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Rheem · Heat pump

21 Low pressure control (LPC) open

Medium severity Rheem/Ruud PRL-JEC heat pump (Comfort Control2 ICC)

What the control is telling you

The ICC sees the LPC open. The LPC opens near 15 PSIG and closes near 40 PSIG; it is ignored for the first 90 seconds of compressor run and during defrost.

Applies to: (-)PRL-JEC 2-stage 16 SEER heat pumps: RPRL/UPRL-024JEC, -036JEC, -048JEC, -060JEC

Likely causes

  • Low refrigerant charge
  • Frozen indoor coil (cooling)
  • Dirty indoor coil or filter (cooling)
  • Indoor blower not running (cooling)
  • Frozen outdoor coil (heating)
  • Outdoor fan not running (heating)
  • Expansion valve (TXV) not working correctly

Test and repair steps

  1. Cooling replace the filter, check the indoor coil for dirt/ice and verify the indoor blower runs.
  2. Heating check the outdoor coil for ice and that the outdoor fan runs; force a defrost test (SW2) to check defrost.
  3. Check suction pressure and charge; leak-test if low.
  4. Check TXV operation (superheat, bulb mounting, equalizer line).
  5. Check LPC wiring at the ICC LPC input.

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Source: Rheem (-)PRL-JEC Heat Pump Installation Instructions, 12.6 ICC Diagnostic Codes, p.30. Summarized in our own words; check the original manual for your model.

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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.