Lennox S40 - Page 70

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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
421
Service
Urgent
OU EIM W External
Miswire Fault
The W output terminal on the outdoor unit is not wired correctly. Voltage sensed on W output terminal when
Y1 out is deactivated.
Automatically clears
once voltage is not
sensed on output or
power is cycled.
422 Service Soon
OU Compressor Top
Cap Switch Open
Compressor top cap switch exceeding thermal limit.
• Check condenser fan motor, TXV and indoor unit blower motor.
• Check for stuck reversing valve or clogged refrigerant lter.
• Lennox Variable Capacity Outdoor Units: Check to ensure that one of the wires from the top cap switch
has not been disconnected from one of the TP terminals on the outdoor control. Reconnect wire if
disconnected.
• Check superheat and sub-cooling.
Automatically
clears when error is
corrected.
423 40
Service
Soon/Service
Urgent
OU Inverter CT Circuit
Fault
The inverter has detected a circuit issue.
• When this condition is detected the outdoor control will stop outdoor unit operations and start the anti-short
cycle timer – service soon condition.
• Outdoor control will lockout unit after 10 strikes within an hour – service urgent condition.
• Inverter LEDs will ash code 40
• Refer to the unit service documentation for troubleshooting procedures.
Inverter ash code 40:
The sequence is:
Red LED: Four Flashes
Green LED: Off
NOTE: Inverter normal operations with no error code present is as follows. Red LED is ON and Green LED
is OFF.
A service soon
alert code will clear
automatically when
the inverter detects
the condition no longer
exist and will send
a clear alert code
message.
To clear service urgent
alert code disconnect
power to outdoor unit
and restart.
424 Service Soon
OU Liquid Line Sensor
Faulty
The liquid line temperature sensor has malfunctioned.
• In normal operation after outdoor control recognizes sensors, the alert code will be sent if a valid
temperature reading is lost.
• Compare liquid line sensor resistance to temperature / resistance charts in unit installation instructions.
• Replace sensor pack if necessary.
• At the beginning of (any) conguration, furnace or air handler control will detect the presence of the
sensor(s).
• If detected (reading in range), appropriate feature will be set as ‘installed’ and shown in the thermostat
‘About’ screen.
Automatically clears
upon conguration, or
sensing normal values.
426
Service
Urgent
OU Excessive Inverter
Alarms
After 10 faults within 60 consecutive minutes, the control will lockout. Inverter will ash codes 12 to 14 and
53.
NOTE: These inverter codes do not count towards this lockout condition.
To clear disconnect
power to outdoor
control and restart