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Lennox · Heat pump

10 Unknown device detected

High severity

What the control is telling you

Outside of commissioning, the thermostat found a device it does not know and put it in soft disable (two horizontal lines on furnace/air handler/outdoor 7-segment display; green LED 3 s on / 1 s off on damper module or EIM). S30/S40 thermostat alert code 10.

Applies to: Lennox communicating heat pumps incl. variable-capacity inverter units in S30/S40 smart thermostat systems

Likely causes

  • A new communicating device was added after the original setup
  • A control board was replaced and the system was not reconfigured

Test and repair steps

  1. Find the soft-disabled control (two horizontal lines on its display, or green LED 3 s on / 1 s off).
  2. Confirm the added device is Lennox communicating compatible.
  3. S30 go to Menu > Settings > Advanced Settings, open View Dealer Control Center, then pick Equipment > Reset All Equipment. The thermostat will find every Lennox communicating device again.
  4. S40 go to Menu > Settings > Advanced Settings, open View Service Support Center, then Equipment Setting > Reset and pick Reset HVAC Equipment.
  5. Clear reconfigure the system (code clears after reconfiguration).

Settings for these units

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.8. 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.