McQuay ALS Fault Code E10

E10
Phase loss or reversal
Critical
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

McQuay ALS Fault Code E10 is a critical safety alarm indicating: Phase loss or reversal. The most common causes include Missing phase. Estimated repair time: 30-60 minutes (requires electrical power diagnostics at disconnect). This alarm requires immediate attention by a certified HVAC technician.

Alarm Description

Phase loss or reversal

Brand: McQuay  |  Model: ALS (Air-Cooled Screw Chiller)  |  Code: E10  |  Severity: Critical

Observable Symptoms

  • Phase monitor relay indicates phase loss or reversal
  • Compressor may run backwards or fail to start
  • Three-phase voltage readings are unbalanced

What to Check First

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

Quick Start: Check phases

Probable Causes

  • Missing phase
  • Incorrect sequence
  • Blown fuse

Recommended Inspection Steps

  1. Check phases
  2. Verify sequence
  3. Replace fuses

Required Tools & Equipment

  • Digital multimeter
  • OEM service manual
  • Safety PPE (gloves, safety glasses)
  • Safety PPE (gloves, safety glasses, face shield)

Estimated Repair Time

30-60 minutes (requires electrical power diagnostics at disconnect)

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 McQuay service representative for warranty-covered repairs

Related Fault Codes

Other McQuay ALS codes that may be related:

E01E02E03E04E05

OEM Service Manual Reference

OEM Reference: McQuay ALS Air-Cooled Screw Chiller Service Manual. Available through Daikin Applied technical support.

Frequently Asked Questions

What does McQuay ALS fault code E10 mean?

Fault code E10 on a McQuay ALS chiller indicates: Phase loss or reversal. This is a critical safety alarm that requires diagnostic attention.

What causes McQuay ALS alarm code E10?

Common causes include: Missing phase; Incorrect sequence; Blown fuse

How do I fix McQuay ALS error code E10?

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 McQuay 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 McQuay ALS service procedures.