Lennox EL296UHV Error Code E 111: Line Voltage Polarity Reversed
What Does Code E 111 Mean?
Code E111 on the Lennox EL296UHV means the SureLight integrated control detected reversed line-voltage polarity — the 120V hot conductor is landed where neutral should be, and vice versa. The control checks polarity because a correct hot-to-neutral reference is fundamental to how the furnace runs its safety circuits, and it will hold off normal operation while the reversal exists.
Proper polarity matters on this furnace beyond simple wiring convention. Flame sensing works by passing a small rectified current from the flame rod through the burner to ground; that circuit relies on the hot and neutral being on their correct terminals. With polarity reversed, the furnace may refuse to run or may struggle to confirm a flame, which is exactly why the manufacturer treats E111 as a safety-related fault rather than a nuisance alarm.
Reversed polarity almost always originates at installation, after electrical panel or receptacle work, or when the furnace is fed from an outlet that was itself mis-wired. The system resumes normal operation about five seconds after the wiring is corrected. Because the fix involves live line-voltage conductors, it is electrician or HVAC-technician work, not a homeowner task. This code is distinct from the ground-related codes E112 (no ground detected, unit shuts down) and E117 (poor ground, warning only), though a sloppy installation can produce more than one of them at once.
What You'll Notice
- The furnace will not start or run, and "E 111" is shown on the seven-segment LED
- The code appeared immediately after a new install or after panel/outlet work
- The furnace also has trouble proving flame or trips on flame-related faults
- The problem started after the furnace was moved to a different circuit or receptacle
- Operation does not return until an electrician corrects the wiring
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Hot and neutral wires reversed at furnace connection | Most common | ✗ Call a pro → |
How This Is Diagnosed
A technician verifies polarity at the furnace's line-voltage connection with a meter, confirming which conductor is actually hot relative to ground and comparing it to how the wires are landed on the furnace terminals. Finding hot and neutral swapped confirms E111 directly.
If the furnace itself is wired correctly, they trace the circuit back toward the disconnect, receptacle, or panel to find where the reversal was introduced — a common finding when the furnace plugs into an outlet that was itself mis-wired. Once the conductors are on their correct terminals, the control clears the fault within a few seconds and normal operation resumes.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- "E 111" is displayed — reversed line-voltage wiring must be corrected by an electrician
- The code appeared right after installation, an outlet change, or panel work
- Flame-proving or ignition problems accompany the polarity code
- You are not certain which conductor at the furnace is hot and which is neutral
Frequently Asked Questions
Can I fix reversed polarity myself?
No. Correcting E111 means working on live 120V conductors and verifying them with a meter, which is electrician or HVAC-technician work. Swapping the wrong wires can create a shock or fire hazard.
Why does a furnace care about which wire is hot?
The flame-sensing circuit passes a small current to ground using the neutral as its reference. Reversed polarity disrupts that reference, so the furnace holds off to keep its safety monitoring reliable.
The furnace was fine for years — why now?
Polarity almost never changes on its own, so E111 usually follows recent work: a receptacle swap, panel service, or the furnace being connected to a different circuit. Tracing back to the most recent change usually finds the reversal.
✓ Verified against manufacturer service manual — March 2026