Navien
Freeze Protection / Low Temperature Lockout
Navien furnace locks out occasionally during very cold weather without a clear error code, outdoor unit or piping appears frosted
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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
Inadequate antifreeze concentration (if used), Exposed piping in unconditioned spaces, Outdoor sensor misreading, Power outages disabling freeze protection
How to Fix / Troubleshooting
Safety: If pipes are suspected frozen, do not force operation; inspect carefully for splits or leaks as they thaw.
- Protect piping: Insulate all hydronic piping in unconditioned spaces and seal air leaks that allow cold drafts onto the Navien unit or piping.
- Check outdoor sensor: Verify correct placement and operation of the outdoor temperature sensor. Replace if readings are clearly wrong.
- Antifreeze (if applicable): For systems using glycol, have a professional test concentration and adjust to provide adequate freeze protection.
- Backup power: Consider installing backup power for the furnace to maintain freeze protection during outages.
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Repair Difficulty
Medium
3/5
Required Part
Outdoor Temperature Sensor
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