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Lennox · Heat pump

E428 Inverter high main input current (inverter code 22)

High severity

What the control is telling you

High main input current detected; outdoor unit stops. 10 times in an hour = lockout. Inverter LED flash code 22 (red 2 flashes, green 2 flashes). S30/S40 thermostat alert code 428 (shown as E428 on the unit control display).

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

Likely causes

  • High load / high pressure
  • Input power problem

Test and repair steps

  1. Check input power and operating pressures.
  2. Refer to the unit service manual.
  3. Clear by disconnecting power to the outdoor unit and restarting.
  4. Check inverter LEDs flash code 22 = red 2 flashes, green 2 flashes. Normal inverter LEDs with no fault: red ON, green OFF.

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.34. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

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.