What It Means
- LINE FREQUENCY MISMATCH
Lennox Unit controller
Lennox Unit controller Error Code 121
Unit controller
Causes & actions from Lennox
How it shows
- M4 alarm code: 121
Power source line frequency is determined by the entered model number. This alarm is enabled by the Phase Voltage Detection feature. The CORE Unit Controller does not have an automatic clearing method, unit power cycle or reset will be required to re-evaluate the phase sequence again.
Applicable models & manual sources
- MODEL L - M4 UNIT CONTROLLER
LINE FREQUENCY MISMATCH
MODEL L - M4 UNIT CONTROLLER, M4 Unit Controller
Disclaimer: This information is for general reference. Code wording and instructions vary by model. Always follow the service manual for your exact unit.
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