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20

Error 20 — DC voltage or AC voltage low

Lennox · EL18KSLV Series Outdoor Units

What does 20 mean?

Low voltage has been detected by the compressor drive module. This could be due to a low AC input voltage or a low DC bus voltage.

Common Causes

  • Low AC voltage
  • Low DC BUS voltage

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check the incoming AC voltage to the unit.

  2. 2

    Measure the DC BUS voltage.

  3. 3

    Inspect wiring connections for the power supply.

Browse all codes in this manual (43)
Verified technical data. Last updated: April 2026

Related Faults

1Error 1 — EEPROM malfunction or damage10Error 10 — Outdoor defrost sensor failure11Error 11 — Suction temperature sensor failure
Source: Lennox EL18KSLV Series Outdoor Units
Open Manual (Page 66)Search more codes in this manual