Rheem HVAC Error Code 21: How to Fix It

Q: What does Rheem error code 21 mean?

Error code 21 means the pressure switch failed to open during startup, indicating the inducer motor isn't creating proper airflow or there's a blockage in the venting system.

Q: Can I reset Rheem error code 21 myself?

You can try resetting by turning off power for 30 seconds, but error code 21 typically requires fixing the underlying inducer motor or venting issue before the system will operate normally.

Q: Is it safe to run my furnace with error code 21?

No, never attempt to bypass or ignore error code 21. This safety feature prevents dangerous conditions like carbon monoxide buildup when proper ventilation isn't working.

Q: How much does it cost to fix Rheem error code 21?

Repair costs range from $150-$400 if it's a simple blockage or tubing issue, up to $300-$600 for inducer motor replacement, or $200-$350 for pressure switch replacement by a professional.

Q: How often should I clean my furnace vents to prevent error code 21?

Inspect and clean exhaust vents at least twice yearly, especially before heating season. Remove any debris, bird nests, or ice buildup that could block proper airflow.

Abstract

Rheem HVAC error code 21 indicates the pressure switch failed to open during startup, typically caused by a faulty inducer motor or blocked venting. This safety feature prevents the furnace from operating when proper airflow isn't detected, protecting your home from potential carbon monoxide hazards.