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Lennox · Furnace

E276 Watchguard calibration failure

High severity EL296UHVLennox SL280UHVLennox SL297NV

What the control is telling you

Pressure switch calibration failed; 1-hour soft lockout.

Applies to: EL296UHV(X) series furnaces with integrated control 103130-XX only

Likely causes

  • Vent system problem
  • Pressure switch wiring fault

Test and repair steps

  1. Inspect vent and intake piping for restrictions.
  2. After snow, ice or freezing fog, check intake and exhaust terminations and remove any obstruction.
  3. Check pressure switch wiring and connections.
  4. Check the condensate trap and the condensate hose screens at the cold end header box for blockage (power off; twist and pull screens, rinse); prime the trap with 10 fl. oz. (300 ml) of water if dry. If furnace and coil drains are combined, the A/C drain must be vented or the pressure switch will not work properly.
  5. Check hoses and inducer operation.
  6. Clears when calibration finishes successfully.

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Source: Lennox EL296UHV(X) Unit Information / Service Literature, Table 5 Ignition Control 103130-XX Diagnostic Codes, p.36, Maintenance p.87. 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.