HVACopedia

Lennox · Air conditioner

E410 Open low pressure switch

Low severity

What the control is telling you

Low side pressure is below the switch limit; the system stops and restarts when the switch closes (dealer information). S30/S40 thermostat alert code 410 (shown as E410 on the unit control display).

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

Likely causes

  • Low charge
  • Low indoor airflow / frozen coil
  • Restriction

Test and repair steps

  1. Check operating pressures and charge.
  2. Check indoor airflow and filter.
  3. Clears automatically once fixed.

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.30. 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.