Rheem Error Code 21
Low pressure control open
Error Code Summary
| Brand | Rheem |
| Error Code | 21 |
| Meaning | Low pressure control open |
| Cause | Low pressure switch tripped or loss of charge |
| Recommended Action | Check for leaks, verify refrigerant charge, inspect expansion device |
How to Fix Rheem Error 21
- 1
Power Cycle the Unit
Turn off the unit at the breaker, wait 5 minutes, then restore power. Some errors auto-clear after a restart.
- 2
Identify the Issue
Error 21 means: Low pressure control open. The most common cause is: Low pressure switch tripped or loss of charge.
- 3
Take Corrective Action
Check for leaks, verify refrigerant charge, inspect expansion device
- 4
Test the System
After completing repairs, run the system and monitor for the error code. If it recurs, the issue may require professional diagnosis.
Safety Notice
Always disconnect power before performing any electrical work. If you're not a certified HVAC technician, contact a qualified professional for repairs involving refrigerant, electrical components, or compressor work.
Frequently Asked Questions
What does Rheem error code 21 mean?
Rheem error code 21 indicates: Low pressure control open. This is typically caused by: Low pressure switch tripped or loss of charge.
How do I fix Rheem error code 21?
To fix Rheem error code 21: Check for leaks, verify refrigerant charge, inspect expansion device. If the error persists after these steps, contact a qualified HVAC technician.
Is Rheem error code 21 serious?
Error code 21 (Low pressure control open) should be addressed promptly to prevent further damage to your Rheem system. Always turn off the unit if you notice unusual sounds, smells, or continued malfunction.