Lennox EL296UHV Error Code E 240: Low Flame Current
What Does Code E 240 Mean?
Error code E240 on the Lennox EL296UHV indicates low flame current during run mode. The flame sensor is a metal rod positioned in the burner flame that generates a tiny electrical current (measured in microamps) to confirm the burners are lit. When this current drops below the expected threshold during heating, the control logs this alert.
The furnace may continue to operate with this code, but the flame signal is marginal. If the flame current drops further, the furnace will lose flame detection entirely, causing it to shut down during operation and eventually lock out (E273). This code serves as an early warning that maintenance is needed.
The most common cause is a buildup of oxidation, carbon, or silica residue on the flame sensor rod. Over time, this insulating layer reduces the sensor's ability to conduct the small current needed for flame detection. A secondary cause is poor unit grounding — the flame sensing circuit requires a clean electrical ground path to function properly.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Dirty flame sensor | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- E240 returns after cleaning the flame sensor
- The flame sensor rod is cracked or physically damaged
- You also see E273 (soft lockout from flame failures)
- The furnace shuts down intermittently during heating cycles
- You suspect a grounding issue (other electrical anomalies in the home)
Sources
- Unit Information - icomfort ENABLED EL296UHV(X) Series Units
✓ Verified against manufacturer service manual — March 2026