HVACopediaCarrier · Heat pump · Other
Single-stage communicating heat pump: pressure switch protection and lockout
What happens, in order
- Control sees a high or low pressure switch open
- Compressor contactor drops out and the outdoor fan keeps running for 15 minutes; the matching fault code shows
- After 15 minutes, if cooling is still called for and the switch has reset, the contactor energizes again
- If the switch is still open after 15 minutes the outdoor fan turns off; it resumes on a cooling call when the switch closes
- If the high or low pressure switch trips on five consecutive cycles the unit locks out for 4 hours and shows the lockout code
- Low ambient mode (Infinity control) low pressure switch is ignored for the first 3 minutes; if it trips after that the fan is turned off for 10 minutes with the compressor running, and if it has not closed after 10 minutes the normal LPS trip shutdown happens
Timings and thresholds
| Item | Value |
|---|---|
| Fan run after switch trip | 15 min |
| Retry after trip | 15 min |
| Consecutive trips to lockout | 5 |
| Lockout time | 4 hours |
| Low ambient LPS ignore at start | 3 min |
| Low ambient fan off after LPS trip | 10 min |
Applies to: Carrier / Bryant / Payne split heat pumps with HK32EA defrost control boards (Performance Series and Comfort Series)
Models
More Carrier heat pump sequences
- Single-stage communicating heat pump: time delays and operating functions · Startup
- Variable-speed unit: power-up and compressor time delays · Startup
- Non-communicating heat pump: heating cycle (HK32EA001/007 and 003/008) · Heating
- Non-communicating heat pump: cooling with 5-minute compressor delay (HK32EA003/008) · Cooling
- Non-communicating heat pump: time/temperature defrost and Quiet Shift · Defrost
- Single-stage communicating heat pump: demand defrost, Auto interval and Quiet Shift-2 · Defrost
- Variable-speed heat pump: demand defrost with Auto interval · Defrost
- Variable-speed unit: high pressure switch protection and lockout · Other
Related
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Source: Carrier-Bryant residential A/C + HP Application Guideline and Service Manual (R-410A, 24-25), System Function and Sequence of Operation, Defrost Control. 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.