HVACopediaLennox · Air handler
E117 Poor ground
What the control is telling you
The reporting unit has poor earth grounding. S30/S40 thermostat alert code 117 (shown as E117 on the unit control display).
Applies to: Lennox communicating air handlers and EIM-equipped indoor units in S30/S40 smart thermostat systems
Likely causes
- Weak or high-resistance ground connection
Test and repair steps
- Provide proper grounding for the unit and check earth ground for the system.
- Lennox reference Corp0123L10.
- Clears 30 seconds after the issue is corrected.
Save it for the next call
Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.
Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.16. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.