Lennox Signature XP21 Series Installation And Service Procedure page 35

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
Moderate
Slow flash Off Alert Code
Critical Alert
On Off
Code 413
Moderate
Slow flash On Alert Code
Critical Alert
Fast flash On
Code 415
Critical Alert
Fast flash On
Code 416
Moderate /
Off Fast flash Critical Alert
Code 417
3 fast Moderate /
flashes Off Critical Alert
then pause Code 418
3 fast Moderate /
flashes On Critical Alert
then pause Code 419
3 fast
Critical Alert
flashes
Off
Code 421
then pause
Simultaneous fast
flashes then pause
Fast simultaneous flashing of DS11,
DS13, DS14 and DS15
1. Pause duration is two (2) seconds.
2. Fast flash duration is 1/2 second. Slow flash duration is one (1) second.
Condition Condition Condition
High pressure
fault
412
High pressure
switch lockout
High Discharge
line temperature
414 fault
High Discharge
Line Temperature
Strikes Lockout
Outdoor Coil
Sensor Faulty
Discharge sensor
fault
W output
hardware fault
W output
hardware fault
lockout
W external
miswire fault
Second−stage
None
heat lock−in
OEM mode
Possible Cause(s) Possible Cause(s) Possible Cause(s)
Unit pressure is above the upper limit. System is shut down. Check system operating
pressures and compare to unit charging charts. Clears when pressure switch closes.
Open high pressure switch error count reached 5 strikes. Check system charge using
approach and subcooling temperatures. Check outdoor fan operation. Check for dirt
or debris blocking air flow to outdoor unit. Reset by putting outdoor unit control in test
mode or resetting low voltage power.
Discharge line temperature is > 279ºF. Check system operating pressures and
compare to unit charging charts in installation manual. Clears after discharge
temperature is < 225ºF.
Discharge line high temperature error count reached 5 strikes. Check system charge
using approach and subcooling temperatures. Reset by putting outdoor board in test
mode or resetting low voltage power.
Sensor being detected open or shorted, or temperature is out of sensor range.
Outdoor unit control will not perform demand or time/temperature defrost operation.
(System will still heat or cool.) Clears when outdoor unit control detects proper sensor
readings.
Outdoor unit control detects open or shorted sensor, or temperature that is out of
sensor range. Critical Alert after 10 minutes. Reset by replacing sensor. This fault is
detected by allowing the unit to run for 90 seconds before checking sensor
resistance. If the sensor resistance is not within range after 90 seconds, the board will
count one fault. After 5 faults, the board will lock out. Check for proper sensor reading
and attachment to line. Replace if out−of−spec.
When auxiliary heat output is detected as active. Fault in the heat pump control. Re-
place heat pump control. See figure 47 for further details.
If heat pump control recognizes five output hardware fault events during a single cool-
ing demand, the heat pump control will initiate a lockout. See figure 47 for further
details.
When auxiliary heat output is detected as active after compressor has been de−en-
ergized. See figure 47 for further details.
If the unit is in non−communicating mode and it goes to second stage due to ambient
temperature being below second stage lock−in setting (E48).
Factory test mode.
Page 35
Solution Solution Solution
XP21