Emerson Liebert PEX Series

Questions and Answers

J
John PenaAug 14, 2025
What to do if the Emerson Liebert PEX compressor won't start?
- A
  Alexander RuizAug 14, 2025
  If your Emerson Air Conditioner compressor isn't starting, there are several potential causes: * **Power Issues:** Ensure the main power switch is on, and check the fuse or circuit breaker, as well as the connection cable. * **Overload:** The power might be overloaded, causing the MCB to trip. In this case, manually reset and check the average current. * **Loose Connections:** Verify and tighten all circuit connections. * **Compressor Coil Issues:** Inspect the motor winding for shorts and replace if necessary.
M
Miranda WhiteAug 21, 2025
Why is my Emerson Liebert PEX Air Conditioner compressor so noisy?
- T
  Thomas Moore MDAug 21, 2025
  A noisy Emerson Air Conditioner compressor can be caused by several factors: * **Liquid Returned:** This refers to the handling methods of low suction pressure or liquid returned. * **Lubricant Loss:** Try adding lubricant to the compressor. * **Transportation Fixture:** Ensure the transportation fixture of the compressor has been removed.
M
Megan MooreAug 27, 2025
Why does my Emerson Liebert PEX Air Conditioner compressor stop after 5 minutes?
- J
  julian46Aug 27, 2025
  If your Emerson Air Conditioner compressor stops after running for a short period, it could be due to refrigerant leakage. The LP switch might not close, or the pressure reading from the LP sensor of the dual cooling unit might be too low or incorrect. To resolve this: 1. Check the suction pressure. 2. Inspect the cable containing the LP switch. 3. Verify that the LP sensor reading and actual pressure meet the ±0.3bar requirement. (The HP sensor value can be read from the SERVICE MENUS/DIAGNOSTICS, which displays the absolute pressure).
J
Jacob IngramAug 31, 2025
What causes the contactor not to close and the Emerson Air Conditioner compressor not to start?
- K
  Kathleen LewisAug 31, 2025
  If the contactor isn't closing and your Emerson Air Conditioner compressor won't start, it could be due to: * **No Cooling Demand:** Check the iCOM controller state. * **High Voltage Switch Action:** Inspect the high voltage switch. * **Contactor Failure:** Check the contactor and verify the 24Vac voltage between E1 and terminals P32-10 (compressor 1) and P32-12 (compressor 2).
W
Whitney MaldonadoSep 3, 2025
Why does my Emerson Liebert PEX Air Conditioner have low discharge pressure?
- Y
  ymacdonaldSep 3, 2025
  Low discharge pressure in your Emerson Air Conditioner can stem from: * **Water System Issues (water-cooled):** If you have a water-cooled system, check the water system for excessive flow or low input water temperature. * **Refrigerant Leak:** Locate and repair any refrigerant leaks, then add refrigerant. * **Fan Speed Controller Fault (air-cooled):** For air-cooled units, if the fan speed controller is faulty and the output voltage remains at 100% regardless of condensing pressure changes, replace the controller.
C
Christopher GonzalezSep 6, 2025
Why won't the heating system start and the contactor close on my Emerson Liebert PEX Air Conditioner?
- J
  Jared RiveraSep 6, 2025
  If the heating system of your Emerson Air Conditioner won't start and the contactor won't close, consider the following: * **No Heating Demand:** Verify the iCOM controller state and check for humidifying demand. * **Heating Auxiliary Relay Failure:** Check the heating auxiliary relay and its cable. * **Safety Device Open:** For two-stage heating, check terminals P34-1 and P34-2. If the heating system starts, the safety device is open. Remove the jumper and electric heater, and check that the manual reset switch is open and the automatic reset switch isn't damaged. Use an Ohm meter to check the resistance status of the electric heater to determine if it's damaged.
J
johnsonjosephSep 9, 2025
What causes suction and discharge pressures to remain unchanged after starting my Emerson Air Conditioner?
- B
  Brian NewmanSep 10, 2025
  If the suction and discharge pressures of your Emerson Air Conditioner remain unchanged after startup, it could be due to: * **Compressor Issues:** If the compressor is reversed, exchange any two L lines. If the compressor internal air tightness has failed, replace the compressor.
E
erika09Nov 16, 2025
How to fix an Emerson Liebert PEX Air Conditioner FC fan that won't start?
- N
  Nicolas GriffinNov 16, 2025
  If the FC fan of your Emerson Air Conditioner isn't starting, consider these potential causes and solutions: * **No Main Power:** Examine the rated voltage of L1, L2, and L3 of the fan. * **Circuit Breaker:** Check the circuit breaker of the main fan. * **Overload:** Manually reset the circuit breaker and examine the current value. * **Contactor Issues:** Check for 24Vac voltage between P36-3 and E1. If present but the contactor doesn't engage, replace the contactor. * **Control Board Failure:** Check for 24Vac voltage between P36-3 and E1. If absent, check if the green LED beside silicon control Q5 on the control panel is on. * **Fuse Panel Failure:** If 24Vac is absent between P36-3 and E1, and the green LED beside Q5 is off, check if LED DS4 beside F4 on the fuse panel is o...
G
George McmillanNov 23, 2025
What to do if the EC fan on my Emerson Liebert PEX won't start?
- N
  Nicole BurtonNov 23, 2025
  If the EC fan on your Emerson Air Conditioner fails to start, here are potential causes and solutions: * **Circuit Breaker Disconnection:** Examine the circuit breaker of the main fan. * **Contactor Won't Close:** Check for 24Vac voltage between P36-3 and E1. If present but the contactor doesn't close, replace it. * **Control Board Failure:** Check for 24Vac voltage between P36-3 and E1. If absent, check if the green LED beside silicon control Q5 on the control panel is on. * **Fuse Panel Failure:** If 24Vac is absent between P36-3 and E1, and the green LED beside Q5 is off, check if LED DS4 beside F4 on the fuse panel is on, or test F4 for burnout. * **Air Flow Loss Switch Alarm:** 1) Check whether there is 0 ~ 10Vdc analog signals output from P51, if not, check the control boa...

Summary

Chapter 1 Overview

Model Description

Details the model description of the Liebert.PEX series air conditioner, including various configuration parameters.

Product Introduction

Provides an overview of the Liebert.PEX series air conditioner as a precision environment control system.

Product Appearance

Illustrates the physical appearance of the Liebert.PEX series air conditioner, showing different unit configurations.

Main Components

Outlines the primary components of the Liebert.PEX air conditioner, including indoor unit, outdoor unit, and iCOM controller.

Chapter 2 Mechanical Installation

Movement, Unpacking, and Inspection

Details the procedures for safely moving, unpacking, and inspecting the air conditioner unit.

Installation Notes

Provides essential guidelines and considerations for a correct and optimal installation of the air conditioner.

System Installation Arrangement

Covers the overall system arrangement and illustrates installation modes for air-cooled and water-cooled series.

Installing Indoor Unit

Explains the requirements for the equipment room and the necessary installation space for the indoor unit.

Installing Outdoor Unit

References the manual for detailed installation instructions of the outdoor unit for air-cooled series.

Piping

Details piping procedures for air-cooled and water-cooled units, including pipe sizes and connections.

Lowering Fan and Removing Fixtures

Guides on lowering fans and removing transport fasteners and vibration absorbers for EC fan systems.

Installation Inspection

Lists items to check after mechanical installation is completed to ensure proper setup.

Chapter 3 Electrical Installation

Work Introduction and Installation Notes

Covers work introduction, installation notes, and wires to connect at site for electrical installation.

Wiring of Indoor Unit

Details locating electrical interfaces, connecting power, and control cables for the indoor unit.

Wiring of Outdoor Unit (For Air-Cooled Series)

Explains connecting control signal and power cables for the outdoor unit of air-cooled series.

Installation Inspection

Provides a checklist for inspecting electrical installation to ensure all connections and components are correct.

Chapter 4 System Power-On Commissioning

Location of MCBs

Identifies the locations of Miniature Circuit Breakers (MCBs) within the electrical control box.

Power-On Commissioning Of Air-Cooled Series

Details preparation, commissioning procedures, and inspection after commissioning for air-cooled series units.

Power-On Commissioning Of Water-Cooled Series

Outlines preparation, commissioning procedures, and inspection after commissioning for water-cooled series units.

Chapter 5 iCOM Controller

LCD

Describes the Liquid Crystal Display (LCD) on the front panel for monitoring and configuration.

Button And Indicator Panel

Explains the function of buttons and indicators on the iCOM controller's interface panel.

Structure Chart Of Control Menu

Refers to Appendix 3 for the menu structure of the iCOM Controller.

Startup Interface

Shows the initial interface displayed on the LCD after the system is powered on.

Main Interface

Details the general equipment status displayed on the LCD, including temperature, humidity, and system status.

USER MENUS

Describes the user-accessible menus for monitoring and adjusting system parameters.

SERVICE MENUS

Outlines advanced service menus for professional personnel to configure and diagnose the system.

ADVANCED MENUS

Covers password level, factory setup, and password management within advanced system settings.

MBV Settings

Details settings related to the Motorized Ball Valve (MBV) for system control.

Event Name and Definition

Lists and defines various event names and their corresponding meanings for system monitoring.

Chapter 6 Application Of INTELLISLOT

Introduction Of Host Communication Cards

Introduces TCP/IP and 485 communication cards for host communication.

Installation Of Host Communication Cards

Provides instructions for installing host communication cards into the air conditioner unit.

Commission Of Host Communication Component

Details commissioning procedures for HyperTerminal, 485, and TCP/IP communication cards.

Host Communication Networking Diagram

Illustrates networking diagrams for TCP/IP and 485 communication cards.

Chapter 7 System Operation And Maintenance

System Diagnosing Test

Explains system diagnosing tests, including self-diagnosis function and electric control part checks.

Filter

Details filter inspection, replacement, and setpoint adjustment for optimal system operation.

Fan Components

Covers maintenance checks for FC and EC fan components, including bearings, belts, and motors.

Infrared Humidifier

Provides guidance on cleaning the water pan and replacing lamps for the infrared humidifier.

Electric Heater

Describes checks for electric heaters, including temperature switches and potential faults.

Cooling System

Details checks for cooling system components like suction pressure, discharge pressure, and superheat degree.

Compressor

Guides on compressor maintenance, fault diagnosis, and replacement procedures.

Chapter 8 Troubleshooting

Fan Fault Removal

Troubleshooting guide for fan failures, including power supply, circuit breakers, and motor issues.

Compressor and Cooling System Troubleshooting

Addresses issues related to compressor startup, cooling system pressures, and refrigerant.

Troubleshooting of Infrared Humidifier

Details troubleshooting steps for infrared humidifier issues like no water or contactor failure.

Troubleshooting of Heating System

Covers troubleshooting for heating system failures, including demand, relays, and safety devices.

Appendix 1 Composition Of Electrical Control Box

Appendix 2 Circuit Diagram

Appendix 3 Menu Structure Of iCOM Controller