21 Low pressure control (LPC) open

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.

Settings for these units

Outdoor unit clearances · Rheem/Ruud PRL-JEC heat pump (Comfort Control2 ICC)

Do not reduce the 60 in. discharge or 24 in. service clearances.

Inlet clearances under 6 in. reduce capacity and efficiency.

Models that show this code

4 models in Rheem/Ruud PRL-JEC heat pump (Comfort Control2 ICC)

Other codes on the same units

• 7 flashes (L terminal) L-terminal fault output: Open run circuit
• 8 flashes (L terminal) L-terminal fault output: Control mis-operation
• 09 Low secondary (control) voltage
• 9 flashes (L terminal) L-terminal fault output: Low control voltage
• 27 Low line voltage or no line voltage
• 28 High line voltage
• 29 High pressure control (HPC) open
• 30 ICC fuse open