Lennox Furnace Code E250: What It Means & How to Fix It
Compiled & reviewed by the HVAC Flash Codes editorial team · Updated 2026-06-25 · confidence: high
⛔ Stop — call a licensed pro
What does Lennox furnace code e250 mean?
Primary limit switch circuit open — the limit-circuit safety has tripped, typically from overheating due to low airflow. If the limit doesn't close within 3 minutes the unit enters a 1-hour soft lockout (Watchguard). On older red-LED boards this same condition is 7 flashes. Most often caused by Restricted supply airflow from a dirty/clogged air filter.
E250
What your control shows. Your Lennox furnace displays Code E250 on its diagnostic readout.
What Lennox furnace code e250 means
Primary limit switch circuit open — the limit-circuit safety has tripped, typically from overheating due to low airflow. If the limit doesn't close within 3 minutes the unit enters a 1-hour soft lockout (Watchguard). On older red-LED boards this same condition is 7 flashes.
Common causes
Restricted supply airflow from a dirty/clogged air filter
Blocked or closed supply registers/return grilles, or restrictive ductwork
Overheating from low airflow (blower or duct restriction)
High gas pressure / over-firing (a technician must verify)
Homeowner-safe steps to try
Turn the thermostat OFF and let the furnace cool fully
Replace or clean the air filter — the most common airflow cause
Open and unblock all supply registers and clear return grilles
Cycle power (furnace switch/breaker off 30+ seconds, then on) once airflow is restored
When to call a licensed HVAC technician
If the basic checks below don't clear the code, the fault recurs, or anything involves the gas valve, burners, flame sensor or wiring, stop and book a licensed HVAC technician. Repairs to the combustion or gas system are not DIY.
⚠️ Safety first. Gas furnaces burn fuel and produce combustion gases. If you ever smell gas (a rotten-egg or sulfur odor), hear hissing, or your carbon-monoxide alarm sounds, do not touch light switches, thermostats, or the furnace — leave the home immediately and call your gas utility's emergency line or 911 from outside. Homeowners should limit themselves to simple, safe steps: setting the thermostat, checking and replacing the air filter, confirming the furnace switch and breaker are on, keeping supply registers and return grilles open, and clearing snow, ice, or debris from outdoor vent and intake terminations. Never bypass, jumper, or reset safety switches (limit, flame-rollout, or pressure switches), never open the gas valve or burner compartment, and never attempt combustion, electrical, or control-board repairs yourself. Error codes point toward a problem but are not a substitute for proper diagnosis — when in doubt, turn the system off and call a licensed HVAC technician. Keep working carbon-monoxide detectors on every level of your home.
When to call a pro: Call a licensed HVAC technician if the code returns after the filter and airflow are confirmed clear, or if the furnace short-cycles — repeated limit trips can indicate a failing blower, heat exchanger, or over-firing. Never bypass or jumper the limit switch. If you smell gas, leave immediately and call your gas utility or 911 from outside.
Lennox furnace code e250 FAQ
What does Lennox furnace code e250 mean?
Primary limit switch circuit open — the limit-circuit safety has tripped, typically from overheating due to low airflow. If the limit doesn't close within 3 minutes the unit enters a 1-hour soft lockout (Watchguard). On older red-LED boards this same condition is 7 flashes.
What causes Lennox furnace code e250?
Common causes: Restricted supply airflow from a dirty/clogged air filter; Blocked or closed supply registers/return grilles, or restrictive ductwork; Overheating from low airflow (blower or duct restriction); High gas pressure / over-firing (a technician must verify).
Can I fix Lennox furnace code e250 myself?
You can safely try: Turn the thermostat OFF and let the furnace cool fully; Replace or clean the air filter — the most common airflow cause; Open and unblock all supply registers and clear return grilles; Cycle power (furnace switch/breaker off 30+ seconds, then on) once airflow is restored. Call a licensed HVAC technician if the code returns after the filter and airflow are confirmed clear, or if the furnace short-cycles — repeated limit trips can indicate a failing blower, heat exchanger, or over-firing. Never bypass or jumper the limit switch. If you smell gas, leave immediately and call your gas utility or 911 from outside.
Sources: lennox.com · lennox.com. General information for homeowners, not professional advice — confirm against your furnace's manual and a licensed technician.