Lennox EL296UHV Error Code E 274: Soft Lockout - Limit Open
What Does Code E 274 Mean?
Error code E274 on the Lennox EL296UHV indicates a soft lockout caused by the limit circuit opening repeatedly or remaining open for longer than 3 minutes. The furnace has exceeded its maximum number of recycles attempting to complete a heating call, and the system has shut down for a 1-hour soft lockout to prevent further overheating.
This is an escalation of E250 (limit switch circuit open). When the limit switch trips once, the furnace tries to recover by shutting off the burners and running the blower to cool down. If the limit keeps tripping on subsequent attempts — or never closes within 3 minutes — the control board gives up and enters the 1-hour lockout as E274.
The root cause is the same as E250: insufficient airflow causing the furnace to overheat. A dirty air filter is by far the most common culprit. Blocked vents, collapsed ductwork, or a failing blower can also cause it. Because E274 means the overheating happened multiple times, it is important to address the underlying airflow restriction before the furnace attempts to run again after the lockout period.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Dirty air filter restricting airflow | Most common | ✓ DIY fix → |
How to Fix It: Replace the Air Filter and Restore Airflow
What You'll Need
- Replacement air filter (matching size) Find on Amazon
- Flashlight
Steps
- Turn off electrical power at the breaker and shut off the gas supply valve Locate the furnace circuit breaker and flip it to OFF. Turn the gas shutoff valve to the OFF position (handle perpendicular to the pipe). If you smell gas, leave immediately and call your gas company.
- Replace the air filter Locate and remove the current air filter. If it is dirty or clogged, this is almost certainly causing the repeated overheating. Install a new filter of the correct size with the airflow direction arrow pointing toward the blower. A heavily clogged filter should be replaced, not cleaned.
- Open all supply registers and return grilles Walk through every room and make sure all supply registers and return grilles are fully open and unobstructed. Move any furniture, rugs, or items blocking vents. The furnace needs maximum airflow to prevent the limit switch from tripping.
- Inspect accessible ductwork Check any visible ductwork in the basement, attic, or crawl space for collapsed sections, disconnected joints, or crushed flex duct. A major duct restriction can cause repeated limit trips even with a clean filter.
- Restore power and gas, then test Turn the gas supply valve to ON (handle parallel to the pipe) and flip the circuit breaker to ON. Cycling power resets the lockout timer immediately. Set your thermostat to call for heat and monitor the furnace through the entire heating cycle.
When to Call a Professional
Contact a licensed HVAC technician if:
- E274 returns after replacing the filter and opening all vents
- The blower motor is not running or sounds weak during operation
- You see E250, E252, and E274 appearing together
- The furnace trips the limit switch within the first few minutes of operation
- The duct system appears to be undersized or improperly designed
✓ Verified against manufacturer service manual — March 2026