HVACopediaLennox · Furnace
70501 Smart room sensor internal data fault
What the control is telling you
Room sensor cannot collect samples or readings out of range, or occupancy sensor voltage below 0.2 V or above 2.5 V. S30/S40 thermostat alert code 70501.
Applies to: Lennox communicating gas furnaces (e.g. SL280UHV/SL280UHNV, EL296UHV) in S30/S40 smart thermostat systems
Likely causes
- Sensor fault
Test and repair steps
- Power cycle the Smart Room Sensor.
- Wait 10 minutes for self-clearing (temperature/RH); occupancy self-clears in 45 minutes (3 x 15 minute intervals).
Settings for these units
- Recommended filter size by cabinet width · EL296UHV
- Recommended filter size by cabinet width · Lennox SL280UHV
- Filter sizes by cabinet width · Lennox ML180UHE
- Filter sizes (filter rack kits) · Lennox EL195UHNE
- Filter sizes by cabinet width · Lennox SL297NV
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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.49. 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.