Lennox 10T50 Assembly instructions

507240-03
3/2019
Supersedes 11/2018
Equipment Interface
Module Installation and
Setup Guide
(10T50)

2
Shipping and Packing List.................................................................2
Application and Requirements..........................................................2
Indoor Transformer Requirements................................................... 2
Equipment ....................................................................................... 2
Installation...........................................................................................5
Conguration Setup...........................................................................5
EIM, 24VAC Furnace and Lennox Communicating Heat Pumps .... 5
EIM, Lennox Communicating Furnace and 24VAC Heat Pump ...... 5
Unit Type Jumpers........................................................................... 5
Heat Stage Jumper Positions .......................................................... 6
Air Temperature Sensor Connections.............................................. 6
Lennox Communicating Terminal Connections ............................... 6
Dual-Fuel Terminal Connections ..................................................... 7
Conventional Terminal Connections................................................ 7
LED Indicators ................................................................................. 7
Soft Disable ..................................................................................... 8
iComfort Wi-Fi Commissioning (Conventional Outdoor Unit) .......... 8
iComfort S30 Commissioning (Conventional Outdoor Unit) ............ 9
Operating Environment Specications ............................................9
Unit Dimensions ...............................................................................10
Duel-Fuel Operations .......................................................................10
Field Wiring ....................................................................................... 11
Alert Codes and Troubleshooting...................................................17
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 (iComfort Wi-FI®or iComfort®S30) using the R,
i+, i-, and C terminals. The EIM is the interface between non-communicating
HVAC equipment and Lennox communicating HVAC equipment. The
control supports the following equipment applications:
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
LENNOX COMMUNICATING
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
tions, additional components
may need to be added, see figure
5 on page 8.
Lennox Communcating
Thermostat
Equipment Interface
Model (EIM)
24VAC Air Handler or
Furnace (Indoor Unit)
Lennox
communicating
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)
ICOMFORT
WI-FI
ICOMFORT
S30
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.

5
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 11 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 11. Those diagrams will indicate all
required jumper settings on the EIM and wiring connections.
EIM, 24VAC Furnace and Lennox Communicating Heat Pumps
See“Figure13.Dual-Fuel-ConventionalFurnacewithLennoxCommunicating
Heat Pump” on page 12 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 6) 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 12. Dual-Fuel - Lennox Communicating Furnace with
Conventional Heat Pump” on page 12f 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 6) to the applicable number of heat pump heating stages.
3. Use the Lennox communicating thermostat to complete the
commissioning procedure.
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 being by using the
following table and gure. 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 Fur-
nace 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

6
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
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
Table 5. Communicating Terminals
Label Function / Description
R 24VAC communication power Input
i+ Communication high – data line
i- Communication low – data line
C 24VAC communication common power Input

7
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-com-
municating 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-communi-
cating 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 heat-
ing)
In systems with communicating IFC, the EIM
(HP) B output is connected to a non-communi-
cating 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
Table 7. Conventional Terminals
Label Description Function
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)
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
Table 7. Conventional Terminals
Label Description Function
DS 24VAC dehumidication signal output. The DS terminal is powered when
there is not a dehumidication call.
CClass II, 24VAC trans-
former 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 trans-
former 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 pow-
er 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).

8
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.
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.
iComfort Wi-Fi 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 system devices screen, touch the yes button to add or
remove non-communicating equipment.
2. A non-communicating device list will appear, select Outdoor Unit
Type and then touch edit.
3. Under Outdoor Unit Type, select the applicable 1 or 2-stage unit.
Touch save to continue.
4. Under non-communicating device list, select Outdoor Unit Capacity
and then touch edit.
5. Touch either the up or down arrows to selected the applicable Outdoor
Unit Capacity. Valid options are 18, 24, 30, 36, 42, 48 and 60. Touch
save to continue.
This completes the conguring of the conventional outdoor unit.

9
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.
Figure 6. Adding Conventional Outdoor Unit
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 7. Unit Dimensions
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.

10
Wiring example for the DT1 Discharge Temperature Probe is in “Figure 14.
Dual-Fuel - Conventional Furnace with Conventional Heat Pump” on page
13.
Lennox Communicating
Thermostat
Equipment Interface
Model (EIM)
24VAC
Furnace
24VAC conventional
DUAL−FUEL WITH DEFROST TEMPERING
(EIM, 24VAC Furnace and Communicating Heat Pump)
Heat Pump
(Outdoor Unit)
Outdoor Sensor
(Included with
Heat Pump)
Defrost Tempering
(Available only if
furnace is variable
Optional
NOTE: iComfort Wi-Fi
Thermostat with firmware
version 2.1 or higher)
capacity
or multi-stage)
Wiring Legend
4-wire communicating
ICOMFORT
WI-FI
ICOMFORT
S30
Lennox
Communicating
Figure 8. EIM, Conventional Furnace and Lennox Communicating Heat Pump
Lennox
Communicating
Thermostat
Wiring Legend 4-wire communicating
24VAC conventional
DUAL−FUEL WITH DEFROST TEMPERING
(EIM, Communicating Furnace and 24VAC Heat Pump
24VAC
Conventional Heat
Pump
(Outdoor Unit)
X2658 Outdoor
Sensor Required
Equipment Interface
Model (EIM)
NOTE: iComfort Wi-Fi
Thermostat with firmware
version 2.1 or higher)
ICOMFORT
WI-FI
ICOMFORT
S30
Lennox
Communicating
Furnace
Figure 9. EIM, Conventional Furnace and Conventional Heat Pump

11
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 10 on page 12
Air Conditioner Conventional Air Handler Conventional Air Conditioner AHC Set to number of air handler electric heat
stages. Figure 10 on page 12
Heat Pump Conventional Air Handler Conventional Heat Pump HP
Set to number of heat pump compressor
stages.
Figure 11 on page 12
Dual Fuel Conventional Furnace Lennox Communicating Heat
Pump IFC Figure 13 on page 12
Dual Fuel Lennox Communicating
Furnace Conventional Heat Pump HP Figure 12 on page 12
Dual Fuel Conventional Furnace Conventional Heat Pump IFC Figure 14 on page 13
Dual Fuel with
iHarmony
Lennox Communicating
Furnace Conventional Heat Pump HP Figure 17 on page 14
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 15 on page 13
Hot Water Coil with
Aquastat Blower
Control
Conventional Air Handler* Lennox Communicating Air
Conditioner or Heat Pump IFC Figure 16 on page 13
Accessories -
Dehumidiers,
humidiers, HEPA
Bypass Filter (HRV
/ ERV)
Conventional Air Handler or
Furnace
Conventional Air Conditioner or
Heat Pump IFC Figure 18 on page 15
Accessories - EDA
Humiditrol and
LVCS Ventilation
Control
Conventional Air Handler or
Furnace
Conventional Air Conditioner or
Heat Pump IFC Figure 19 on page 16
* 24VAC conventional air handler or CBX32MV(-6), CBA38MV or CBX40UHV used as 24VAC conventional.

12
REMOVE JUMPER BETWEEN R AND W2
IF PRESENT. IT MAY CAUSE
ERRONEOUS ALERT CODE 125.
LENNOX COMMUNICATING
THERMOSTAT
Figure 10. Conventional Furnace or Air Hander with Conventional Air Conditioner
REMOVE JUMPER BETWEEN R AND W2
IF PRESENT. IT MAY CAUSE
ERRONEOUS ALERT CODE 125.
LENNOX COMMUNICATING
THERMOSTAT
Figure 11. Conventional Air Hander with Conventional Heat Pump
LENNOX COMMUNICATING
THERMOSTAT
SET “HEAT STAGES” TO NUMBER
OF COMPRESSOR HEAT STAGES
Figure 12. Dual-Fuel - Lennox Communicating Furnace with Conventional Heat
Pump
IF THERE IS A JUMPER INST
ALLED
BETWEEN R AND W2 ON INDOOR UNI
T,
THEN REMOVED. IF NOT REMOVE IT
MA
Y CAUSE ERRONEOUS ALERT
CODE 125
.
REMOVE JUMPER BETWEEN R AND W2 IF
PRESENT. IT MAY CAUSE ERRONEOUS ALERT
CODE 125.
LENNOX COMMUNICATING
THERMOSTAT
LENNOX COMMUNICATING OUTDOOR
UNIT HAS BUILT-IN OUTDOOR TEMP
SENSOR WHICH CAN BE USED FOR
BALANCE POINTS FOR SYSTEM.
SET “HEAT STAGES” TO NUMBER
OF COMPRESSOR HEAT STAGES
Figure 13. Dual-Fuel - Conventional Furnace with Lennox Communicating
Heat Pump

13
REMOVE JUMPER BETWEEN R AND W2
IF PRESENT. IT MAY CAUSE
ERRONEOUS ALERT CODE 125.
LENNOX COMMUNICATING
THERMOSTAT
SET “HEAT STAGES” TO NUMBER
OF COMPRESSOR HEAT STAGES
Figure 14. Dual-Fuel - Conventional Furnace with Conventional Heat Pump
LENNOX COMMUNICATING
THERMOSTAT
LENNOX
COMMUNICATING
HEAT PUMP OR
AIR CONDITIONER
Figure 15. Baseboard Heat - Conventional Air Handler (CBX32MV(-6) or CBX40UHV)
with either a Lennox Communicating Air Conditioner or Heat Pump
REMOVE JUMPER BETWEEN R AND W2
IF PRESENT. IT MAY CAUSE
ERRONEOUS ALERT CODE 125.
Figure 16. Hot Water Coil Heat with Aquastat Blower Control - Conventional Air
Handler (CBX32MV(-6) or CBX40UHV)

14
LENNOX COMMUNICATING
THERMOSTAT
LENNOX COMMUNICATING
FURNACE
SET HEAT STAGES TO THE NUMBER
OF COMPRESSOR STAGES
Figure 17. Dual-Fuel - Lennox Communicating Furnace, iHarmony Zoning and Conventional Heat Pump

15
REMOVE JUMPER
BETWEEN R AND
W2 IF PRESENT.
IT MAY CAUSE
ERRONEOUS ALERT
CODE 125.
LENNOX COMMUNICATING
THERMOSTAT
HCWHD3
ERV/HRV and HEPA
HCWHD3
DEHUMIDIFIER
ERV / HRV
Figure 18. Optional Accessories with Conventional Indoor Unit (HEPA Bypass Filter, ERV/HRV, 24VAC Humidier and HCWHD3 Humidier)

16
REMOVE JUMPER BETWEEN R AND W2
IF PRESENT. IT MAY CAUSE
ERRONEOUS ALERT CODE 125.
LENNOX COMMUNICATING
THERMOSTAT
Figure 19. Conventional Indoor and Outdoor Units (EDA Humiditrol and LVCS Ventilation Control System)

17
Alert Codes and Troubleshooting
Error codes are transmitted to the thermostat. No codes are stored in the EIM.
Table 10. Alert Codes and Troubleshooting
Alert Code Priority
Condition
Applicable System
Component(s)
Alert Text Component or System Operational State
and Troubleshooting Tip How to clear the alert code
10 Critical
All Lennox Communicating
thermostats.
Communicating air handler,
furnace, outdoor unit, EIM
and iHarmony.
The thermostat has
found an unknown de-
vice on the system.
Lennox communicating 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 it in a soft disable
state.
The soft disable control will indicate as follows:
√ On air handler, furnace and outdoor controls, the state is displayed
by double horizontal lines on seven-segment display.
√ On the damper control module or equipment inter face equipment,
the green LED will blink three sec onds on and one second o󰀨.
Cycling power to the soft disabled control may clear the condition.
If cycling power does not clear the soft disabled state then replace
control.
Clear alert code by recon-
guring the system
12 Critical
All Lennox Communicating
thermostats.
Lennox Communicating
furnace, EIM or air handler
The thermostat cannot
nd a Lennox commu-
nicating indoor unit
Lennox communicating thermostat did not nd an indoor unit. Make
sure there is an Lennox communicating indoor unit on the system.
√ Check R, i+, i- and C connections and voltages.
√ Ohm wires and cycle power.
√ Check for voltage and missing component.
√ Verify that equipment interface module is congured as air handler
or furnace when used with a non-communicating indoor unit.
√ Go to menu > 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.
105 Critical
All Lennox Communicating
thermostats.
Lennox Communicating
furnace, air handler, outdoor
unit, EIM or iHarmony
A system component
has lost communication
with the system.
System component (device) is unable to communicate.
√ This may indicate the existence of other active alert codes.
√ In most cases errors are related to electrical noise. Verify that high
voltage power is separated from the low voltage communication
wires.
√ Check for incorrectly wired or loose connections be tween system
components (devices).
√ Check for a high voltage source of noise close to the system.
Automatically clears when
the system detects the
issue no longer exists.

18
Table 10. Alert Codes and Troubleshooting
Alert Code Priority
Condition
Applicable System
Component(s)
Alert Text Component or System Operational State
and Troubleshooting Tip How to clear the alert code
114 Moderate /
Critical
Lennox Communicating
Furnace, air handler, EIM or
IHarmony
There is a frequency /
distortion problem with
the power to a specic
system component.
√ This alert code may indicate transformer overload ing.
√ 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 dis abled – 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.
Automatically clears when
the system detects the
issue no longer exists.
115 Critical Lennox Communicating
Furnace, air handler or EIM
Primary 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 compo nents (devices)
connected to system.
√ This alert code may require the installation of an ad ditional or larger
VA transformer.
Automatically clears when
the system detects the
issue no longer exists.
120 Moderate
All Lennox Communicating
thermostats.
Lennox communicating
furnace, air handler, outdoor
unit, EIM or iHarmony
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.
√ Check all wiring connections.
Automatically clears after
an unresponsive system
component (device) re-
sponds to any inquiry.
124 Critical
All Lennox Communicating
thermostats.
Lennox communicating
furnace, air handler, outdoor
unit, EIM or iHarmony
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.
√ Ohm wires.
√ Cycle power.
√ Check voltage at component.
This alert code stops all associated system operations and waits for a
heartbeat message from the system component that is not communi-
cating.
Automatically clears after
communication is re- estab-
lished with applicable sys-
tem component (device).
125 Critical
All Lennox Communicating
thermostats.
Lennox communicating
furnace, air handler, outdoor
unit, EIM or iHarmony
There is a hardware
problem on a system
component control.
There is a control hardware problem.
√ Replace the control if the problem prevents opera tion and is
persistent.
√ Damper control module will remain in non-zone mode (all dampers
open) for ve minutes after priori ty condition no longer exist.
√ Remove jumper if present on indoor unit between R and W2 if
equipment interface module is in use.
Automatically clears 300
seconds after the issue no
longer exists.

19
Table 10. Alert Codes and Troubleshooting
Alert Code Priority
Condition
Applicable System
Component(s)
Alert Text Component or System Operational State
and Troubleshooting Tip How to clear the alert code
130 Moderate EIM Air handler jumper is
missing.
√ Conguration jumper missing on equipment inter face module.
√ Install the missing jumper.
NOTE: This is applicable in non-communicating applications only).
Automatically clears after
the missing or incorrectly
installed jumper is installed
or corrected.
131 Critical
All Lennox Communicating
thermostats.
Lennox communicating
furnace, air handler, outdoor
unit, EIM or iHarmony
System component
control parameters are
corrupted.
√ Replace the system component control if heating or cooling is not
available.
√ Try resetting the thermostat.
Will automatically clear
when system component
(device) passes memory
self-test or system compo-
nent control is re placed.
132 Critical Lennox communicating Air
handler, EIM or iHarmony
System component
control software is cor-
rupted
√ Recycle power.
√ If failure re-occurs, replace the system component control.
Manual system power reset
is re quired to recover from
this alert code.
180 Critical Lennox communicating
Furnace, air handler or EIM
The thermostat has
found a problem with
a system component’s
outdoor temperature
sensor.
In normal operation after system component control recognizes sen-
sors, the alarm will be sent if valid temperature reading is lost.
√ Compare outdoor sensor resistance to temperature / resistance
charts in unit installation instructions.
√ Replace sensor 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 Moderate
Lennox communicating
Furnace, air handler, EIM or
iHarmony
There is a discharge
air temperature sensor
issue.
Compare discharge temperature sensor resistance to temperature /
resistance charts in system component installation instruction.
√ Replace discharge air sensor if failed.
√ If applicable, iHarmony will operate in non-zone mode (all dampers
open).
NOTE: 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.
Automatically clears 30
seconds after condition is
detected as recovered or
after system restart.
345 Critical Lennox communicating Air
handler, EIM or heat pump
The O relay on the
system component has
failed. Either the pilot
relay contacts did not
close or the relay coil
did not energize.
Possible O relay / stage 1 failure.
√ Pilot relay contacts did not close or the relay coil did not energize.
√ Replace system component (device) control.
√ If error is applicable to the XC/XP 25, the outdoor control will need
to be replaced.
Automatically clears after
the fault recovered follow-
ing reset.
347 Critical Lennox communicating
Furnace, air handler or EIM
The Y1 relay on the
applicable system
component has failed.
Either the pilot relay
contacts did not close
or the relay coil did not
energize.
√ System operation will stop.
√ Possible Y1 relay / stage 1 failure.
√ Pilot relay contacts did not close or the relay coil did not energize.
√ There is no input back to the applicable system component control.
Automatically clears
after reset and Y1 input
sensed.

20
Table 10. Alert Codes and Troubleshooting
Alert Code Priority
Condition
Applicable System
Component(s)
Alert Text Component or System Operational State
and Troubleshooting Tip How to clear the alert code
380 Moderate /
Critical EIM
Interlock relay failure
(IFC or AHC mode
only).
√ Interlock relay is energized, but input is not sensed after three
seconds.
√ There will be no heating or cooling due to this alert code – moderate
condition.
√ De-energize interlock relay and energize after ve minutes if
demand is still present – critical condition.
Automatically clears after
fault recovered.
381 Moderate /
Critical EIM
Interlock relay stuck
(IFC or AHC modes
only)
√ Interlock relay continuously sensed (with relay o󰀨).
√ There is no heating and cooling operation – moderate condition.
√ After 10 minutes if event still exist it will be escalated – critical
condition.
Automatically clears 30
seconds after fault clears
382 Moderate EIM
Relay W1 failure
(IFC and AHC modes
only)
W1 relay is energized but input is not sensed after three seconds. Automatically clears when
W1 relay input is sensed.
418 Moderate EIM and Lennox
communicating outdoor unit
There is a faulty W
output circuit.
√ W terminal is energized while in cooling mode.
√ Possible cause may be a stuck closed relay on the control, or
something external to the control that is energizing W terminal when
it should not be energized.
√ Disconnect any wiring from the W terminal.
√ If 24VAC is still on the terminal, then it is a stuck relay.
√ If 24VAC disappears, then there is a need to check any of the wires
hooked up to the W terminal.
Automatically clears after
fault signal is re moved.
419 Critical EIM and Lennox
communicating outdoor unit
The W output has re
ported more than ve
errors
√ The system will shut down the outdoor unit.
√ The W output (alert code 418) on the outdoor unit has reported more
than ve strikes.
√ Disconnect thermostat wire from W and verify there is no 24VAC on
the W.
√ If 24VAC is present, replace the outdoor control.
Automatically clears after
power recycled.
420 Critical Lennox communicating Air
handler or EIM
The heat pump defrost
cycle has taken more
than 20 minutes to
complete
√ Defrost cycle lasts longer than 20 minutes.
√ Check heat pump operation.
√ This is applicable only in communicating indoor unit with non-
communicating heat pump.
Automatically clears when
W1 signal is re moved.
421 Critical EIM and Lennox
communicating outdoor unit
The W output terminal
on the outdoor unit is
not wired correctly.
Voltage sensed on W output terminal when Y1 out is deactivated.
Automatically clears once
volt age is not sense on
output for power cycled.
594 Moderate /
Critical EIM
Pre-coil discharge air
temperature sensor
problem (DFM mode
only). Advances from
moderate to critical af-
ter ten (10) minutes.
√ Interlock relay energized, but input not sensed after three seconds.
√ No heating and cooling operations.
√ De-energize interlock relay and re-energized ve minutes later if
demand is still present.
Alarm clears ve minutes
after fault clears.