Rheem R802VA07542117MSA Error Code T022_F: Main Limit Switch Open

What Does Code T022_F Mean?

Your Rheem R802VA07542117MSA is an 80% two-stage furnace with a variable-speed, constant-CFM/PWM blower. The main limit switch is a temperature-sensing safety mounted near the heat exchanger that opens whenever the plenum runs hotter than it should. The Bluetooth Communicating IFC watches this switch on every heat call: when it opens, the control cuts the gas valve so the burners stop adding heat and logs T022_F. Overheating at the limit almost always traces back to airflow — the burners produce their normal heat for whichever stage is firing, but not enough air is moving across the heat exchanger to carry that heat away.

On this variable-speed board the blower is commanded to hold a target airflow (CFM) using a PWM signal, ramping its RPM up as duct resistance rises. When a filter clogs or registers are closed, the blower tries to compensate, but there is a limit to how hard it can push against a badly restricted duct, so the heat-exchanger temperature climbs until the limit opens. That is why the two most common causes a homeowner can fix are a dirty air filter and blocked or closed supply and return registers.

T022_F is the troubleshooting-level, earliest rung of the main-limit escalation ladder on this board. If the main limit circuit instead stays open for more than 150 seconds, the IFC reads that as a dead-blower condition and raises code A022_F, an alarm-level fault that triggers a one-hour lockout. If the overheat keeps repeating, the furnace latches code A111_F, the one-hour lockout for the main limit switch. Clearing the airflow restriction now, while it is still just a filter or register issue, is what keeps the furnace from climbing to those harder lockouts.

What You'll Notice

• The burners light and deliver warm air, then shut off before the room reaches temperature while the blower keeps running to cool the heat exchanger (short-cycling on overheat)
• Air from the registers starts hot, then turns cool as the limit cuts the gas
• The alphanumeric LED blinks out "T022_F" digit by digit with a pause between digits
• A visibly gray, matted, or clogged air filter and weak airflow at the supply registers
• One or more rooms have their supply registers closed or blocked by furniture, rugs, or boxes

Common Causes

How This Is Diagnosed

Because T022_F is an overheating fault driven by restricted airflow, the cause is isolated by airflow first: pull the air filter and see whether it is dirty enough to block light, then walk the house and confirm every supply and return register is open and unobstructed. Those are the most common and the only homeowner-safe contributors. If the filter is clean and all registers are open and the code still returns, a technician confirms the variable-speed blower actually reaches its commanded CFM and measures the temperature rise across the furnace before ever condemning the limit switch itself.

How to Fix It: Restore Airflow: Replace the Filter and Open Blocked Registers

What You'll Need

• New furnace filter (correct size) 🛒 Find at FiltersFast · 🛒 Find at Amazon
• Flashlight

Steps

1. Turn off electrical power at the breaker or switch AND shut off the gas supply Flip the furnace circuit breaker to OFF, or use the dedicated power switch on or near the furnace, then turn the manual gas shutoff valve to OFF (handle perpendicular to the pipe). If you smell gas, leave immediately and call your gas company. Do not continue this procedure until the gas smell is gone.
2. Locate and inspect the air filter Find the filter in the return-air duct or the blower-compartment slot and slide it out. Hold it up to a light. If light does not pass through easily, or you see a mat of dust and hair, it is restricting airflow enough to overheat the heat exchanger on this variable-speed model.
3. Replace a dirty filter with the correct size Slide in a new filter of the exact same dimensions (printed on the cardboard frame), oriented so the airflow arrow points toward the blower. Avoid jumping to a much denser high-MERV filter than the furnace was set up for, since that can itself restrict airflow and re-trip the limit.
4. Open and unblock every supply and return register Walk the house and make sure supply registers and return grilles are fully open and not covered by rugs, furniture, or closed dampers. The constant-CFM blower needs a clear path for air to return to and leave the furnace; too many closed registers raise the temperature rise and trip the limit.
5. Restore gas and power and watch a full cycle Turn the gas valve back to ON and restore electrical power. Set the thermostat to call for heat and watch a complete cycle: the burners should light and stay lit, and warm air should keep flowing without the burners cutting out early.

When to Call a Professional

Contact a licensed HVAC technician if:

• The filter is clean and all registers are open but T022_F keeps returning
• The blower does not start, runs slowly, or makes grinding or humming noises
• The fault escalates to the alarm-level A022_F or the one-hour lockout A111_F
• The burners light but the furnace still shuts down on the limit within a minute or two despite good airflow
• You smell a hot or burning odor from the ductwork when the furnace runs

✓ Verified against manufacturer service manual — March 2026