A. O. Smith · Early Voltex hybrid (FPTU, 2015 manual)
A. O. Smith Early Voltex hybrid (FPTU, 2015 manual) error code SF
Air filter
What it means
The air filter is dirty.
What A. O. Smith says to do
1. Turn off power at the circuit breaker/fuse box. 2. Clean the air filter. See "Air Filter Maintenance" section.
Last checked 2026-10-03.
Safety first
- WARNING! Working near an energized circuit can result in severe injury or death from electrical shock. (troubleshooting/maintenance sections)
- NOTE: The diagnostic codes listed are the most common. If a diagnostic code not listed is displayed, contact Residential Technical Assistance referencing the number on the front of this manual. (p.20-21)
From the manufacturer's manual for this series.
The same code on other models
Codes mean different things on different heaters. Match the series to the model number on your rating label.
- A. O. Smith Voltex hybrid with letter codes (HPTU, 2016–2019): SF
- Whirlpool Hybrid HPSE2K50/66/80: SF
Other Early Voltex hybrid (FPTU, 2015 manual) codes
- - / -- / --- (System diagnostic)
- ICE (Defrost)
- HPO (Out of operating range)
- EUC (Upper element)
- ELC (Lower element)
- ECF (Compressor short cycling)
- E20 or E21 (Upper temperature sensor)
- E30 or E31 (Lower temperature sensor)
- E50 or E51 (Suction temperature sensor)
- E10 or E11 (Coil temperature sensor)
- E40 or E41 (Discharge temperature sensor)
- Edr (Dry fire)
- EPL (Low supply voltage)
- EDH (Discharge temperature high)
- EoF (Condensate pump failure)
- ECL (Suction pressure low)
- EEE (EEPROM failure)
- ECC (Compressor not functioning)
- ECE (Power supply error)