F23
Siemens
Utility Supply Voltage Out of Range
Controller displays F23 Utility Voltage Fault; generator may start unexpectedly or refuse to transfer back to utility.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Actual utility undervoltage or overvoltage, Loose sensing wires from ATS to controller, Incorrect utility voltage settings, Failed utility voltage sensing circuit
How to Fix / Troubleshooting
Safety first: Work on utility connections only with the main breaker open and following local electrical codes. This work is best performed by a licensed electrician.
- Verify utility voltage: Measure line-to-line and line-to-neutral voltages at the ATS utility terminals. Compare to nominal values and Siemens transfer thresholds.
- Inspect sensing wiring: Check the low-voltage sensing wires from the ATS or utility terminals to the Siemens controller. Tighten loose terminals and repair damaged conductors.
- Check controller settings: In the controller menu, verify that utility voltage thresholds and phase configuration match the actual supply.
- Monitor utility stability: If utility voltage is fluctuating or out of spec, contact the power company. The generator is correctly detecting a problem.
- Controller/ATS service: If measured utility voltage is normal but F23 persists, the utility sensing circuit in the controller or ATS may be faulty and require replacement.
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Repair Difficulty
Hard
4/5
Required Part
ATS Utility Voltage Sensing Module
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