A. O. Smith · Voltex AL Smart / Signature 900 Standard (HPTS, HPS10)
A. O. Smith Voltex AL Smart / Signature 900 Standard (HPTS, HPS10) error code HPO
Heat pump out of operating range
info
What it means
The ambient and/or water temperature is outside the heat pump's operating range. The heat pump will not operate at ambient temperatures below 37°F or above 120°F, or if the average water temperature in the tank is below 55°F. The unit operates in Electric Mode until temperatures return to the heat pump's range.
What A. O. Smith says to do
This is a normal status display. The manual gives no action for it.
Last checked 2026-10-03.
Safety first
- WARNING! Working near an energized circuit can result in severe injury or death from electrical shock. (p.28)
- WARNING! When you are finished, be sure all covers are secured to reduce the risk of fire and electric shock. (p.28)
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 MAX / Signature 900 Premium (HPTA, HPA10): HPO
- A. O. Smith Voltex 120V plug-in (HPTV, HPV10): HPO
- A. O. Smith Voltex hybrid with letter codes (HPTU, 2016–2019): HPO
- A. O. Smith Early Voltex hybrid (FPTU, 2015 manual): HPO
- Whirlpool Hybrid HPSE2K50/66/80: HPO
Other Voltex AL Smart / Signature 900 Standard (HPTS, HPS10) codes
- 001 (Dry-fire)
- 003 (Upper thermistor sensor failure)
- 004 (Lower thermistor sensor failure)
- 006 (Internal Processor Error)
- 009 (Power supply voltage too low)
- 021 (Upper element circuit failure)
- 022 (Lower element circuit failure)
- 025 (Heat pump coil temperature sensor)
- 026 (Heat pump suction temperature sensor)
- 027 (Heat pump discharge temperature sensor)
- 028 (Ambient temperature sensor failure)
- 031 (Water leak)
- 044 (SAC anode depleted)
- 046 (Shut-off valve)
- 048 (Battery low energy)
- 080 (Air filter dirty)
- 081 (Condensate management)
- 083 (Compressor suction pressure too low)
- 084 (Compressor not functioning)
- 085 (Compressor discharge temperature too high)
- 086 (Fan speed feedback)
- ICE (Heat pump defrost)
- CLR (Error code cleared)