Lennox EL296UHV Error Code E 274: Soft Lockout - Limit Open
What Does Code E 274 Mean?
Error code E 274 on the Lennox EL296UHV is a soft lockout triggered by the high-limit circuit opening repeatedly, or staying open longer than 3 minutes. The furnace has used up its recycle attempts trying to finish a heat call while overheating, so the SureLight integrated control shuts the unit down for a one-hour soft lockout to stop the cycle of overheating.
E 274 is the escalated version of E250. A single limit trip shows up as E250: the burners cut off and the variable-speed ECM blower keeps running to cool the exchanger. If the limit closes quickly, the furnace recovers. But if it keeps tripping on each attempt, or never closes within 3 minutes, the control stops trying and locks out as E 274. In other words, seeing E 274 means the overheating has already happened several times, not just once.
The underlying cause is the same as E250: not enough air moving across the heat exchanger. A dirty, clogged air filter is by far the most common reason, followed by closed or blocked supply and return vents. Because this is a two-stage furnace, high fire produces the most heat and is where a marginal airflow restriction most easily pushes the limit over its trip point. Clearing the restriction before the lockout ends is important, because otherwise the furnace will simply overheat and lock out again on its next attempt.
Unlike a hard lockout, this soft lockout releases itself: it auto-clears after roughly one hour, or immediately if you cycle power at the breaker, or once a full heat cycle completes successfully. Related airflow codes on this board include E250 (the single-trip warning) and E291 (the blower measuring heating airflow below its minimum). Persistent E 274 with a clean filter points to something a technician must handle, such as a weak ECM blower, a failing limit switch, or a collapsed duct.
What You'll Notice
- The seven-segment LED on the SureLight control shows E then 274
- The furnace is completely shut down and will not fire for up to an hour
- Before the lockout, the burners were lighting and cutting off early several times
- The house temperature has dropped well below the thermostat setpoint
- The air filter is visibly dirty, or vents around the house are closed or blocked
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Dirty air filter restricting airflow | Most common | ✓ DIY fix → |
How to Fix It: Clear the Airflow Restriction and Reset the Lockout
What You'll Need
- Replacement air filter (matching size) 🛒 Find at FiltersFast · 🛒 Find at Amazon
- Flashlight
Steps
- Turn off electrical power at the breaker and shut off the gas supply valve Flip the furnace circuit breaker (or service switch) to OFF, then turn the gas shutoff valve to the OFF position, with the handle perpendicular to the pipe. If you smell gas, leave immediately and call your gas company.
- Replace the air filter Remove the filter from the blower compartment or return duct. Because E 274 means the furnace overheated repeatedly, a clogged filter is the prime suspect. Install a new filter of the correct size with the airflow arrow pointing toward the blower. Replace a heavily clogged filter rather than trying to clean it, and avoid dense high-MERV media if the furnace was not set up for it.
- Open every supply register and return grille Walk the whole house and confirm all supply registers and return-air grilles are fully open and clear of furniture, rugs, and curtains. The furnace needs maximum airflow to keep the limit from tripping again after the lockout ends.
- Visually check accessible ductwork Where you can safely see ducts in the basement, attic, or crawl space, look for a collapsed or crushed flex duct or a disconnected joint. A major duct restriction can retrip the limit even with a fresh filter. Do not open the blower housing or sealed duct.
- Restore gas and power to reset, then test Turn the gas valve back to ON, with the handle parallel to the pipe, and flip the breaker back ON. Cycling power resets the lockout timer immediately instead of waiting the full hour. Set the thermostat to call for heat and watch the furnace through a complete cycle, including high fire.
When to Call a Professional
Contact a licensed HVAC technician if:
- E 274 returns after the filter is replaced and all vents are open
- The blower motor is not running or sounds weak during operation
- E250, E252, and E 274 keep appearing together
- The high-limit trips within the first few minutes of each start
- The duct system appears undersized or was recently altered
Frequently Asked Questions
How long does the E 274 lockout last?
It is a one-hour soft lockout. It auto-clears after roughly an hour, or immediately if you cycle power at the breaker, or once a full heat cycle finishes successfully. Fix the airflow restriction first so it does not simply lock out again.
What is the difference between E250 and E 274?
E250 is a single high-limit trip. E 274 is the escalation: the limit tripped repeatedly or stayed open more than about 3 minutes, so the furnace entered a one-hour soft lockout. Both come from the same restricted-airflow cause.
Can I just keep resetting the breaker to get heat?
Repeatedly resetting without fixing the airflow forces the furnace to overheat again each cycle, which stresses the heat exchanger. Clear the restriction — filter and vents — before relying on the furnace again.
Why did this happen on the coldest night when I need heat most?
Cold nights make the furnace run on high fire more often, which produces the most heat and needs the most airflow. A filter or vent restriction that was tolerable on mild days can push the limit over its trip point under that heavier demand.
Sources
✓ Verified against manufacturer service manual — March 2026