Lennox S40 - Page 72

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Table 21. Lennox S40 Smart Thermostat Alert Codes and Troubleshooting
E2A=Errors to Action, GF= Gas Furnace, AH=Air Handler, IU=Indoor unit (GF or AH), HP=Heat Pump, AC=Air Conditioner, OU=Outdoor Unit (AC or HP), PA=Pure Air S, ZA=Zone system,
SRS=Smart Room Sensor, TS=Thermostat , IAQ- IAQ Monitor and WE=Wi-Fi Extender
Alert
Code
Inverter
Flash
Code
Priority
Condition
Actual Displayed Alert
Text Under dealer control
center > Notications
Component or System Operational State and Troubleshooting Tip
How to clear
alert code
429 23
Service
Soon/Service
Urgent
OU Inverter DC Link
Low Voltage
The inverter has detected a DC link low voltage condition.
• On a call for compressor operation, if DC link power in inverter does not rise above 180 VDC for 2- and
3-ton models, 250 VDC for 4- and 5-ton models within 30 seconds, the control will display a service soon
code.
• If condition is detected, outdoor unit will stop (compressor and fan) – service soon condition.
• An anti-short cycle timer is initiated. If condition occurs 10 times within a 60 consecutive minutes, system
will lock out and display alert code 429 – service urgent condition.
• The outdoor control anti-short cycle timer will time out and the unit will recycle the demand.
• Inverter LEDs will ash code 23.
• Refer to the unit service documentation for detailed troubleshooting procedures. Perform test function and
verify inverter DC link and line input voltage and current. Also check input to lter board and reactor before
replacing inverter board. To perform this test, go to menu > settings > advanced settings > view dealer
control center > tests.
Inverter ash code 23.
The sequence is:
• Red LED: Two Flashes
• Green LED: Three Flashes
NOTE: Inverter normal operations with no error code present is as follows. Red LED is ON and Green LED
is OFF.
Troubleshooting Suggestions:
• Check wire connections (U, V and W) at inverter plug in harness and compressor.
• Check the resistance of compressor windings. If not in range, replace compressor.
• Check compressor to ground. If ground issue, replace compressor.
• Check input power (Single Phase - 208/230VAC + 10%. If out of range, correct main power issue.
• Check DC Link voltage and MICOM Sensing voltage. If out of range, replace inverter. if okay, possible
mechanical issue with compressor.
Go to outdoor unit service manual for detail troubleshooting procedures and require values for testing DC link
voltages and various insulation resistance characteristics.
Automatically clears
when the system
detects that the issue
no longer exists.