Vertiv Liebert PEX4 Series User manual

Liebert® PEX4TM Series
User Manual
Precision Air Conditioning

Copyright by Vertiv Co. Ltd.
The content in this document is subject to change without notice. All rights, including rights of translation,
reproduced by printing, copying or similar methods, and even of parts, are reserved. Violators will be liable for
damages. All rights, including rights deriving from patent license or registration of a utility model or design,
are reserved. No part of this document may be reproduced or transmitted in any form or by any means
without the prior written consent of Vertiv Co. Ltd.
Notice
The purchased products, services, and features are stipulated by the contract made between Vertiv Co.,
and the customer. All or part of the products, services, and features described in this document may not be
within the purchasing scope or the usage scope. Unless otherwise specied in the contract, all statements,
information, and recommendations in this document are provided “AS IS” without warranties, guarantees or
representations of any kind, either express or implied. The information in this document is subject to change
without notice. Every eort has been made in the preparation of this document to ensure the accuracy of
the contents, but all statements, information, and recommendations in this document do not constitute a
warranty of any kind, express or implied.
Vertiv Co., Ltd.
China
Homepage: www.vertiv.com
E-mail: [e-mail]
Customer service hotline: [phone]
Asia Pacic
Homepage: www.vertiv.com.
E-mail: [e-mail]
For Technical Support, users may contact the nearest Vertiv Co. local sales oice or service centre.

Purpose of the Document
This document applies to the series of precision air conditioners and cooling solutions which maintain optimal
environmental control of technological ecosystems at minimal operating costs. This document gives an
overview of the specications, installation, commissioning, and maintenance procedures with troubleshooting
from the user perspective. The gures used in this document are for reference only.
Please read this manual carefully before installing, maintaining, and troubleshooting.
Liebert PEX4 Air-cooled precision CRAC is a professional device, only professionals are permitted to access the
unit and is kept in a place where access is restricted to common people.
Styling used in this Guide
The styles used in the manual will be dened as mentioned in the following table:
Situation Description
Warning/Danger/Cauon • The Warning/Danger/Caution note indicates a hazardous or potentially
harmful situation that can result in death or injury. It also indicates in-
structions that need to be adhered to, failing which may result in danger
and safety issues thereby having an adverse eect on the reliability of
the device and security. Even for practices not related to physical injury,
to avoid equipment damage, performance degradation, or interruption in
service, follow the warning instruction, carefully.
Note
• The Note section indicates additional and useful information. It also calls
attention to best practices and industry-best protocols that are
standardized and help make maximum utilization of the resources at
hand. Helpful information related to the product also comes under the
Note heading, helping the users with the denitions, concepts, and
terminologies used in the manual.
Version History
Version Revision Date Issue Changes
1.0 08.04.2019 ---

Safety Precautions and Measures
The important safety precautions and measures that should be followed during the installation and
maintenance are described in the following sections.
Read the manual prior to installation and operation of the unit. Only qualied personnel should move, install,
or service this equipment.
Before working on the equipment, the user reads and considers all precautions, compliance and safety
measures. The unit control must be used exclusively for the purpose which it is intended for; the
manufacturer takes no liability for incorrect use or a modication to the unit control.
Adhere to all the Warnings and Cautionary measures included in the manual.
Please read this manual carefully before installing, maintaining and troubleshooting; especially the
Warning/Danger/Caution information in the User Guide. Apart from the User Guide, also pay attention
to the warning labels on the unit and its components.
This manual is retained for the entire service life of the unit. The user must read all the precautions, danger,
warnings, and cautionary measures mentioned in the manual prior to carrying out any operations on the unit.
Each unit is equipped with an electric insulation which allows the users to work in safe conditions. The main
switch is positioned on the electrical panel cover; to access it, open the right door. Before any maintenance
operation, switch o the unit with this electrical insulation device to eliminate risks such as electrical shocks,
burns, automatic restarting, moving parts, and remote control. The panel key, supplied along with the unit,
must be kept by the personnel responsible for the maintenance. The protective covers can be removed after
the electric power has been cut o by opening the main switch.
In the following sections, notice the various cautionary measures and warnings that need to be read carefully
prior to installing or operating the system.
Disconnect the local and remote power supplies prior to working with the unit.
Prior to the installation process, read all the instructions, verify if all the parts are in place, and check the
nameplate to ensure the voltage matches the available utility power for the unit.
The controller doesn’t isolate power from the unit even in the O mode, and some internal components still
require and receive power during the O mode.
If the unit door is open while the fans are operating, the airow may result in abrupt slamming of the door
resulting in injury. Another aspect is the presence of small objects in the fans bay that can result in object
ejection during the fan start-up and there is a probable risk of being hit by these objects resulting in grievous
injury and causing equipment damage.
The unit contains uids and gases under high pressure. Therefore, the pressure should be relieved before
working with the piping.

Various components such as compressors, refrigerant discharge lines, and humidiers are extremely hot during
the unit operation. Therefore, allow suicient time for the unit to cool down before working with the unit cabinet.
Handle the unit with extreme caution and wear safety equipment such as protective gloves, safety shoes, and
arm protection while working with the hot compressors, discharge lines, and reheats.
There is a risk of water leaking that can damage both the equipment and the building. Eective water drain
connection and facilities should be available. Installation should be precise. Implementation of the application
and service practices should be appropriate and fault-free. Failure to comply with these norms will result in
water leakage from the unit. Water leakage can lead to massive damage and loss of critical equipment in the
hosting ecosystem. Therefore, care should be taken to ensure that the unit is not located directly above any
equipment that could sustain damage due to water and excessive moisture. Use of a leak detection system for
the unit and system supply lines are recommended by Vertiv Co.

Vertiv | Liebert PEX4 | User Manual i
Table of Contents
Table of Contents
Chapter 1: Product Overview................................................................................................................................................................................1
1.1. Product Introduction................................................................................................................................................................................................1
1.2. Model Description....................................................................................................................................................................................................2
1.4. Components of PEX4 Model ........................................................................................................................................................................4
1.4.1. Cabinet ..................................................................................................................................................................................................................4
1.4.2. Air Filter................................................................................................................................................................................................................4
1.4.3. EC Fans.................................................................................................................................................................................................................4
1.4.4. Inverter Scroll Compressor................................................................................................................................................................4
1.4.5. Oil Return Arrangement....................................................................................................................................................................... 5
1.4.6. EMI Filter.............................................................................................................................................................................................................. 5
1.4.7. Refrigeration Circuit.................................................................................................................................................................................. 5
1.4.8. Electronic Expansion Valve (EEV).............................................................................................................................................6
1.4.9. Evaporator Coil..............................................................................................................................................................................................6
1.4.10. Dehumidication- EC Fan.................................................................................................................................................................7
1.4.11. Remote Air-Cooled Condenser.....................................................................................................................................................7
1.4.12. Water-Under-Floor Sensor................................................................................................................................................................7
1.4.13. Controller............................................................................................................................................................................................................7
1.4.14. Color Display and HMI Features.................................................................................................................................................7
1.4.15. Monitoring.........................................................................................................................................................................................................7
1.5. Additional Features .................................................................................................................................................................................................8
1.5.1. Humidier ...........................................................................................................................................................................................................8
1.5.2. Electrical Heating........................................................................................................................................................................................9
1.5.3. Upow Plenum.............................................................................................................................................................................................10
1.5.4. Long Piping Kit (Air Cooled System) ....................................................................................................................................10
1.5.5. Smoke Detectors.......................................................................................................................................................................................10

Vertiv | Liebert PEX4 | User Manual ii
Table of Contents
1.5.6. Fire Detectors ...............................................................................................................................................................................................10
1.5.7. High-Eiciency Filter...............................................................................................................................................................................11
1.5.8. Low Temperature Kit..............................................................................................................................................................................11
1.6. Operating & Storage Environmental Requirements..............................................................................................................12
1.6.1. Operating Requirements.....................................................................................................................................................................12
1.6.2. Storage Requirements .........................................................................................................................................................................12
Chapter 2: Installation...............................................................................................................................................................................................13
2.1. Pre-installation ...........................................................................................................................................................................................................13
2.1.1. Transportation & Movement............................................................................................................................................................13
2.1.2. Unpacking .......................................................................................................................................................................................................14
2.1.3. Inspection..........................................................................................................................................................................................................16
2.2. Installation Preparation (Site Preparation)................................................................................................................................... 16
2.2.1. Equipment Room Requirements................................................................................................................................................16
2.2.2. Installation Space Requirements ............................................................................................................................................ 17
2.2.3. Maintenance Space Requirement ...........................................................................................................................................18
2.2.4. Installation Tools.......................................................................................................................................................................................19
2.2.5. System Arrangement during Installation.........................................................................................................................20
2.2.6. System Installation Mode................................................................................................................................................................ 22
2.3. Mechanical Installation ....................................................................................................................................................................................24
2.3.1. Indoor Unit Size and Weight (Product Dimension).................................................................................................24
2.3.2. Dimension and Weight of Condenser .................................................................................................................................25
2.3.3. Base Plate Cut-out Position and Dimension.................................................................................................................26
2.3.4. Position and Dimension of Air Outlet on Top Cover.............................................................................................29
2.3.5. Indoor Installation ...................................................................................................................................................................................30
2.4. Installation Considerations...........................................................................................................................................................................32
2.5. Pipe Installation Unit (Air-cooled Units).........................................................................................................................................32

Vertiv | Liebert PEX4 | User Manual iii
Table of Contents
2.5.1. Condensate Drain Piping Connection of the Indoor Unit.................................................................................33
2.5.2. Humidication Inlet Pipe Connection.................................................................................................................................33
2.6. Refrigerant Piping Connection.................................................................................................................................................................35
2.6.1. Refrigerant Piping Connection General Principle.....................................................................................................36
2.6.2. Refrigerant Requirement ................................................................................................................................................................38
2.6.3. Copper Pipe Brazing Requirements......................................................................................................................................39
2.7. Lowering the Fan.................................................................................................................................................................................................... 41
2.7.1. Removing Transportation Fixing Plate of Compressor........................................................................................44
2.7.2. Removing of Fasteners of Infrared Humidier............................................................................................................45
2.7.3. Removing of Fasteners from Electrode Humidier................................................................................................45
2.7.4. Removing Pipe Fasteners................................................................................................................................................................ 47
2.7.5. Installation Inspection ........................................................................................................................................................................47
2.8. Electrical Installation.........................................................................................................................................................................................48
2.8.1. Installation Notes......................................................................................................................................................................................48
2.8.2. Wiring of Indoor Unit............................................................................................................................................................................48
2.8.3. Connecting Control Cables ..........................................................................................................................................................50
2.8.4. Connecting Water-Under-Floor Sensor.............................................................................................................................51
2.8.5. Remote Shutdown .................................................................................................................................................................................51
2.8.6. Customized Alarm Terminal ........................................................................................................................................................52
2.8.7. External General Alarm ....................................................................................................................................................................52
2.8.8. Connecting Solenoid Valve of Pipe Extension Kit (Optional)......................................................................52
2.8.9. Wiring of Condenser.............................................................................................................................................................................53
2.8.10. Connecting Power Cables of Condenser ......................................................................................................................53
2.8.11. Electrical Installation Inspection .............................................................................................................................................55

Vertiv | Liebert PEX4 | User Manual iv
Table of Contents
Chapter 3: Controller Operating Instruction...................................................................................................................................56
3.1. HMI Display.................................................................................................................................................................................................................. 56
3.2. Light Indicator ..........................................................................................................................................................................................................57
3.3. Start-Up Interface..................................................................................................................................................................................................57
3.4. User Menu................................................................................................................................................................................................................... 58
3.4.1. Password Interface................................................................................................................................................................................. 60
3.4.2. Menu ..................................................................................................................................................................................................................62
3.4.3. Alarm Menu...................................................................................................................................................................................................62
3.5. Unit Status...................................................................................................................................................................................................................69
3.5.1. Temperature and Humidity Status..........................................................................................................................................69
3.5.2. Power Information Display .............................................................................................................................................................. 71
3.6. Hardware and Software Information....................................................................................................................................................71
3.7. Remote Monitoring Mode..............................................................................................................................................................................72
Chapter 4: General Maintenance ................................................................................................................................................................73
4.1. Manual Operation Function..........................................................................................................................................................................73
4.2. Electrical Connection Inspection...........................................................................................................................................................73
4.3. Control Component Appearance Inspection.............................................................................................................................74
4.4. Water Leak Detector..........................................................................................................................................................................................75
4.5. Air Filter...........................................................................................................................................................................................................................75
4.6. Fan Kit Maintenance .........................................................................................................................................................................................76
4.7. Infrared Humidier................................................................................................................................................................................................76
4.8. Electrical Heater.....................................................................................................................................................................................................77
4.9. Cooling System ......................................................................................................................................................................................................78

Vertiv | Liebert PEX4 | User Manual v
Table of Contents
Chapter 5: Troubleshooting..............................................................................................................................................................................79
5.1. Componentwise Alarm and Solutions ................................................................................................................................................79
5.1.1. Fan Troubleshooting...............................................................................................................................................................................79
5.1.2. Heating System Troubleshooting ........................................................................................................................................... 80
5.1.3. Compressor and AC System Troubleshooting........................................................................................................... 80
5.1.4. Infrared Humidier Troubleshooting.....................................................................................................................................84

Vertiv | Liebert PEX4 | User Manual 1
Product Overview
Chapter 1: Product Overview
1.1. Product Introduction
Liebert PEX4 series air conditioning is a medium and large-scale precision environmental control system, with
high reliability, high sensible heat ratio and with high energy eiciency ratio, suitable for equipment room or
computer room environment. It is designed to ensure a reasonable operating environment for critical system
such as sensitive equipment, industrial process equipment, communications equipment and servers.
Liebert PEX4 series air conditioning includes 10 models of cooling unit (35 kW, 45 kW, 50 kW, 60 kW, 70 kW, 80
kW, 90 kW, 100 kW 110 kW, 120 kW). These models are available in both upow and downow congurations
which are further dierentiated as small cooling capacity (35 kW, 45 kW, 50 kW, 60 kW) with variable frequency
drive single compressor and large cooling capacity units (70 kW, 80 kW, 90 kW, 100 kW, 110 kW, 120 kW)
with two variable frequency compressors. To improve further eiciency of the conguration, EC fan and
Electronic Expansion Valve (EEV) are the standard options. PEX4 also uses micro-channel evaporator, standard
distribution air supply temperature sensor, but heating and humidication are optional. The optional humidier
(infrared or electrode) is available according to dierent requirements.
The PEX4 unit is compatible to both at and ‘V’ type outdoor unit. Outdoor unit has pressure regulating fan
speed to meet the system cooling demand. It improves the operational reliability of the system and also results
in minimal noise pollution. In case of high-temperature applications, PEX4 can also be available with an optional
LVC condenser spray device to meet the cooling requirements of the data center or equipment room or similar
ecosystem.

Vertiv | Liebert PEX4 | User Manual 2
Product Overview
1.2. Model Description
This chapter introduces models, appearance, components, optional conguration and refrigerant requirements
of PEX4. The Liebert PEX4 series precision air conditioner (“PEX4” for short hereafter) is professional
equipment, which is a medium-large size precision environment control system, suitable for the equipment
room or computer room, featuring high reliability, high sensible heat ratio and large air ow. Liebert PEX4 model
appearance is shown in Figure 1-1.
Upflow Model
Downflow Model
Figure 1-1 Liebert PEX4 Models

Vertiv | Liebert PEX4 | User Manual 3
Product Overview
1.3. Model Nomenclature
Table 1-1 Liebert PEX4 Model Nomenclature
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
P 1 0 6 0 D A 1 3 8 0 9 0 2 E 1 D 0 0 N C E 0 4 0
Digit 1,2 Product Model Digit 18 Installation Option
P PEX4 L Air-Cooled, Long pipe> 30 m
Digit 3 Net Cooling Capacity kW C Low Temp Kit
0-9 Nominal Net Cooling Capacity - kW BLow Temp Kit+Long Piping
Digit 4 Net Cooling Capacity kW Digit 19 Monitoring
0-9 Nominal Net Cooling Capacity - kW 0 RS485
Digit 5 Net Cooling Capacity kW SSIC Card
0-9 Nominal Net Cooling Capacity - kW Digit 20 Sensor
Digit 6 Air Discharge N Supply Air Temp Sensor
U Upflow A Supply Air Pressure Sensor
D Downflow FSmoke & High Temp Sensor
Digit 7 System Type H High Temp Sensor
A Air Cooled SSmoke Sensor
Digit 8 Airow 1Supply Air Pressure & Smoke
1 EC Plug Fan – Standard Static 2 Supply Air Pressure & High Temp
Digit 9 Power Supply 3 Supply Air Pressure & Smoke & High Temp
3 380 V to 415 V, 3 Ph+N~50 Hz/ 60 Hz 4Supply Air Temp & Smoke Sensor
Digit 10 Cooling System 5 High Temp & Supply Air Temp Sensor
8 R-410a EC Scroll Compressor, Single Circuit 6 Supply Air Sensor & Supply Air Temp Sensor
9 R-410a EC Scroll Compressor, Dual Circuit 7 High Temp & Supply Air Temp Sensor & Smoke Sensor
Digit 11 Humidication 8 Supply Air Sensor & Supply Air Temp & Smoke Sensor
0 None 9 Supply Air Pressure & High Temp & Supply Air Temp Sensor
H Infrared Humidication
BSupply Air Pressure & Smoke & High Temp & Supply Air
Temp Sensor
SElectrode Humidication
Digit 12 Display Digit 21 Packaging
9 9-Inch HMI PPackaging – Standard Cardboard And Wooden Pallet
Digit 13 Re-Heating C Packaging – Wooden Crate Export
0 None Digit 22 Special Requirements
1Electrical Heating Std. 1 Stage ASFA – None
2 Electrical Heating Opt. 2 Stage E For Export
Digit 14 Filtration Digit 23 Order Identier
2 G4 (EU4) 0 Standard ESP
3 F5 (EU5) 1High ESP 50 Pa
Digit 15 Coil and Valves 2 High ESP 100 Pa
E Standard DX Air Cooled Coil, EEV 3 High ESP 150 Pa
Digit 16 Enclosure Options 4High ESP 200 Pa
1 Standard color black orange peel grain coating, ZP7021 Digit 24 Order Identier
Digit 17 Main Switch High Voltage Option 1-9 Factory Code
D Main Non-Locking Disconnect Digit 25 Order Identier
ADual power automatic Switching (interlock contactor) 0-9 Factory Code
The standard components are represented in ‘Bold Italic’ font in Table 1-1.

Vertiv | Liebert PEX4 | User Manual 4
Product Overview
1.4. Components of PEX4 Model
1.4.1. Cabinet
The cabinet frame is constructed of 2.5 mm, 2.0 mm, and 1.2 mm folded galvanized steel. The exterior panels are
constructed of 1.2 mm zinc coated sheet steel and insulated with foam insulation. The cabinet is powder coated
in Charcoal Grey color and have a textured nish. The hinged front doors can be removed and include the
captive 1/4 turn fasteners. PEX4 cabinet is divided into two sections- power module and cooling module. Power
module is comprising of compressor (s) and control section.
1.4.2. Air Filter
The lter panels can be removed from the front of the unit. Filtration is provided by V/ A form and the dry
disposable media housed in a metal frame. The rated eiciency is in accordance with EU4/ MERV8 standards.
The unit is tted with a Filter Dierential Pressure Switch, which is connected to the microprocessor controller
to provide ‘Filter Clogged’ warning indication.
1.4.3. EC Fans
The unit is tted with one/ two direct-driven, high eiciency, single inlet, backward curved, centrifugal
‘plug’ type fan (s), with aluminum nozzle (s) and PP Plastic impeller (s). The fan motors are Electronically
Commutated (EC), IP54, with internal protection and speed regulation via controller signal. The fans is statically
and dynamically balanced. For down-ow applications, the EC fan is mounted within the raised oor for higher
energy eiciency. A minimum raised oor height of 450 mm is required.
1.4.4. Inverter Scroll Compressor
PEX4 indoor unit is equipped with one/two (depending on capacity - >60 kW– two) scroll compressor driven
by inverter. It has a wide speed range of 1000 RPM to 7200 RPM to help part load eiciency. The compressor
is charged with lubricating oil, designed for operating with green refrigerant i.e. R410a. Each compressor has an
internal motor protection and is mounted on vibration isolators. Wide range of 30% to 120% of rated capacity is
attained by the system.
PEX4 uses scroll compressor with inverter drive arrangement can adjust the speed according to the change of
refrigeration demand automatically, which greatly improves the overall energy eiciency of the system. Inverter
system has a drive arrangement, which is compact in size with built-in DC reactor, that supports large torque
under low speed with small torque ripple and speed control accuracy of ± 0.5%. It has high thermal reliability,
long service life and CE certication.

Vertiv | Liebert PEX4 | User Manual 5
Product Overview
Figure 1-2 Scroll Compressor
1.4.5. Oil Return Arrangement
The unit’s intelligent oil return logic allows the proper return of oil to the compressor during the part load
period. When the oil return adjustment is required, to maintain the running time of return oil, the compressor
sets the return oil running speed.
1.4.6. EMI Filter
The PEX4 unit comes with a built-in Electromagnetic Interference (EMI) lter to suppress the interference
which is generated by inverter drive system. EMI-lter conforms with class B standard and IEC No: EN55014-1.
1.4.7. Refrigeration Circuit
The refrigeration system is of the direct expansion type and includes one or two hermetic scroll compressors
(with inverter drive arrangement), equipped with crankcase heaters and rota-lock connections. The system
includes an auto reset high pressure control and low pressure control; also has EEV, high sensitivity refrigerant
sight glass, large capacity lter dryer with rota-lock connections and charging/access ports in each circuit. Each
circuit only connects to one compressor.
• Do not use inferior quality refrigerant.
• For any consequences resulting from inferior quality refrigerant, Vertiv does not assume warranty
responsibility.

Vertiv | Liebert PEX4 | User Manual 6
Product Overview
1.4.8. Electronic Expansion Valve (EEV)
Each circuit has two EEVs for better refrigerant distribution with a common drive to control both valves.
The EEV is designed to collect temperature and pressure signals simultaneously to accurately modulate the
refrigerant mass ow and to precisely regulate the ow of refrigerant. EEV has a wide operating envelope, also
reduces the condensing pressure, thereby resulting in substantial energy savings. EEV also helps in maintaining
constant superheat.
Figure 1-3 Electronic Expansion Valve
1.4.9. Evaporator Coil
In PEX4 series parallel ow tube evaporator is adopted, as shown in Figure 1-4. It uses aluminum material that
reduces the weight of the evaporator and also reduces the copper consumption. At the same time, the design
of the micro-channel greatly reduces the refrigerant charge amount and enhances heat transfer, optimizes the
air bypass. Each cooling module consists of two separate evaporators, ‘V’ pattern for upow unit and ‘A’ pattern
for downow unit.
Figure 1-4 Evaporator Coil

Vertiv | Liebert PEX4 | User Manual 7
Product Overview
1.4.10. Dehumidication- EC Fan
For dehumidication, the Compressor operates a specic cycle which uses an Electronic Expansion Valve (EEV)
control logic called Te. This EEV control logic adjusts EEV opening (normally closed) to reduce the surface
temperature of the coil below the return dew point condition.
1.4.11. Remote Air-Cooled Condenser
Refer to “LSF/LDF condenser User Manual” and “LVC Series Condenser User Manual.”
1.4.12. Water-Under-Floor Sensor
Each unit is supplied with single water under oor point detector as standard. The alarm is triggered when the
‘water-under-oor sensor alerts the controller upon detection of water.
1.4.13. Controller
The Controller provides a simple operational user-interface and it is developed by using the latest and highly
advanced PID regulation technology. The controller features self-recovery power failure and protection against
high/low voltage. An accurate running status of the major components can be viewed through the menu
operation. It uses RS485 to congure Modbus protocol or SIC card (optional) to congure SNMP protocol.
1.4.14. Color Display and HMI Features
PEX4 is equipped with 9-inch color display, which enables monitoring of operating status of the precision AC
through menu-driven operations. It features auto restart function with high and low voltage protection, phase
loss protection, and phase reversal protection. It can display up to 500 historical alarms.
It also has HMI features such as Temperature control– Proportional, PI, PID, Position Increment; dierent
scenario for Room cooling or Optimizing aisle cooling. The cooling capacity is controlled via sensors such as
return air temperature/ supply air temperature/ remote rack temperature sensors, etc. The Inverter compressor
capacity helps in modulation for variable speed. The HMI also facilitates Supply and Return Air control, Heating
control, EEV control, EC fan control, Humidication control, and Static Air Pressure control.
1.4.15. Monitoring
Liebert PEX4 inverter air conditioner series is capable of connecting to the Building Management System/
Building Automation System using the following protocols:
• Modbus RTU – Modbus Remote Terminal Unit (RTU) communication protocol over a RS-485 serial network
(also known as Modbus RTU RS-485)
• SNMP (need to choose SIC card which is an optional component)

Vertiv | Liebert PEX4 | User Manual 8
Product Overview
1.5. Additional Features
1.5.1. Humidier
There are two options- Infrared humidier and Electrode humidier
• Infrared Humidier
The infrared humidier (shown in Figure 1-5) consists of infrared humidier lamp, water injection valve,
humidifying water dish, temperature alarm protection devices and water level alarm device. The infrared
humidier in the Liebert PEX4 series provides quicker and more responsive operation which is quite important
for mission-critical applications. These humidiers reduce the dependency of water quality.
No. Description No. Description
1 Inlet pipe 2 Outlet joint
Figure 1-5 Infrared Humidifier
• Electrode Humidier
The electrode humidier uses the electrodes to boil the water in humidier bottle to produce steam for
humidifying purpose. It has dierent requirement for water quality and sizes of inlet/ outlet pipes with respect to
standard. Steam from the cylinder is mixed with the discharge air from the evaporating coil by a copper steam
distributor. The humidication rate for 1-bay unit is 5 kg and for 2-bay unit the humidication rate is 8 kg.

Vertiv | Liebert PEX4 | User Manual 9
Product Overview
Figure 1-6 Electrode Humidifier
1.5.2. Electrical Heating
In the PEX4 models, the PTC (PTC= Positive Temperature Co-eicient) heaters are used and it features
with fast temperature rising speed, automatic regulation of air temperature and power consumption. Its
caloric value not only maintains Dry Bulb Temperature but also compensates temperature drops due to
dehumidication. The lower surface temperature of the heater prevents the air from being ionized, thereby
extending the service life. The 1-stage heater capacity is 9 kW for models P1035 to P1060 and 12 kW for rest of
the models; for 2-stage, it is 18 kW & 24 kW. The material used for heating is metal. The safety devices, used in
the reheater are two automatic reset Overheat Switches and one manual reset Overheat Switch.
No. Description No. Description
1Zero line (blue) 5 Live line (red)
2 Temperature controller soleplate 6 Temperature controller soleplate
3 Live line (red) 7 Live line (red)
4Temperature controller soleplate
Figure 1-7 Electrical Heater

Vertiv | Liebert PEX4 | User Manual 10
Product Overview
1.5.3. Upow Plenum
For upow system, the plenum of the same size can be selected with the unit. All plenums have grills to regulate
the airow and can manually control the grills for dierent air directions. The material used for Plenum is hot
galvanized plate with spraying material.
Figure 1-8 Plenum
1.5.4. Long Piping Kit (Air Cooled System)
The long piping kit is mandatory if the eld piping equivalent length is more than 30 m. It is used with both
check valve and solenoid valve. The long piping kit prevents the refrigerant from returning and concentrating
after the compressor is turned o, ensuring the normal start of the compressor and make the system safer.
1.5.5. Smoke Detectors
The smoke detectors immediately shut-down the system and activate the alarm system when activated. The
smoke detectors are mounted in the electrical panel with the sensing element in the return-air compartment.
The smoke detector is not intended to function as or replace any room smoke-detection system that may be
required by local or national codes. The smoke detectors shall include a supervision contact closure.
1.5.6. Fire Detectors
The re detector can check the eld return air temperature. It triggers re alarm when the smoke level
continues to rise along with elevated room temperature, or the temperature is too high and reaches the re
alarm threshold. The primary purpose of the sensor is to examine the air temperature and to initialize the
anti-re measures installed in the facility. Fire detector trips at 125 F±6 F, and when re alarm occurs the unit
will shutdown. Refer Figure 1-9.