Lennox EL296UHV Error Code E 115: Low 24V Power
What Does Code E 115 Mean?
Error code E115 on the Lennox EL296UHV indicates that the 24-volt control circuit voltage has dropped below the acceptable range (18 to 30 volts). The control board will attempt to restart if the voltage recovers. This is a power supply issue on the low-voltage side of the system, not the main 120-volt supply.
The most common cause is too many accessories drawing power from the furnace's 24-volt transformer. Devices like powered humidifiers, electronic air cleaners, zone damper controllers, and smart thermostats all draw current from the same transformer. When the combined load exceeds the transformer's capacity, the voltage sags and triggers E115.
The solution typically involves either reducing the load on the transformer (by powering some accessories from a separate transformer) or replacing the existing transformer with a higher-VA (volt-ampere) rated unit. A technician can measure the 24-volt circuit load and determine the appropriate fix. The alarm clears automatically once proper voltage is restored.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Too many accessories drawing power from 24V transformer | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The furnace shows E115 and restarts repeatedly
- You recently added a humidifier, air cleaner, or other 24V accessory
- The system works sometimes but fails during peak demand
✓ Verified against manufacturer service manual — March 2026