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technicalpaperTP_14001_GB

IT Cooling technical paper

Close Control Air Conditioning

technicalpaper Close Control Air Conditioning

2 RC GROUP S.p.A. ● TP_14001_GB

INDEX

1 INTRODUCTION 3

2 CCAC VS. COMFORT: DIFFERENCES BETWEEN THE TWO AIR CONDITIONING TYPOLOGIES EXPLAINED IN SIX POINTS 4

2.1 DEFINITION 4 2.2 MAIN APPLICATIONS 5 2.3 FEATURES 5 2.4 AIR CONDITIONERS MAIN CHARACTERISTICS 6 2.5 WORKING CHARACTERISTICS @ 26°C / 50%; 35°C 6 2.6 AIR CONDITIONERS WORKING CHARACTERISTICS @ 26°C / 50%; 35°C 7

3 THE PRECISION AIR CONDITIONING’S MAIN APPLICATION: DATA CENTER 8

3.1 TECHNOLOGY STATE OF THE ART 8 3.1.1 COOLING CAPACITY CONTROL ON SUPPLY AIR TEMPERATURE 8 3.1.2 EXTENDED THERMAL-HYGROMETRIC CONDITIONS 10 3.1.3 UNIFORM LOAD DISTRIBUTION ON ALL MACHINES (LOAD SHARING) 11 3.1.4 VARIABLE SET POINT FOLLOWING THERMAL LOAD (FLOATING SET POINT) 12 3.1.5 VARIABLE WATER FLOW TO AIR CONDITIONERS 12 3.1.6 VARIABLE WATER FLOW TO CHILLERS 12 3.2 CHOICE FACTORS OF AIR CONDITIONING SYSTEM FOR DATA CENTER 13 3.2.1 TOTAL THERMAL LOAD 13 3.2.2 THERMAL LOAD LAY-OUT AND TYPOLOGIES 13 3.2.3 ELECTRONIC EQUIPMENT FEATURES 13 3.2.4 ROOMS CHARACTERISTICS 13 3.2.5 SITE GEOGRAPHICAL LOCATION AND CLIMATE CONDITIONS 14 3.2.6 SITE NORMATIVE CHARACTERISTICS 14 3.2.7 TIER CLASSIFICATIONS AND AIR CONDITIONERS AND CHILLERS COMPONENTS 14 3.3 DATA CENTER INDOOR LAY-OUT 15 3.3.1 PERIMETER INSTALLATION 15 3.3.2 IN-ROW / IN-RACK INSTALLATION 15 3.3.4 CONTAINMENT 16 3.4 DATA CENTER INDEX / CLASSIFICATIONS 17 3.4.1 INDEX PUE/DCIE 17 3.4.2 TIER CLASSIFICATION 19 3.5 RC GROUP PROPOSAL FOR HIGH EFFICIENCY DATA CENTER 21 3.5.1 DATA CENTER WITH HIGH LOADS 21 3.5.2 DATA CENTER WITH MEDIUM-LOW LOADS 22 3.5.3 DATA CENTER WITH HOT SPOT 23

4 OTHER PRECISION AIR CONDITIONING APPLICATIONS 24

5 TAYLOR-MADE SERVICE BY RC GROUP 25

6 PRECISION AIR CONDITIONING GLOSSARY 26

7 REFERENCES 31



1 INTRODUCTION

Close Control Air Conditioning (CCAC) was created in the 70’s in order to meet the needs of a very

technological and specialized élite: keeping the thermal-hygrometric (temperature and relative humidity)

and air purity conditions within strict limits in rooms where the first computers used to work.

It was clear that those devices emitted a great amount of heating, and that their working operations

could be guaranteed only at appropriate indoor climate conditions.

Consequently Closed Control Air Conditioning acquired its own peculiar connotation which makes it

different from “comfort” air conditioning.

The aim of this paper is to provide information regarding CCAC’s main features, which differ from the

“comfort” air-conditioning ones, and the main applications and services RC Group supplies.



2 CCAC VS. COMFORT: DIFFERENCES BETWEEN THE TWO AIR CONDITIONING TYPOLOGIES EXPLAINED IN SIX POINTS

2.1 DEFINITION The differences between CCAC and comfort are clearly described as follows, showing the two different

air-conditioning typologies’ targets.

CCAC

Closed Control Air Conditioning has the aim

to provide the right electronic and other

devices working which emit sensible heat by

keeping and controlling, within strict limits,

the treated air’s following parameters:

• temperature

• relative humidity

• purity.

COMFORT

Comfort conditioning has the aim to provide

the health of the people who live/work

indoor, by keeping and controlling the

treated air temperature. Only recently some

relative humidity controlling air conditioners

have entered the market.



2.2 MAIN APPLICATIONS The following list is to confirm the differences: detailed descriptions of CCAC main applications are

shown in the following pages.

CCAC

• Data Centers

• Telephone rooms

• Containers for mobile TLC

• Power Rooms

• Measurement rooms

• Radar Rooms

• CAT Rooms

• Control Rooms

COMFORT

• Houses

• Offices

• Hospitals

• Hotels

• Shopping centres

• Cinemas and Theatres

• Airports

• Congress halls

2.3 FEATURES Different needs/characteristics of both air conditioning systems are displayed below.

CCAC

• None or limited people presence

• Thermal load:

- sensible: 90 to 100%

- latent: 0 to 10%

• Operating: H24; 365 day/year

• Control: Temperature + Relative

Humidity

• High filtration efficiency (min. G4)

• Stand-by units required

COMFORT

• People presence

• Thermal load:

- sensible: 65 to 70%

- latent: 30 to 35%

• Operating: 10-12 h/d; 100 day/year (Europe)

• Control: only Temperature

• No filtration efficiency requirements

• Stand-by units not required



2.4 AIR CONDITIONERS MAIN CHARACTERISTICS CCAC air conditioning series are wider for versions/configurations/options equipment, and they use the

most advanced control systems:

CCAC • Single or double refrigerant circuit

• Up-flow/down-flow/displacement air

delivery

• Advanced microprocessor

• Control on supply and return air

• Wide optional availability

COMFORT

• Single refrigerant circuit

• Up-flow air delivery

• Basic microprocessor

• Return air control

• Limited optional availability

Logos, Trade Marks and Companies Name are property of respective Owners

2.5 WORKING CHARACTERISTICS @ 26°C / 50%; 35°C As for total cooling capacity, close control air conditioner has higher energy efficiency and lower power

input:

CCAC (mod.NEXT.DX.O.S 082.P2 H7 RC Group)

• TOTAL Cooling Capacity: 81,4 kW • SENSIBLE Cooling Capacity:76,4 kW

• Sensible Heat Ratio: SHR = 0,94

• Compressors power input: 19,1 kW

• Air Flow: 20.870 m3/h

• Fans power input: 4,18 kW

• EER (on TOTAL) = 3,5 kW/kW

• EER (on SENSIBLE) = 3,3 kW/kW

• OFF-COIL Air Temperature: 14,0 °C

COMFORT

(competitor)

• TOTAL Cooling Capacity: 85,4 kW

• SENSIBLE Cooling Capacity:55,4 kW



• Air Flow: 15.984 m3/h




• OFF-COIL Air temperature: 9,5 °C



2.6 AIR CONDITIONERS WORKING CHARACTERISTICS @ 26°C / 50%; 35°C As for Sensible air conditioning, close control air conditioner has higher energy efficiency and lower

engaged power:

CCAC (mod.NEXT.DX.O.S 082.P2 H7 RC Group)


• SENSIBLE Cooling Capacity:53,2 kW



• Air flow: 14.500 m3/h





COMFORT

(competitor)


• SENSIBLE Cooling Capacity:55,4 kW • Sensible Heat Ratio: SHR = 0,65


• Air flow: 15.984 m3/h





Logos, Trade Marks and Companies Name are property of respective Owners

IMPORTANT As shown, it is clear that a comfort air conditioner is not suitable for close control air conditioning

applications due to the following technical-economical reasons :

• Not suitable for heavy duty service 24h/365d/year.

• High dehumidification, as a consequence of the low value of sensible heat ratio SHR. It would

require a humidification operation to take relative humidity to nominal values leading to additional

energy costs.

• Low EER values and resulting high energy costs.

The advantage achieved for buying a comfort conditioner at a lower price is reset by a lower energy

efficiency in a short time, easy to calculate as pay-back time. There is, furthermore, an hidden cost which

is very difficult to quantify in advance: the one due to possible electronical equipment stops, as comfort

conditioners are not suitable for heavy duty service required by the precision air conditioning.



3 THE PRECISION AIR CONDITIONING’S MAIN APPLICATION: DATA CENTER

Data Center represents the precision air conditioning ‘s main and most widespread application. In the

latest years we witnessed the increase of data processing and the resulting growth in dimensions and

energy consumption. The current financial and economical heavy crisis started at the beginning of the

XXI century has dramatically highlighted the issue of energy efficiencies and environmental

sustainability. The current Data Center managers showed great awareness towards this matter and

transmitted their needs to suppliers.

The message has been acknowledged by the whole industry: the precision air conditioning has been

able to provide the most suitable answers to the needs of systems with increasingly higher energy

efficiency coming from designers and current Data Center managers.

These pages has the aim to inform about and update the technology state of the art, to furnish details

on the methods, the indexes and the institutions of classification and certification and to provide a view

of RC Group’s products series and systems for the current high efficiency Data Center.

3.1 TECHNOLOGY STATE OF THE ART

From the beginning of the XXI century, industry has provided air conditioning systems and liquid chillers

manufacturers with a new generation of components which take full advantage of electronics and the

new heat exchange technologies to maximize energy efficiency.

Nowadays all air conditioning systems by RC Group for Data Center extensively use these

components; in detail:

• plug fans and axial fans, all equipped with EC brushless motors;

• scroll compressors with inverter BLDC motors ;

• oil-free magnetic levitation centrifugal compressors;

• air to gas microchannel coil heat exchangers;

• electronic expansion valves;

• two-way chilled water valves;

• PID microprocessor control systems.

The high efficiency achieved by current RC Group air conditioning systems allows to apply them in the

latest Data Center that require:

3.1.1 COOLING CAPACITY CONTROL ON SUPPLY AIR TEMPERATURE

The latest electronic devices require cold air entering from the front and hot air exit from the back

allowing to create “hot and cold aisles” in Data Center, instead of keeping uniform temperature in the

area,

As for air conditioning, it means to grant a constant cooling air temperature for the equipment (cold aisle

temperature), supply air temperature, ranging from 20°C and 24°C, and to accept a return air

temperature to the a/c unit (hot aisle temperature) often at 35°C if not higher. What shown above is the

reason of the cooling capacity control based on supply air temperature.



The machine selection has to be done firstly considering the needed air flow, and once identified the

cabinet size suitable for such air flow, it is possible to proceed with the evaluation using RC World

selection software.

Energy and economical benefits due to higher working temperatures are clear:

• DX air conditioners: possibility to work with high evaporating temperatures with EER increasing

and resulting machine size reduction;

• CW air conditioners: possibility to work with higher in/out chilled water temperatures with

resulting size reduction and chiller increasing EER.

RC Group air conditioners suitable for cooling capacity control based on supply air temperature are:

• NEXT EVO DX INVERTER

• NEXT EVO CW

• COOLSIDE EVO

• COOLROW

All these machines are equipped with the new control system with microprocessor MP.EVO whose main

features are:

• Cooling capacity control on supply air temperature set point;

• Fans speed control on return air temperature or underfloor pressure set point;

• Dew-point calculation on heat Exchange coil;

• Serial management of main components.

Picture 1 - Installation with hot and cold aisles and supply air temperature control



3.1.2 EXTENDED THERMAL-HYGROMETRIC CONDITIONS

The latest electronic equipment are able to properly operate at less strict temperature and relative

humidity conditions than in the past. ASHRAE has identified 4 areas, from A1 to A4, defining new

temperature limits and relative humidity which devices can work with. In current Data Halls supply air

temperature ranging from 22°C to 24°C are required with return air temperature up to 35°C or 36°C

(area A3 of diagram ASHRAE).

As for chilled water, we can observe the temperatures’ and delta T’s increase: today we deal with in/out

water temperatures’ requests = 23°C/17°C, or in/out = 28°C/18°C resulting in:

• increasing the free-cooling working time, with “packaged” units or with standard A Class chillers

in series or in by-pass with adiabatic dry coolers;

• reducing power absorbed by pumping system.

Sometimes this requires to redesign and recalculate the chilled water coils, that work with a lower water

flow than the one used before.

Picture 2 – Psychrometric Chart with climate fields according to ASHRAE



3.1.3 UNIFORM LOAD DISTRIBUTION ON ALL MACHINES (LOAD SHARING)

Electrical motors EC (Electronically Commutated) and BLDC (BrushLess DC) which equip both fans and

compressors have two common characteristics:

1. possibility to follow exactly thermal load variations;

2. higher energy efficiency at partial loads.

The latter point has radically changed “stand-by” meaning: no longer some machines at 100% and

others in stand-by, but all operating machines at a partial load. The following units by RC Group

represent the best solution for “load sharing” operations:

• air conditioners NEXT EVO CW, NEXT EVO DX INV, COOLSIDE EVO; COOLROW

• chillers UNICO & FRIGO TURBO FL; UNICO TURBO FL FREE; GLIDER FREE & EAGLE

FREE.

Energy saving achieved are significant, as the schemes below well display.

Picture 3 – Actual vs. new stand-by management

Picture 4 – Traditional system vs. load sharing

No longer “N” machines at 100% and others in stand-by, but ACTIVE STAND-BY

Stand-by

TRADITIONAL LOAD SHARING

Air flow: 24.000 m3/h Fans power input:

4,5kW x 3 = 13,5kW x 8.760 h/y = 118.260 kWh/y

Air flow: 16.500 m3/h Fans power input:

1,5kW x 4 = 6,0kW x 8.760 h/y = 52.560 kWh/y



3.1.4 VARIABLE SET POINT FOLLOWING THERMAL LOAD (FLOATING SET POINT)

The current control systems with PID microprocessor allow the control of indoor thermal load /outdoor air temperature and change chiller set point by adapting it to load variation. Energy and economical benefits are significant both in start-up phase of Data Center, not used at 100% and with timing load variations when project condition is achieved. Set-point compensation is a standard function of the microprocessor fitted in the RC Group chillers.

3.1.5 VARIABLE WATER FLOW TO AIR CONDITIONERS

Two-way modulating CHW valves fitted in the latest chilled water units allow the use of variable water flow inverter-driven pumps, with consequent energy saving.

RC Group air conditioners, equipped with two-way chilled water valve, are:

• NEXT EVO CW

• COOLSIDE EVO CW

• COOLROW CW

3.1.6 VARIABLE WATER FLOW TO CHILLERS

The combination of inverter-driven compressors and flooded evaporators allows to dispel the taboo of a constant water flow in the chiller. These components, if controlled by a high performing microprocessor system, grant the right operation with a variable water flow ranging from 60 to 110% and they give benefits in:

• Pumping energy saving;

• Saving in buying components and in system building, as there is a unique pump for primary and secondary circuit and the CHW units are equipped with 2-way and not 3-way valves.

RC Group Chillers UNICO & FRIGO TURBO FL; UNICO TURBO FL FREE are able to work with variable water flow.



3.2 CHOICE FACTORS OF AIR CONDITIONING SYSTEM FOR DATA CENTER

There are several factors that play an important role in choosing the air conditioning system that grants an high working flexibility, a better energy efficiency and a short pay-back time, by respecting reliability levels and relative TIER class availability (to see chap. 3.4.2). We list the most important ones as follows:

3.2.1 TOTAL THERMAL LOAD

determine the system choice:

• chilled water for high or medium-high loads (> 400 kW – 500 kW);

• direct expansion for low or medium-low loads (< 150 kW - 200 kW).

The line between chilled water use or direct expansion use is not so marked, and not-clear situations could happen, and a close evaluation of both systems is required.

3.2.2 THERMAL LOAD LAY-OUT AND TYPOLOGIES

determine the conditioner typology choice:

• for perimeter installation, if there are uniform loads;

• for in-row/in-rack installations in case of “hot spot”.

3.2.3 ELECTRONIC EQUIPMENT FEATURES

determine the choice of temperature distribution in the room:

• hot aisles/cold aisles, if the equipment take cold air from the front and they deliver it hot from the

back; “mirror” installation. In this case air conditioners will control cooling capacity on supply air

temperature;

• uniform temperature in the whole room, if the equipment take cold air from the bottom and

deliver hot air to the top; “traditional” installation. In this case air conditioners will control cooling

capacity on return air temperature.

3.2.4 ROOMS CHARACTERISTICS

determine the choice of physical/geometrical air conditioners characteristics:

• UNDER (down flow air delivery), if there is a raised floor;

• OVER (up-flow air delivery), if there is no raised floor and/or if the direct air distribution to the

room is required ;

• DISPLACEMENT (displacement air delivery), if there are variable loads and/or there is the need

of selecting air conditioners regardless of whether there is a raised floor or not.



3.2.5 SITE GEOGRAPHICAL LOCATION AND CLIMATE CONDITIONS

Determine the choice of system energy characteristics:

• Air conditioners or chillers with free-cooling sections for installations in cold/continental climate

zones;

• Conventional conditioners or chillers for installations in temperate/hot climate zones .

The energy analysis is determining in such choice.

3.2.6 SITE NORMATIVE CHARACTERISTICS

determine the choice of indoor or outdoor units characteristics:

• Water cooled room air conditioners and liquid chillers if it is possible to have water as dissipating

fluid;

• Air cooled chillers and condensers/dry coolers in low noise version in case of strict noise

requirements.

3.2.7 TIER CLASSIFICATIONS AND AIR CONDITIONERS AND CHILLERS COMPONENTS

determine the machines’ total number and the working mode choice:

• load sharing (all units work at partial load) if: EC fans, oil free compressors with magnetic

levitation and BLDC compressors are fitted in the units;

• traditional (some units al 100% and others in stand-by) if units are equipped with traditional

components.



3.3 DATA CENTER INDOOR LAY-OUT

3.3.1 PERIMETER INSTALLATION

Conditioners are placed along walls in Data Center or in aisle/technical outdoor space. The latter

solution allows control and maintenance operations without entering the electronic equipment area.

Picture 5 – Perimeter installation in rooms and technical aisle

3.3.2 IN-ROW / IN-RACK INSTALLATION

Conditioners are installed between a rack and another with air supply in the cold aisle and air return from

the hot aisle (in-row installation), or with air supply and return directly inside the rack (in-rack installation).

Picture 6 – In-row & in-rack Installations



3.3.3 HOT / COLD AISLE

Electronic devices taking cold air from the front and discharging hot air from the back allow to create

hot and cold aisles within the Data Center and make uniform (in the whole volume) room temperature

not necessary.

Picture 7 - Hot aisle – cold aisle installations

3.3.4 CONTAINMENT

Cold aisle closure with doors and covers between racks to keep the “produced” cold in the occupied

volume. In some installations the hot aisle is closed and kept at negative pressure.

Picture 8 - Cold aisle containment

22°C 22°C

35°C 35°C 35°C



3.4 DATA CENTER INDEX / CLASSIFICATIONS 3.4.1 INDEX PUE/DCIE

A Data Center energy efficiency is defined by PUE index or by DCiE that compare infrastructure total

power installed (IT systems + cooling + protection + backup + miscellaneous), with the power used by IT

equipment for data processing et vice versa.

• PUE (Power Usage Effectiveness) = Infrastructure total power / IT equipment power [kW/kW,

absolute value].

• DCiE (Data Center Infrastructure Efficiency) = IT equipment power / Infrastructure total power [kW/kW, percentage].

The PUE or DCiE starting value represents a reference value of energy efficiency and it identifies a test

ambient for repeating further measurements. By comparing starting values with the final ones, data

centers managers are able to analyse the results of possible initiatives to increase the energy efficiency

and/or to evaluate energy indexes in certain working conditions (partial PUE and DCIE). In any time, it is

possible to compare engaged power of IT systems with total power used by the infrastructure.

PUE = Infrastructure Total Power / IT Equipment Power DCiE = IT Equipment Power / Infrastructure Total Power

Picture 9 - Power Usage Effectiveness - PUE (Source: Green Grid)

PUE DCiE Efficiency Level

3.0 33% Very Low

2.5 40% Low

2.0 50% Medium

1.5 67% High

1.2 83% Very High

Provider

Power

• Switch • UPS • Battery backup

Cooling

• Chillers • CRAC

IT Systems

• Servers • Memory • Equipment

Infrastructure Total Power IT Systems

Power

Building Load System request

LOADS FOR PUE CALCULATION



Picture 10 - Power input of Data Center

Cooling systems represent over 40% of the data center energy consumption and they have an incisive

impact on the efficiency level of the data center.

PUE and DCiE indexes are defined by Green Grid, a consortium of over 175 associates IT all over the

world that joins efforts of global industry to reach a measurement system, processes, methods and new

technologies standardization to improve and increase the data center and business computing

ecosystems energy efficiency. The mission of Green Grid, a no-profit organisation , is to become the

major worldwide authority in the field of efficient energy use by working very closely with the final users,

technology providers and governments all over the world. Among the methods used to reach such goal

we point out data collection and analysis, developing technology evaluation, procedures for the

operators development.

Nowadays there are still companies without a documented strategy to reduce energy consumption in

the data center, even if many agree with the fact that the energy consumption data represent a growing

source of concern.

Green Grid provides for everyone a forum where IT operators meet to discuss the different options to

increase resources efficiency. Solutions and recommendations are regularly published, and some

decisions from this forum represent nowadays a sectors standard.

Chillers 33%

Close Control Air Conditioner 9%

IT Systems 30%

PDU 5%

UPS 18%

Humidifier 3%

Switch 1%

Lighting 1%

ELEC

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DIS

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In addition to PUE/DCiE, Green Grid is developing other indexes, such as:

• Carbon Usage Effectiveness (CUE TM),

• Water Usage Effectiveness (WUE TM)

• Data Center Productivity (DCP TM)

3.4.2 TIER CLASSIFICATION

Functional and design features of the data center infrastructure are uniquely defined by TIER classification, developed by Uptime Institute and it is nowadays an international standard.

Uptime Institute, founded in 1993, has been a pioneer in creating and promoting a final users

community and they made available their own knowledge in order to improve reliability and the 24h

availability in the data center and in IT organizations.

Nowadays, more than 100 Uptime Institute network members exchange information and suggestions,

and along with Uptime Institute itself , they can take part in conferences, sites tours etc... reserved to

members only.

Among Uptime Institute main activities, addressed to companies and professionals dealing with data

center, we point out: education, publishing, seminars , certifications, technical consultancy and others…

Uptime Institute has tested and keeps on developing several innovations that have then become

standards in the Data Center:

• hot / cold aisle layout;

• energy calculation parameters;

• cost analysis models;

• double power input specifications;

• TIER classification for reliability evaluation.

There are 4 TIER classes:

TIER I: Data Center with single distribution line/network, respectively one for Power and one for Cooling;

no redundant component.

Availability: 99,671% (8731.18 h/year of uninterrupted operation; down time: 28.82 h/year).

TIER II: Data Center with single distribution line/network, respectively one for Power, one for Cooling;

redundant components make possible maintenance during operation. 99.982 % Availability: 99.982 %

(8758.42 h/year of uninterrupted operation; down time: 1.58 h/year).

TIER III: Data Center with multiple distribution line/network, respectively for Power and Cooling and only

one is active; redundant components make possible maintenance during operation. 99.982 %.

Availability: 99.982 % (8758.42 h/year of uninterrupted operation; down time: 1.58 h/year).

TIER IV: Data Center with multiple distribution line/network respectively for Power and cooling, all active

with redundant components. Possibility of maintenance during operation and fault tolerance. All cooling

systems, chillers e HVAC, have double power supply. Availability: 99.995 % (8759.56 h/year of

uninterrupted operation: down time: 0.44 h/year).



CLASS TIER I TIER II TIER III TIER IV

ACTIVE COMPONENTS TO SUPPORT THE IT

LOAD; REDUNDANCY

N=needed; only the active components

required to support the IT load; no redundancy

N+1=needed +1 active component in addition

to those required to support the IT load, 1 redundant component

N+1=needed +1 active component in addition

to those required to support the IT load, 1 redundant component.

N after any failure = availability of all active components needed to

support the IT load after any fault

NETWORKS / DISTRIBUTION SYSTEMS FOR

POWER & COOLING

Single network/system Single network/system Dual network/system,

one active, and the other in stand-by

Dual network/system both active

MAINTENANCE DURING OPERATION

No No Yes Yes

SINGLE FAULT TOLERANCE

No No No Yes

CONTAINMENT No No No Yes

CONTINUOUS COOLING

According to heating load



Yes (A Class)

AVAILABILITY 99,671% (8.731.18 h/year of no-stop

operation)

99,741% (8.737.31 h/year of no-stop

operation)

99,982% (8.758.42 h/year of no-stop

operation)

99,995% (8.759.56 h/year of no-stop

operation)

STOP TIME 28.82 h/year 28.69 h/year 1.58 h/year 0.44 h/year



3.5 RC GROUP PROPOSAL FOR HIGH EFFICIENCY DATA CENTER 3.5.1 DATA CENTER WITH HIGH LOADS

Picture 11 – Large Data Center

The solution providing the highest energy efficiency is represented by a chilled water system consisting

of:

• Precision air conditioners NEXT EVO CW (6,2 kW – 248 kW) with EC fans, two-way chilled water

valve, temperature control on both air supply and return ;

• Free-cooling chillers UNICO TURBO FL FREE (400 kW – 1550 kW) equipped with EC fans, oil

free centrifugal compressors with magnetic levitation and flooded evaporator & GLIDER EVO FREE (288 kW – 1339 kW) equipped with EC fans and screw compressors with modulating

capacity control,

or conventional high efficiency chillers UNICO TURBO FL (280 kW – 1500 kW) with EC fans, oil

free centrifugal compressors with magnetic levitation and flooded evaporator.

Energy analysis is needed to choose the most suitable chiller.

UNICO TURBO FL GLIDER EVO FREE NEXT EVO CW NEXT EVO CW PLUS



3.5.2 DATA CENTER WITH MEDIUM-LOW LOADS

Picture 12 – Medium Data Center

The solution providing the highest energy efficiency is represented by a direct expansion system

consisting of:

• Close control air conditioners NEXT EVO DX INVERTER (7,3 kW – 102 kW) equipped with EC

fans and scroll compressors BLDC inverter, temperature control on both air supply and return;

• Remote air condensers with EC fans.

With appropriate site weather conditions , it is possible to achieve energy efficiency even higher thanks

to a direct expansion system with a free-cooling section consisting of:

• Close control air conditioners NEXT EVO DW INVERTER (7,3kW – 102kW) with FREE-

COOLING section, EC fans and scroll compressors BLDC inverter, temperature control on both

air supply and return

• Remote air dry coolers with EC fans;

• Pumping group with free-cooling valve.

NEXT EVO INVERTER DX/DW UNDER

NEXT EVO INVERTER DX/DW OVER



3.5.3 DATA CENTER WITH HOT SPOT

Picture 13 – Data Center with hot spot

The solution providing the highest energy efficiency is represented by COOLSIDE EVO system with direct expansion for in-row/in-rack installation consisting in:

• Indoor evaporating unit COOLSIDE EVO (4,5 kW – 53,1 kW) with plug-fan EC fans ‘in row’

version (for application hot aisle/cold aisle or ‘in rack’ version, for a close loop air

delivery/discharge all inside the rack, temperature sensor on air delivery and return;

• Outdoor motocondensing unit MCAI with scroll compressor BLDC inverter, EC axial fans, micro

channel condensing coils.

Possibility to match up to three indoor evaporating units to single outdoor motocondensing unit.

For complete close control air conditioners and chillers series by RC Group, please refer to the Product

General Catalogue.

COOLSIDE EVO DX SYSTEM COOLSIDE EVO DX SYSTEM Three indoor evaporating units with outdoor motocondensing unit.



4 OTHER PRECISION AIR CONDITIONING APPLICATIONS

Despite signs of saturation, especially in Europe, Telecommunications (TLC) keep on representing the

second market for close control air conditioning after Data Center. It is possible to divide the market in:

Fixed Telecommunication: telephone rooms are comparable to traditional small/medium Data Center

now equipped with perimeter machines with temperature control and return air and without hot/cold aisle

logic. All current precision conditioners series by RC Group can be used for telephone rooms air

conditioning; a pay-back time evaluation is needed in case of high efficiency units with or without free-

cooling.

Mobile Telecommunication: containers and small mobile telecommunication stations use small

precision air conditioning, from 5kW up. 20kW, all equipped with free-cooling section. Series available:

• Packaged air conditioners for outdoor installation (MINIPAC and MARK for outdoor installation);

• Packaged air conditioners for indoor installation (ENERTEL and MARK for indoor installation);

• Split conditioners with outdoor motocondensing (ENERGY SPLIT).

Other close control air conditioning applications:

• Power rooms • Measurement rooms • Radar rooms • CAT rooms (Computed Axial Tomography) / NMR (Nuclear Magnetic Resonance) • Control rooms • UPS rooms (Uninterruptible Power Supply) • Battery room • Transformers rooms

Most of installations need the use of a limited number of close control air conditioning, so all current RC

Group series can be used. The direct expansion solution is the most suitable, if we consider heat load to

be dissipated, but the incidental availability of chilled water used for other rooms with higher heat load

makes convenient the installation of chilled water air precision conditioning. This is the case of

power/UPS/battery/trafo rooms of large Data Centers using the same CHW close control air conditioners

widely installed in Data Halls.

Another interesting opportunity belongs to seasonal availability of chilled water for summer air

conditioning in the offices; in this case the best solution is represented by direct expansion machines

with one additional coil (extra-circuit EC) fed by chilled water from chiller and not needed for offices.

Conditioner will use chilled water coil in hot season; compressors is stand-by and it works if needed and

when chiller stops. Also in all of these cases, a pay-back time evaluation is necessary.



5 TAYLOR-MADE SERVICE BY RC GROUP

Innovation, flexibility and timing, are some of the successful features in precision air conditioning. The

last two play an important role in taking the most ambitious projects.

Despite a wide standard products series for models numbers and multi-functions features, not all Users

needs can be satisfied. In these cases RC Group, with its high skilled team, is willing to implement

changes on current products or to manufacture “ad hoc” products for a particular installation. Thanks to

taylor-made service, RC Group meant to create a “virtuous circle” with users/consultants and

agents/distributors with a continuous exchange of requests/information leading to the creation of a

suitable product and to customer loyalty . Many “ad hoc” requests have then been developed and now

they are included in machine standard equipment. The taylor-made service, available for chillers and air

conditioners, has represented RC Group trump card in taking projects of large Data Centers of important

International Banks, TLC Operators, cloud computing owners… .

CUSTOMERS

INFORMATION

DISTRIBUTORS

CONSULTANTS



6 PRECISION AIR CONDITIONING GLOSSARY

• °C – Celsius degrees.

• °F - degrees Fahrenheit; for temperature analysis. °C = 5/9 · (°F – 32)

• A - Ampère, measurement unit for electrical current.

• Absorbed power - energy absorbed by a machine for their components operation (as compressors, fans, pumps, and any additional devices).

• AC – Alternate Current; naming given to power available in a sinusoidal wave form. AC is known as preferred method of delivering and using power in the industrial age due to the ease of voltage transformation with static devices (transformers).

• ACAE - Air Conditioning Airflow Efficiency . It defines the amount of heat removed per standard cubic foot of airflow per minute [ft3/min] . 1.0 ft3/min = 1.699 m3/h.

• Air By-pass – Cold air flow returning to conditioner without crossing IT equipment.

• Aisle – opened area between racks. It is good to install racks “as mirror”, to create “hot aisles” & “cold aisles” within Data Center.

• ASHRAE - American Society of Heating, Refrigeration and Air Conditioning Engineers, International technical society giving standards in heating, refrigerating, air conditioning.

• BACnet – Data communication protocol for BMS and control networks.

• BAS & BMS – Tags for “Building Automation System” & “Building Management System” both meaning: supervision systems.

• Brushless DC electric motor (BLDC motors, BL motors) - also known as electronically commutated motors (ECMs, EC motors) are synchronous motors that are powered by a DC electric source via an integrated inverter/switching power supply, which produces an AC electric signal to drive the motor

• BTU - British Thermal Unit, unit for energy. 1 kWh = 3413 Btu.

• C / H – (Cooling / Heating).

• Cabinet – containment space for IT devices, knows as rack.

• CAC – Cold Aisle Containment : acronym defining containment (closing) of cold aisle to increase energy efficiency.

• CapEx – Capital Expenditure, it defines the cost of purchasing capital equipment, for example machines.

• Carbon Footprint – a measurement of CO2 emission of product, organization or person. Impact of these emissions on climate changes is so measured. Its measure unit is kg of CO2 and/or CO2 equivalent.

• CFD – Computational Fluid Dynamics, the technique allowing to study the fluid dynamic problems with a computer

• CFM – “cubic feet per minute”, measurement unit for flow rate. 1 CFM = 1,699 m3/h.

• Chiller unit - unit which supplies chilled water.

• Close control air conditioning – It is the complex of all operations where temperature, relative humidity, air purity are kept within close limits to grant the most proper operation of electronic equipment.

• Close-Coupled Cooling – Cooling technology with conditioners close to server rack, to reduce at minimum cooling air path towards devices.

• CO2 – chemical symbol for carbon dioxide. It is produced by combustion and human beings by breathing.

• Coil—heat exchanger, generally between fluid and air, where fluid (refrigerant gas or water) flows inside the copper pipes and air air crosses the external surface

• Cold Spot – Area in the room where air temperature is below wanted levels. Generally it is caused by ineffective air flow distribution or by set-point too low.

• Compressor- machine which increases refrigerant pressure in gas phase by reducing its volume (volumeter scroll or screw compressor), or by varying its speed (centrifugal compressor).

• Condenser- Exchanger where refrigerant becomes liquid (condensation) from gas by cooling itself due to the action of another fluid (air or water) whom it gives heat to.

• Cooling cycle- complex of state changes of a fluid which allows to "transfer" heat from a low temperature source to an high temperature one. There are 4 steps: compression, condensation, expansion (or lamination), evaporation.

• COOLROW – Close control air conditioning by RC Group for “in/row” installations available in direct expansion version and chilled water version.



• COOLSIDE EVO – close control air conditioning by RC Group for “in/row – in/rack” installations available in direct expansion version and chilled water version.

• Cos φ – Power factor.

• CR – Computer room.

• CRAC – Computer room air conditioner. Sometimes it is used for close control air conditioning.

• CRAH - Computer room air handler, It defines a chilled water precision air conditioner. Acronym less referred to, as chilled water precision conditioners are defined CRAC.

• Critical Load – electronic devices whose uptime (correct working) is fundamental, typically matched to an UPS.

• CUE - Carbon Usage Effectiveness, a metric defined by the Green Grid, it is a unit of sustainability in terms of data center specific carbon emissions. CUE is calculated by dividing the CO2 total emissions caused by total data center energy" by "the energy consumption of the IT computing equipment". Another choice is to calculate CUE is by multiplying the data center yearly PUE by the Carbon Emissions Factor for the area as determined by the EPA. CUE units are Kilograms of carbon dioxide per kilowatt hour.

• CW – Chilled water.

• D / H – Dehumidification / Humidification.

• DC – Data Center.

• DC – Direct current.

• DC – Dry-cooler.

• Dead band – a control technique which prevents oscillation or unnecessary cycling of a controlled parameter. As for CRAC or CRAH units the right set of band width compared to the set point prevents unnecessary and too short cycles of compressor and start / stop or CHW valve opening / closing

• Dehumidification- the thermo-dynamic process to eliminate some water from air.

• Delta T – difference in temperature across a machine. Power is defined by : P [kCal/h] = mass flow [kg/h] · specific heat [kCal/kg*K] · delta-t [K]

• Dew point – temperature at which air reaches water vapor saturation. The latest ASHRAE spec for data center environmental conditions include a higher limit for relative humidity based on dew point.

• Differential pressure – the difference in pressure between two areas/points of the room. If there is raised floor, the differential between underfloor pressure and room pressure is kept constant by changing air conditioning fans speed.

• Direct expansion means that evaporation of refrigerant within a heat exchange coil happens by direct contact with air to be cooled and coil surface itself.

• Dry cooler – liquid to air heat exchanger; radiator with finned coils and fans.

• Dry-bulb temperature - air temperature measured with a dry-bulb thermometer with no effect on air relative humidity.

• DW – naming RC Group defining direct expansion water cooled precision air conditioners with built-in plate-condenser.

• DX – Direct expansion..

• DX – naming RC Group defining direct expansion air cooled precision air conditioners matched to a remote condenser.

• EC – naming RC Group defining EXTRA-CIRCUIT optional, additional chilled water exchanger which works as back-up to main exchanger in precision conditioners, both direct expansion and chilled water units.

• EER (Energy Efficiency Ratio) it defines energy efficiency of a machine working in cooling. An EER equal to 3 means that, per 1 kWh of energy consumed, machine makes available 3 kWh of cooling energy to cool the space.

• Energy Class- Products classification based on their EER. A class is the most efficient, G class is the least efficient. The reference value depends on machine typology.

• Energy source a source to be found in nature that is used to have a thermal exchange. Air, ground or water are energy sources.

• ESD – Electrostatic discharge.

• ESEER (European Seasonal Energy Efficiency Ratio) extends EER meaning to yearly efficiency of refrigeration equipment. It is a correct mix of different seasonal operating circuits defined by Eurovent/CEN, and in particular the partial load ones.

• EUROVENT - is an independent organization that certifies products for cooling and air conditioning. It is the main reference for producers and users, who can check products data.



• Evaporating tower a device to cool process fluid or fluid of a cooling machine, taking advantage of latent heat of evaporating water. There are opened towers, where fluid to be cooled is close to outdoor air, and closed towers, known as evaporating chillers.

• Evaporator - exchanger where refrigerant evaporates (it becomes gas from liquid phase) and by heating, absorbs heat from another fluid (air or water) by cooling it.

• Expansion valve essential and needed device of refrigerant circuit for pressure reduction (expansion) of refrigerant allowing its following evaporation with heat absorption.

• External pressure – available supply pressure of a fan or a pump to overcome the pressure drops of the plant. It is measured in Pa or kPa.

• Extraordinary maintenance emergency or improving interventions operations, carried out by authorized service centers.

• Fan coil unit- a kind of room terminal unit. It is made of a air to water heat exchanger that heats or cools an air flow by exchanging heat with water, a fan to change air flow, a filter and a set of fins for air distribution..

• Floor void – free space under a raised floor also known as plenum under-floor.

• Fossil fuel- natural component base of actual fuels as natural gas, petroleum (and petroleum derivatives) and coal.

• Free cooling - a fluid cooling due to low outdoor temperatures, with or without compressors partial working with energy saving. On units outdoor air is directly deliver to rooms, while on chillers it cools exchangers where fluid to be cooled circulates

• FRIGO SCREW – water cooled liquid chillers by RC Group available in A and A+ Energy Class with screw compressors.

• FRIGO TURBO FL – water cooled liquid chillers by RC Group with very high energy efficiency and equipped with magnetic levitation compressor.

• ft2 – square feet, measurement unit for surface. 1 ft2 = 0,092903 m2

• GLIDER EVO – air cooled chillers by RC Group with screw compressors in standard “only cooling” version and with free-cooling section.

• GPM – Gallons Per Minute, measurement unit for flow rate. 1 GMP (U.S.) = 0,2271 m3/h

• Greenhouse effect- it identifies the effect due to greenhouse gas delivery in the atmosphere. Gas make sunbeams cross and their energy become heat, the same gas does not allow radiations reflections towards space, causing so a temperature increasing. For some years gas excess ( CO2 in particular) has been increasing this effect which causes Earth temperature increasing.

• H2O condensation circuit – Condensing water circuit of a chiller cooled by dry cooler or cooling towers.

• H2O plant circuit – water circuit feeding heat exchangers of an AHU cooled by a chiller

• HAC – Hot Aisle Containment, it defines containment (closing) of hot aisle to increase energy efficiency.

• HDG – Hot Dipped Galvanized.

• Heat exchanger - a component to transfer heat between two fluids without mixing them.

• Hot Spot – area between a rack or a set of racks, where ambient temperature is higher than acceptable levels, due to an insufficient air distribution or a not proper cooling.

• hp – horsepower, measurement unit for power. 1 hp = 0,7457 kW.

• HPDC - High-Performance Data Center, a Data Center with an average thermal load exceeding 10kW/rack.

• hr or h – hour, measurement unit for time.

• Humidification the atmosphere is, at every temperature, a mix with vapor water. Humidification is the thermo-dynamic process to add requested vapor water to air.

• HVAC – Heating Ventilation and Air Conditioning, System, tag indicating components/systems for indoor air temperature control.

• Hydronic system air conditioning plant using water in medium phase. A chiller cools water which through a pumps is made circulate within pipes and delivered to indoor units placed in rooms to be conditioned.

• IDEA – intelligent high efficiency defrosting system patented by RC Group for heat pumps and multifunction chillers

• in – Inch. measurement unit for length. 1in = 2,54cm

• Inverter - a device electronically managed to change engine rotational speed.

• IP - Internet Protocol, technology using internet for communications.



• K – degrees Kelvin – measurement unit for temperature known worldwide.

• Kit ELN – tag of the optional for a very high noise level reduction for RC Group chillers.

• Kit LNO – tag of the option to reduce noise level for RC Group chillers.

• kW – kilowatt; measurement unit for power 1 kW= 860 kCal/h.

• Latent cooling – the process of condensing water out of air.

• Latent heat – heat delivered or absorbed by a fluid during a status change, from gas to liquid or from liquid to solid et vice versa, without temperature changes. For example, when we heat water up to 100°C water increases temperature (it is absorbing sensible heat) over 100°C, if we keep on giving heat (at ambient pressure), water evaporates, changes status without increasing temperature and it absorbs latent heat.

• Liquid Cooling – general term to define a cooling technology using a liquid (fluid) to discard heat. In data center, two fluids are used to discard heat : chilled water (CW) and refrigerant (DX).

• m2- square meter, measurement unit for surface known worldwide.

• m3/h – cubic meter per hour, measurement unit for flow rate.

• MANTA – in packaged water cooled and split air cooled for matching to remote condensers liquid chillers by RC Group equipped with scroll compressors. Versions “only cooling” or reversible heat pump on refrigerant or water.

• NEXT & NEXT EVO CW – perimeter type precision air conditioners by RC Group in direct expansion with ON/OFF scroll compressors and chilled water version.

• NEXT EVO INV – perimeter type precision air conditioners by RC Group in direct expansion version with scroll BLDC inverter-driven compressors.

• Noise level - a value of the noise of a machine in the site.

• OpEx – operating expenditure, ongoing expenses related to operating data center.

• Packaged or self-contained - feature of having condensing and evaporating units in the same cabinet, in opposition to "split" feature. Free-cooling conditioners for containers for mobile communication are packaged.

• Partial load operation - reduction of cooling and/or heating performance of an air conditioner to meet the load of the plant.

• Planned maintenance control and cleaning operations that take regularly place according to a fixed planning.

• Plug-fan - a high efficiency backward-curved airfoil impeller fan, without housing directly driven by an electric motor.

• Pressure drop – pressure reduction in a fluid (as water, air or refrigerant) due to mechanical frictions, sections variations, curves and blocks that can be found within pipes and ducts.

• PYXIS – air cooled chillers by RC Group with scroll compressors available in standard “only cooling” and reversible heat pump version.

• Refrigerant - fluid in cooling machine circuits allowing heat transfer.

• Rh – relative humidity, in %.

• ROI - Return on Investment, a measure of money earned by an entity as a percentage of the total value of its assets that are invested.

• Room terminal unit terminal device of a conditioning system installed in the room.

• RPM – revolution per minute, measurement unit for angular speed.

• Scroll compressor – Compressor with two spirals, one fixed and the other rotating, one inside the other. From the exterior gas is pushed toward the centre of the spirals. During the path chamber volume is reduced while increasing gas pressure. There is a low number of rotating components, and so high reliability, there are no vibrations and it is quite noiseless.

• Sensible cooling – the process of lowering the air dry-bulb temperature, without condensation.

• Sensible heat - heat exchanged or absorbed by a fluid that results in reducing or increasing temperature. With latent heat it forms total heat.

• Set Point - value to which controlled variable has to be compared with. In Data Center variables are room temperature and relative humidity, in/out chilled water temperature, or any other parameter concerning operating point required by an air conditioner or a chiller.

• Split - air conditioner divide into two sections outdoor unit can be the condensing or the motocondensing one, while indoor unit can be the evaporating or the motoevaporating one.



• TEWI (Total Equivalent Warming Index or Impact) is a parameter evaluating system impact on greenhouse effect. For an air conditioning it is about the direct impact of fluid and CO2 production due to its operation: best the working system, lower the TEWI, and lower environmental impact.

• U – measurement unit of the vertical dimension of a rack. 1 U = 1,75 in = 44,45 mm. A 42U is 1,87 m high

• UNICO TURBO FL – liquid chiller RC Group with magnetic levitation centrifugal compressors and very high efficiency available in “only cooling” standard version and with free-cooling section.

• UPS - Uninterruptible Power Supply, it is a device used to keep the equipment permanently power in alternate current. Two typologies: static UPS using batteries to store emergency power, rotating UPS consisting of a “package” machine housing all functions required to electrical generators and traditional coils UPS.

• V - Volt, measurement unit for electrical potential.

• VA - Volt-Ampere, measurement unit for apparent power.

• VFD - Variable Frequency Drive, or inverter, a device which supplies AC power of varying frequency, generally used to control the speed of induction motors.

• W – Watt – measurement unit for power, used worldwide.

• Wet-bulb temperature - air temperature measured with a wet-bulb thermometer, the temperature at which a wet surface can be cooled by evaporating. This temperature is influenced both by dry-bulb temperature and air dew temperature. Drier the air, lower the air wet-bulb temperature.

• Workstation - the complex of personal computers, monitors, printers used to system management and control (a system like air conditioning system, life safety system, break-in alarm system).

• WPSF – Watt per Square Foot, measurement unit for power density. In a Data Center it refers to total load in a particular space divided by total area of this space. This parameter is used to define the total capacity of cooling and power systems and it is used in conjunction with point load (amount of load in a small area, such a rack).



7 REFERENCES

ASHRAE, https://www.ashrae.org Green Grid, http://www.thegreengrid.org/ Uptime institute, http://uptimeinstitute.com/


Data in this book may change without notice

RC GROUP S.p.A. • Via Roma, 5 • 27010 Valle Salimbene (PV), Italy www.rcgroup.it • Tel. +39 (0) 382 433 811 • Fax +39 (0) 382 587 148

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