Lennox Smart Technician App Commissioning Screens
Screen Titles Selections or Status
Congratulations
Setup is completed. Select Finish. This will take you to the Service
Center screen to make any additional changes required to the
system.
Service Center
If not other changes are require, you can terminate the connection
to the thermostat by select Disconnect from XXXXXXXX located at
the bottom on the screen.
Servicing using the Lennox Smart Technician App
To use Lennox Smart Technician App as a service tool, the commissioning
of the system must have already been completed.
NOTE: Currently there is a default timer for 30 minutes to complete any service
procedures before the thermostat will automatically log you out. The
duration of the timer cannot be adjusted.
1. Download and install the Lennox Smart Technician App if not already
installed.
2. From the thermostat home screen, go to Menu > Settings > Advanced
Settings > View Support Service Control Center and select Connect
To Lennox Smart Technician App.
3. The thermostat will start broadcasting is Thermostat ID.
4. Start the Lennox Smart Technician App and follow the app screen
prompts.

17
Multiple Thermostats - Group ID
Multiple S40 thermostats in a home can be assigned to a group (up to nine
groups with up to ve (5) thermostats in each group). All thermostats in a group
can communicate with other thermostats in the same group over a single 2.4
GHz Wi-Fi network.
IMPORTANT
If the home will have multiple S40 thermostats then they all MUST be on the
same 2.4GHz Home Wi-Fi network in order to communicate with each other.
Do not use 5 GHz.
All S40 thermostats can be grouped together. If you have a S30 or E30, they
will NOT be appear on the S40 thermostat.
Default Group ID 1. Range is 1 to 9.
NOTE: If a thermostat is set to Group 0, then there is no connectivity with
another S40 thermostat within the home on the same 2.4Ghz Wi-Fi
network.
Group IDs can be changed by going to Settings > Advanced Settings > View
Support Service Control Center > Equipment Settings > Thermostat and
look for Group ID.
Restarting thermostat
To restart the thermostat, go to > Settings > Advanced Settings > View
Support Service Control Center > Equipment Settings > Reset > Restart
Thermostat.
Commissioning Using the Thermostat
The following procedures are written for commissioning the system using
the Thermostat interface. When power is rst applied to the system all
communicating devices attached to the system (air handler or furnace, outdoor
unit, PureAir S or zoning control) will automatically be congured using optimal
factory default settings based on system type, capacity and other conguration
considerations.
NOTE: If there is a PureAir S Air Purication System installed, during
commissioning the blower will turn on and run at three different CFM
settings for the PCO lter calibration to take place. This may be well
in advance before the display is fully up and running. This is a normal
process. The blower may run as long as ninety (90) seconds at each
CFM setting to complete the lter calibration.
1. Apply power to the thermostat.
IMPORTANT
If after applying power to the thermostat a “System Under Test” screen appears,
it could indicate either the system is under reconguration or is unable to
communicate with the indoor unit. Check wiring connections between the
thermostat wall plate and indoor unit for loose or incorrect connections.
2. A Welcome screen will appear. Select the desired language to be used.
Options are English, Franҫais and Español. Select the right arrow to
continue.
3. On the Choose Setup Route screen there are three options:
»Continue setup process through the thermostat
»Continue setup process through the mobile app
Select option 1 and select the right arrow to continue.
Dealer Information
IMPORTANT
Enter dealer ID number. If not available, enter phone number associated
with the dealer account. This will the enable ability to perform advanced
diagnostics and remote sharing if permitted by homeowner.
This screen in the commissioning sequence is the dealer service center screen
where the dealer ID and/or phone number can be added. Once the system
is connected to the Internet, the remaining information will be populated
automatically by the Lennox server based on the dealer name or phone
number entered. All information can be entered manually if desired however.
Information that can be manually entered is name, email website, dealer
address which includes address 1, address 2, city, state and zip/postal code.
Once completed touch continue.
General Settings
On this screen general information needs to be veried or changed. Touch
any item to change its contents. A pop-up screen will appear that will allow the
information to be added or changed.
1. Select country / region.
2. Select time and date which includes time, date, time zone and daylight
savings time (ON/OFF).
3. Select temperature unit (Fahrenheit or Celsius).
4. Once completed touch the right arrow.

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Equipment Found Screen
Communicating Equipment Found
This screen will display any communicating equipment the system has detected
(air handler, furnace, outdoor unit, PureAir S, thermostat and smart zoning
system during initial commissioning of the system.
NOTE: When a Lennox Equipment Interface Module (EIM) is used and
congured as either a furnace or air handler, then the component
would appear as either EIM-Furnace or EIM-Air Handler. When using
an EIM the outdoor unit may be either a Lennox communicating or any
standard 24VAC non-communicating unit.
NOTE: Not all equipment may be visible from the equipment found system
screen. Touch and swipe up to access additional information (if
applicable) listed at the bottom of the system box.
If non-communicating equipment needs to be added, it can be done so from
this screen.
Adding / Removing Non-Communicating Equipment
When selecting the non-communicating (24VAC) equipment icon, a screen
will appear listing equipment that can be added. When selecting an applicable
component, a green check will appear next to the item. The capacity selection
of the outdoor unit will also be displayed on the screen after selecting the
applicable outdoor equipment type.
NOTE: A temporary dialog box will appear indicating: Updating - Wait while
we check for dependencies.
NOTE: Selecting an outdoor unit type only appears if a communicating outdoor
unit is not detected by the system. Selections are one or two-stage
heat pumps or air conditioners. Outdoor unit capacity will also have to
be set. Other non-communicating equipment that can be added are:
Ventilator Type
NOTE: For ventilation equipment, a Lennox Equipment Interface Module
(22X18) will be required.
Options are:
»None
»Fresh Air Damper
»1 or 2 Speed ERV (energy recovery ventilation)
»1 or 2 Speed HRV (heat recovery ventilation)
Outdoor Unit Type
NOTE: The outdoor unit type option only appears when no communicating
outdoor unit is found attached to the system.
»1 Stage A/C Unit
»2 Stage A/C Unit
»1 Stage HP Unit
»2 Stage HP Unit.
Humidiers
Options are:
»Not Installed
»Bypass (24VAC Humidier)
Dehumidier
Options are:
»Not Installed
»Humiditrol
»Auxiliary Dehumidier
Once completed select the right arrow icon.
Lennox Smart Zoning (Optional)
IMPORTANT
The Lennox Smart Room Sensor is not compatible with systems using the
Lennox Smart Zoning System (formally know as iHarmony) installed.
This screen will only appear if the smart zoning system is detected. This screen
allows you to rename each zone. You may use the preset names or any custom
name you may desire. If zoning is not applicable, proceed to the next section.
1. Touch on any zone to rename it. A screen will display that lists several
predened names that can be used which are master bedroom, guest
bedroom, kitchen, living room, media room, dining room, library or custom.
When a predened name is selected, a green check-mark will appear next
to the selected name.
2. When creating a custom name, touch custom, enter a name and touch
back to return to the previous screen. A new unique zone name can be
created for all four zones.
3. Once completed touch continue.

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Setup Airow per Zone
This screen will allow the installer to setup the airow per zone. The types of
circulation per zone are:
• Blower Circulation Airow (gray) which includes total, assigned, minimum
and maximum airow.
• Heating Circulation Airow (red) which includes total, assigned, minimum
and maximum airow.
• Cooling Circulation Airow (blue) which includes total, assigned, minimum
and maximum airow.
Reminders
This screen allows you to set reminders as either disabled or 3, 6, 12 or 24
months and also custom by specic date. The other options on this screen set
the reminder event either by calendar date or actual system run-time.
Reminders may be set for Replace lter 1, Replace lter 2, Replace UV bulb,
Replace humidier pad, PureAir™ maintenance, Maintenance reminder,
Ventilation maintenance and Ventilation lter.
Once a reminder is set for a specic item, touch done to return to the previous
screen. An “expires on date” will appear next to the item just set.
1. Touch on the circled green arrow to touch a specic zone. The zone settings
will expand to allow the installer to adjust CFMs for each circulation airow
type. Use the plus and minus buttons to adjust CFMs up and down.
2. Once completed touch continue. The next screen that will appear is the
Dealer Control Center.
System Name
On this screen you can rename your system.
Commissioning Completion
Once commissioning is completed, the system will leave you at the Dealer
Control Center. You can either touch exit to go to the main screen or perform
any function listed in the various categories displayed.
Helping Homeowner Connect Thermostat to the Home
Wi-Fi
Wi-Fi Limitations
• The thermostat cannot connect to a home wireless router that uses more
than 32 characters in the wireless access point name (visible or hidden).
• The thermostat will support up to a 63 character Wi-Fi password. Passwords
cannot contain blank spaces or % symbol.
• If the home Wi-Fi connection is unsecured, then Wi-Fi security MUST be
enabled. Consult your router documentation on how to enable Wi-Fi security.
• Never use a home guest account.
• Never use an open unsecured router connection.
• Always use a secure connection physically located in the home where the
thermostat is located.
IMPORTANT
If the home will have multiple S40 thermostats then they all MUST be on the
same 2.4GHz Home Wi-Fi network in order to connect to each other. Do not
use 5 GHz.
Home Wi-Fi Access Point is Visible
1. From the thermostat’s home screen, go to Menu > Settings > Wi-Fi.
2. Slide the option to the ON position to enable Wi-Fi.
3. Press on Not Connected to display a list of available access points.
4. Locate home network and select the network name.
5. Enter the home Wi-Fi network password and press join to continue. If
successful the Thermostat Connective Status indicator as illustrated
below will show check marks across all connections.
Lennox S40
Smart Thermostat Router Internet Service Provider Server
Figure 14. Thermostat Connectivity Status
NOTE: Whether connecting to a visible or hidden network, if successful, a
check mark will appear above both the router, and Internet icons. For
information on connecting to hidden networks, please reference the
S40 Homeowner Guide.
Home Wi-Fi Access Point is Hidden
1. Slide the option to ON to enable Wi-Fi.
2. Wi-Fi network will show not connected. Press on “not connected”.
3. Scroll down and select other.
4. The “enter new network information” screen will appear. Enter the name
of the hidden network.

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NOTE: The thermostat can connect to a home wireless router that uses up to
32 characters in the access point name (visible or hidden). DO NOT
connect to a guest access point.
5. Select Security. Options are: none, WEP, WPA, WPA2 and WPA3. If your
home Wi-Fi connection is unsecured, then Wi-Fi security must be enabled
using WEP, WPA, WPA2 or WPA3 via the router before proceeding.
Consult your router documentation on how to enable Wi-Fi security.
6. Once security type is selected, a password eld will appear. Enter the
password to connect to your home Wi-Fi network.
NOTE: If you wish to see the characters you are typing, check show password.
The thermostat will support up to a 63 character password. Passwords
cannot contain blank spaces or % symbol.
7. Press join.
Whether connecting to a visible or hidden network, if successful, a check mark
will appear above both the router and Internet icons.
Wi-Fi Terminology
The following terminology is used in this troubleshooting section:
• Received Signal Strength Indication (RSSI). This indicates the signal
strength of the Wi-Fi router being received by thermostat. So the higher the
RSSI number (or less negative in some devices), the stronger the signal.
• Wireless networks supported by this thermostat are:
Table 4. Supported Wi-Fi Standards
Standard Description
802.11b
Released in September 1999, it’s most likely that your rst home
router was 802.11b, which operates in the 2.4GHz frequency and
provides a data rate up to 11 Mbps.
802.11g
Approved in June 2003, 802.11g was the successor to 802.11b,
able to achieve up to 54Mbps rates in the 2.4GHz band, matching
802.11a speed but within the lower frequency range.
802.11n (Wi-Fi 4) Approved in October 2009 and allows for usage in two frequencies -
2.4GHz and 5GHz, with speeds up to 600Mbps.
802.11ac (Wi-Fi 5)
Current home wireless routers are likely 802.1ac-compliant, and
operate in the 5 GHz frequency space with support speeds up to
866.7 Mbps
NOTE: MIMO is not supported.
• Internet Protocol Address (IP address). This is an address assigned by your
home router for each network device (e.g., computer, printer, thermostat).
Electromagnetic Interference Causing Poor Connectivity: Locate the
thermostat and router away from other devices that could possibility interfere
with wireless communications. Some examples of other devices that could
interfere are:
• Microwave ovens
• Wireless cameras
• Portable phones and bases
• Baby monitors
• Wireless speakers
• Bluetooth devices
• Garage door openers
• Neighbor’s wireless devices
To eliminate a possible source of interference, temporally disable any devices
and see if Wi-Fi performance has improved.
Received Signal Strength Indication (RSSI)
The ideal signal strength range for the thermostat is -1 to -69 RSSI. The signal
strength can be viewed from the thermostat interface.
1. Press NETWORK SETTINGS; this screen shows a graphical view of
buttons representing OPEN and SECURE wireless networks, along with
button for adding a network.
2. Select the access point that has already been established and connected.
3. When selecting the right arrow (>), a screen will appear which will display
an option to forget the network. Additional information displayed on the
screen is IP address, subnet mask, router IP, DNS, MAC Address, Speed,
wireless type, BISSID and RSSI.
NOTE: If the RSSI signal strength is anywhere between -1 to -69, then the
signal strength is sufcient. If outside this range, then either relocate
the router closer to the thermostat, add a repeater, or move the
thermostat. Adjusting antenna on router or extender/repeater may
resolve the issue.