Lennox XP17-024-230-01 Installation And Service Procedure page 32

NOTE — System fault and lockout seven-segment display alarm codes takes precedence over system status codes
(cooling, heating stages or defrost/dehumidification). Only the latest active fault or lockout alarm code if present will be
displayed. If no fault or lockout codes are active, then system status are routinely displayed.
Alert
Alarm Description
Codes
The outdoor
E 105 communication with the rest of the
system.
There is a delay in the outdoor unit
E 120
responding to the system.
The iComfortt-enabled thermostat
has lost communication with the out­
E 124
door unit for more than 3 minutes.
There is a hardware problem with the
E 125
outdoor unit control.
There is an internal communication
E 126
problem with the outdoor unit control.
The outdoor unit control parameters are
E 131
corrupted
The iComfortt-enabled thermostat has
E 180 found a problem with the outdoor unit's
ambient sensor.
Either the compressor ran for more than
E 401
18 hours continuously.
The compressor ran for less than 3
E 403 minutes to satisfy a thermostat demand
(short-cycling)
The secondary voltage for the outdoor
unit has fallen below 18VAC. If this
E 409
continues for 10 minutes, the system
will shut down.
The outdoor unit pressure is below the
E 410
required limit.
The low pressure switch has opened 5
times during one cooling cycle. As a
E 411
result, the system will shutdown.
The outdoor unit pressure is above the
required limit. The system will shut
E 412
down.
The high pressure switch has opened 5
times during one cooling cycle. As a
E 413
result, the iComfortt
thermostat will shutdown.
XP17
Table 12. Seven-Segment Display Alert Codes
Equipment is unable to communicate. This may indicate the existence of other alarms / codes. In
unit has lost
most cases errors are related to electrical noise. Make sure high voltage power is separated from
RSBus. Check for mis-wired and/or loose connections between the stat, indoor unit and outdoor
unit. Check for a high voltage source of noise close to the system. This is a self-recoverable error.
Typically, this alarm/code does not cause any issues and will clear on its own. The alarm / code is
usually caused by a delay in the outdoor unit responding to the thermostat. Check all wiring
connections. Cleared after unresponsive device responds to any inquiry
Equipment lost communication with the thermostat. Check the wiring connections, ohm wires and
cycle power. The alarm stops all associated HVAC operations and waits for a heartbeat message
from the unit that's not communicating. The alarm / fault clears after communication is re-estab­
lished.
There is a control hardware problem. Replace the outdoor control if the problem prevents operation
and is persistent. The alarm / fault is cleared 300 seconds after the fault recovers
There is an internal hardware problem on the control. Typically the control will re-set itself. Replace
the control if the problem prevents operation and is persistent. The alarm / fault is cleared 300 sec­
onds after the fault recovers.
Reconfigure the system. Replace the control if heating or cooling is not available
In normal operation after outdoor control recognizes sensors, 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)
configuration, furnace or air-handler control will detect the presence of the sensor(s). If detected
(reading in range), appropriate feature will be set as 'installed' and shown in the iComfortt-enabled
thermostat 'About' screen. The alarm / fault will clear upon configuration, or sensing normal values.
Compressor ran more than 18 hours to satisfy a single thermostat demand. If the unit is 2-stage, the
high-speed will lock-out and the unit will run at low-speed. If it is a HP and ODT <65ºF, the system will
not raise an alarm. Confirm that the system is properly charged with refrigerant. Check for stuck
reversing valve, excessive cooling load and properly sized equipment. Confirm that the evaporator
coil is clean. The alarm clears after 30 consecutive normal run cycles or a power reset.
Compressor runs less than 3 minutes to satisfy a thermostat demand (short-cycling). Confirm that
the system is properly charged with refrigerant. Check the condensation float switch and TXV. The
alarm clears after 4 consecutive normal compressor run cycles or a power reset.
Secondary voltage is below 18VAC. After 10 minutes, operation is discontinued. Check the indoor
line voltage, transformer output voltage. The alarm clears after the voltage is higher than 20VAC for
2 seconds or after a power reset.
Unit pressure is below the lower limit. The system is shutdown. The low pressure switch for
HFC-410A will open at 40PSIG and close at 90PSIG. Confirm that the system is properly charged
with refrigerant. Check TXV, indoor unit blower motor, dirty filters or clogged refrigerant filter. Con­
firm that the evaporator coil is clean. The alarm clears after the pressure switch closes or after a
power reset
Open low pressure switch error count reached 5 strikes. The low pressure switch for R410A will
open at 40PSIG and close at 90PSIG. Confirm that the system is properly charged with refrigerant.
Check TXV, indoor unit blower motor, dirty filters or clogged refrigerant filter. Confirm that the
evaporator coil is clean. The alarm clears after a power reset
Unit pressure is above the upper limit. System is shut down. The high pressure switch for HFC-410A
will open at 590PSIG and close at 418PSIG. Confirm that the system is properly charged with
refrigerant. Check condenser fan motor, TXV, indoor unit blower motor, stuck reversing valve or
clogged refrigerant filter. Confirm that the outdoor unit is clean. The alarm clears after 4 consecutive
normal compressor run cycles, the pressure switch closes or a power reset
Open high pressure switch error count reached 5 strikes. System is shut down. The high pressure
switch for HFC-410A will open at 590PSIG and close at 418PSIG. Confirm that the system is prop­
erly charged with refrigerant. Check condenser fan motor, TXV, indoor unit blower motor, stuck re­
-enabled
versing valve or clogged refrigerant filter. Confirm that the outdoor unit is clean. The alarm clears
after a power reset.
Possible Causes and Clearing Alarm
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