kSIST FprEN ISO 19659-4:2025

SLOVENSKI STANDARD
oSIST prEN ISO 19659-4:2025
01-februar-2025
Železniške naprave - Ogrevalni, prezračevalni in klimatski sistemi za vozna
sredstva - 4. del: Osnovni konstrukcijski parametri, preskusni in kontrolni elementi
za enoto HVAC (ISO/DIS 19659-4:2024)
Railway applications - Heating, ventilation and air conditioning systems for rolling stock -
Part 4: Basic design parameters, test and inspection items for the HVAC unit (ISO/DIS
19659-4:2024)
Bahnanwendungen - Heizung, Lüftung und Klimatisierung von Schienenfahrzeugen -
Teil 4: Grundlegende Konstruktionsparameter, Messungen und Prüfungen für die
HLK‑Einheit (ISO/DIS 19659-4:2024)
Applications ferroviaires - Systèmes de chauffage, ventilation et climatisation pour le
matériel roulant - Partie 4: Partie 4 : Paramètres de conception de base, éléments de
test et d'inspection pour l'unité de conditionnement dair (ISO/DIS 19659-4:2024)
Ta slovenski standard je istoveten z: prEN ISO 19659-4
ICS:
45.060.01 Železniška vozila na splošno Railway rolling stock in
general
oSIST prEN ISO 19659-4:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN ISO 19659-4:2025
oSIST prEN ISO 19659-4:2025
DRAFT
International
Standard
ISO/DIS 19659-4
ISO/TC 269/SC 2
Railway applications — Heating,
Secretariat: AFNOR
ventilation and air conditioning
Voting begins on:
systems for rolling stock —
2024-11-25
Part 4:
Voting terminates on:
2025-02-17
Design parameters, test and
inspection items for the HVAC unit
Applications ferroviaires — Systèmes de chauffage, ventilation et
climatisation pour le matériel roulan —
Partie 4: Paramètres de conception, éléments de test et
d'inspection pour l'unité de conditionnement d’air
ICS: 45.060.01
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 19659-4:2024(en)
oSIST prEN ISO 19659-4:2025
DRAFT
ISO/DIS 19659-4:2024(en)
International
Standard
ISO/DIS 19659-4
ISO/TC 269/SC 2
Railway applications — Heating,
Secretariat: AFNOR
ventilation and air conditioning
Voting begins on:
systems for rolling stock —
Part 4:
Voting terminates on:
Design parameters, test and
inspection items for the HVAC unit
Applications ferroviaires — Systèmes de chauffage, ventilation et
climatisation pour le matériel roulan —
Partie 4: Paramètres de conception, éléments de test et
d'inspection pour l'unité de conditionnement d’air
ICS: 45.060.01
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2024
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
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TO SUBMIT, WITH THEIR COMMENTS,
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NOTIFICATION OF ANY RELEVANT PATENT
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Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 19659-4:2024(en)
ii
oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviations . 1
3.1 Terms and definitions .1
3.2 Abbreviations .2
4 Prerequisites (design parameters) for the HVAC unit . 2
4.1 General .2
4.2 Design parameters to be provided to the HVAC unit manufacturer .2
4.2.1 HVAC unit installation requirements .2
4.2.2 Air flow requirements .3
4.2.3 Cooling/Heating performance requirements .4
4.2.4 Electric/Electronic requirements .7
4.2.5 Control requirements . .8
4.2.6 Structure requirements .10
4.2.7 Strength requirements .10
4.2.8 Component requirements.11
4.2.9 Maintenance requirements .11
4.2.10 Environmental requirements .11
4.2.11 Noise and vibration requirements. 12
4.3 Summary of design parameters . 12
5 Specification .12
5.1 General . 12
5.2 Test/inspection items and requirement specification by the HVAC unit manufacturer . 12
5.2.1 Air volume flow rate and system pressure drop test . 12
5.2.2 Cooling/Heating test . . 12
5.2.3 Functional test. 13
5.2.4 Cooling/Heating operation and safety checks . 13
5.2.5 Noise test . 13
5.2.6 Blocked forces (if applicable) . 13
5.2.7 Shock and vibration test .14
5.2.8 Water tightness test .14
5.2.9 Air tightness test (if applicable) .14
5.2.10 Air leakage test (if applicable) .14
5.2.11 Electrical insulation resistance and dielectric test .14
5.2.12 Starting characteristics test . 15
5.2.13 Refrigerant leakage test . . . 15
5.2.14 Mass and Centre of gravity measurement . 15
5.2.15 Visual, dimensional and constructional inspection. 15
5.2.16 Maintainability demonstration . 15
5.2.17 Marking / labelling inspection . 15
5.2.18 EMC test . . 15
5.2.19 Specific materials and parts tests. 15
5.3 Classification of test/inspection items .16
6 Validation and verification . 17
6.1 General .17
6.2 Recording and measuring instruments .17
6.2.1 General .17
6.2.2 Recording .17
6.2.3 Measuring instruments . .17
6.3 Test/inspection procedures including test facility and equipment, Data to be recorded,
Position of measuring points and Criteria .17

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6.3.1 Air volume flow rate and system pressure drop test .17
6.3.2 Cooling/Heating test . . 20
6.3.3 Functional test.27
6.3.4 Cooling/Heating operation and safety checks . 28
6.3.5 Noise test .31
6.3.6 Blocked forces test . 35
6.3.7 Shock and vibration test . 36
6.3.8 Water tightness test . 38
6.3.9 Air tightness test .41
6.3.10 Air leakage test .43
6.3.11 Electrical insulation resistance and dielectric test .45
6.3.12 Starting characteristics test (if applicable) .47
6.3.13 Refrigerant circuit tightness test . 48
6.3.14 Mass and Centre of gravity measurement . 50
6.3.15 Visual, dimensional and constructional inspection.52
6.3.16 Maintainability demonstration . 53
6.3.17 Marking/labelling inspection . 53
6.3.18 EMC test . . 54
6.3.19 Specified materials and parts tests .57
6.4 Test/inspection report . 58
6.4.1 General information . 58
6.4.2 Each test and inspection result .59
Annex A (informative) List of the design parameters to be provided to the HVAC unit
manufacturer .60
Bibliography .68

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oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 269, Railway applications, Subcommittee SC 2,
Rolling Stock.
A list of all parts in the ISO 19659 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

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ISO/DIS 19659-4:2024(en)
Introduction
Since the HVAC unit is one of the main components of the HVAC system, its quality and performance is a key
issue to improve thermal comfort and energy efficiency for rolling stock.
The purpose is:
— to develop a common international standard for the validation of a HVAC unit,
— to establish methodologies and requirements on a component basis to demonstrate compliance with the
contractual technical specifications of the HVAC unit,
— to establish a clear scope of responsibility in case performance issues occur after mounting the HVAC
unit on the rolling stock.
The justification is:
Currently, we have no common international standard for the validation of a HVAC unit,
Generally, existing national and regional HVAC unit standards are for air-conditioning systems in buildings
and a few standards for rolling stock,
Therefore, there is a need to unify the methodologies of the HVAC unit standards into one single document.
This will not affect any existing national or regional standard.

vi
oSIST prEN ISO 19659-4:2025
DRAFT International Standard ISO/DIS 19659-4:2024(en)
Railway applications — Heating, ventilation and air
conditioning systems for rolling stock —
Part 4:
Design parameters, test and inspection items for the HVAC unit
1 Scope
This document covers the following as a guideline:
— the design parameters to be provided to the HVAC unit manufacturer by the rolling stock manufacturer
(“Customer”)and the railway operator,
— the test/inspection items, requirements and methods used by the HVAC unit manufacturer to verify that
the HVAC unit complies with the design parameters .
This document is applicable to HVAC units for the passenger area and driver’s cabs in urban (metro,
tramway), suburban, regional and main line vehicles.
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.
ISO 19659-1, Railway applications — Heating, ventilation and air conditioning systems for rolling stock — Part
1: Terms and definitions
ISO 19659-2, Railway applications — Heating, ventilation and air conditioning systems for rolling stock — Part
2: Thermal comfort
ISO 19659-3, Railway applications — Heating, ventilation and air conditioning systems for rolling stock — Part
3: Energy efficiency
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 19659-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/

oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
3.2 Abbreviations
CMM Coordinate Measuring Machine
DB Dry Bulb
FEM Finite Element Method
FFT Fast Fourier Transform
FST Fire, Smoke and Toxicity
GWP Global Warming Potential
HF High Frequency
PTU Portable Testing Unit
RPM Revolutions per Minute
TCMS Train Control Monitor System
VOC Volatile Organic Compounds
WB Wet Bulb
4 Prerequisites (design parameters) for the HVAC unit
4.1 General
The design parameters shall be clearly specified in the contractual technical specification so that the HVAC
unit manufacturer can design and build the HVAC unit to meet the customers requirements.
These shall meet the local laws and legislation requirements.
This clause gives an overview of the design parameters that should be specified as good engineering practice
including the parameters to calculate the total annual energy consumption and the total annual energy
efficiency of the HVAC unit. The latter is important, as in most cases, after the traction system, the HVAC
system is the second largest power consumer on the train.
4.2 Design parameters to be provided to the HVAC unit manufacturer
4.2.1 HVAC unit installation requirements
As a minimum, the following design parameters shall be provided:
— Type of the railway vehicle (high speed, commuter, Cat. 1, Cat. 2, Cat. 3 in ISO 19659-2);
— Type of the HVAC unit (compact, split in ISO 19659-1);
— HVAC unit location (roof mounted, roof embedded, ceiling mounted, on floor mounted, under floor
mounted in ISO 19659-1);
— Number of the HVAC units per railway vehicle.

oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
4.2.2 Air flow requirements
4.2.2.1 Air Volume Flow Rates
The following items shall be considered for air flow requirements:
a) Fresh Air Volume Flow Rate
— Fresh air volume flow rate per person depending on operating conditions as defined in ISO 19659-2
or local standard
— Number of passengers (Normal/Maximum)
NOTE In case free cooling mode is required, fresh air volume flow rate could be higher. Free cooling mode is
defined in ISO 19659-1.
b) Supply Air Volume Flow Rate based on following heat gains:
— Heat transfer (including glazing)
— Heat emission from person defined in ISO 19659-2
— Fresh air / outside air (defined in ISO 19659-1) (ventilation)
— Passenger door cycling air infiltration
— Solar radiation (glazing and opaque surfaces) defined in ISO 19659-2
— Heat emission of supply fans/motors and other equipment defined in ISO 19659-2
— Lighting and Miscellaneous internal heat gains defined in ISO 19659-2
c) Return Air Volume Flow Rate
d) Exhaust Air Volume Flow Rate
— Air Volume flow rate required to be exhausted from technical cabinets, WCs, galleys, etc. and to
compensate the fresh air volume rates to maintain the required vehicle inside pressure
e) Infiltration Air Volume Flow Rate
4.2.2.2 Back pressure at air interfaces
The following items shall be considered for back pressure at air interfaces:
a) Fresh air inlet back pressure
— Pressure loss through the ducts
— Type and efficiency of air filters in 4.2.8
— Filter condition (clean/dirty)
— External contamination
— Drip or mist separator
— Dampers action
— Back pressure due to train speed, especially in case of a high-speed train
— Back pressure due to other equipment

oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
b) Supply air outlet back pressure
— Pressure loss through the ducts
— Dampers action
— Mechanical parts friction
— Diffusers
— Vehicle internal pressure
c) Return air inlet back pressure
— Pressure loss through the ducts
— Type and efficiency of air filters in 4.2.8
— Filter condition (clean/dirty)
— Internal contamination
— Dampers action
— Vehicle internal pressure
d) Exhaust air back pressure, if applicable
— Pressure loss through the ducts
— Back pressure due to train speed, especially in case of a high-speed train
— Back pressure due to other equipment
— Dampers action
— Vehicle internal pressure
4.2.2.3 Air flow distribution
Air flow distribution (uniformity of air speed, temperature) e.g., at the supply air flow outlet(s) shall be
considered.
4.2.3 Cooling/Heating performance requirements
4.2.3.1 Common requirements
The design conditions shall be specified as described in ISO 19659-2:
a) Exterior design conditions
— Temperature and corresponding relative humidity
— Solar radiation
— Altitude
— Train speed
b) Extreme exterior conditions
c) Fresh air volume flow rate
oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
d) Interior design conditions
— Temperature and maximum corresponding relative humidity
— Latent and sensible loads
The thermal impact of other systems on the train and / or of the infrastructure on the HVAC system shall be
specified and taken into account.
NOTE Other systems are for example braking resistors, battery cooling system and traction converter. An
example for the infrastructure would be recycling of expelled air due to tunnel or station platform.
The maximum total annual energy consumption and maximum power consumption of the HVAC unit should
be specified.
Based on the above and the car data, the information for the design and testing of the HVAC unit shall be
derived.
4.2.3.2 Cooling performance requirements
The following design parameters in 4.2.3.1 shall be provided:
a) Exterior condition (air temperature and relative humidity)
— Design point, maximum operating point, minimum operating point
b) Mixed air condition or interior condition (air temperature and relative humidity)
— Design point, maximum operating point, minimum operating point
c) Cooling capacity (total cooling capacity/sensible cooling capacity) or supply air condition (in combination
with supply air volume flow rate from 4.2.2). If different cooling capacity will be required for pre-cooling
mode, degraded mode, free cooling mode or other condition, cooling capacity and condition should be
specified.
d) Local air temperature (in case that they are different from exterior value)
— Fresh air inlet
— Outdoor heat exchanger air inlet
e) Information if the system has reheat conditions to control inside maximum humidity level
f) Filter condition (clean/dirty), e.g. 20 % of surface covered, 10 % reduction in air volume flow rate
g) Heat exchangers condition (clean/dirty), e.g. 20 % of surface covered, 10 % reduction in air volume flow rate
h) Pressure drop caused by outside air flow speed or other factors affecting the total pressure drop of
outdoor heat exchanger area in the HVAC unit
In addition, the following information shall be provided:
i) Additional operating point to calculate the total annual energy consumption for the HVAC unit, if any
(refer to ISO 19659-3)
4.2.3.3 Heating performance requirements (electric heater type)
The following design parameters in 4.2.3.1 shall be provided:
a) Exterior condition (air temperature)
— Design point, maximum operating point

oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
b) Mixed air condition or interior condition (air temperature)
— Design point, maximum operating point
c) Heating capacity or supply air condition (in combination with supply air volume flow rate from 4.2.2)
If different heating capacity will be required for pre-heating mode, degraded mode, or other condition,
heating capacity and condition should be specified.
NOTE Heating capacity can be provided by other equipment such as electric heater installed under passenger
seat. The heating capacity for design of HVAC unit is the capacity required for HVAC unit only.
d) Local air temperature (in case that they are different from exterior value)
— Fresh air inlet
e) Filter condition (clean/dirty)
f) Maximum allowable duct temperature
In addition, the following information shall be provided:
g) Additional operating point to calculate the total annual energy consumption for the HVAC unit, if any
(refer to ISO 19659-3)
h) Information about exhaust heat recovery system (system schematic, operation, etc.) to cooperate with
the HVAC unit, if exist
4.2.3.4 Heating performance requirements (heat pump type)
The following design parameters in 4.2.3.1 shall be provided:
a) Exterior condition (air temperature and relative humidity)
— Design point, maximum operating point, minimum operating point
NOTE Relative humidity is only relevant for outdoor heat exchanger.
b) Mixed air condition or interior condition (air temperature)
— Design point, maximum operating point, minimum operating point
c) Heating capacity or supply air condition (in combination with supply air volume flow rate from 4.2.2)
NOTE 1 Heating capacity may be provided by other equipment such as electric heater installed under passenger
seat. Heating capacity for design parameter of HVAC unit should be specified as capacity required for HVAC unit only.
NOTE 2 If different heating capacity will be required for pre-heating mode, degraded mode, or other condition,
heating capacity and condition should be specified.
d) Local air temperature (in case that they are different from exterior value)
— Fresh air inlet
— Outdoor heat exchanger air inlet
e) Filter condition (clean/dirty)
f) Maximum allowable duct temperature
g) Heat exchangers condition (clean/dirty)
h) Pressure drop caused by outside air flow speed or other factors affecting the total pressure drop of
outdoor heat exchanger area in the HVAC unit

oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
In addition, the following information shall be provided:
i) Additional operating point to calculate the total annual energy consumption for the HVAC unit, if any
(refer to ISO 19659-3)
j) Information about exhaust heat recovery system (system schematic, operation, etc.) to cooperate with
the HVAC unit, if exist
4.2.4 Electric/Electronic requirements
4.2.4.1 General
The scope of this section covers the use of on board electrical and electronic equipment inside the HVAC unit
on rolling stock.
Electronic and electrical equipment inside the HVAC unit shall be designed and manufactured to meet the
full performance specification requirement for the actual temperatures occurring at the location of the
equipment concerned. The design shall take into account temperature rises within cubicles to ensure that
the components do not exceed their specified temperature ratings.
4.2.4.2 Electronic requirement
4.2.4.2.1 General
Electrical machinery produces electromagnetic interference and therefore, it is important to reduce this as
much as possible so that other sensitive electrical/ electronic devices do not malfunction e.g., by other on
train electronic/electrical equipment or hand-held radio-transmitters.
The requirements of IEC 62236-3-2 or other equivalent standard shall be fulfilled when the HVAC unit is
operating.
4.2.4.2.2 Immunity requirements
The electronic components within the HVAC unit shall have immunity from specified fast transients, surges,
electrostatic discharges and radio frequencies.
4.2.4.2.3 Emission requirements
The conducted and radiated disturbances generated by electronic components within the HVAC unit shall
respect the specified emission limits.
4.2.4.3 Power supply
4.2.4.3.1 Supply from accumulator battery
For equipment supplied from a battery, the following information shall be provided:
— nominal and rated voltage,
— minimum and maximum voltage during a specific time interval,
— D.C. ripple factor,
— interruptions of voltage to be taken into account (frequency and duration),
— allowable power consumption for the HVAC unit (normal, reduced power supply) under different
conditions (e.g., design conditions, extreme conditions and emergency ventilation),
— allowable power consumption for the HVAC unit in operational points of Operational point matrix for
calculation total annual energy consumption,

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ISO/DIS 19659-4:2024(en)
4.2.4.3.2 Supply by a static converter or an independently driven generator/alternator
For equipment supplied from a static converter or a rotating set, the following information shall be provided:
— nominal and rated voltage,
— minimum and maximum voltage during a specific time interval,
— number of phases and availability of neutral line,
— fundamental frequency and tolerance,
— harmonics,
— maximum allowed imbalance,
— minimum allowed power factor,
— interruptions of voltage to be taken into account (frequency and duration),
— maximum inrush current,
— allowable real and apparent power consumption for the HVAC unit (normal, reduced power supply)
under different conditions (e.g., design conditions, extreme conditions and emergency ventilation) in kW
and kVA,
— allowable power consumption for the HVAC unit in operational points of Operational point matrix for
calculation total annual energy consumption.
4.2.4.3.3 Supply with overhead line or third rail
For equipment for which the power supply is derived directly from the overhead line or third rail, power
supply shall be according to IEC 60850 or other equivalent standard.
The following information shall be provided:
— nominal and rated voltage,
— minimum and maximum voltage during a specific time interval,
— interruptions of voltage to be taken into account (frequency and duration),
— allowable power consumption for the HVAC unit (normal, reduced power supply) under different
conditions (e.g., design conditions, extreme conditions),
— allowable power consumption for the HVAC unit in operational points of Operational point matrix for
calculation total annual energy consumption.
4.2.4.4 Other design parameters
— dielectric test voltages for rated insulation voltage,
— electrical insulation resistance,
— maximum impedance / minimum cross section of catenary line earthing (for roof-mounted equipment
with catenary line).
4.2.5 Control requirements
The HVAC unit shall be provided with a microprocessor-based control to control the elements of the HVAC
unit / system according to the required operation as specified by the contractual technical specification.

oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
The HVAC unit will typically communicate with the TCMS and other components over communication bus
and/or digital and/or analogue inputs and outputs.
The HVAC unit shall be provided with protection functions to prevent excessive temperatures. These can
include:
— air flow sensing device or fan feedback signal,
— overheat protection device with automatic reset to interrupt the power supply,
— overheat protection device with manual reset, independent from other protections, to interrupt the
power supply,
— Electrical heater with intrinsic overtemperature protection (e.g. PTC heaters).
The HVAC unit shall be provided with protection functions to prevent excessively high or low pressures in
the refrigerating circuit. These can include:
— high pressure switch,
— low pressure switch,
— pressure relief devices.
The required behaviour of the HVAC unit in case of fire inside and in case of fire outside of the train shall be
specified.
When a protection function is activated, this should give feedback to the HVAC controller and/or to the TCMS.
Depending on the required functions, the HVAC unit may also comprise of following elements (not
exhaustive):
a) sensor/switch:
— temperature sensor / switch (air),
— humidity sensor (air),
— CO sensor (air),
— VOC (Volatile organic compounds) sensor (air),
— differential pressure sensor / switch (air),
— smoke sensor / switch (air),
— pressure sensor / switch (refrigerating circuit),
b) damper
c) valve
d) relay
e) contactor
f) circuit breaker
g) fuse
h) voltage/phase sequence/over current detection
i) motor
j) converter/inverter/transformer

oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
k) hard wired external signal e.g., interior temperature setting selector
In case the microprocessor-based control is unavailable, it is recommended to have a back-up solution with a
degraded temperature control, while maintaining the above-mentioned protection functions.
In case a certain functionality is required when a power supply is unavailable, this functionality shall be
specified.
4.2.6 Structure requirements
The following design parameters shall be provided:
a) to mount the HVAC unit correctly and firmly, and to minimise vibration:
— fixation method (to secure the HVAC unit to the vehicle),
— mechanical interference from other systems on the train and / or of the infrastructure on the
service route,
— interface information (mechanical, electrical, maintenance),
— critical dimensions,
— allowable weight.
b) to avoid incorrect air flows through the HVAC unit:
— information about local pressures at air in- and outlets, which might produce reverse air flow due to
aerodynamic effects,
— limits regarding leakages and maximum/minimum outside pressure to be considered (air tightness
applicable to operation on high speed lines with tunnels).
Example
maximum leakage factor at static gauge pressure 400 Pa
-3 3 2
→ f = 1,32 x 10 m /m s.
max
c) to avoid water ingress into the car interior:
— rain amount,
— rainfall duration,
— car washing water amount, angle and pressure,
— washing duration,
— maximum acceleration, inclination and cant for condensate drainage,
— conditions (temperature, relative humidity and running time) to check that there is no condensate
carry over.
4.2.7 Strength requirements
The following design parameters shall be provided:
a) lifting information and limitation
b) shock and vibration test (relevant standard: IEC 61373 or other specified standards) to be applied
c) proof and fatigue load cases for FEM calculations, including number of cycles for the latter

oSIST prEN ISO 19659-4:2025
ISO/DIS 19659-4:2024(en)
d) concentrated load on covers, frames, etc. (for example, maximum weight of the maintenance personnel,
in case the maintenance personnel are required to travel from one end of the car to the other.)
The stress impact by other systems on the train and / or by the infrastructure around the train shall be
specified and considered.
NOTE For example, maximum pressure variation around the railway vehicle which is generated when running
into a tunnel and/or passing by an oncoming railway vehicle.
4.2.8 Component requirements
The following design parameters shall be provided:
a) to select suitable materials and parts:
— the local regulations and standards for fire, smoke and toxicity,
— specification for materials and parts and relevant standards if exist,
— filter class according to ISO 16890-1 and design conditions (dust level, filter grade/life).
b) manufacture information and notices:
— marking / labelling [model number, rated cooling capacity, rated heating capacity, rated voltage/
frequency, refrigerant (name/charge amount), weight, manufacturing date/serial number/
manufacturer, et
...