The short answer
E250 on a Lennox furnace in Northern Virginia means the limit switch circuit is open. The furnace got hotter inside than it’s built to, and a safety switch shut the burners off. Most of the time the reason is airflow: a packed filter, closed or blocked vents, or a blower that isn’t moving enough air. Change the filter first. If E250 comes back, or it turns into E274, call.
What Lennox says E250 and E274 mean
Lennox’s service manuals call E250 “limit switch circuit open.” It isn’t a lockout by itself. When the furnace cools and the switch closes, it goes back to heating. If the limit stays open longer than 3 minutes, the furnace goes into a one-hour soft lockout.
E274 is the next step: a soft lockout because the last try failed on the limit, or the limit stayed open more than 3 minutes. In plain words, it tripped often enough that the furnace stopped trying for an hour. Lennox uses two kinds of lockout. A soft lockout waits an hour, then tries again on its own if the thermostat still wants heat. A hard lockout stays off until someone turns the power off and back on.
On a Merit furnace with a red light, the same trip blinks a different count by model: 4 flashes on an ML180UH or ML195UH (primary limit open), 4 flashes on an ML296UHV (limit or rollout switch open), and 7 flashes on an ML180UHE (primary or secondary limit open).
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What you’ll notice
The furnace lights, runs a few minutes, and the burners go out while the blower keeps running. The air coming out of the vents turns lukewarm, then cool. A while later it tries again. The house never quite gets to the temperature on the thermostat, and some rooms stay cold. Sometimes there’s a hot, dusty smell (furnace burning smell). If it’s starting and stopping every few minutes, that’s short cycling, and a limit trip is one of the usual reasons.
Why a Lennox furnace trips the limit
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| The cause | How you’d tell | Who fixes it |
|---|---|---|
| A packed filter | Gray and matted. Hold it to a light and you can’t see through it. | You |
| Closed or blocked vents and returns | Registers shut in empty rooms, a couch over the return. | You |
| A dirty blower wheel | Years of dust caked on the blades. Airflow weak at every vent. | A tech |
| A weak blower motor or capacitor | The blower hums, starts slow, or runs slower than it used to. | A tech |
| A dirty AC coil on top of the furnace | Airflow weak even with a new filter. | A tech |
| The furnace firing too hard | Gas pressure set high. Lennox lists the firing rate first. | A tech |
| A failed limit switch | Less common. Tested with a meter, never guessed. | A tech |
| Ductwork too small for the furnace | E250 from the first winter after the install. | A tech |
Lennox’s own fix list for E250 and E274 is short: check the firing rate, check for a blockage, check the airflow. Two of those three are about air.
What you can do right now
Change the filter. Then open every supply vent and make sure nothing sits over the return grille. Heavy pleated filters choke some furnaces even when they’re new (which filter to buy).
Reset it once. Turn the furnace switch off, count to ten, and turn it back on. Take a photo of the code before you reset anything. A reset can clear what’s showing, and that number saves the tech time and you money.
Watch one cycle. If the burners stay lit until the house warms up and shuts off normally, the filter was it. If it trips again the same day, stop resetting it and call.
What not to do
Don’t jump the limit switch or bend its wires to get heat back. That switch is what keeps the heat exchanger from overheating, and a heat exchanger that cooks year after year cracks. A cracked one can leak carbon monoxide into the air you breathe (cracked heat exchanger).
What the fix usually costs
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| The fix | Our price |
|---|---|
| Blower wheel pulled and cleaned | $300 to $440 |
| Run capacitor replaced | $240 to $370 |
| Blower motor replaced | $670 to $2,400, most around $1,500 |
| Control board replaced | $550 to $1,180 |
The diagnostic is a flat $99. A limit switch, if that’s what failed, gets priced in writing before we start. Our heating check is $67 per system, through December 31: furnace, heat pump or boiler. On a furnace, for $229 (regularly $467) we also pull the blower wheel and clean it blade by blade. If the blower wheel is the problem, that deep clean fixes it for less than the repair price.
If the repair is a big one on an older furnace, get a second look before you spend it. Our free second opinion costs you nothing, and the estimator shows what a new system costs with $1,500 off already in the price. Thinking about brands? Lennox vs Trane lays out the difference.
Every Lennox code in one place: Lennox error codes.
The system we put in first
Built to take a beating. Put in by our crew.
Heat lamps, snow and rain on one outdoor unit: that’s Trane’s own film. We’re a Trane Comfort Specialist, on Trane’s own dealer locator, and when you pick a Trane, our crew puts it in.
Films: Trane’s own.
Call or book a Lennox repair
Call (703) 997-9757. We answer day or night. Or book online and pick a time. The diagnostic is a flat $99, and you see the repair price in writing before we touch anything. Furnace running fine and you want to keep it that way? Book the $67 heating check from goswiftpro.com/cookiesoffer (book by November 30) and a box of warm cookies comes with the visit. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276. More on Lennox repair in Northern Virginia.
Questions people ask
What does E250 mean on a Lennox furnace?
The limit switch circuit is open. The furnace ran too hot inside and the switch shut the burners off. Restricted airflow, most often a dirty filter, is the usual reason.
Can a dirty filter cause a Lennox E250 code?
Yes, and it’s the first thing to check. A packed filter cuts the airflow over the heat exchanger, the furnace overheats, and the limit opens. Change it and watch one full heating cycle.
What’s the difference between E250 and E274 on a Lennox?
E250 means the limit is open right now. E274 is a one-hour soft lockout because the limit opened on the last try or stayed open more than 3 minutes.
Is it safe to keep resetting a Lennox furnace with E250?
Once is fine. If it trips again the same day, stop. Running a furnace that keeps overheating wears out the heat exchanger, and a cracked one can leak carbon monoxide.
