Lennox S40 - Page 67

67
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
406
Service
Urgent
OU Compressor Open
Start Circuit
The required amount of current is not passing through the START current transformer.
Automatically clears
after current is sensed
in START sensor, or
after power reset.
407
Service
Urgent
OU Compressor Open
Run Circuit
The required amount of current is not passing through RUN current transformer.
Automatically clears
after current is sensed
in RUN sensor, one
normal compressor run
cycle, or after power
reset
408
Service
Urgent
OU Compressor
Contactor Welded
The compressor is running continuously.
Automatically
clears one normal
compressor run cycle
or after power reset.
409 Service Soon
OU Control Board Low
24VAC
The secondary voltage for the applicable system component has fallen below 18VAC. This may be due to:
• Secondary voltage is below 18VAC.
• If this continues for 10 minutes, the thermostat will turn off the applicable system component.
Automatically clears
after voltage is
detected as higher than
20VAC for two seconds
or after power reset.
410
Information
Only-Dealer
OU Open Low
Pressure Switch
Unit low pressure is below the required limit.
• Check operating pressures.
• Low pressure switch opens at a specic pressure (system shuts down) and closes at a specic pressure
(system restarts).
Automatically clears
when the system
detects that the issue
no longer exists.
411
Service
Urgent
OU Low Pressure
Switch Strikes Lockout
The low pressure switch has opened ve times during one cooling or heating demand.
• Thermostat will shut down the outdoor unit.
• Open low pressure switch error count reached ve strikes.
• Check system charge using both approach and sub-cooling methods.
• Reset by putting outdoor unit control in test mode or resetting low voltage power.
Automatically clears
when the system
detects that the issue
no longer exists.
412
Information
Only-Dealer
OU Open High
Pressure Switch
The unit high pressure is above the upper limit.
• System will shut down.
• Conrm that the system is properly charged with refrigerant.
• Check condenser fan motor, expansion valve (if installed), indoor unit blower motor, stuck reversing valve
or clogged refrigerant lter.
• Conrm that the outdoor unit is clean.
Automatically clears
after the high pressure
switch closes or a
power reset