HVACopediaLennox · Air handler
E116 High secondary (24 VAC) voltage
What the control is telling you
24 VAC power at the furnace or air handler is high (range is 18 to 30 VAC). S30/S40 thermostat alert code 116 (shown as E116 on the unit control display).
Applies to: Lennox communicating air handlers and EIM-equipped indoor units in S30/S40 smart thermostat systems
Likely causes
- Wrong line voltage to the equipment
- Wrong transformer tap
Test and repair steps
- Measure 24 VAC and line voltage (120 V, 240 V etc.) to the equipment.
- Correct the voltage; clears when the control senses proper voltage.
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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.
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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.