Lennox LSB Fault Code E20

E20
Compressor surge alarm
Warning
SAFETY WARNING: Commercial chillers contain high-pressure refrigerants and high-voltage electrical components (208V-4160V). Only EPA Section 608 certified technicians should perform diagnostic work. Always follow lockout/tagout procedures and wear appropriate PPE. Do not attempt repairs without proper training and equipment.
AI Summary

Lennox LSB Fault Code E20 is a warning alarm indicating: Compressor surge alarm. The most common causes include Near surge line. Estimated repair time: 1-2 hours. This alarm requires immediate attention by a certified HVAC technician.

Alarm Description

Compressor surge alarm

Brand: Lennox  |  Model: LSB (Water-Cooled Chiller)  |  Code: E20  |  Severity: Warning

Observable Symptoms

  • Controller displays alarm code and description
  • Chiller may be locked out or running in degraded mode
  • Alarm indicator light is illuminated on control panel

What to Check First

Before diving into detailed diagnostics, start with this quick first check:

Quick Start: Check conditions

Probable Causes

  • Near surge line
  • Condenser conditions severe
  • Charge incorrect

Recommended Inspection Steps

  1. Check conditions
  2. Verify condenser
  3. Check charge
  4. Inspect guide vane

Required Tools & Equipment

  • PT chart for refrigerant type
  • Safety PPE (gloves, safety glasses, face shield)

Estimated Repair Time

1-2 hours

When to Call a Professional

  • If the fault persists after completing all recommended inspection steps
  • If you observe unusual noises, vibrations, or oil leaks from the compressor
  • If refrigerant charge levels are outside OEM specifications and EPA-certified recovery is needed
  • If electrical measurements show voltage imbalance greater than 2% between phases
  • If the fault recurs immediately after reset, indicating an unresolved safety condition
  • Contact an authorized Lennox service representative for warranty-covered repairs

Related Fault Codes

Other Lennox LSB codes that may be related:

E01E02E03E04E05

OEM Service Manual Reference

OEM Reference: Lennox LSB Chiller Service Manual. Available through Lennox Commercial technical support.

Frequently Asked Questions

What does Lennox LSB fault code E20 mean?

Fault code E20 on a Lennox LSB chiller indicates: Compressor surge alarm. This is a warning alarm that requires diagnostic attention.

What causes Lennox LSB alarm code E20?

Common causes include: Near surge line; Condenser conditions severe; Charge incorrect

How do I fix Lennox LSB error code E20?

Follow the recommended inspection steps below. Start with the quick check, then proceed through each step. If the fault persists after all steps, contact an authorized Lennox service representative.

Disclaimer: All lookup data is for reference only. Do not use this information to replace certified professional HVAC technician judgment. Always refer to original OEM official service manual for Lennox LSB service procedures.