Lennox Signature XP21 Series Installation And Service Procedure page 34

System fault and lockout LED (DS11 / DS14) alarm codes takes precedence over system status LED codes (cooling, heating stages or
defrost/dehumidification). Only the latest active LED fault or lockout alarm code if present will be displayed. If no fault or lockout codes are active, then
system status LEDs are routinely displayed. See notes 1 and 2 in table below for duration of fast / slow flashes and pause.
Heat Pump Control
icomfortt icomfortt icomfortt
LEDs
Thermostat Thermostat Thermostat
DS11 DS11
Display Display Display
DS14 Red DS14 Red
Green Green
1 fast flash
Off
then pause applicable
2 fast
Off flashes
applicable
then pause
2 fast
flashes
On
applicable
then pause
1 fast flash
Off
then pause applicable
2 fast
flashes Off
applicable
then pause
2 fast
flashes
On
applicable
then pause
Moderate
None Alert Code
Moderate
None Alert Code
Critical Alert
None
Code 124
Critical Alert
None
Code 125
Moderate /
None Critical Alert
Code 126
Critical Alert
None
Code 131
Moderate /
Simultaneous fast
Critical Alert
flashes
Code 180
Moderate
Alert Code
None
Moderate
Off Alert Code
Slow flash
Critical Alert
Off On
Code 411
XP21
Condition Condition Condition
First−stage
Not
compressor
heating
Second−stage
Not
compressor
heating
Not
Defrost
First−stage
Not
compressor
cooling
Second−stage
Not
compressor
cooling
Not Dehumidification
mode
Device
communication
105 failure
Unresponsive
device
120
Active subnet
controller missing
for 180 seconds
Hardware Failure
Internal control
communication
failure
Corrupted control
parameters
Ambient sensor
problem
Low 24VAC. Sec-
ondary voltage is
409
low.
Low pressure
fault
410
Low pressure
switch lockout
Possible Cause(s) Possible Cause(s) Possible Cause(s)
These are codes that show status of operation whether the system is operating in either
in first or second stage heating or cooling operation, defrost or in the dehumidification
modes.
ALERT STATUS
Equipment is unable to communicate. Indicates numerous message errors. In most
cases errors are related to electrical noise. Make sure high voltage power is sepa-
rated 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. Fault clears after communication is restored.
Usually caused by delay in outdoor unit responding to indoor unit poling.
Recycle power. Check all wiring connections. Cleared after unresponsive
device responds to any inquiry.
Equipment lost communication with the thermostat. Check four wiring connections,
ohm wires and cycle power at the thermostat. Alert stops all services and waits for
heartbeat message from thermostat (subnet controller). Cleared after valid thermostat
(subnet controller) message is received.
Hardware problem on the control. Cycle power on control. Replace if problem
prevents service and is persistent. Cleared 300 seconds after fault recovered.
Internal communication on heat pump control. Alert will clear 300 seconds after fault
has recovered.
Reconfigure the system. Replace control if heating or cooling is not available. Only
applicable in the communicating mode, not in start up. Exit from Commissioning and
Execute ´Set Factory Default mode´. Control will still operate on default parameter
settings.
If sensor detects an open, shorted or out−of−temperature range. heat pump control will
revert to time/temperature defrost operation. System will still heat or cool.
Secondary voltage is below 18VAC. After 10 minutes, operation is discontinued.
Clears the code after voltage is higher than 20 VAC for 2 seconds or after power re-
set.
Unit pressures below the lower limit. System is shut down. Clears after pressure
switch closes.
Open low pressure switch error count reached 5 strikes. Check system charge using
approach and subcooling temperatures. Reset by putting outdoor unit control in test
mode or resetting low voltage power.
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Solution Solution Solution