E422
Lennox
Low Line Voltage / Brownout Condition
Lennox system reports E422 low line voltage; outdoor unit may not start or may drop out during compressor start.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Undersized branch circuit wiring, Loose connections at breaker or disconnect, Utility brownouts, Shared circuit with high-load appliances
How to Fix / Troubleshooting
Safety: Turn off power at the breaker before tightening any electrical connections.
- 1. Check breaker and wiring size: Confirm the breaker and wire gauge match the Lennox unit's MCA/MOP ratings on the nameplate. Undersized wiring can cause voltage drop.
- 2. Tighten connections: With power off, tighten the breaker lugs, disconnect lugs, and unit line voltage terminals. Look for discoloration or melted insulation.
- 3. Avoid shared circuits: Ensure the air conditioner is on a dedicated circuit, not shared with large appliances like ovens or dryers.
- 4. Monitor utility voltage: If low voltage occurs mainly during peak demand times, contact your utility provider. A hard-start kit (installed by a technician) can sometimes help compressors start under marginal voltage.
Warning: Operating under low voltage can overheat and damage the compressor and motors.
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Repair Difficulty
Hard
4/5
Required Part
Lennox Outdoor Disconnect Assembly
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