HVACopediaCarrier · Heat pump · Other
Variable-speed unit: high pressure switch protection and lockout
What happens, in order
- High pressure switch opens (opens about 600 psig, closes about 470 psig at 77 F) and code 31 is shown
- After 6 minutes, if there is still a call and the switch has reset, the PEV opens for 150 s to equalize pressure
- Compressor and fan then restart one stage lower and keep stepping down if the switch trips again
- The step-down and return to top stage clear after 2 hours of running with no more trips
- If it trips again at the lowest stage the fault is raised to code 84 (high pressure lockout); from stage 5 this takes five trips in a row, from stage 1 just one
Timings and thresholds
| Item | Value |
|---|---|
| Retry delay | 6 min |
| PEV equalize | 150 s |
| Reset of step-down | 2 h accumulated run without trips |
| HPS opens | 600 psig |
| HPS closes | 470 psig |
Codes you may see during this
Applies to: Carrier Infinity 25VNA8 variable-speed heat pump and 24VNA9 variable-speed air conditioner
Models
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Related
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Source: Carrier Infinity 25VNA8/24VNA9 variable-speed heat pump and A/C service manual, Time Delays, Defrost, High and Low Pressure Protection. Written in our own words; timings can differ by model and software version, so check the manual for your exact unit.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.