Rheem Error Code L21: Low pressure control lockout (Heat Pump)
Rheem error code L21 on a heat pump means: Low pressure control lockout. It is also called Rheem diagnostic code L21.
Homeowner? What Rheem code L21 means for you
Call a technician Your heat pump is reporting: Low pressure control lockout. The heat pump has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Safe things you can check yourself
- Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
- Check both breakers and the outdoor disconnect box beside the outdoor unit; all should be ON.
- Look at the air filter. If it is grey and clogged, replace it; a blocked filter causes many shutdowns.
- In winter, keep snow and ice off and away from the outdoor unit. A short defrost cycle with steam is normal.
- Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.
Call (647) 657-2977Book a service call
Licensed technicians serving Vaughan, Toronto and the GTA.
What does Rheem error code L21 mean?
Active protection after repeated LPC trips. Cooling: LPC opened 3 times in one call - hard lockout. Heating: 3 trips within 120 minutes in one call - hard lockout; or 3 trips in one call with outdoor ambient below 5°F - soft lockout that clears by itself once ambient rises above 5°F. Display alternates L and 21.
Applies to: (-)PRL-JEC 2-stage 16 SEER heat pumps: RPRL/UPRL-024JEC, -036JEC, -048JEC, -060JEC
Common causes of Rheem code L21
- Low refrigerant charge
- Frozen indoor or outdoor coil
- Dirty indoor coil/filter or indoor blower not running (cooling)
A technician checks these and 2 other possible causes on site before replacing any part.
Rheem models that use code L21
RPRL-024JECRPRL-036JECRPRL-048JECRPRL-060JEC
Other Rheem Heat Pump codes
All Rheem Heat Pump error codes →
Rheem code L21: homeowner questions
What does Rheem code L21 mean?
Low pressure control lockout. Active protection after repeated LPC trips. Cooling: LPC opened 3 times in one call - hard lockout. Heating: 3 trips within 120 minutes in one call - hard lockout; or 3 trips in one call with outdoor ambient below 5°F - soft lockout that…
Is it safe to keep using my heat pump with code L21?
It depends on the cause. The heat pump has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Can I reset Rheem code L21 myself?
You can try one reset (power off for 30 seconds, then on). If Rheem code L21 comes back, the cause is still there and a licensed technician should check it.
Who can fix Rheem code L21 near me?
Aurora Star Tech Inc. repairs Rheem heat pumps in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Homeowner help: AC Running But Not Cooling: What to Check · Heat Pump Not Heating or Blowing Cold Air
Troubleshooting guides
- Heat pump will not defrost / incomplete or excessive defrost Rheem · Heat Pump
- Insufficient cooling / pressure problems Rheem · Heat Pump
- Outdoor fan runs but compressor does not Rheem · Heat Pump
- Outdoor unit will not run Rheem · Heat Pump
Source: Rheem (-)PRL-JEC Heat Pump Installation Instructions, 12.4 Active Compressor Protection Mode / 12.6 ICC Diagnostic Codes, p.24, 30. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.