Lennox XC20-036-230-01 Installation And Service Procedure page 34

Table 6. Outdoor Control 7-Segment Display Alert Codes and Inverter LED Flash Codes
NOTE - System fault and lockout codes take precedence over system status codes (cooling, heating operating percentages or defrost/dehumidification).
Only the latest active fault or lockout codes are displayed (if present). If no fault or lockout codes are active, then system status codes are displayed. Alert
codes are also displayed on the iComfort Wi-Fi
Inverter LED Flash
Code (number of
Alert Inverter
Code
Codes
Red LED
E 436 62 6 flashes
E 437 65 6 flashes
E 438 73 7 flashes
E 439 12 1 flash
E 440 13 1 flash
XC20
®
thermostat.
Priority
flashes)
Green LED
Moderate /
2 flashes
Critical
Moderate /
5 flashes
Critical
Moderate /
3 flashes
Critical
2 flashes Moderate
3 flashes Moderate
Alarm Description
Inverter heat sink temperat­
ure exceeded limit. Occurs
when the heat sink temper­
ature exceeds the inverter
limit. Inverter issues code
13 first, then slows down to
allow the heat sink to cool. If
temperature remains high,
outdoor unit stops (com­
pressor and fan). Anti-short
cycle is initiated. If condition
occurs 5 times within an
hour, system is locked out.
To clear, disconnect power
to outdoor unit and restart.
Heat sink temperature
sensor fault has occurred
(temperature less than 4ºF
or greater than 264ºF after
10 minutes of operation)
.
The inverter has detected a
PFC over current condition.
This would be caused by a
high load condition, high
pressure, or outdoor fan fail­
ure. Outdoor control will dis­
play the code when the in­
verter has the error. After 3
minutes, the inverter will re­
set and the compressor will
turn on again. If it happens
10 times within a 60 minute
rolling time period, the OD
control will lock out opera­
tion of the outdoor unit and
display a critical code.
Compressor slowdown due
to high input current.
Heat sink temperature is
approaching limit. The
compressor speed auto­
matically slows to reduce
heat sink temperature. The
control sets indoor CFM
and outdoor RPM to values
according to demand per­
centage rather than the ac­
tual Hz. Alarm is automatic­
ally cleared.
34
Possible Causes and Clearing Alarm
Issue: Feedback from supplier tear down of inverter in­
dicates that the screws that hold the inverter to the invert­
er board were loose causing poor contact between these
two components.
Corrective Action: Tighten screws that hold the heat
sink to the inverter control board.
NOTE: Wait five minutes to all capacitor to discharge be­
fore checking screws.
Occurs when the temperature sensor detects a temperat­
ure less than 0.4ºF or greater than 264ºF after 10 minutes
of operation. If condition is detected, outdoor unit will stop
(compressor and fan). Anti­short cycle is initiated. If con­
dition occurs 5 times within an hour, system will lock out.
To clear disconnect power to outdoor unit and restart. If
problem persists, replace inverter.
Issue: Possible issue is system running at high pres­
sures. Check for high pressure trips or other alert codes in
room thermostat and outdoor control.
Input current is approaching a high limit. Compressor
speed automatically slows. The control continues send­
ing the inverter speed demanded by the thermostat. The
control sets indoor CFM and outdoor RPM to values ac­
cording to demand percentage rather than the actual Hz.
Alarm is automatically cleared.
Issue: Feedback from supplier tear down of inverter in­
dicates that the screws that hold the inverter to the invert­
er board were loose causing poor contact between these
two components.
Corrective action: Tighten screws that hold the heat sink
to the inverter control board.
NOTE: Wait 5 minutes to all capacitor to discharge before
checking screws.