Lennox E113 Error Code

What does Lennox E113 mean?

E113 indicates the AC line voltage supply to the furnace or air handler is above the acceptable operating range (higher than the nameplate rating). The control monitors incoming line voltage and shuts down the system when overvoltage is detected. The alert clears five seconds after voltage returns to the correct range.

Symptoms

• E113 or 'High AC Line Voltage' displayed on the thermostat.
• System shuts down and will not operate while overvoltage persists.
• Alert may appear after utility maintenance or transformer work in the neighborhood.
• May occur on equipment near the panel where voltage is not reduced by wire resistance.

Common causes

• Utility supply voltage above nameplate rating (typically above 132VAC on a 120VAC system or above 264VAC on a 240VAC system).
• Neutral wire open or loose at the panel causing voltage imbalance and phase-to-neutral overvoltage.
• Utility transformer mis-tap providing voltage above design level.
• Surge or transient from utility grid switching.

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Diagnostic steps

1. Measure line voltage at the equipment terminal block

   With the system running, measure voltage between Line and Neutral at the equipment. Document the reading and compare to nameplate rating. Also measure Line-to-Ground to check for a neutral issue.

2. Measure voltage at the main panel

   Check supply voltage at the main breaker to determine whether the overvoltage originates at the utility service or within the building. If panel voltage is also high, the issue is utility-side.

3. Inspect the neutral conductor for looseness or open circuits

   An open neutral on a 240VAC system can cause one leg to rise above its rated voltage. With power off, check neutral connections at the panel, meter base, and any junction boxes for loose lugs.

4. Contact the utility company if voltage is consistently high

   If voltage at the panel consistently exceeds the rated service voltage, contact the utility to inspect their transformer tap. This is not an equipment defect — it is a supply problem requiring utility-side correction.

When to call a professional

Persistent overvoltage from the utility requires the utility company's involvement. An open or loose neutral is an electrical hazard requiring a licensed electrician. Do not operate the equipment while E113 is active — sustained overvoltage damages motor windings, control boards, and other electrical components.