Lennox EL296UHV Error Code E 112: Ground Not Detected
What Does Code E 112 Mean?
Code E112 on the Lennox EL296UHV means the SureLight integrated control cannot detect a valid earth ground, so it shuts the furnace down. This is deliberately a hard shutdown rather than a warning, because grounding underpins both electrical safety and the furnace's ability to sense flame. The control will not run heating or cooling until a proper ground path is restored.
On this furnace the flame-sensing circuit relies on a clean ground reference to carry its small sensing current away from the burner. Without a solid ground, that measurement becomes unreliable, and unreliable flame sensing on a gas appliance is a safety problem — hence the full stop. The system resumes normal operation about five seconds after proper grounding is re-established.
The usual causes are a ground wire that was never connected during installation, a ground conductor that has corroded or broken loose at a terminal, or an interrupted ground path somewhere between the furnace and the electrical panel's grounding system. E112 sits at the severe end of a pair with E117 ("poor ground detected"): E117 is a warning that the furnace keeps running through, while E112 means the ground is missing badly enough that the control refuses to operate at all. Restoring grounding is line-voltage and diagnostic work for an electrician or HVAC technician, not a homeowner repair.
What You'll Notice
- The furnace is completely shut down and will not heat, with "E 112" on the seven-segment LED
- The ground wire at the furnace looks disconnected, loose, or corroded
- The code appeared after a new installation that may never have been grounded
- The furnace also shows flame-sensing or polarity faults
- Operation only returns after the ground connection is repaired
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Missing or broken ground wire connection | Most common | ✗ Call a pro → |
How This Is Diagnosed
A technician confirms whether a ground conductor is present and properly landed at the furnace, then checks continuity of that ground back toward the electrical panel and its grounding electrode system. A missing or high-resistance path confirms E112.
They look for the common break points — an unconnected ground lug from a rushed install, a corroded terminal, or a conductor that vibrated loose — and restore a low-resistance bond. Because grounding also affects flame sensing on this board, the technician typically verifies the furnace proves flame normally once the ground is solid and the code has cleared.
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:
- The furnace has shut down and shows "E 112"
- The ground wire at the furnace is visibly disconnected, loose, or corroded
- The furnace was recently installed and may never have been properly grounded
- Flame-sensing or polarity codes appear together with the ground fault
Frequently Asked Questions
Why did my furnace shut down completely instead of just warning me?
E112 means no usable ground was detected, and grounding is tied to safe flame sensing on this furnace. The control treats a missing ground as serious enough to stop operation rather than run with it, which is why it is a shutdown and not a warning like E117.
Is this something I can fix by tightening a screw?
Restoring the ground involves working with line-voltage wiring and verifying continuity back to the panel, so it should be done by an electrician or HVAC technician rather than as a DIY fix.
How is E112 different from E117?
E117 is a poor-ground warning that the furnace keeps running through, while E112 means the ground is effectively absent and the furnace stops. Both point to the grounding path, but E112 is the more severe of the two.
✓ Verified against manufacturer service manual — March 2026