Lennox EIM Assembly instructions

507240-03
6/2021
Supersedes 3/2020
Equipment Interface Module (EIM)
Installation and Setup Guide

2
Shipping and Packing List.................................................................2
Application and Requirements..........................................................2
Indoor Transformer Requirements................................................... 2
Equipment ....................................................................................... 2
Installation...........................................................................................4
Conguration Setup...........................................................................4
EIM, 24VAC Furnace and Lennox Communicating Heat Pumps .... 4
EIM, Lennox Communicating Furnace and 24VAC Heat Pump ...... 4
Unit Type Jumpers........................................................................... 5
Heat Stage Jumper Positions .......................................................... 5
Air Temperature Sensor Connections.............................................. 6
Lennox Communicating Terminal Connections and Wiring
Recommendations........................................................................... 6
Dual-Fuel Terminal Connections ..................................................... 6
Conventional Terminal Connections and Wiring Requirement ........ 6
LED Indicators ................................................................................. 7
Soft Disable ..................................................................................... 7
iComfort S30 Commissioning (Conventional Outdoor Unit) ............ 8
Operating Environment Specications ............................................8
Unit Dimensions .................................................................................8
Duel-Fuel Operations .........................................................................9
Field Wiring .......................................................................................10
Alert Codes and Troubleshooting...................................................16
TABLE OF CONTENTS Shipping and Packing List
Quantity Description
1 Equipment Interface Module.
1 Installation and setup guide
1Warranty certicate
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.
Application and Requirements
Indoor Transformer Requirements
The following lists the required indoor unit transformer rating (VA) for
specic congurations.
Table 1. System VA Loading Chart
Conguration Minimum Transformer Rating
(VA)
2-Stage HP, 3-Stage Electric heat 70
2-Stage HP, 2-Stage Furnace (with tempering) 70
2-Stage HP, 2-Stage Furnace (without tempering) 50
2-Stage AC, 2-Stage Furnace 40
Equipment
The Equipment Interface Module (EIM) is used with an Lennox
communicating thermostat using the R, i+, i-, and C terminals. The EIM is
the interface between non-communicating HVAC equipment and Lennox
communicating HVAC equipment.
NOTE: EIM will support single-stage outdoor units with single-stage or
variable-stage indoor furnaces.

3
OUTDOOR AIR SENSOR
CONNECTIONS
DISCHARGE AIR
SENSOR CONNECTIONS
ICOMFORT
®
CONNECTIONS
NON-COMMUNICATING TERMINALS
STATUS LED
COMMUNICATION INDICATOR
LED
DUAL-FUEL
CONNECTIONS
UNIT TYPE JUMPER
TERMINALS
HEAT STAGES
JUMPER TERMIINALS HEAT PUMP CAPACITY
JUMPER TERMINALS
3 AMP FUSE
Figure 1. Terminals and LEDs
CAUTION
Electrostatic discharge can a󰀨ect electronic components. Take precautions during unit installation and service to protect the unit’s electronic controls.
Precautions will help to avoid control exposure to electrostatic discharge by putting the unit, the control and the technician at the same electrostatic
potential. Neutralize electrostatic charge by touching hand and all tools on an unpainted unit surface before performing any service procedure

4
Lennox Communicating
Thermostat
Equipment Interface
Model (EIM)
24VAC Air Handler or
Furnace (Indoor Unit)
iComfort-enabled
Air Conditioner or
Heat Pump
(Outdoor Unit)
Wiring Legend
4−wire communicating
24VAC conventional
EIM with Air Hander or Furnace (Indoor Unit)
and either a Air Conditioner or Heat Pump
(Outdoor Unit)
24VAC Air
Conditioner
or Heat Pump
(Outdoor Unit)
NOTE: For dual-fuel applications, additional components may be need to be added.
Figure 2. System View
WARNING
Controls in this module are sensitive to moisture. Do NOT secure this
module to the sheet metal cabinet where moisture may condense during
periods of high humidity. Secure the module to a nearby wooden stud, if
possible.
Installation
IMPORTANT
The Lennox communicating thermostat paired with the Equipment
Interface Module (EIM) will work with most 24VAC furnaces, air handlers,
air conditioners and heat pumps (up to 2-stages of cooling and 3-stages
of heat).
The Lennox communicating thermostat without the Equipment Interface
Module (EIM) will work with Lennox communicating HVAC equipment.
1. Remove the module cover.
2. Mount the Equipment Interface Module (EIM) near the indoor unit.
3. Use the wiring diagrams reference in the sectoin titled “Field Wiring”
on page 10 to complete the wiring connections for the specic
application and conguration.
Conguration Setup
How the EIM is congured is determined by the system components.
NOTE: Changing jumper positions after the control has been powered-up
requires recommissioning for the change to be recognized.
NOTE: When the Equipment Interface Module is replaced,
recommissioning the Lennox communicating thermostat will also
need to be re-accomplished. See the Lennox communicating
thermostat Setup Guide for recommissioning procedure.
The following examples are two typical congurations used with the EIM.
There are other applications as well and are address in the wiring diagrams
section titled “Field Wiring” on page 10. Those diagrams will indicate all
required jumper settings on the EIM and wiring connections.
EIM, 24VAC Furnace and Lennox Communicating Heat Pumps
See “Figure 12. Dual-Fuel - Conventional Furnace with Lennox
Communicating
Heat Pump (1 or 2-Stage)” on page 11 for wiring details.
1. Set the EIM Unit Type Jumper to IFC.
2. Set the EIM Heat Stage Jumper (see “Table 3. Heat Stage Jumpers”
on page 5) to the applicable number of furnace heat stages or
number of electric heat stages.
3. Use the Lennox communicating thermostat to complete the
commissioning procedure.
EIM, Lennox Communicating Furnace and 24VAC Heat Pump
See “Figure 11. Dual-Fuel - Lennox Communicating Furnace with
Conventional Heat Pump (1 or 2-Stage)” on page 11f or wiring details.
1. Set the EIM Unit Type Jumper to Heat Pump.
2. Set the EIM Heat Stage Jumper (see “Table 3. Heat Stage Jumpers”
on page 5) to the applicable number of heat pump heating stages.
3. Use the Lennox communicating thermostat to complete the
commissioning procedure.

5
NOTE: For two-stage heat pump go to the heat pump defrost control,
locate P3 - low ambient thermostat pins and disable this function
by removing the installed jumper and relocating it to one pin only.
Unit Type Jumpers
Set the unit type jumper for the type of indoor unit, Use the following
table and gure as a guide. The factory default setting is IFC. If jumper is
missing from the jumper pins, then alarm 130 is activated.
Table 2. Unit Type Jumpers Positions
Jumper
Position Indoor Unit Outdoor Unit
HP Lennox Communicating
Furnace Conventional Heat Pump
IFC Conventional Furnace Conventional Heat Pump or air
conditioner
AHC Conventional Air Handler
HP IFC AHC
Figure 3. Unit Type Jumper Positions
Heat Stage Jumper Positions
The factory default setting is position 2 (two heat stages). If jumper is
missing from the jumper pins, then alarm 130 is activated. Depending on
the type of equipment and system set up being used:
• Set the number of stages of electric heat (air handler) when jumper pin
selection is AHC selection.
• Set the number of stage of gas heat (Furnace) when jumper pin selection
is IFC.
• Set the number of stages of the compressor when jumper pin selection
is HP.
0 1 2 3
Figure 4. Heat Stage Jumper Positions
Table 3. Heat Stage Jumpers
Label
(Position)
Air Handler Heat
Stages Furnace Heat Stages Heat Pump Stages
Number of
Electric Heat
Stages
Stage
Percentage
Number of
Gas Stages
Stage
Percentage
Number of
Compressors
Stages
Stage
Percentage
0No Electric
Heat 0 1 100% 1 100%
1 1 100% 1 100% 1 100%
2
(default) 250%, 100% 270%. 100% 270%. 100%
3 3
33.5%,
66.5%,
100%
270%,
100% 270%. 100%
NOTE: If jumper is missing, setting defaults to single stage. Changing jumper position
after power-up requires recommission for the change to be recognized.
24VAC Heat Pump Size Setting
Heat pump size must be congured when using a non-communicating
heat pump using the Heat Pump Size jumper (see gure 4 and table 5).
Factory default setting is for 3.0 (3-ton). If jumper is missing from jumper
pins then alarm 130 is activated.
1.
5
2.
0
2.
5
3.
0
3.
5
4.
0
5.
0
Figure 5. Conventional Heap Pump Capacity Jumper Setting

6
Air Temperature Sensor Connections
Refer to “Figure 1. Terminals and LEDs” on page 3 for various
terminal locations.
Table 4. Outdoor Air and Discharge Air Sensors
Label Function / Description
Outdoor Air
Sensor
Show ambient temperatures (optional if weather feed is acceptable or
outdoor unit is a communicating unit; use X2658 Outdoor Sensor - 2
terminals).
NOTE: Wiring distance between the EIM and the outdoor temperature
sensor can not exceed 150 feet (45 meters) when wired with
minimum 22AWG (Recommend) 18AWG dedicated two-
conductor thermostat cable.
Discharge Air
Sensor
Optional for diagnostics of indoor air; use 88K38 Discharge Air Sensor -
2 terminals.
Lennox Communicating Terminal Connections and Wiring
Recommendations
Table 5. Communicating Terminals
Label Function / Description Thermostat Wiring
R 24VAC communication power Input 18AWG unshielded
i+ Communication high – data line 18 - 22AWG shielded
(recommended)
i- Communication low – data line
C24VAC communication common
power Input 18AWG unshielded
IMPORTANT
Use 18AWG unshielded thermostat cable (eld-provided) for power
terminals (R and C) and all non-communicating terminals. Highly
recommend using 18 - 22AWG shielded thermostat cable for
communications terminals ( i+ and i-) which will help eliminate any noise
interference.
Dual-Fuel Terminal Connections
Table 6. Dual-Fuel Terminals
Label Description Function
DFTS
Pre-coil discharge
air temperature (2
terminals)
The pre-coil discharge air sensor should be
installed downstream of the gas heat exchanger
and before the in door coil when a heat pump is
used and defrost tempering is required.
It must be placed in free airow, where other
accessories (such as humidiers, UV lights, etc.)
will not interfere with its accuracy. Wiring distance
between the EIM and the discharge air sensor
should not exceed 10 feet when using 18AWG
thermostat wire.
W1-DEF Defrost signal input
This input is used in systems with non-
communicating heat pumps for defrost indication.
The input provides a nominal load of 50 mA, 24
VAC.
0
Heat Pump Reversing
Valve (Powered for
cooling)
In systems with communicating IFC, the EIM (HP)
O output is connected to a non-communicating
heat pump compatible with O signal for reversing
valve operation. A 24VAC signal is generated on
O for cooling operation, while the terminal is open
for heating operation.
B
Heat Pump Reserving
Valve
(Powered for
heating)
In systems with communicating IFC, the EIM (HP)
B output is connected to a non-communicating
heat pump compatible with B signal for reversing
valve operation. A 24VAC signal is generated on
B for heat pump operation, while the terminal is
open for cooling operation.
Conventional Terminal Connections and Wiring Requirement
Table 7. Conventional Terminals
Label Description Function
18AWG unshielded thermostat cable (eld-provided) for
all non-communicating connections
W1 1st - stage heat output (1st stage gas heat output when congured as IFC
and 1st stage electric heat output when congured as AHC.
W2 2nd - stage heat output (2nd stage gas heat output when congured as
IFC and 2nd stage electric heat output when congured as AHC.
W3 3rd - stage heat output (3nd stage electric heat output when congured as
AHC)

7
Table 7. Conventional Terminals
Label Description Function
18AWG unshielded thermostat cable (eld-provided) for
all non-communicating connections
G
Indoor blower control (continuous fan) (monitoring only). G input may be
connected to IAQ devices such as LVCS, HRV or ERV to turn the indoor
blower on and o󰀨.
Y2 2nd - stage compressor output
Y1 1st - stage compressor output
DS 24VAC dehumidication signal output. The DS terminal is powered when
there is not a dehumidication call.
CClass II, 24VAC
transformer common
R and C terminals are used to receive power
from the indoor unit and capable of providing
the power to the EIM and all the associated
loads. The R power input uses a 3A fuse
(Lennox part number 25J4901.
RClass II. 24VAC
transformer power
H24VAC humidier signal output
OHeat pump reversing
valve (24VAC = cool)
Used as reversing valve output for heat
pumps. The EIM uses a single-pole dual
throw relay to generate O and B signals.
Normally the O output is open and B output
at 24VAC during heating calls. During cooling
calls O is 24VAC and B open. With relay de-
energized 24VAC is present on O terminal.
When power o󰀨/ or control reset, 24VAC
power shall not be present on the O
terminal.
BHeat pump reversing
valve (24 VAC = heat)
LED Indicators
This control has two green LED to indicate status and communication
activity One LED is labeled Status and the other is labeled RSBUS.
RSBUS LED
The RSBus LED ashes when information is being communicated over
the RSBus.
Status LED
The following table lists all status LED information.
Table 8. Status LED (Green)
Green LED Function / Description
Steady On Remains steady ON until the device sends its start-up
message.
Blinks 3 second OFF and 1
second ON Soft disable state
Blinks 2 second ON and 2
second OFF
Service is being provided (W, Y or G relay is ON, or G
input ON
Blinks 1 second ON and 1
second OFF
When alarms are present, you may review alarm(s) listed
either on the homeowner notication screen or the menu
/ settings > advanced settings > dealer control center
> notications screen. Information will be listed in either
location on how to clear the alert code(s).
Soft Disable
Soft disabling is when the Lennox communicating thermostat detects
an unknown control such as a indoor or outdoor unit control, iHarmony®
zoning system or Equipment Interface Module (EIM) on the system
communication bus. The thermostat sends the unknown control a
message to go into soft disable mode until component is properly
congured.
The Lennox communicating thermostat will not display any code for a
soft disabled control. When soft disabling occurs only the control that has
been disabled will display the blinking LED status. In this case, the control
blinks three seconds OFF and one second ON.
Use the following procedure if the equipment interface module is
displaying the soft disable code.
1. Conrm proper wiring between all devices such as thermostat, EIM,
indoor and outdoor unit).
2. Cycle power to the control that is displaying the soft disable code.
3. Touch the Lennox icon on the thermostat home screen and hold until
the installer warning screen appears.
4. Touch yes to continue.
5. Touch Setup and then conrm to continue.

8
6. Use this Thermostat? Touch press here to continue.
7. Touch the next button to continue past the next three screens.
8. From the System Devices list, touch reset ALL to reset all devices.
9. Touch the conrm button.
The thermostat will reboot and start through the setup process again.
IMPORTANT
If any jumpers were set incorrectly AFTER commissioning was
completed, then reposition jumpers to correct positions. Re-running the
commissioning procedure will be required at the Lennox communicating
thermostat.
This completes the conguring of the conventional outdoor unit.
iComfort S30 Commissioning (Conventional Outdoor Unit)
Both unit capacity and number of compressor stages are required to be
congured through the Lennox communicating thermostat. Once the
outdoor unit has been installed and connected to the equipment interface
module, go to the thermostat and start the conguration process.
1. From the equipment found screen, touch the non-communication
equipment location to add non-communicating equipment.
2. A add/remove equipment screen will appear. Under Outdoor Unit
Type, select the applicable 1 or 2-stage unit.
3. Touch either the plus or minus buttons to selected the applicable
Outdoor Unit Capacity. Valid options are 18, 24, 30, 36, 42, 48 and
60.
4. Touch save to continue.
Operating Environment Specications
The Equipment Interface Module is designed to operate in the following
environmental conditions.
• Operating Temperature Range: 40°F to 176°F (40° C to 80°C).
• Shipping and Storage Temperature Range: 40° F to 185°F (40°C to
85°C).
• Operating Humidity Range: 10% to 90% non-condensing at 104°F.
Unit Dimensions
8” (203mm)
6” (152mm)
1-5/8” (42mm)
Figure 6. Unit Dimensions

9
Duel-Fuel Operations
To use the EIM in dual-fuel mode, the following equipment combinations
and conguration is required.
Defrost Air Tempering Kit (67M41) will be required. The included DT1
discharge temperature probe is inserted in the furnace air outlet between
the furnace and the indoor coil to keep the furnace from overheating
the coil which would cause heat pump high pressure tripping during the
defrost cycling. The DT1 is only needed with non-communicating furnaces
and is not required for air handlers.
Wiring example for the DT1 Discharge Temperature Probe is in “Figure
13. Dual-Fuel - Conventional Furnace with Conventional Heat Pump
(1 or 2-Stage)” on page 12.
Lennox Communicating
Thermostat
Equipment Interface
Model (EIM)Furnace
24VAC conventional
Heat Pump
(Outdoor Unit)
Outdoor Sensor
(Included with
Heat Pump)
Defrost Tempering
(Available only if
furnace is variable
Optional
capacity
or multi-stage)
Wiring Legend
4-wire communicating
Lennox
Communicating
Non-Communicating
Figure 7. EIM, Conventional Furnace and Lennox Communicating Heat Pump
Wiring Legend 4-wire communicating
24VAC conventional
24VAC
Conventional Heat
Pump
(Outdoor Unit)
X2658 Outdoor
Sensor Required
Equipment Interface
Model (EIM)
Lennox
Communicating
Thermostat
Lennox
Communicating
Furnance
Figure 8. EIM, Conventional Furnace and Conventional Heat Pump

10
Field Wiring
Table 9. Wiring Diagrams
System Type Indoor Unit Outdoor Unit EIM Jumper Settings Diagrams
Unit Type Number and Type of Heat Stages
Air Conditioner Conventional Furnace Conventional Air Conditioner IFC Set to number of furnace stages. Figure 9 on page 11
Air Conditioner Conventional Air Handler Conventional Air Conditioner AHC Set to number of air handler electric heat
stages. Figure 9 on page 11
Heat Pump Conventional Air Handler Conventional Heat Pump HP
Set to number of heat pump compressor
stages.
Figure 10 on page 11
Dual Fuel Conventional Furnace Lennox Communicating Heat
Pump IFC Figure 12 on page 11
Dual Fuel Lennox Communicating
Furnace Conventional Heat Pump HP Figure 11 on page 11
Dual Fuel Conventional Furnace Conventional Heat Pump IFC Figure 13 on page 12
Dual Fuel with
iHarmony
Lennox Communicating
Furnace Conventional Heat Pump HP Figure 16 on page 13
Baseboard Heat Conventional Air Handler* Lennox Communicating Air
Conditioner or Heat Pump IFC
Set to the number of heat pump
compressor stages or air handler electric
heat stages.
Figure 14 on page 12
Hot Water Coil with
Aquastat Blower
Control
Conventional Air Handler* Lennox Communicating Air
Conditioner or Heat Pump IFC Figure 15 on page 12
Accessories -
Dehumidiers,
humidiers, HEPA
Bypass Filter (HRV
/ ERV)
Conventional Air Handler or
Furnace
Conventional Air Conditioner or
Heat Pump IFC Figure 17 on page 14
Accessories - EDA
Humiditrol and
LVCS Ventilation
Control
Conventional Air Handler or
Furnace
Conventional Air Conditioner or
Heat Pump IFC Figure 18 on page 14
* 24VAC conventional air handler or CBX32MV(-6), CBA38MV or CBX40UHV used as 24VAC conventional.

11
REMOVE JUMPER BETWEEN R AND W2
IF PRESENT. IT MAY CAUSE
ERRONEOUS ALERT CODE 125.
ICOMFORT SERIES
THERMOSTAT
Y2
Out
BL
Figure 9. Conventional Furnace or Air Hander with Conventional Air Conditioner
(1 or 2-Stage)
REMOVE JUMPER BETWEEN R AND W2
IF PRESENT. IT MAY CAUSE
ERRONEOUS ALERT CODE 125.
ICOMFORT SERIES
THERMOSTAT
Y2 OUT
BL
Figure 10. Conventional Air Hander with Conventional Heat Pump (1 or 2-Stage)
ICOMFORT SERIES
THERMOSTAT
Y2
Y2 OUT
BL
Y2 OUT IS FOR TWO-STAGE UNITS
ONLY (XP16 & XP19)
Figure 11. Dual-Fuel - Lennox Communicating Furnace with Conventional Heat
Pump (1 or 2-Stage)
IF THERE IS A JUMPER INSTALLED
BETWEEN R AND W2 ON INDOOR UNIT,
THEN REMOVED. IF NOT REMOVE IT
MAY CAUSE ERRONEOUS ALERT
CODE 125.
REMOVE JUMPER BETWEEN R AND W2 IF
PRESENT. IT MAY CAUSE ERRONEOUS ALERT
CODE 125.
ICOMFORT SERIES
THERMOSTAT
Y2 OUT
BL
NOTE: NOT APPLICABLE FOR VARIABLE CAPACITY OUTDOOR UNITS.
Figure 12. Dual-Fuel - Conventional Furnace with Lennox Communicating
Heat Pump (1 or 2-Stage)

12
REMOVE JUMPER BETWEEN R AND W2
IF PRESENT. IT MAY CAUSE
ERRONEOUS ALERT CODE 125.
ICOMFORT SERIES
THERMOSTAT
Y2 OUT
BL
Figure 13. Dual-Fuel - Conventional Furnace with Conventional Heat Pump
(1 or 2-Stage)
ICOMFORT SERIES
THERMOSTAT
Y2 OUT
BL
Figure 14. Baseboard Heat - Conventional Air Handler (CBX32MV(-6) or
CBX40UHV) with either a Lennox Communicating Air Conditioner or Heat Pump
Figure 15. Hot Water Coil Heat with Aquastat Blower Control - Conventional Air
Handler (CBX32MV(-6) or CBX40UHV)

13
ICOMFORT SERIES
THERMOSTAT
Y2 OUT
BL
3
2
Figure 16. Dual-Fuel - Lennox Communicating Furnace, iHarmony Zoning and Conventional Heat Pump

14
REMOVE JUMPER
BETWEEN R AND
W2 IF PRESENT.
IT MAY CAUSE
ERRONEOUS ALERT
CODE 125.
ICOMFORT SERIES
THERMOSTAT
Figure 17. Optional Accessories with Conventional Indoor Unit (HEPA Bypass Filter,
ERV/HRV, 24VAC Humidier and HCWHD3 Humidier)
REMOVE JUMPER BETWEEN R AND W2
IF PRESENT. IT MAY CAUSE
ERRONEOUS ALERT CODE 125.
ICOMFORT SERIES
THERMOSTAT
Y2 OUT
BL
Y2 OUT
BL
Figure 18. Conventional Indoor and Outdoor Units (EDA Humiditrol and LVCS
Ventilation Control System)

15
Alert Codes and Troubleshooting
Alert Code Types
To expand a specication notication to access a more detail description of the alert code, press the down arrow to expand the description.
• Service Urgent alerts are displayed on Home (user) screen under the homeowner and installer alert buttons. Service Urgent means that a service
call is needed to get the system running.
• Service Soon / Service Urgent means that the system will likely recover on its own and no interaction is necessary. Typically, either after a specic
timer period or a specic number of instances, some Service Soon alerts will escalate to Service Urgent.
• Service Soon alerts are found only in under the installer alert button.
• Information Only-Dealer is information only and helps Lennox interpret test results and understand complicated behaviors. Information Only are
not reported to homeowner or dealer.
Communication System: When communication controls are operating in a communication system, all jumper and link setting on controls are ignored.
Jumpers and link setting are treated as defaults and would only be active if the system was converted to a non-communicating system.
Error codes are transmitted to the thermostat. No codes are stored in the EIM.
Table 1. Alert Codes and Troubleshooting
GF= Gas Furnace, AH=Air Handler, ID=Indoor unit (GF or AH), HP=Heat Pump, AC=Air Conditioner, OD=Outdoor Unit (AC or HP), PA=Pure Air S, ZA=Zone system and
TS=Thermostat
Alert
Code
Priority
Condition
Actual Displayed
Alert Text
Under dealer
control center >
Notications
Component or System Operational State and Troubleshooting Tip How to clear
alert code
10 Service
Urgent
Unknown
Device Detected
The thermostat when NOT in conguration mode has detected an unknown device. Typically the thermostat will
send a command to the unknown device and place the device into a soft disable state. The soft disable control
will indicate so as follows:
On air handler, furnace and outdoor controls, the soft-disabled state is displayed by double horizontal lines on
seven-segment display.
On the damper control module, the green LED will ash 3 seconds on and 1 second o󰀨.
On the equipment interface module, the green LED will ash 3 seconds on and 1 second o󰀨.
A new communicating device has been added to the system since the original conguration setup was completed.
Go to menu > settings > advanced settings > view dealer control center > equipment and press reset all
equipment. This will allow the system to auto-detect any Lennox communicating devices attached.
Clear alert code by
reconguring the system.

16
Table 1. Alert Codes and Troubleshooting
GF= Gas Furnace, AH=Air Handler, ID=Indoor unit (GF or AH), HP=Heat Pump, AC=Air Conditioner, OD=Outdoor Unit (AC or HP), PA=Pure Air S, ZA=Zone system and
TS=Thermostat
Alert
Code
Priority
Condition
Actual Displayed
Alert Text
Under dealer
control center >
Notications
Component or System Operational State and Troubleshooting Tip How to clear
alert code
12 Service
Urgent
Indoor Unit Not
Detected
Thermostat did not nd an indoor unit. Make sure there is an Lennox communicating indoor unit on the system.
Check for voltage and missing component.
Check R, i+,i- and Cconnections at mag-mount or subbase, smart hub and all attached communicating
components.
Ohm wires for electrical continuity.
Cycle power to both indoor unit rst and then thermostat.
Verify that equipment interface module (if applicable) is congured as either an air handler or furnace when used
with a non-communicating indoor unit.
Go to menu > settings > advanced settings > view dealer control center > equipment and press reset all
equipment. This will allow the system to auto-detect any Lennox communicating components attached.
Replace indoor unit control if there is no response.
Automatically clears when
the system detects that the
issue no longer exists.

17
Table 1. Alert Codes and Troubleshooting
GF= Gas Furnace, AH=Air Handler, ID=Indoor unit (GF or AH), HP=Heat Pump, AC=Air Conditioner, OD=Outdoor Unit (AC or HP), PA=Pure Air S, ZA=Zone system and
TS=Thermostat
Alert
Code
Priority
Condition
Actual Displayed
Alert Text
Under dealer
control center >
Notications
Component or System Operational State and Troubleshooting Tip How to clear
alert code
105 Service
Urgent
Communication
Problem
One of the system components has lost communication with the system. The system component (device) is
unable to communicate.
S30 - Access dealer control center, select notications icon, review alert code details to determine which device
or unit has the communication problem. Review both active and cleared alerts.
Wi-Fi – Press and hold the Lennox logo on the bottom right of stat for 5 seconds to access the dealer control
center. Follow the prompts to access the dealer / installer screen and select the “Alerts” tab. Review alert code
details to determine which device or unit has the communication problem. Review both active and cleared
alerts.
Zoning - Remove wire from smart hub to iHarmony control and just have wiring from furnace.
Troubleshooting:
Check each control for additional codes
In most cases issues are related to electrical noise. Verify that high voltage power is separated from the low
voltage communication wires.
Check for proper grounding on line voltage and low voltage wiring, transformer and equipment.
Check for incorrectly wired or loose or spliced connections between system components (devices or units).
Make sure all unused wires are tied together and taken back to the C terminal on the indoor control board as
shown in the installation and setup guide.
Disconnect all wiring to other system components (except thermostat to indoor unit) and reconnect one device at
a time and recommission system each time a device is reconnected until the issue is located.
Zoning: If zoning is installed and is wired directly from smart hub to iHarmony control then disconnect that wiring.
Run control wiring from the iHarmony control directly to the indoor unit control. Wiring diagrams are provided in
the iHarmony Installation and Setup Guide.
Float Switch: When using a oat switch, use isolation relay to break common wire to outdoor unit. For testing
purposes, remove oat switch from the circuit.
Firmware and Accessories: Make sure that smart hub has correct rmware version for added accessory. (Example:
Pure Air S and/or Apple Home Kit must have software version 3.4 or higher before it will connect to system
properly. (If software is not updated in system it will cause system operation issues).
Inductive voltage from surrounding sources. Check each wire in AC mode to C on circuit board.
> Good voltage is .03-.3VAC inductive voltage is not an issue.
> Acceptable can be up to .7VAC with moderate success.
> Some units have worked with up to 1.2VAC with occasional success.
> Voltage over 1.2VAC needs to be addressed.
Automatically clears when
the system detects the
issue no longer exists.

18
Table 1. Alert Codes and Troubleshooting
GF= Gas Furnace, AH=Air Handler, ID=Indoor unit (GF or AH), HP=Heat Pump, AC=Air Conditioner, OD=Outdoor Unit (AC or HP), PA=Pure Air S, ZA=Zone system and
TS=Thermostat
Alert
Code
Priority
Condition
Actual Displayed
Alert Text
Under dealer
control center >
Notications
Component or System Operational State and Troubleshooting Tip How to clear
alert code
114
Service
Soon/Service
Urgent
AC Line
Frequency /
Distortion Prob
In most cases the errors will have something to do with the transformer(s) phasing, input power or output loading (amperage load).
For the air handler control only, alert code 114 is generated only if the measured line frequency is below 57Hz or above 63Hz and remains
out of range for 10 consecutive seconds. We count power line cycles and determine line frequency every 1 second of time based on the
processor’s quartz crystal oscillator. We have a fair amount of ltering on when we consider a power line cycle to have occurred, so there
would have to be really bad distortion for it to count an extra cycle or miss a real cycle.
Voltage low enough to miss a cycle would generate an alert code 115. There are lots of events, such as power utility substation switching, that
could occasionally make our power line frequency o󰀨 by one count. These are rare one-time events and I don’t know anything other than a
generator with bad frequency that could cause problems long enough to cause this alert code.
There is a frequency / distortion problem with the power to a specic system component. This alert code may indicate transformer
overloading.
Check the voltage and line power frequency.
Check the generator operating frequency, if the system is running on back-up power.
Correct voltage and frequency problems.
System will resume normal operation ve seconds after fault recovered.
All applicable system component outputs are disabled – moderate condition.
After 10 minutes, the priority condition is escalated – critical condition.
Damper control module will operate in central mode only until proper voltage is restored or frequency distortion is resolved – moderate condition.
If connected to iHarmony, set damper control module transformer jumper to system transformer. Check for proper wiring. Replace 40VAC
furnace transformer with 70VAC transformer. Re-commission system.
NOTE: The unitary control (outdoor unit control board) whether it is a single, two-stage or multi-stage control is not displaying alert code 114.
115 Service Soon Low Secondary
(24VAC) Voltage
24VAC power to a system component control is lower than the required range of 18 to 30VAC.
Check and correct voltage.
Check for additional power-robbing system components (devices) connected to system.
This alert code may require the installation of an additional or larger VA transformer.
Damper control module will operate in non-zone mode until proper voltage is restored.
Automatically clears when
the system detects the
issue no longer exists.

19
Table 1. Alert Codes and Troubleshooting
GF= Gas Furnace, AH=Air Handler, ID=Indoor unit (GF or AH), HP=Heat Pump, AC=Air Conditioner, OD=Outdoor Unit (AC or HP), PA=Pure Air S, ZA=Zone system and
TS=Thermostat
Alert
Code
Priority
Condition
Actual Displayed
Alert Text
Under dealer
control center >
Notications
Component or System Operational State and Troubleshooting Tip How to clear
alert code
120 Service Soon Unresponsive
Device
There is a delay in the system component responding to the system. Typically this alert code does not cause
any operational issues and will clear on its own.
This alert code is usually caused by a delay in the outdoor unit responding to the thermostat.
Leaking voltage from strands within the bundle.
> Land only the R wire on the Rterminal to load the bundle with 24VAC.
►Typically only the R wire needs to be landed to identify if voltage is leaking.
► If voltage is present checking the other wires is informational only but not needed.
► If voltage is not present checking the other wires one at a time would be needed.
> Check each loose wire in AC mode to Con circuit board.
► Good voltage is .03 -.3VAC leaking voltage is not the issue.
►Acceptable can be up to .7VAC with moderate success.
► Some units have worked with up to 1.2VAC with occasional success.
►Voltage over 1.2VAC needs to be addressed.
Automatically clears after
an unresponsive system
component (device)
responds to any inquiry.
124 Service
Urgent
Tstat Lost
Communication
To Smarthub
The thermostat has lost communication with a system component for more than three minutes. System
component has lost communication with the thermostat.
Check the wiring connections between components.
Ohm wires.
Cycle power.
Any component that is miss-wired may cause a false component code to be shown on system component.
Disconnect all wiring to other system components and check communication one at a time.
NOTE: When using a oat switch, use isolation relay to break common wire to outdoor unit. For testing
purposes, remove oat switch from the circuit
This alert code stops all associated system operations and waits for a heartbeat message from the system
component that is not communicating.
Automatically clears after
communication is re-
established with applicable
system component
(device).

20
Table 1. Alert Codes and Troubleshooting
GF= Gas Furnace, AH=Air Handler, ID=Indoor unit (GF or AH), HP=Heat Pump, AC=Air Conditioner, OD=Outdoor Unit (AC or HP), PA=Pure Air S, ZA=Zone system and
TS=Thermostat
Alert
Code
Priority
Condition
Actual Displayed
Alert Text
Under dealer
control center >
Notications
Component or System Operational State and Troubleshooting Tip How to clear
alert code
125 Service
Urgent
Control
Hardware
Problem
There is a hardware problem on a system component control. There is a control hardware problem.
In system using iHarmony zoning, the system will remain in non-zone mode (all dampers open) for ve minutes
after priority condition no longer exist.
In systems using a Equipment Interface Module, remove jumper if present on indoor unit between Rand W2.
In systems using a PureAir S, the pure air control board jumper selector is missing.
If none of the above tips are applicable, then replace the control if the problem prevents operation and is
persistent.
Automatically clears ve
minutes after the issue no
longer exists.
132 Service
Urgent
Device Control
Software Fault
System component control software is corrupted.
Recycle power.
If failure re-occurs, replace the system component control.
Manual system power reset
is required to recover from
this alert code.
180 Service Soon
Outdoor
Temperature
Sensor Problem
The thermostat has found a problem with the outdoor temperature sensor. In normal operation after system
component control recognizes sensors, the alert code will be sent if valid temperature reading is lost.
Compare outdoor sensor resistance to temperature / resistance charts in unit installation instructions. Replace
sensors pack if necessary.
At the beginning of (any) conguration, furnace, air-handler control or equipment interface module will detect the
presence of the sensor(s).
If detected (reading in range), appropriate feature will be set as ‘installed’ and shown in the ‘About’ screen.
Automatically clears upon
conguration, or sensing
normal values.
310 Service Soon
Discharge Air
Temp Sensor
Problem
There is a discharge air temperature sensor issue.
Conrm there is no short or open circuits in the Lennox communicating thermostat connections to any of the other
components in the communication system.
Compare discharge air temperature sensor (DATS) resistance to temperature / resistance charts in system
component installation instruction.
Replace discharge air sensor if necessary.
NOTE: Issues with a DATS connected to a damper control module or equipment interface model will not
generate an alert code.
Automatically clears 30
seconds after condition is
detected as recovered or
after system restart.