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XP21
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
LEDs
SolutionPossible Cause(s)Condition
icomfortt
Thermostat
Display
DS11
Green
SolutionPossible Cause(s)Condition
icomfortt
Thermostat
Display
DS14 Red
DS11
Green
SolutionPossible Cause(s)Condition
icomfortt
Thermostat
Display
DS14 Red
Off
1 fast flash
then pause
Not
applicable
First−stage
compressor
heating
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.
Off
2 fast
flashes
then pause
Not
applicable
Second−stage
compressor
heating
On
2 fast
flashes
then pause
Not
applicable
Defrost
1 fast flash
then pause
Off
Not
applicable
First−stage
compressor
cooling
2 fast
flashes
then pause
Off
Not
applicable
Second−stage
compressor
cooling
2 fast
flashes
then pause
On
Not
applicable
Dehumidification
mode
ALERT STATUS
None
Moderate
Alert Code
105
Device
communication
failure
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.
None
Moderate
Alert Code
120
Unresponsive
device
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.
None
Critical Alert
Code 124
Active subnet
controller missing
for 180 seconds
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.
None
Critical Alert
Code 125
Hardware Failure
Hardware problem on the control. Cycle power on control. Replace if problem
prevents service and is persistent. Cleared 300 seconds after fault recovered.
None
Moderate /
Critical Alert
Code 126
Internal control
communication
failure
Internal communication on heat pump control. Alert will clear 300 seconds after fault
has recovered.
None
Critical Alert
Code 131
Corrupted control
parameters
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.
Simultaneous fast
flashes
Moderate /
Critical Alert
Code 180
Ambient sensor
problem
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.
None
Moderate
Alert Code
409
Low 24VAC. Sec-
ondary voltage is
low.
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.
Off
Slow flash
Moderate
Alert Code
410
Low pressure
fault
Unit pressures below the lower limit. System is shut down. Clears after pressure
switch closes.
Off On
Critical Alert
Code 411
Low pressure
switch lockout
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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