IEC TS 62610-2:2011

IEC/TS 62610-2


®


Edition 1.0 2011-07



TECHNICAL



SPECIFICATION



SPÉCIFICATION
TECHNIQUE
Mechanical structures for electronic equipment – Thermal management for
cabinets in accordance with IEC 60297 and IEC 60917 series –
Part 2: Design guide: Method for the determination of forced air-cooling
structure

Structures mécaniques pour équipements électroniques – Gestion thermique
pour les armoires conformes aux séries CEI 60297 et CEI 60917 –
Partie 2: Guide de conception: Méthode pour la détermination de la structure
de refroidissement par ventilation forcée


IEC/TS 62610-2:2011

---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC/TS 62610-2


®


Edition 1.0 2011-07



TECHNICAL



SPECIFICATION



SPÉCIFICATION
TECHNIQUE
Mechanical structures for electronic equipment – Thermal management for
cabinets in accordance with IEC 60297 and IEC 60917 series –
Part 2: Design guide: Method for the determination of forced air-cooling
structure

Structures mécaniques pour équipements électroniques – Gestion thermique
pour les armoires conformes aux séries CEI 60297 et CEI 60917 –
Partie 2: Guide de conception: Méthode pour la détermination de la structure
de refroidissement par ventilation forcée


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX Q
ICS 31.240 ISBN 978-2-88912-588-3

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

---------------------- Page: 3 ----------------------
– 2 – TS 62610-2  IEC:2011



CONTENTS

FOREWORD . 3


INTRODUCTION . 5

1 Scope and object . 6

2 Thermal interfaces . 6


2.1 Baseline thermal conditions . 6

2.2 Reference temperature . 6

2.3 Syntax of surfaces of a generic subrack, chassis or cabinet . 7

2.4 Preferred airflow conditions . 8
2.5 Cabinet airflow volume and temperature rise management . 9
3 Forced air thermal flow chart for cabinet equipment . 10
3.1 General . 10
3.2 Evaluation of the actual thermal performance of subrack or chassis . 11
3.3 Cabinet airflow considerations . 11
3.4 Arrangement of subracks and/or chassis equipment within the cabinet . 11
3.5 Selection of cabinet mounted forced air device(s) . 12
3.6 Thermal operating environment . 12
Annex A (informative) Limitation of application and background information . 14
Bibliography . 16

Figure 1 – Syntax of surfaces of a forced air cooled generic subrack or chassis to be
mounted into a cabinet . 7
Figure 2 – Syntax of surfaces of a forced air cooled generic cabinet . 7
Figure 3 – Preferred air flow patterns . 9
Figure 4 – Air flow volume management . 10
Figure 5 – Forced air thermal flow chart for cabinet equipment . 11
Figure 6 – Thermal operating environment (Cabinet sectional side view) . 12
Figure 7 – Example of effect of reference temperature on cabinet operating
temperature range . 13
Figure A.1 – Thermal network model for a plug-in unit in subrack or chassis . 15

Table 1 – Preferred airflow pattern . 8

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TS 62610-2  IEC:2011 – 3 –


INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________



MECHANICAL STRUCTURES FOR ELECTRONIC EQUIPMENT –

THERMAL MANAGEMENT FOR CABINETS IN ACCORDANCE

WITH IEC 60297 AND IEC 60917 SERIES –



Part 2: Design guide: Method for the determination

of forced air-cooling structure




FOREWORD
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The main task of IEC technical committees is to prepare International Standards. In
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• the required support cannot be obtained for the publication of an International Standard,
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• the subject is still under technical development or where, for any other reason, there is the
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Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 62610-2 TS Ed.1.0, which is a technical specification, has been prepared by
subcommittee 48D: Mechanical structures for electronic equipment, of IEC technical

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– 4 – TS 62610-2  IEC:2011


committee 48: Electromechanical components and mechanical structures for electronic

equipment.


The text of this technical specification is based on the following documents:


Enquiry draft Report on voting


48D/459/DTS 48D/470/RVC



Full information on the voting for the approval of this technical specification can be found in

the report on voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of IEC 62610 series, under the general title Mechanical structures for
electronic equipment – Thermal management for cabinets in accordance with IEC 60297 and
IEC 60917 series, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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TS 62610-2  IEC:2011 – 5 –


INTRODUCTION


Power dissipation of high-end servers, telecommunication equipment and electronic

controllers has been increasing rapidly (Moore’s law). Thermal management for electronic

systems has become critical to maintain performance and reliability.


For a long time convection air cooling was an adequate and reliable solution. Typically, the

cooled air entered a system on the bottom and the heated air exits at the top. However, with

increasing packaging density heat dissipation of components required “compartmentalizing” of

functions within a cabinet. Individual subracks and chassis require their own individual cooling

solutions often enhanced by forced air devices such as fans.

In the absence of any guide, subrack and chassis designers typically find their cooling
solutions best suited for their specific application leaving the cabinet system integrator with a
mix of incompatible subrack and/or chassis cooling concepts to deal with.
An improper arrangement of multiple subracks and/or chassis (the equipment) in a cabinet
may cause a severe imbalance of airflow and/or unwanted temperature rises preventing
effective cooling of the cabinet installed equipment. Two typical undesirable factors may be
triggered by such an imbalanced airflow and/or unwanted temperature rise(s) within a cabinet.
The required airflow volume to each individual cabinet mounted equipment may fall short. The
air-intake temperature of each cabinet mounted subrack and/or chassis may increase as
exhaust air of one equipment may increase the air-intake temperature of another equipment.
As a result, unwanted temperature rise of components may occur.
The intention of this guide is to educate the subrack and/or chassis system designer and the
cabinet integrator to provide for compatible forced air cooling solutions.
This guide is based on the mechanical structures as defined in the IEC 60297 and IEC 60917
series of standards.

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– 6 – TS 62610-2  IEC:2011


MECHANICAL STRUCTURES FOR ELECTRONIC EQUIPMENT –

THERMAL MANAGEMENT FOR CABINETS IN ACCORDANCE

WITH IEC 60297 AND IEC 60917 SERIES –



Part 2: Design guide: Method for the determination

of forced air-cooling structure








1 Scope and object
This part of IEC 62610 provides for compatible methods of forced air cooled cabinets
assembled with associated subracks and/or chassis in accordance with the IEC 60297 and
IEC 60917 series.
This design guide contains the following:
a) Thermal interfaces of subrack and/or chassis based equipment in a cabinet
• Reference temperature
• Preferred airflow conditions
• Airflow volume conditions
• Standard air
b) Procedures for determining compatible forced airflow conditions in a cabinet by applying
typical thermal interface conditions
The drawings used are not intended to indicate product design. They are only explanatory
indications for determining forced air-cooling structure.
The terminology used complies with IEC 60917-1.
2 Thermal interfaces
2.1 Baseline thermal conditions
In order to enable reproducible and comparable values, standard air is defined at the air inlet
to be used for the determination of the thermal capability and requirement parameters of
products.

3
NOTE Standard air as defined for this purpose has a density of 1,2 kg/m , a relative humidity of 50 %, a
5
temperature of 20 °C, a pressure of 1,013 × 10 Pa. A specified heat capacity is 1 005 J/kgK at these conditions.
These values are aligned with the fan industry specifications, common test practices and electronic industry
expectations.
2.2 Reference temperature
The thermal operating temperature of subrack and chassis in the cabinet should be defined at
the air inlet, and this temperature is called reference temperature in this technical
specification.
Reference temperature is defined as the temperature of an objective ambient air of the
equipment in the cabinet which is a starting point for a rise in internal temperatures of the
equipment, and, at the same time, influences internal temperatures of it.
At one typical equipment which consists of a subrack and a forced air-cooling device,
temperatures of internal air and inside components of the subrack are determined as certain

---------------------- Page: 8 ----------------------
TS 62610-2  IEC:2011 – 7 –


values from “reference temperature”. And, “reference temperature” of the equipment cabinet

can be considered as equivalent with its intake air temperature, because the heat dissipating

path of the forced air-cooling is dependent on ventilation characteristics of the equipment.

(see Clause A.2)


The air intake is the initial point of an upstream airflow where air flows into the equipment to

cool its inside. The intake air temperature of the equipment (T3-nr) as supplied by the ambient

temperature (T4) could be identical (see Figure 6).


NOTE Generally, the intake air temperature is measured at the positions from 30 mm to 50 mm away from the
outline of the equipment to avoid the influence of heat radiation. At the air intake opening, if the temperature is not

considered as homogeneous because the opening is so wide, several positions (3 to 5) should be defined as

reference temperature positions, and the average temperature should be taken as the intake air temperature.
2.3 Syntax of surfaces of a generic subrack, chassis or cabinet
In order to define airflow patterns of subrack and/or chassis based equipment mounted within
a cabinet the syntax of the outer surfaces is defined as in Figure 1.

T (top)
R (rear)
SL (side-left)
SR (side-right)
F (front)
IEC  1700/11
B (bottom)

Figure 1 – Syntax of surfaces of a forced air cooled generic subrack
or chassis to be mounted into a cabinet

T (top)
R2 (upper-rear)
SL (side-left)

SR (side-right)
F (front)
R1 (lower-rear)
B (bottom)
IEC  1701/11

Figure 2 – Syntax of surfaces of a forced air cooled generic cabinet

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– 8 – TS 62610-2  IEC:2011


2.4 Preferred airflow conditions


In order to facilitate an efficient cabinet airflow design, it is necessary to define the preferred

airflow pattern of the cabinet mounted equipment. It is important that the cold air entry is not

contaminated by the hot air exit (separation of the air entry path and the air exit path). The

essential principles of cooling airflow direction are "FRONT to REAR" and "BOTTOM to TOP".


The complete syntax of airflow pattern in Table 1 is as follows :


Intake definition [＋ additional intake definition] → exhaust definition [＋ additional exhaust

definition]

The intake and exhaust definition corresponds to the syntax of the surfaces as shown in
Figure 1 and Figure 2.
Table 1 – Preferred airflow pattern
Airflow pattern within subrack or chassis-
b
Airflow pattern within cabinet
a
based equipment
F → T, F→ R2
F → R
F+B → T, F+B → T+R1
F+B →R
F+B → T+R2, F+B → R1+R2
a
Subracks or chassis with forced air-cooling devices.
b
Cabinets with forced air-cooling devices.

Subracks and chassis which do not comply to the preferred airflow pattern as described in this
technical specification should provide for additional airflow management devices such as
deflectors. These additional deflectors should bring the equipment in line with a preferred
airflow pattern.
The following figures illustrate preferred airflow patterns in a cabinet as per Table 1.
The arrangements shown in this figure are typical only.

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TS 62610-2 © IEC:2011 – 9 –



Cabinet

T T
Equipment T

T

R2
R2




F F F

F
F
F


Equipment
B
B
(1) F  R2 (2) F  T(3) F+B  T
(1) F → R2 (2) F → T (3) F + B → T
T
T
T T
R2
R2
R2
R2
F
F
F
F
F
F
R1
R1
R1
R1
B
B B
B
BB
(4) F(4) F + B+ B→  T +T+ R1R1 (5) F + B → T+ R2 (6) F + B → R1 + R2
(5) F+B  T+R2 (6) F+B  R1+R2

IEC  1702/11



Figure 3 – Preferred air flow patterns
2.5 Cabinet airflow volume and temperature rise management
The cabinet with forced air-cooling devices should have enough cooling capability for power
dissipation in order to maintain the cooling capacities of various types of subracks or chassis
with air-cooling devices in it.
The cabinet with one or more such subracks and chassis shall have exhaust air ventilation
capacity more or equal than the sum of subracks’ and chassis’ airflow volume. This means
that the cabinet does not impede respective subracks ventilation capacities.
The airflow volume of the cabinet mounted forced air devices (F4) shall be sized to match the
combined air volume as produced by the forced air devices of the subrack(s) (F3-2) and
chassis (F3-1) in the cabinet.

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– 10 – TS 62610-2 © IEC:2011




Total airflow volume of equipments: ΣF3-n ≦ Airflow volume of the cabinet: F4














F3-n Airflow volume of equipments
F4 Airflow volume of cabinet
Figure 4 – Air flow volume management
NOTE The power dissipation of air-exit fans should be considered to evaluate the exhaust air temperature rise of
the equipped cabinet.
3 Forced air thermal flow chart for cabinet equipment
3.1 General

The flow chart as shown in Figure 5 identifies the forced airflow procedure for cabinet
equipment.
The details of each step in the flow chart are explained in the following subclauses.

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TS 62610-2  IEC:2011 – 11 –





Evaluation of the actual thermal performance

of the subrack or chassis

- air flow pattern

Step 1
- air flow volume

- temperature rise





Cabinet air flow considerations

Step 2


Arrangement of subracks and/or chassis
equipment within the cabinet
Step 3

Selection of cabinet mounted forced air
Step 4 device(s)

Thermal operating environment
Step 5

IEC  1704/11


Figure 5 – Forced air thermal flow chart for cabinet equipment

3.2 Evaluation of the actual thermal performance of subrack or chassis
For the thermal management of cabinet mounted subracks and/or chassis equipment it is
important to take the following into account:
a) The airflow pattern (See Table 1)
b) The airflow volume
c) The operating temperature range

d) The temperature rise limitation
3.3 Cabinet airflow considerations
The airflow in the application specific operating environment where the cabinet is installed
should be investigated. The airflow pattern for the cabinet is chosen from the related Table 1.
3.4 Arrangement of subracks and/or chassis equipment within the cabinet
Ideally, all cabinet mounted subrack and/or chassis equipment have the same compatible
airflow pattern chosen from Table 1. Incompatible airflow pattern of an individual subrack
and/or chassis equipment may be mitigated by suitable airflow dividers or airflow deflector
panels in order to prevent cabinet airflow imbalance and to control the airflow within the
cabinet.

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– 12 – TS 62610-2  IEC:2011


3.5 Selection of cabinet mounted forced air device(s)


The cabinet mounted forced air device(s) shall be chosen to realize that the cabinet airflow

volume (F4) balances or exceeds the combined airflow volume (F3-n) provided by the

subrack(s) and /or chassis.


ΣF3-n ≦ F4

F3-n Airflow volume of subrack or chassis in the cabinet

F4 Airflow volume of the cabinet, created by the cabinet mounted forced air device(s)

3.6 Thermal operating environment
The individual subrack and/or chassis equipment operating temperature range is defined as
T3-n (min) to T3-n (max) defined by the specifications for cooling of each subrack or chassis
equipment.
The inlet air temperature of each subrack and/or chassis equipment mounted on a cabinet,
corresponding exactly to the reference temperature of each equipment described in 2.2, "T3-
nr" shall be within the operating temperature range T3-n(max/min).
T3-n (min) ≦ T3-nr ≦ T3-n (max) for each equipment
For example, the following both conditions shall be fulfilled under the operating temperature
range of the equipped cabinet T4 (max/min) in the case of Figure 6.
T3-1 (min) ≦ T3-1r ≦ T3-1 (max)
T3-2 (min) ≦ T3-2r ≦ T3-2 (max)
Airflow
Airflow
T3-1r
T3-1r

T4
T4
T3T3-2r-2r

IEC  1705/11

Figure 6 – Thermal operating environment (Cabinet sectional side view)
T3-nr Reference temperature of concerned subrack(s) or chassis mounted on a
cabinet
T3-n (min) Minimum operating temperature for subrack(s) or chassis
T3-n (max) Maximum operating temperature for subrack(s) or chassis
T4 Ambient temperature around an equipment cabinet
NOTE 1 The operating temperature range of the equipped cabinet T4 (max/min) depends on its application.

---------------------- Page: 14 ----------------------
TS 62610-2  IEC:2011 – 13 –


NOTE 2 In case that the equipment cabinet has air inlet filters or air outlet filters, decreasing of the airflow

volume due to pressure loss by the filters should be considered.

NOTE 3 Figure 7 shows the relation between reference temperature and operating temperature range of an

equipment cabinet. If the reference temperature of subrack(s) and/or chassis (T3-nr) goes down form the condition

of “T3-nr > T4” to “T3-nr = T4”, the operating temperature range of the equipment cabinet moves to the right side
as shown in Figure 7.


It means that the ambient around the equipment cabinet can be taken as higher temperature

and demand for the performance of HVAC (Heating Ventilation Air Conditioning) of the

cabinet can be moderated.


It also indicates that the reference temperature of subrack(s) or chassis higher than the

ambient temperature around the equipment cabinet (T3-1r >T4, as the solid line) is caused
mainly by imbalance of airflow.
The dotted line shows the case of a reference temperature of subrack(s) or chassis equal with
the ambient temperature around the equipment cabinet (T3-1r =T4).
A and B indicate the operating temperature ranges of the cabinet for each case.


T3-1r >T4
T3-nr
T3-1r =T4
T3-1(max)
T3-1(min)
A T4
B
Cabinet operating temperature range
Vertical axis:   reference temperature of concerned n-subrack or chassis mounted on cabinet
Horizontal axis: ambient temperature around cabinet to be installed

IEC  1706/11

Figure 7 – Example of effect of
...