HVACopediaLennox · Air handler
546 Zone sensor parameters reset after power restore
What the control is telling you
The zone sensor found an EEPROM (settings memory) problem right after power-up; system goes to energy save mode and keeps running. S30/S40 thermostat alert code 546.
Applies to: Lennox communicating air handlers and EIM-equipped indoor units in S30/S40 smart thermostat systems
Likely causes
- Zone sensor memory fault
Test and repair steps
- Replace the zone sensor.
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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.45. Summarized in our own words; check the original manual for your model.
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