IEC 62966-2:2020
(Main)Mechanical structures for electrical and electronic equipment - Aisle containment for IT cabinets - Part 2: Details of air flow, air separation and air cooling requirements
Mechanical structures for electrical and electronic equipment - Aisle containment for IT cabinets - Part 2: Details of air flow, air separation and air cooling requirements
IEC 62966-2:2020 is dedicated to aisle containment techniques for information technology (IT) equipment typically used in data centres, describes the quantification of its air tightness, in particular the air loss ratio that describes the content of the volumetric flow not used for cooling the IT equipment. This ratio provides an index of efficiency, being inversely proportional to efficiency (the lower this ratio, the higher the efficiency). This document provides methods to measure an aisle containment air leakage rate and defines a classification system for aisle containment leakage.
This document defines:
- the measurement of the air leakage of the individual components of an aisle containment;
- a method for calculating the air leakage of an aisle containment based on its individual components;
- a method for calculating the air leakage rate of an aisle containment in relation to the utilised IT equipment;
- a classification system for aisle containment leakage.
Structures mécaniques pour équipements électriques et électroniques - Confinement d’allées pour les baies informatiques - Partie 2: Détails des exigences relatives au flux d’air, à la séparation des flux d’air et au refroidissement par air
IEC 62966-2:2020 est dédiée aux techniques de confinement pour les équipements informatiques typiquement utilisés dans les centres de données, décrit la quantification de leur étanchéité, et plus particulièrement le taux de fuite d’air, qui définit le débit volumique qui ne sert pas à refroidir les équipements informatiques. Ce taux constitue un indice de rendement, fonctionnant à proportionnalité inverse (plus le taux diminue, plus le rendement augmente). Le présent document donne des méthodes pour mesurer le taux de fuite d’air d’un confinement, et définit un système de classification des fuites du confinement.
Le présent document définit:
- la mesure des fuites d’air des composants individuels d’un confinement;
- une méthode de calcul des fuites d’air d’un confinement, basée sur ses composants individuels;
- une méthode de calcul du taux de fuite d’air d’un confinement, en fonction des équipements informatiques utilisés;
- un système de classification des fuites du confinement.
General Information
Standards Content (Sample)
IEC 62966-2 ®
Edition 1.0 2020-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Mechanical structures for electrical and electronic equipment – Aisle
containment for it cabinets –
Part 2: Details of air flow, air separation and air cooling requirements
Structures mécaniques pour équipements électriques et électroniques –
Confinement d’allées pour les baies informatiques –
Partie 2: Détails des exigences relatives au flux d’air, à la séparation des flux
d’air et au refroidissement par air
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IEC 62966-2 ®
Edition 1.0 2020-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Mechanical structures for electrical and electronic equipment – Aisle
containment for it cabinets –
Part 2: Details of air flow, air separation and air cooling requirements
Structures mécaniques pour équipements électriques et électroniques –
Confinement d’allées pour les baies informatiques –
Partie 2: Détails des exigences relatives au flux d’air, à la séparation des flux
d’air et au refroidissement par air
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.240 ISBN 978-2-8322-8510-7
– 2 – IEC 62966-2:2020 © IEC 2020
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Determination of the air leak rate . 9
4.1 Determination of the air leak rate of the individual components of an aisle
containment . 9
4.2 Components and system characteristic curves . 10
4.2.1 General . 10
4.2.2 Equipment requirements . 11
4.3 Measurement procedure . 11
4.3.1 Measurement conditions . 11
4.3.2 Preparing the elements of the test housing for measurement . 11
4.3.3 Measurement of the air leak rate . 13
4.4 Test report . 14
4.5 Measurement precision . 14
5 Air leakage rate of the aisle containment – Creation of an overall system
characteristic curve for the aisle containment . 15
6 Determination of the air leak rate – Determination of the air leak rate of the overall
system in operation, including the IT equipment . 15
Annex A (informative) Aisle containments according to operation mode . 17
A.1 Allocation of the aisle containments according to operation mode . 17
A.1.1 General . 17
A.1.2 Types of climate control . 17
A.1.3 Closed-circuit climate control . 17
A.1.4 In-line climate control . 17
A.2 Cold aisle containment . 18
A.2.1 Principle of the cold aisle containment . 18
A.2.2 Objective of the cold aisle . 18
A.2.3 Climate control . 18
A.3 Hot aisle containment . 18
A.3.1 Principle of the hot aisle containment . 18
A.3.2 Objective of the hot aisle . 19
A.3.3 Climate control . 19
A.4 Cold and hot aisle containment . 19
A.4.1 Principle of the cold and hot aisle containment . 19
A.4.2 Objective of the cold aisle in a cold and hot aisle containment . 20
A.4.3 Climate control . 20
Annex B (informative) Thermodynamic variables within aisle containments . 21
B.1 Air pressure . 21
B.1.1 General . 21
B.1.2 Minimum differential pressure . 21
B.1.3 Overpressure in hot aisle containments . 21
B.1.4 Negative pressure in hot aisle containments . 21
B.1.5 Overpressure in cold aisle containments . 21
B.1.6 Negative pressure in cold aisle containments . 21
B.2 Directions of flow . 22
B.2.1 Directions of flow "from the front to the back" . 22
B.2.2 Direction of flow "to the side" . 22
B.3 Flow velocities . 22
B.3.1 Closed-circuit climate control . 22
B.3.2 In-line climate control . 22
B.3.3 Design of the aisle containments . 22
B.4 Temperatures and humidity . 23
B.4.1 General . 23
B.4.2 Temperatures . 23
B.4.3 Humidity . 23
Bibliography . 24
Figure 1 – Example of the components – Roof . 9
Figure 2 – Example of the components – Door . 10
Figure 3 – Example of the components – Enclosures . 10
Figure 4 – Sealing the installation level . 12
Figure 5 – Example of a connecting design to the neighbouring enclosure . 12
Figure 6 – Example of a connecting design to the roof . 13
Figure 7 – Example of a connecting design to the end door . 13
Figure 8 – Example of component and system characteristic curves . 14
Figure 9 – Example of a hydraulic addition of individual characteristic curves . 15
Figure 10 – Classification of aisle containment by class factors . 16
Figure A.1 – Example of an in-line climate control . 17
Figure A.2 – Example of a cold aisle containment . 18
Figure A.3 – Example of a hot aisle containment . 19
Figure A.4 – Example of a cold and hot aisle containment . 20
– 4 – IEC 62966-2:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MECHANICAL STRUCTURES FOR
ELECTRICAL AND ELECTRONIC EQUIPMENT –
AISLE CONTAINMENT FOR IT CABINETS –
Part 2: Details of air flow, air separation and air cooling requirements
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
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indispensable for the correct application of this publication.
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62966-2 has been prepared by subcommittee 48D: Mechanical
structures for electrical and electronic equipment, of IEC technical committee 48: Electrical
connectors and mechanical structures for electrical and electronic equipment.
The text of this International Standard is based on the following documents:
FDIS Report on voting
48D/722/FDIS 48D/727/RVD
Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62966 series, published under the general title Mechanical structures
for electrical and electronic equipment – Aisle containment for it cabinets, can be found on the
IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.
– 6 – IEC 62966-2:2020 © IEC 2020
INTRODUCTION
Cabinets of the IEC 60297 and IEC 60917 standard series are used as enclosures of electronic
and electrical equipment in many different fields of application. A wide field of application is
represented by enclosures equipped with electronic information technology (IT) equipment.
They are frequently set up in large numbers in server rooms and data centres. During their
operation, the electronic equipment installed generates a considerable amount of heat that will
be removed from the equipment by means of cooling air. Precise adjustment of the supply air
temperature and a sufficient cooling air flow are indispensable prerequisites for the fail-safe
operation of equipment in information technology.
It is a common practice to set up cabinets in rows. The server cabinets along the rows are
usually arranged in such a way that surfaces with cold supply air inlets face each other across
an aisle, and surfaces with hot exhaust air outlets also face each other across an aisle. This
row configuration is generally known as hot aisle/cold aisle configuration. Moreover, air is
supplied and discharged exclusively via the front and rear panels of the server cabinets, which
are frequently perforated doors. It is assumed that inside the IT equipment, the cooling air is
moved in a horizontal direction, taking it in at the front and discharging it at the rear.
This part of IEC 62966 specifies the quantification of the air separation, in particular the air leak
rate that describes the content of the volumetric flow not used for cooling in the aisle
containment for information technology (IT) cabinets. The objective of this document is to
stipulate properties and requirements of aisle containment ensuring cost effective installation,
energy-efficient and user-friendly operation of IT equipment in data centres server rooms.
The fan pressurization method (overpressure at the system and elements) is used to categorize
the air tightness of the aisle containment. In doing so, it is used to quantify the air tightness, in
order to compare aisle containments with regard to the air tightness. It is also useful for finding
leaks, or to determine the improvement due to improving the air tightness. The fan
pressurization method cannot measure the air leak rate, but serves as a basis for determining
the air leak rate by calculation. The method can be used to determine air leak rates of the aisle
containment at low-pressure and overpressure on the inside compared with the surroundings.
Thus, this allows a categorization of the elements of an aisle containment – the enclosure – to
be determined.
For this purpose, aisle containment is dismantled into typical individual elements, for example
enclosures, doors and roof covers. The corresponding characteristic curves of these
components are recorded separately and added to the system characteristic curve of the aisle
containment.
The quality of the resulting aisle containment is then classified using a differential pressure
measurement.
The IEC 62966 series, Mechanical structures for electrical and electronic equipment – Aisle
containment for IT cabinets, is subdivided into the following parts:
• IEC 62966-1: Dimensions and mechanical requirements
• IEC 62966-2: Details of air flow, air separation and air cooling requirements
• IEC 62966-3: Aspects of operational safety of IT equipment and users of aisle containment
IEC 62966-1 defines geometric dimensions and mechanical properties ensuring undisturbed,
energy-efficient and user-friendly operation of the data centre.
IEC 62966-2 provides the methods and process to get the aisle containment air leakage and
define the classification (evaluation) system on the aisle containment air leakage, for designers
and users of aisle containments for IT cabinets based on the IEC 60297 and IEC 60917 series.
IEC 62966-3 deals with aspects of safely operating IT equipment in aisle containment, with
respect to special fire-protection and fire-fighting issues. It also describes the nature of the
doors for access to the aisle containment and possible access control.
MECHANICAL STRUCTURES FOR
ELECTRICAL AND ELECTRONIC EQUIPMENT –
AISLE CONTAINMENT FOR IT CABINETS –
Part 2: Details of air flow, air separation and air cooling requirements
1 Scope
This part of IEC 62966, dedicated to aisle containment techniques for information technology
(IT) equipment typically used in data centres, describes the quantification of its air tightness, in
particular the air loss ratio that describes the content of the volumetric flow not used for cooling
the IT equipment. This ratio provides an index of efficiency, being inversely proportional to
efficiency (the lower this ratio, the higher the efficiency). This document provides methods to
measure an aisle containment air leakage rate and defines a classification system for aisle
containment leakage.
This document defines:
a) the measurement of the air leakage of the individual components of an aisle containment;
b) a method for calculating the air leakage of an aisle containment based on its individual
components;
c) a method for calculating the air leakage rate of an aisle containment in relation to the utilised
IT equipment;
d) a classification system for aisle containment leakage.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 62966-1, Mechanical structures for electrical and electronic equipment – Aisle containment
for IT equipment – Part 1: Dimensions and mechanical requirements
ISO 9972, Thermal performance of buildings – Determination of air permeability of buildings –
Fan pressurization method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
air leak rate
ratio of the volumetric air flow not used for cooling to the total volumetric air flow
– 8 – IEC 62966-2:2020 © IEC 2020
3.2
aisle containment
boundary that separates the inner volume from the surroundings, usually comprising the base
(floor), access doors or end-piece on the front side, roof elements and containment doors of
the enclosure (cabinet), that contain the IT equipment
3.3
base
area bounded by the doors of the opposite-facing bayed enclosure
(cabinet) suites and the aisle doors or walls
3.4
doors
end piece of an aisle containment on both ends or on one end that
ensures access to the inside of the aisle containment
3.5
roof elements
upper construction of the aisle containment as an upper end piece
3.6
enclosure
server and network cabinets that accommodate IT equipment
3.7
inner volume
volumes of the aisle containment limited by doors, roof elements,
bases and enclosures
3.8
IT equipment
all (active) components that are installed in an enclosure
3.9
supply air
cooling air before entering the IT equipment and other IT related supporting systems, whose
temperature is suitable to absorb the heat flow from the equipment
3.10
supply air temperature
temperature of the supply air to the enclosures.
3.11
exhaust air
heated supply air after exiting the IT equipment that has absorbed the heat flow
3.12
exhaust air temperature
temperature of the exhaust air from the enclosures of an isle containment
3.13
cold aisle
area in front of the enclosures of an aisle containment that is supplied with the supply air
3.14
hot aisle
area behind the enclosures of an aisle containment into which the exhaust air flows
3.15
operation point
work point of the overall system at a specified time, set via the selected operating parameters
3.16
design point
operating parameters that are used as a basis for correct operation
3.17
air flow unit
equipment unit fitted in an aisle containment able to provide for example through air conditioning
or forced ventilation, the supply of cooling air mass to the entire aisle containment
4 Determination of the air leak rate
4.1 Determination of the air leak rate of the individual components of an aisle
containment
The following description is used to determine the air leak rate of the individual components of
an aisle containment. The same method shall be used for special design adaptations.
The individual components are measured on a test rig. A component characteristic curve is
recorded (pressure drop ∆p versus volumetric air flow). The system characteristic curve is
generated by grouping all of the component characteristic curves.
The quality of the technically correct installation of the entire aisle containment has a decisive
influence on the air leak rate. For this reason, all interfaces of the individual components shall
be made air tight. The individual components are defined in 62966-1:
• roof (see Figure 1)
• door (see Figure 2)
• enclosures (see Figure 3)
Figure 1 – Example of the components – Roof
– 10 – IEC 62966-2:2020 © IEC 2020
Figure 2 – Example of the components – Door
Figure 3 – Example of the components – Enclosures
4.2 Components and system characteristic curves
4.2.1 General
The determination of the system characteristic curves shall be carried out based on ISO 9972.
4.2.2 Equipment requirements
4.2.2.1 Air flow unit for supplying mass air flow
The relationship of mass air flow to the volumetric flow shall be established via the air density
(mean value with reference to supply air temperature and exhaust air temperature). The unit
shall generate a differential pressure across the specimen that can be evaluated, and shall be
able to supply a constant volumetric flow over the overall measurement range. The air flow unit
shall be able to generate overpressure as well as negative pressure in the aisle containment.
In some cases, the existing climate control components can also be used as long as they fulfil
the same requirements.
4.2.2.2 Differential pressure measuring instrument
An instrument for measuring the pressure difference of the air with a preferred measuring
accuracy of ±1,0 Pa in a range of 0 Pa to 30 Pa.
4.2.2.3 Volumetric flow measuring instrument
An instrument for measuring the volumetric air flow with a preferred measuring accuracy of ±5 %
of the measured volumetric air flow.
4.2.2.4 Temperature sensors
A measuring instrument for determining the temperature with a preferred measuring accuracy
of ±0,5 K.
4.3 Measurement procedure
4.3.1 Measurement conditions
The accuracy of the measurement described is strongly dependent on the measuring
instruments used. The total error of the measurement shall be a maximum of 5 %.
As no influence shall be present from external ambient influences (weather) during the
measurement, to standardise the measurement only the geodetic altitude of the location and
the temperature of the surrounding rooms shall be determined. The atmospheric pressure in Pa
shall be reported.
4.3.2 Preparing the elements of the test housing for measurement
For the measuring procedure described in this part of the document, it is a requirement that the
area in which the IT equipment will typically be installed shall be sealed air tight
(see Figure 4).
The doors and roof elements shall correspond with the finished state of the aisle containment,
and be closed. The individual elements of the test housing shall be equipped with the respective
construction elements of the connecting components for the measurement in such a manner
that the interfaces of the individual elements correspond with the future assembly. The
interfaces to other elements that are joined air tight do not need to be considered during the
test (see Figure 5, Figure 6, Figure 7).
In accordance with the manufacturer’s instructions, gaps and mounting spaces shall be covered
with the appropriate covers, brushes, foam seals, etc.
– 12 – IEC 62966-2:2020 © IEC 2020
Figure 4 – Sealing the installation level
Figure 5 – Example of a connecting design to the neighbouring enclosure
Figure 6 – Example of a connecting design to the roof
Figure 7 – Example of a connecting design to the end door
4.3.3 Measurement of the air leak rate
To carry out corrections according to the density of the air, temperatures shall be documented
before, during and after the measurement. During the measurement, the flow rate and pressure
difference shall be recorded.
– 14 – IEC 62966-2:2020 © IEC 2020
The measuring instrument is connected in such a manner that the pressure difference between
the surroundings and the inner volumes of the aisle containment can be measured.
The measurement using the air flow unit is carried out in steps that are no larger than 5 Pa
differential pressures. Measurement for the volumetric flow and the pressure difference shall
be documented. The smallest pressure difference shall be 2 Pa. The highest pressure
difference shall not exceed 30 Pa. The maximum volumetric flow can be up to 1 000 m /h.
Moreover, the structural integrity of the elements to be measured cannot be changed; otherwise
the measurement shall be cancelled.
Two measurement series shall be carried out, one for overpressure and one for negative
pressure (see Clause 6). At least five measuring points shall be recorded for each measurement
series. Data with higher differential pressures are more accurate than those that are lower.
Thus, with smaller differential pressures, the measurement shall be carried out with care.
Figure 8 shows how the pressure loss curves of the individual components a to a determine
1 3
the total pressure loss curve of the element using the example of the top cover.
Figure 8 – Example of component and system characteristic curves
4.4 Test report
The test report shall include at least the following details:
a) all details that are required to identify the tested objects;
b) a reference to the existing standard and all deviations from this;
c) equipment used;
d) measurement data:
– room temperature;
– table of the pressure differences generated, and their volumetric flows;
– system characteristic curve (differential pressure as a function of the volumetric flow).
4.5 Measurement precision
The measurement accuracy of a pressure test depends on many factors. An estimation of their
confidence range in the assessment shall be included for each variable derived. The accuracy
can be estimated by the error propagation calculation. The uncertainty shall be less than 5 %.
5 Air leakage rate of the aisle containment – Creation of an overall system
characteristic curve for the aisle containment
To determine the system characteristic curve of specific aisle containment, the system
characteristic curves of the hydraulically parallel switched individual elements shall be added.
In doing so, the determined volumetric flows of these individual elements are added at the same
differential pressure.
To determine the leaking air volumetric flow of specific aisle containment, the leaking air
volumetric flow shall be read from the overall system characteristic curve at a specified
differential pressure (see Figure 9).
Key
a to a : individual components
1 3
a : total pressure loss curve
global
Figure 9 – Example of a hydraulic addition of individual characteristic curves
6 Determination of the air leak rate – Determination of the air leak rate of the
overall system in operation, including the IT equipment
For the final determination of the air leak rate of the overall system in operation, the total
volumetric flow of the system should be determined.
The following procedures are possible:
a) Reading of the supplied air quantity at the cooling system.
b) Calorimetric determination
1) reading the electric power consumption of the equipment to be cooled;
2) determining the temperature difference between supply air and exhaust air;
3) F P ρ××cT .
( )
IT v p
c) Reading the volumetric air flow of the IT equipment.
=
– 16 – IEC 62966-2:2020 © IEC 2020
The leaking air volumetric flow (V ) results from reading the previously determined overall
Leakage
system characteristic curve. Then the air leak rate efficiency is calculated as follows:
V
Leakage
η=
VV+
Leakage Server
Two cases are to be considered for energy efficient and server-compatible climate control:
Overpressure in the cold aisle or negative pressure in the hot aisle (see B.1.4 to B.1.6, in
Annex B).
For classification of the overall system, operating at the design point, see Figure 10.
Figure 10 – Classification of aisle containment by class factors
Annex A
(informative)
Aisle containments according to operation mode
A.1 Allocation of the aisle containments according to operation mode
A.1.1 General
The typical application areas for aisle containments are described according to the type of
climate control. Furthermore, sub-classifications present the different design shapes of the aisle
containments and their application. This sub-classification explains the purposes and special
features with regard to climate control.
A.1.2 Types of climate control
The type of climate control provided by the supply air also influences the air distribution of the
supply air within the aisle containment. In this Annex A, the following limitations of the types of
climate control are carried out on the basis of the types that can be used for aisle containments.
A.1.3 Closed-circuit climate control
In the case of floor air routing, the supply air is routed into the cold aisle via a double floor with
perforated floor plates. The exhaust air is dispersed from the surroundings. This is the most
frequent type of climate control.
With ceiling air routing, the supply air is routed via suspended supply air ducts into the cold
aisle. The exhaust air is dispersed from the surroundings.
A.1.4 In-line climate control
Horizontal air routing of the supply air into the cold aisle (see Figure A.1). These types of units
are set up in the bayed enclosure suites. They convey the supply air directly into the cold aisle
without further mechanical components (air ducts) and directly extract the exhaust air at the
rear. A raised floor or air ducts above the enclosures are not required.
Figure A.1 – Example of an in-line climate control
– 18 – IEC 62966-2:2020 © IEC 2020
A.2 Cold aisle containment
A.2.1 Principle of the cold aisle containment
The cold aisle in front of the enclosures or between two bayed enclosure suites with opposite-
facing fronts is separated from the remaining room of the data centre (see Figure A.2).
Figure A.2 – Example of a cold aisle containment
A.2.2 Objective of the cold aisle
The aim of the cold aisle containment is to ensure an equal, uniform temperature distribution in
front of the enclosures of the enclosed bayed enclosure suites. As a result a uniform supply air
temperature, which is an important variable for IT equipment, can be ensured.
A.2.3 Climate control
Both closed-circuit climate control and in-line climate control can be used for cold aisle
containment.
A.3 Hot aisle containment
A.3.1 Principle of the hot aisle containment
The hot aisle behind the bayed enclosure suites or between two bayed enclosure suites with
opposite-facing rear faces is separated from the remaining room of the data centre (see
Figure A.3).
Figure A.3 – Example of a hot aisle containment
A.3.2 Objective of the hot aisle
The aim of the hot aisle containment is to achieve the warmest possible exhaust air temperature,
and thus a greater difference between the exhaust air temperature and the supply air
temperature. This high temperature difference leads to a low volumetric flow, and thus higher
efficiency of the climate control. However, it shall be considered that the temperature difference
as concerns the air is determined by the performance of the IT equipment installed and not by
the climate control.
A.3.3 Climate control
In-line climate control can be used in the case of the hot aisle containment. Closed-circuit
climate control is only possible with the hot aisle containment in conjunction with the use of air
ducts that return the hot air back to the climate control unit.
A.4 Cold and hot aisle containment
A.4.1 Principle of the cold and hot aisle containment
The cold aisle in front of the bayed enclosure suites or between two bayed enclosure suites
with opposite-facing fronts is separated from the remaining room of the data centre. At the same
time, the hot aisle behind the bayed enclosure suites or between two bayed enclosure suites
with opposite-facing rear faces is also separated from the remaining room of the data centre
(see Figure A.4).
– 20 – IEC 62966-2:2020 © IEC 2020
Figure A.4 – Example of a cold and hot aisle containment
A.4.2 Objective of the cold aisle in a cold and hot aisle containment
The aim of the cold aisle is to ensure an equal, uniform temperature distribution in front of the
enclosures in the enclosed bayed enclosure suites. This ensures a uniform supply air
temperature for the IT equipment. The aim of the hot aisle containment is to achieve the
warmest possible exhaust air temperature, and thus a greater difference between the exhaust
air and the supply air. This high temperature difference leads to a low volumetric flow as well
as more efficient climate control. A combination of hot and cold aisle containment is permissible
and recommended if both advantages are required. For economic reasons, the hot and cold
aisle enclosure should only be selected if both benefits are actually required in operation.
A.4.3 Climate control
In-line climate control can be used in the case of the cold aisle/hot aisle containments. However,
closed-circuit climate control is only possible to a limited extent by using air ducts that return
the hot air.
Annex B
(informative)
Thermodynamic variables within aisle containments
B.1 Air pressure
B.1.1 General
Depending on the type and utilisation of the IT equipment, there are different demands on the
volumetric air flows. Frequently, CRAC (computer room air conditioner) systems are operated
with constant volumetric air flow that often leads to overpressure or vacuum pressure in the
aisle containment.
Overpressures should be compensated using bypasses (air flaps). However, bypasses lead to
a lower exhaust air temperature or a higher supply air temperature, and have an adverse effect
on the efficiency of a system as the potential of the heat quantity delivery is reduced via the air
side.
B.1.2 Minimum differential pressure
The minimum differential pressure is the pressure that allows an aisle containment to be
operated in a safe manner. The following constraints shall be observed here:
– Non-homogeneous power dissipations and volumetric air flows of the IT equip
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