Quick answer: Lennox code 250 (E250) means the furnace’s limit switch circuit is open, which almost always means the furnace got too hot. The most common cause is restricted airflow from a dirty filter or closed vents. If the limit does not reset within a few minutes, the furnace goes into a one-hour soft lockout.
Safety first: if you smell gas, do not reset or relight anything. Leave the home and call Nicor Gas at 1-888-642-6748 or 911 from outside.
What Does Lennox Error Code 250 Mean?
Lennox describes code 250 as limit switch circuit open. The high-limit switch is a safety device that shuts off the burners if the heat exchanger area gets too hot. Lennox notes that if the limit does not close within 3 minutes, the furnace enters a 1-hour soft lockout before trying again.
Common Causes of Code 250
- A dirty or clogged air filter, by far the most common cause.
- Closed or blocked supply vents and return grilles.
- A dirty AC coil above the furnace restricting airflow.
- Blower problems, such as a dirty wheel or failing motor.
- Undersized or restricted ductwork.
- Overfiring from incorrect gas pressure, or a failed limit switch.
Safe Checks You Can Do First
- Replace the air filter if it is dirty. Check it monthly in winter.
- Open supply vents throughout the house and make sure return grilles are not blocked by furniture.
- Let the furnace cool and restart by turning the furnace switch off for 30 seconds and back on.
If code 250 returns with a clean filter and open vents, the furnace needs service. Repeated overheating stresses the heat exchanger, so do not keep resetting it.
What a Technician Will Check
We measure static pressure and temperature rise to see whether airflow is in range, check gas pressure and firing rate, inspect the blower and AC coil, and test the limit switch. If the problem is ductwork, we explain the options. Our furnace repair starts with a $75 diagnostic and a flat-rate price before any work.
Seeing a Lennox code in the Northwest Suburbs?
Pure Comfort Heating and Cooling is a Lennox Premier Dealer in Streamwood, IL. Diagnostics are $75, or $99 on evenings, weekends and holidays, and you approve a flat-rate price before any repair. Phones are answered 24/7.
Frequently Asked Questions
Can a dirty filter really cause code 250?
Yes. A clogged filter is the most common reason a furnace overheats and trips the limit. Replace it and restart the furnace.
How long is the lockout after code 250?
Lennox notes the furnace enters a one-hour soft lockout if the limit does not close within three minutes. It will try again after that.
Is it bad to keep resetting a furnace with code 250?
Yes. Repeated overheating stresses the heat exchanger. If the code returns with a clean filter and open vents, call for service.
Do you fix limit switch problems on all Lennox models?
Yes. We service all Lennox furnaces, including the SL280, EL280, EL296, EL297V and SLP99V, and every other major brand.
We service Lennox furnaces from our shop in Streamwood across Streamwood, Bartlett, Hoffman Estates, Schaumburg, Elgin, Hanover Park, Roselle and the rest of the Northwest Suburbs.
Looking up a different code? See our full Lennox furnace error code guide.