Lennox Signature XP21 Series Installation And Service Procedure page 53

Alert
Alarm Description
Codes
The discharge line temperature is high-
er than the recommended upper limit of
E 414
279ºF.
The discharge line temperature has
E 415 been consistently higher than the rec-
ommended upper limit of 279ºF.
The outdoor coil sensor is either open,
short−circuited or the temperature is out
E 416 of sensor range. As a result the outdoor
unit control will not perform any defrost
tempering.
The outdoor unit discharge sensor is ei-
ther open, short−circuited or the tem-
perature is out of sensor range. As a re-
E 417
sult the outdoor unit control will not per-
form any defrost tempering.
E 418 There is a faulty W output circuit.
The W output on the outdoor unit has re-
ported more than 5 errors. As a result,
E 419
the system has shutdown the outdoor
unit.
The heat pump defrost cycle has taken
E 420
more than 20 minutes to complete.
The W output terminal on the outdoor
E 421
unit is not wired correctly.
NOTE Additional codes may be found in icomfortt thermostat manual.
Description
Power up / Reset: Unit type and number of stages is displayed.
Verify configuration with information published on the unit name-
plate. If the information is incorrect, refer to flow chart Manually
Configuration of Unit Type to re−configure control.
Power up / Reset following display of self−dis-
covered configuration: Unit nominal capacity is
displayed, if not programmed then three horizontal
lines and the decimal point are displayed for 2 sec-
onds.
Power up / Reset following display of nominal
capacity: Fan Profile code. (a single or two digit
number) See table 18 for applicable fan RPM pro-
file.
Table 20. Seven−Segment Display Alert Codes (continued)
Discharge line temperature is > 279ºF. Confirm that the system is properly charged with refrigerant.
Check system operating pressures and compare to unit charging charts in installation manual.
Confirm that the outdoor unit is clean. The alarm clears after the discharge temperature is < 225ºF.
Discharge line high temperature error count reached 5 strikes. Confirm that the system is properly
charged with refrigerant. Check system operating pressures and compare to unit charging charts in
installation manual. Confirm that the outdoor unit is clean. The alarm clears after the discharge tem-
perature is < 225ºF. The alarm clears after a power reset.
Coil sensor being detected open or shorted, or temperature is out of coil sensor range. Outdoor unit
control will not perform demand or time/temperature defrost operation. System will still heat or cool.
Check the resistance of the coil sensor and compare to temperature resistance chart. Replace coil
sensor if needed. The alarm clears when outdoor unit control detects proper coil sensor readings or
after a power reset.
Outdoor unit control detects open or shorted discharge sensor, or temperature that is out of
discharge sensor range. Check the resistance of the discharge sensor and compare to
temperature resistance chart − replace if needed. Reset by replacing the discharge sensor. This
fault is detected by allowing the unit to run for 90 seconds before checking discharge sensor
resistance. If the discharge 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. The alarm clears after a power reset.
Faulty W output circuit. Confirm that the unit is not running. Check for mis−wiring. Disconnect
thermostat lines from W and verify 24VAC on the W. If 24VAC is present, replace the board.
W output hardware fault count reached 5−strikes.
Defrost cycle lasts longer than 20 minutes. This alarm is applicable with non−communicating heat
pump system only. Check heat pump defrost operation. The alarm is cleared after the "W1" signal is
removed.
Voltage sensed on W and O when Y1 thermostat input is deactivated. Another device or wiring fault
is energizing W Check wiring. The alarm clears when wiring is corrected or after a power reset.
Table 21. Outdoor Control Seven−Segment Unit Status Displays
Possible Causes and Clearing Alarm
Example of Display
1 Stage AC: 1AC
2 Stage AC: 2AC
1 Stage AC: 1HP
1 Stage AC: 2HP
POWER−UP 7−SEGMENT DISPLAY STRING
H P
2
Unit Type / Stages
Power up nominal capacity display of an XP21−036: 36
POWER−UP 7−SEGMENT DISPLAY STRING
H
2 P
Unit Type / Stages
Displays the number of the selected fan profile. 3
POWER−UP 7−SEGMENT DISPLAY STRING
2 H P
Unit Type / Stages
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No Capacity No Fan Profile
3 6
Capacity No Fan Profile
3 6 3
Capacity Fan Profile
XP21