Lennox Furnace Code E115
Warning
Low 24 volt control power. The control voltage has fallen below the acceptable 18 to 30 volt range. The control restarts if the voltage recovers.
Manual wording: “Low 24V - Control will restart if the error recovers. 24-Volt Power Low (Range is 18 to 30 volts).”
Documented for: EL296UHE and SLP98UHV series
Likely causes, most common first
- Additional power-robbing accessories connected to the 24 volt transformer
- Undersized transformer for the installed system
- Shorted or damaged low voltage wiring
What you can safely check yourself
- Check that the furnace door is fully seated
- Turn the furnace power switch off for 30 seconds and back on once
When to call a technician
Measuring 24 volt supply, finding the load that is dragging it down, and sizing a replacement transformer is a technician job.
A Lennox furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- EL296UHE Service Literature (Corp. 1246-L10), Table 4 - Integrated Control Diagnostic Codes (Lennox Industries Inc., EL296UHE series 96% AFUE two-stage upflow/horizontal gas furnace (EL296UH045XE36B, EL296UH070XE36B, EL296UH090XE48C)) · checked 2026-08-25
- SLP98UHV Service Literature (Corp. 1029-L7), Table 14 - LED 7 Segment Status / Error Code and Integrated Control Diagnostic Codes (Lennox Industries Inc., SLP98UHV series variable-capacity communicating gas furnace (66,000-132,000 Btuh)) · checked 2026-08-25