Date: 2025-03

prEN 378-1

Secretariat: CEN/TC 182

Refrigerating systems and heat pumps - Safety and environmental requirements - Part 1: Basic requirements, definitions, classification and selection criteria

Systèmes frigorifiques et pompes à chaleur - Exigences de sécurité et d'environnement - Partie 1 : Exigences de base, définitions, classification et critères de choix

CCMC will prepare and attach the official title page

European foreword 4

Introduction 5

1 Scope 6

2 Normative references 6

3 Terms and definitions 7

3.1 Refrigerating systems 7

3.2 Occupancies, locations 10

3.3 Pressures 11

3.4 Components of refrigerating systems 11

3.5 Piping and joints 14

3.6 Safety accessories 15

3.7 Fluids 16

3.8 Miscellaneous 19

4 Symbols and abbreviated terms 20

5 Classification 23

5.1 General 23

5.2 Classification of system locations 24

5.2.1 General 24

5.2.2 Class I – Mechanical equipment located within the occupied space 24

5.2.3 Class II – Compressors and pressure vessels outside the occupied space 24

5.2.4 Class III – Entire refrigerating system in machinery room or open air 25

5.2.5 Class IV – Ventilated enclosures 25

5.3 Classification of access to occupied spaces, machinery rooms, and open air 25

5.4 Classification of refrigerants 26

6 Determining the room volume and floor area used in refrigerant quantity safety limit calculation 27

6.1 General 27

6.2 Connected spaces calculations 27

6.3 Space size for ducted systems 27

7 Determining the releasable quantity of refrigerant and the refrigerant quantity safety limit 28

7.1 General 28

7.2 Establishing the releasable quantity of refrigerant, m_rq 28

7.3 Defining factors for toxicity and flammability 29

7.4 Establishing the refrigerant quantity safety limit, m_sl 29

7.4.1 General 29

7.4.2 Quantity limit based on toxicity 30

7.4.3 Quantity limit based on flammability 30

7.5 Options for calculation of refrigerant quantity safety limits 32

7.5.1 General 32

7.5.2 Determination of the concentration factor F 32

7.5.3 Determination of the representative height h* 33

7.5.4 Determination of toxicity quantity limit m_tl 33

7.5.5 Determination of m_fl and A_min 33

7.5.6 Surrounding concentration test 34

7.5.7 Required air flow rates to justify the increase of concentration factors of Table 7 34

7.5.8 Quantity limit based on flammability for class IV ventilated enclosure 35

7.6 Additional requirements for spaces below ground 35

7.7 Special requirements for ice rinks 36

Annex A (informative) Equivalent terms in English, French and German 37

Annex B (informative) Total equivalent warming impact (TEWI) 41

Annex C (informative) Examples of classification in Clause 5 44

Annex D (normative) Special requirements for ice rinks 45

D.1 Indoor ice rinks 45

D.2 Outdoor ice rinks and installations for similar sporting activities 45

Annex E (informative) Potential hazards for refrigerating systems 46

Annex F (informative) Calculation examples related to 7.5 48

F.1 Example 1 for 7.5 48

F.2 Example 2 for 7.5 48

F.3 Example 4 for 7.5 48

Annex G (informative) Estimation of leak mass flow rates 50

G.1 General 50

G.2 Leakage during operation 50

G.3 Leakage during adverse operating conditions 52

G.4 Leakage during maintenance operations 52

Annex H (informative) Test and calculation methods for determining releasable charge m_rc 53

H.1 General 53

H.2 Determination of releasable charge by a simulated leak into a space 53

H.2.1 Test set-up 53

H.2.2 Test method 54

H.2.3 Calculated orifice size 55

H.3 Determination of releasable charge by a simulated leak without venting to the atmosphere 55

H.3.1 Test setup 55

H.3.2 Test method 56

H.4 Determination of releasable charge by calculation and test 56

H.4.1 General 56

H.4.2 Refrigerant release between detection and closing the safety shut-off valves 57

H.4.3 Determination of m_r3 57

H.5 Determining the time before the leak is detected, t_r1 59

H.5.1 General 59

H.5.2 Determination of t_r1 by default time 59

H.5.3 Example to determine t_r1 based on effective room concentration for refrigerating systems using A1 and A2L refrigerants 60

H.6 Test conditions for releasable charge limited systems 60

H.7 Methods for determining the releasable charge based on latent heat or sublimation 61

H.7.1 General 61

H.7.2 Determination by calculation 61

Annex I (normative) Refrigerant quantity safety limit or minimum room area determination using surrounding concentration test 63

I.1 General 63

I.2 Room arrangement 63

I.3 Simulated leak 64

I.4 Concentration measurements 64

I.5 Acceptance criteria 65

Annex J (normative) Calculations for refrigerant-containing parts are within an enclosure with openings 66

J.1 Determining the concentration factor for enclosures with openings 66

J.2 Determining the effective release height for enclosures mounted at a specific height 66

Annex K (normative) Stagnation effect with of higher molar mass refrigerants 68

Bibliography 69

European foreword

This document (prEN 378-1:2025) has been prepared by Technical Committee CEN/TC 182 "Refrigerating systems, safety and environmental requirements", the secretariat of which is held by DIN.

This document is currently submitted to the CEN Enquiry.

This document will supersede [1].

prEN 378-1:2025 includes the following significant technical changes with respect to [1]:

— Clause 5 was restructured.

— The examples of systems were removed from Clause 5,

— Clause 6 and Clause 7 were combined to a new Clause 6.

— Annex C (Location and refrigerant charge limitations) was converted into a new Clause 7 of the main body of the standard (Determining the releasable quantity of refrigerant and the refrigerant quantity safety limit).

— The concept of releasable quantity of refrigerant was introduced in a new subclause 7.2.

— Options for calculation of refrigerant quantity safety limits were introduced in a new subclause 7.5.

— Additional requirements for spaces below ground are introduced in new subclause 7.6.

— Annex E was converted into a new [2].

— Annex H with examples related to Annex C were converted to and informative Annex F with examples related to 7.5.

— Examples related to Clause 5 were given in a new Annex C.

— Annex F and Annex G were named Annex D and Annex E.

— New informative Annex G for assumed mass flow rates.

— New informative Annex H for test and calculation methods for determining releasable charge m_rc.

— New normative Annex I for refrigerant quantity safety limit or minimum room area determination using surrounding concentration test.

— New normative Annex J for calculations for refrigerant-containing parts are within an enclosure with openings.

— New normative Annex K for stagnation effect with of higher molar mass refrigerants

[3] consists of the following parts under the general title “Refrigerating systems and heat pumps — Safety and environmental requirements”:

—    Part 1: Basic requirements, definitions, classification and selection criteria;

—    Part 2: Design, construction, testing, marking and documentation;

—    Part 3: Installation site and personal protection;

—    Part 5: Safety classification and information about refrigerants.

[4] applies for operation, maintenance, repair and recovery.

Introduction

This document relates to safety and environmental requirements in the design, manufacture, construction, installation, operation, maintenance, repair and disposal of refrigerating systems regarding local and global environments. It does not relate to the final destruction of the refrigerants.

It is intended to minimize possible hazards to persons, property and the environment from refrigerating systems and refrigerants. These hazards are associated with the physical and chemical characteristics of refrigerants and the pressures and temperatures occurring in refrigeration cycles.

Attention is drawn to hazards such as excessive temperature at compressor discharge, liquid slugging, erroneous operation and reduction in mechanical strength caused by corrosion, erosion, thermal stress, liquid hammer or vibration. Corrosion deserves special consideration as conditions peculiar to refrigerating systems arise due to alternate frosting and defrosting or the covering of equipment by insulation.

The extent to which hazards are covered is indicated in Annex E. In addition, machinery should comply as appropriate with [5] for hazards which are not covered by this document.

Commonly used refrigerants except R717 are heavier than air. Care should be taken to avoid stagnant pockets of heavy refrigerant vapours by proper location of ventilation inlet and exhaust openings. Refrigerants and their combinations with oils, water or other substances, can affect the system chemically and physically. They can, if they have detrimental properties, endanger persons, property and the environment when escaping from the refrigerating system. Refrigerants are selected with due regard to their potential influence on the global environment (ODP, GWP) as well as their possible effects on the local environment. Evaluation of the environmental performance requires a life cycle approach. With regard to global climate change the Total Equivalent Warming Impact approach is generally used as the basis (see Annex B). Reference should be made to the [6] to address other environmental aspects. Many factors influence environmental impacts such as:

—    location of the system;

—    energy efficiency of the system;

—    type of refrigerant;

—    service frequency;

—    refrigerant leaks;

—    sensitivity of charge on efficiency;

—    minimization of heat load;

—    control methods.

Additional investments may be directed towards reducing leaks, increasing energy efficiency or modifying the design in order to use a different refrigerant. A life cycle approach is necessary to identify where additional investments will have the most beneficial effects.

1 Scope

This document specifies the requirements for the safety of persons and property, provides guidance for the protection of the environment and establishes procedures for the operation, maintenance and repair of refrigerating systems and the recovery of refrigerants.

The term “refrigerating system” used in this document includes heat pumps.

This part of EN 378 specifies the classification and selection criteria applicable to refrigerating systems. These classification and selection criteria are used in Parts 2, 3 and 5.

This document applies to:

a) refrigerating systems, stationary or mobile, of all sizes except to vehicle air conditioning systems covered by a specific product standard e.g. [7];

b) secondary cooling or heating systems;

c) the location of the refrigerating systems;

d) replaced parts and added components after adoption of this document if they are not identical in function and in the capacity.

Systems using refrigerants other than those listed in Part 5 of this standard are not covered by this document.

Clause 7 specifies how to determine the refrigerant quantity safety limit in a given space, which, when exceeded, requires additional protective measures to reduce the risk.

This document is not applicable to refrigerating systems which were manufactured before the date of its publication as a European Standard except for extensions and modifications to the system which were implemented after publication.

This document is applicable to new refrigerating systems, extensions or modifications of already existing systems, and for existing stationary systems, being transferred to and operated on another site.

This document also applies in the case of the conversion of a system to another refrigerant type, in which case conformity to the relevant clauses of Parts 1, 2, 3 and 5 of the standard is expected to be assessed.

Product family standards dealing with the safety of refrigerating systems take precedence over horizontal and generic standards covering the same subject.

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 5149‑4:2022, Refrigerating systems and heat pumps — Safety and environmental requirements — Part 4: Operation, maintenance, repair and recovery

IEC 60335‑2‑40:2022, Household and similar electrical appliances - Safety - Part 2-40: Particular requirements for electrical heat pumps, air-conditioners and dehumidifiers

EN 378‑3, Refrigerating systems and heat pumps - Safety and environmental requirements - Part 3: Installation site and personal protection

prEN 378‑3 rev, Refrigerating systems and heat pumps - Safety and environmental requirements - Part 3: Installation site and personal protection

EN 378‑4:2016, Refrigerating systems and heat pumps - Safety and environmental requirements - Part 4: Operation, maintenance, repair and recovery

prEN 378‑5, Refrigerating systems and heat pumps - Safety and environmental requirements - Part 5: Safety classification and information about refrigerants

EN 14276‑2:2020, Pressure equipment for refrigerating systems and heat pumps - Part 2: Piping - General requirements

EN 14624:2020, Performance of portable locating leak detectors and of fixed gas detectors for all refrigerants

EN ISO 14903:2017, Refrigerating systems and heat pumps - Qualification of tightness of components and joints (ISO 14903:2017)

EN ISO 22712:2023, Refrigerating systems and heat pumps - Competence of personnel (ISO 22712:2023)

EN IEC 60079‑10‑1:2021, Explosive atmospheres - Part 10-1: Classification of areas - Explosive gas atmospheres

EN IEC 60335‑2‑89:2022, Household and similar electrical appliances - Safety - Part 2-89: Particular requirements for commercial refrigerating appliances and ice-makers with an incorporated or remote refrigerant unit or motor-compressor

prEN 378‑3:2025, Refrigerating systems and heat pumps - Safety and environmental requirements - Part 3: Installation site and personal protection

prEN 378‑5:2024, Refrigerating systems and heat pumps - Safety and environmental requirements - Part 5: Safety classification and information about refrigerants

prEN 378-5:2026 Refrigerating systems and heat pumps - Safety and environmental requirements - Part 5: Safety classification and information about refrigerants

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

NOTE     See informative Annex A for equivalent terms in English, French and German.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at http://www.iso.org/obp

— IEC Electropedia: available at http://www.electropedia.org/

3.1 Refrigerating systems

3.1.1

refrigerating system

heat pump

combination of interconnected refrigerant-containing parts constituting one closed circuit in which the refrigerant is circulated for the purpose of extracting and delivering heat (i.e. cooling and heating)

3.1.2

self-contained system

complete factory-made refrigerating system in a suitable frame and/or enclosure, that is fabricated and transported complete, or in two or more sections and in which no refrigerant-containing parts are connected on site other than by isolation valves, such as companion valves

3.1.3

unit system

self-contained system that has been assembled, filled ready for use and tested prior to its installation and is installed without the need for connecting any refrigerant-containing parts

Note 1 to entry: A unit system can include factory assembled companion valves.

3.1.4

limit charged system

refrigerating system in which the internal volume and refrigerant charge are such that, with the system idle, the allowable pressure will not be exceeded when complete evaporation of the refrigerant occurs

3.1.5

sorption system

refrigerating system in which refrigeration is effected by evaporation of a refrigerant, the vapour then being absorbed or adsorbed by an absorbent or adsorbent medium respectively, from which it is subsequently expelled at a higher partial vapour pressure by heating and then liquefied by cooling

3.1.6

secondary cooling or heating system

system employing a fluid which transfers heat from the product or spaces to be cooled or heated or from another cooling or heating system to the refrigerating system without compression and expansion of the fluid

3.1.7

sealed system

refrigerating system in which all refrigerant containing parts are made tight by welding, brazing or a similar permanent connection which may include capped valves and capped service ports that allow proper repair or disposal, and which have a tested leakage rate of less than 3 grams per year under a pressure of at least a quarter of the maximum allowable pressure

Note 1 to entry: Joints based on mechanical forces which are prevented from improper use by the need of a special tool (e.g. by glue) are considered as a similar permanent connection.

Note 2 to entry: Hermetically sealed systems in [8] are equivalent to sealed systems in EN378–2.

3.1.8

technically tight system

refrigerating system or part of system which meets the specified level of tightness

Note 1 to entry: The specified level of tightness is the level of tightness tested in accordance with the requirements for tightness testing in Clause 6 of [9].

3.1.9

durably technically tight system

refrigerating system or part of system that is shown to be technically tight and that remains technically tight due to its design, or the technical tightness of which is ensured by means of maintenance and supervision

Note 1 to entry: A refrigerating system or part of system is shown to be technically tight by testing according to Clause 6 of [9].

Note 2 to entry: No release is to be expected from equipment that is durably technically tight.

Note 3 to entry: Equipment that is durably technically tight does not cause any hazardous areas in its surroundings while it is closed.

Note 4 to entry: Durably technically tight equipment includes for example semihermetic compressors, semihermetic pumps, welded or brazed connections and detachable connections which are rarely detached in operation, such as weld-lip seal flanges or tongue and groove flanges.

3.1.10

part of the refrigerating system

several components assembled together and exposed to the same pressure in operation or pressure source, respectively, as determined by the manufacturer

Note 1 to entry: The definitions and describe the most common configurations.

3.1.11

high pressure side

part of a refrigerating system operating at approximately the condenser or gas cooler pressure

3.1.12

low pressure side

part of a refrigerating system operating at approximately the evaporator pressure

3.1.13

mobile system

refrigerating system which is usually in transit during operation

Note 1 to entry: Mobile systems include refrigerated cargo systems in ships, refrigerating systems in fishing boats, air conditioning on board, and transport of refrigerated cargo by road, train and containers.

3.1.14

cascade system

two or more independent refrigeration circuits where the condenser of one circuit rejects heat directly to the evaporator of another

3.1.15

transcritical system

refrigerating system where the compressor discharges refrigerant at a pressure above the critical point

3.1.16

assembly

several components assembled to constitute an integrated and functional whole

Note 1 to entry: Assemblies are often connected together on-site to make a complete refrigerating system.

3.1.17

component

individual functional item of a refrigerating system

3.1.18

fixed refrigerating system

refrigerating system that is intended to be used while fastened to a support or while secured in a specific location

3.1.19

operating state

function that the refrigerating system is in at a specific time during normal operation

EXAMPLE         standby, cooling mode, heating mode and defrosting

3.1.20

pressure equipment

components of the refrigerating system, classified as pressure vessels according to definition , piping including its accessories (e.g. valves) according to definition 3.5, and safety accessories according to definition 3.6

3.1.21

releasable charge limited system

refrigerating system in which the releasable charge is limited by design measures

3.1.22

safety shut-off valve

valve for the purpose of limiting the amount of releasable charge

3.1.23

potential leak point

any point in the refrigerating system that is judged to be a weak point

Note 1 to entry: Potential leak points can include parts under stress or vibration.

3.1.24

intrinsic design method

design principle where the safety of persons or property with respect to leakage of refrigerant is ensured by measures inherent in the design and manufacture of the equipment that comprises the refrigerating system

Note 1 to entry: Limiting the charge of the system to a quantity that cannot give rise to an unsafe condition, including integral airflow in the unit to ensure that leaked refrigerant cannot stagnate and incorporating refrigerant gas detection in the controls of the indoor unit are examples of intrinsic design method.

3.1.25

extrinsic design method

design principle where limiting the charge of refrigerant in a system or part of a system is not the primary method of ensuring the safety of persons or property with respect to leakage of refrigerant from the system

Note 1 to entry: Systems constructed on site using components from several equipment manufacturers and co-ordinated by a system designer will require an extrinsic design method.

3.1.26

ducted system

refrigerating systems where air is directly ducted to the spaces and refrigerant-containing parts are within the ducted airflow

3.1.27

indirect circuit

closed circuit containing heat exchangers that are in direct contact with the substance to be treated

3.2 Occupancies, locations

3.2.1

machinery room

enclosed room or space, with mechanical ventilation, sealed from public areas and not accessible to the public, which is intended to contain components of the refrigerating system

Note 1 to entry: The room may only be entered by authorised persons.

Note 2 to entry: A machinery room can contain other equipment provided design and its installation requirements are compatible with the requirements for the safety of the refrigerating system.

3.2.2

separate refrigeration machinery room

machinery room intended to contain only components of the refrigerating system, accessible only to competent personnel for the purposes of inspection, maintenance and repair

Note 1 to entry: Where the standard refers to the term machinery room, separate refrigeration machinery rooms are included.

3.2.3

occupied space

space in a building which is bounded by walls, floors and ceilings and which is occupied by persons for a significant period

Note 1 to entry: Where the spaces around the apparent occupied space are, by construction or design, not air tight with respect to the occupied space, these may be considered as part of the occupied space. above; e.g. false ceilings voids, crawl ways, ducts, movable partitions and doors with transfer grilles or undercut doors.

3.2.4

hallway

corridor for the passage of people

3.2.5

exit

opening in the outer wall, with or without a door or gate

3.2.6

exit passageway

passageway immediately in the vicinity of the exit through which people leave the building

3.2.7

cold room

room maintained by a refrigerating system at a temperature lower than ambient temperature

3.2.8

open air

unenclosed space, possibly but not necessarily roofed

3.2.9

crawl space

space that is in general accessed for maintenance only and where it is not possible to walk or access by walking

Note 1 to entry: Usually, the height of crawl spaces is less than 1 m.

3.2.10

ventilated enclosure

enclosure containing the refrigerating system that does not enable air to flow from the enclosure to the surrounding space and has a ventilation system that produces airflow from the enclosures to the open air through a ventilation duct

3.3 Pressures

3.3.1

maximum allowable pressure

PS

maximum pressure for which the system or component is designed for, as specified by the manufacturer

Note 1 to entry: PS is the limit which should not be exceeded whether the system is working or not.

Note 2 to entry: The Pressure Equipment Directive 2014/68/EU [10] designates the maximum allowable pressure as the symbol “PS”.

3.4 Components of refrigerating systems

3.4.1

refrigerating installation

assembly of components of a refrigerating system and all the apparatus necessary for its operation

3.4.2

refrigerating equipment

components forming a part of the refrigerating system

EXAMPLE         compressor, condenser, generator, absorber, adsorber, receiver, evaporator, surge drum

3.4.3

compressor

device for mechanically increasing the pressure of a refrigerant vapour

3.4.4

motor-compressor

fixed combination of electrical motor and compressor in one unit

3.4.4.1

hermetic motor-compressor

combination of a compressor and electrical motor, both of which are enclosed in the same housing, with no external shaft or shaft seals

3.4.4.2

semi-hermetic motor-compressor

accessible hermetic motor-compressor

combination consisting of a compressor and electrical motor, both of which are enclosed in the same housing, having removable covers for access, but having no external shaft or shaft seals

3.4.5

open compressor

compressor having a drive shaft penetrating the refrigerant-tight housing

3.4.6

positive displacement compressor

compressor in which compression is obtained by changing the internal volume of the compression chamber

3.4.7

non-positive displacement compressor

compressor in which compression is obtained without changing the internal volume of the compression chamber

3.4.8

pressure vessel

any refrigerant-containing component of a refrigerating system other than:

— coils (including their headers) consisting of pipes with air as secondary fluid;

— piping and its valves, joints and fittings;

— control devices;

— pressure switches, gauges, liquid indicators;

— pressure relief valves, fusible plugs, bursting discs;

— equipment comprising casings or machinery where the dimensioning, choice of material and manufacturing rules are based primarily on requirements for sufficient strength, rigidity and stability to meet the static and dynamic operational effects or other operational characteristics and for which pressure is not a significant design factor. Such equipment may include pumps and compressors.

Note 1 to entry: The semi-hermetic and open type compressors used in refrigerating systems can be subject to the exclusion Article 1.2.j of Directive 2014/68/EU [10] by referring to the working party group guidelines WPG 1/11, 1/12 and 2/34. The compressor manufacturer needs to decide on the basis of a case by case assessment, if the exclusion Article 1.2.j of Directive 2014/68/EU [10] is applicable.

Note 2 to entry: This definition is aligned to Directive 2014/68 EU [10].

3.4.9

condenser

heat exchanger in which refrigerant vapour is liquefied by removal of heat

3.4.10

gas cooler

heat exchanger in a transcritical system in which supercritical refrigerant is cooled by removal of heat

3.4.11

receiver

vessel permanently connected to a system by inlet and outlet pipes for accumulation of liquid refrigerant

3.4.12

accumulator

vessel capable of holding liquid refrigerant and permanently connected between the exit of the evaporator and suction of the compressor

3.4.13

evaporator

heat exchanger in which liquid refrigerant is vaporised by absorbing heat from the substance to be cooled

3.4.14

coil or grid

component of the refrigerating system constructed from pipes or tubes suitably connected and serving as a heat exchanger (e.g. evaporator or condenser)

3.4.15

compressor unit

combination of one or more compressors and associated components

3.4.16

condensing unit

combination of one or more compressors, condensers, receivers (when required) and the associated components

3.4.17

surge drum

vessel containing refrigerant at low pressure and temperature and connected by liquid feed and vapour return pipes to one or more evaporators

3.4.18

internal net volume

volume calculated from the internal dimensions of a vessel, and excluding the volume of the permanent internal parts

3.4.19

type approved component

component for which examination is performed on one or more samples of this component in accordance with a recognized standard for type approval

3.5 Piping and joints

3.5.1

piping

piping such as pipes or tubes (including hoses, bellows, fittings, or flexible pipes) for interconnecting the various components of a refrigerating system

Note 1 to entry: This definition of piping is piping covered in the scope of EN 14276‑2:2020.

3.5.2

joint

connection made between two parts

3.5.3

welded joint

joint obtained by the joining of metal parts in the plastic or molten state

3.5.4

brazed joint

joint obtained by the joining of metal parts with alloys which melt at temperatures higher than 450 °C but less than the melting temperatures of the joined parts

3.5.5

flanged joint

joint made by bolting together a pair of flanged ends

3.5.6

flared joint

metal-to-metal compression joint in which a conical spread is made on the end of the tube

3.5.7

compression joint

joints which achieve tightness by deforming a compressing ring

3.5.8

taper pipe thread joint

pipe joint with tapered threads that achieves tightness with filling material or deformation of thread mount

3.5.9

header

pipe or tube component of a refrigerating system to which several other pipes or tubes are connected

3.5.10

shut-off device

device to shut off the flow of the fluid, e.g. refrigerant, brine

3.5.11

companion valves

pairs of mating stop valves, isolating sections of systems and arranged so that these sections may be joined before opening these valves or separated after closing them

3.5.12

isolating valves

valves which prevent flow in either direction when closed

3.5.13

locked valve

valve sealed or in other ways constrained, so that it can only be operated by a competent person

3.5.14

nominal size

DN

numerical designation of size which is common to all components in a piping system other than components indicated by outside diameters or by thread size

Note 1 to entry: It is a convenient round number for reference purposes and is only loosely related to manufacturing dimensions. The nominal size is designated by DN followed by a number.

3.6 Safety accessories

3.6.1

pressure relief device

PRD

device designed to relieve excessive pressure automatically

3.6.2

pressure relief valve

PRV

pressure actuated valve designed to relieve excessive pressure automatically, by starting to open at a set pressure and re-closing after the pressure has fallen below the set pressure

Note 1 to entry: In some standards a pressure relief valve is called a safety valve.

3.6.3

bursting disc

disc or foil which bursts at a predetermined differential pressure

3.6.4

fusible plug

device containing a material which melts at a predetermined temperature and thereby relieves the fluid

3.6.5

temperature limiting device

temperature actuated device that is designed to prevent the generation of excessive temperatures

3.6.6

switching device for limiting the pressure

pressure actuated device that is designed to stop the operation of the pressure generator

3.6.6.1

pressure limiter

switching device for limiting the pressure which automatically resets

Note 1 to entry: This pressure limiter is designated "PSH" for high pressure protection and "PSL" for low pressure protection.

3.6.6.2

type approved pressure limiter

type approved switching device for limiting the pressure with automatic reset

Note 1 to entry: It is type approved according to [11].

Note 2 to entry: This type approved pressure limiter is designated "PSH" for high pressure protection and "PSL" for low pressure protection.

3.6.6.3

type approved pressure cut out

type approved switching device for limiting the pressure which is reset manually without the aid of a tool

Note 1 to entry: It is type approved according to [11].

Note 2 to entry: If this type of approved pressure cut out is used for pressure protection it is designated "PZH" for high pressure and "PZL" for low pressure.

3.6.6.4

type approved safety pressure cut out

type approved safety switching device for limiting the pressure which is reset manually only with the aid of a tool

Note 1 to entry: It is type approved according to [11].

Note 2 to entry: This type of approved safety pressure cut out is designated PZHH for high pressure protection and PZLL for low pressure protection.

3.6.7

changeover valve

valve serving two safety devices and so arranged that only one can be made inoperative at any one time

3.6.8

overflow valve

pressure relief valve discharging to a part of the refrigerating system with lower pressure

3.6.9

surge protection device

device which shuts down the compressor after a few surge pulses (e.g. by measuring pressure differences across the compressor or current input to the drive motor)

3.6.10

liquid level cut out

switching device for limiting the liquid level

3.6.11

self closing valve

valve that closes automatically e.g. by weight or spring force

3.7 Fluids

3.7.1

refrigerant

fluid used for heat transfer in a refrigerating system, which absorbs heat at a low temperature and a low pressure of the fluid and rejects heat at a higher temperature and a higher pressure usually involving changes of the state of the fluid

3.7.2

refrigerant type

specific nomenclature designation of a chemical compound or blend of compounds used as a refrigerant

3.7.3

refrigerant charge

m

amount of refrigerant, in kg, contained in a refrigerating system

3.7.4

design charge of the system

m_d

charge of refrigerant which is planned to be contained in the system

Note 1 to entry: The design charge is marked on the system nameplate.

3.7.5

installed charge of the system

m_i

charge of refrigerant which is put into the system when it is first set to work, and which is noted in the commissioning record

Note 1 to entry: Notification of the installed charge can be required for regulatory purposes.

3.7.6

refrigerant quantity

m_q

amount of refrigerant, in kg, that may be present in a space but not contained in a system

3.7.7

refrigerant concentration

m_c

refrigerant quantity divided by the volume of the space in which it is contained, in kg/m³

3.7.8

refrigerant quantity safety limit

m_sl

maximum quantity of refrigerant that is allowed in a particular space

3.7.9

releasable charge

m_rc

amount of refrigerant that can leak from a part of a system into a given space

Note 1 to entry: Methods to determine the releasable charge m_rc can be found in Annex H.

Note 2 to entry: Any part of the refrigerant charge that leaks to the outdoor is excluded from the releasable charge.

3.7.10

heat-transfer fluid

fluid for the transmission of heat either without any change in its phase (e.g. brine, water, air) or with evaporating and condensing at approximately the same pressure

Note 1 to entry: When fluids listed in [2] are used they shall conform to all requirements for refrigerants even if they are used as a heat transfer fluid.

3.7.11

toxicity

ability of a fluid to be harmful, or lethal, or to impair a person’s ability to escape due to acute or chronic exposure by contact, inhalation or ingestion

Note 1 to entry: Temporary discomfort that does not impair health is not considered to be harmful.

3.7.12

acute-toxicity exposure limit

ATEL

maximum recommended refrigerant concentration determined in accordance with this document and intended to reduce the risks of acute toxicity hazards to humans in the event of a refrigerant release

3.7.13

oxygen deprivation limit

ODL

concentration of a refrigerant or other gas that results in insufficient oxygen for normal breathing

3.7.14

flammability

ability of a refrigerant or heat-transfer fluid to propagate a flame from an ignition source

3.7.15

lower flammability limit

LFL

minimum concentration of refrigerant that is capable of propagating a flame within a homogeneous mixture of refrigerant and air

3.7.16

practical limit

concentration used for simplified calculation to determine the maximum acceptable amount of refrigerant in an occupied space

Note 1 to entry: CL is determined by toxicity and flammability tests, but practical limit is derived from CL or historically established refrigerant quantity safety limit, m_sl.

3.7.17

concentration limit

CL

maximum refrigerant concentration, in air, in accordance with and specified in 7.1 and established to reduce the risks of acute toxicity, asphyxiation, and flammability hazards

Note 1 to entry: It is used to determine the refrigerant quantity safety limit, m_sl for a specific space.

3.7.18

outside air

air from outside the building

3.7.19

recover

removing refrigerant in any condition from a system and storing it in an external container

3.7.20

recycle

reducing contaminants in used refrigerants by separating oil, removing non-condensables and using devices such as filters, driers or filter-driers to reduce moisture, acidity and particulate matter

Note 1 to entry: The aim of recycling is to reuse the recovered refrigerant.

3.7.21

reclaim

processing used refrigerants to new product specifications

Note 1 to entry: Chemical analysis of the refrigerant determines that appropriate specifications are met. The identification of contaminants and required chemical analysis both are specified in national and international standards for new product specifications.

3.7.22

disposal

to dispose or to convey a product usually for scrapping or destruction

Note 1 to entry:

3.7.23

bubble point

liquid saturation temperature of a refrigerant at a specified pressure at which a liquid refrigerant first begins to boil

Note 1 to entry: The bubble point of a zeotropic refrigerant blend, at constant pressure, is lower than the dew point.

3.7.24

autoignition temperature of a substance

lowest temperature at or above which a chemical can spontaneously combust in a normal atmosphere without an external source of ignition, such as a flame or spark

3.7.25

hazard duration

t_h

total time elapsing from the moment the refrigerant gas concentration constitutes a hazard at any location in the room until the mitigation measures triggered by the refrigerant gas detection system have been implemented 

Note 1 to entry: This is approximately the length of time for which the hazard of high refrigerant gas concentration persists in the space, but it should be noted that the hazard could persist for a short period after the mitigation measures have been initiated.

3.7.26

diffusion time

t_d

time elapsing from the moment the refrigerant gas concentration reaches the alarm trigger level at any location in the room until the concentration reaches the alarm trigger level at any of the sensor locations in the room

3.7.27

response time

t_r

time elapsing from the moment the detector in normal operation is exposed to a defined gas concentration or a leak rate above pre-set threshold until the detector output function is activated

Note 1 to entry: The response time is defined in [12] for indicating detectors and measuring detectors.  Either definition can be used, as appropriate, in this document.

3.7.28

mitigation time

t_m

time elapsing from the moment the refrigerant gas detection system triggers an output until the mitigation measures have been implemented

3.8 Miscellaneous

3.8.1

competence

ability to perform satisfactorily and safely the activities related to a given task

Note 1 to entry: Levels of competence are defined in [13].

3.8.2

self-contained breathing apparatus

breathing apparatus which has a portable supply of compressed air, independent of the ambient atmosphere, where exhaust air passes without recirculation

3.8.3

vacuum procedure

procedure to remove gases and moisture from inside a refrigerating system

3.8.4

factory made

manufactured at a dedicated production location under control of a recognised quality system

3.8.5

operator

natural or legal person exercising actual power over the technical functioning of refrigerating systems

3.8.6

fixed refrigerant gas detector

device which responds to a concentration of refrigerant gas in the environment

3.8.7

fixed refrigerant gas detection system

assembly that comprises all components such as the fixed refrigerant gas detector, contollers, alarms, fans, valves, UPS etc.

4 Symbols and abbreviated terms

Table 1 — Quantities

Table 2 — Constants

Table 3 — Abbreviated terms

5 Classification

5.1 General

For the purpose of this document refrigerating systems shall be classified according to:

— the location in which the system is installed;

— the type of people who have access to the place in which the system is installed;

— the toxicity and flammability characteristics of the refrigerant.

The refrigerant quantity safety limit shall be established by consideration of these classifications.

Where all of the refrigerating system is installed in an occupied space with a single access category then the refrigerant quantity safety limit in the system shall be calculated according to the requirements of that access category.

Where parts of a system are installed in several spaces, each space shall be considered individually. The refrigerant quantity safety limits shall be calculated for each of them, according to Clause 7.

Examples of classification of system locations, categorisation of access and classification of refrigerants are given in Annex C.

5.2 Classification of system locations

5.2.1 General

There are four classes of location for refrigerating systems. The location class shall be determined by consideration of the positioning of the parts of the refrigeration systems and where a leak can flow to through air or other heat transfer fluid.

Where a refrigeration system is distributed across several location classes, each location shall be considered separately, and the most restrictive calculation applies unless releasable charge is used.

5.2.2 Class I – Mechanical equipment located within the occupied space

If the refrigerating system or any of its refrigerant-containing parts are located indoors in occupied space or a non-occupied space that is not sealed from the occupied space or can leak directly into the occupied space, then the requirements for Class I location shall apply unless the system complies with the requirements in 5.2.3 or 5.2.5.

EXAMPLE     Integral plug-in display cabinet.

5.2.3 Class II – Compressors and pressure vessels outside the occupied space

If compressors and pressure vessels are located outside the occupied space, then the requirements for a Class II location shall apply, unless the system complies with the requirements in 5.2.4.

If the evaporator or condenser of the refrigerating system is not within an occupied space but uses a heat transfer fluid to serve this occupied space and a leak of refrigerant into the heat transfer fluid can leak into the occupied space for instance

— due to the heat transfer fluid being ventilation air,

— due to use of an open spray system,

— if the leakage of the heat transfer fluid is caused by leakage of the refrigerant into the heat transfer fluid, 

— through an automatic purge point,

and no compressors nor pressure vessels are located in that indoor space or in a location where a leak will flow direct to that indoor space, then the requirements of a Class II location shall apply.

Coil-type heat exchangers and pipework, including valves, are not considered to be pressure vessels, and therefore may be located in the occupied space.

Leakage via the heat transfer fluid is not considered for systems that conform to all of [9], 6.2.6.8.

EXAMPLE     Cold store.

5.2.4 Class III – Entire refrigerating system in machinery room or open air

If all refrigerant-containing parts are located in a machinery room or open air, then the requirements for a Class III location shall apply, unless the location complies with the requirements in 5.2.5. The machinery room shall conform to the requirements of prEN 378‑3 rev.

EXAMPLE     Water-cooled chiller.

5.2.5 Class IV – Ventilated enclosures

If, with the intent of preventing migration of leaked refrigerant to the surrounding area, refrigerant-containing parts are located in a ventilated enclosure that conforms to the requirements of 6.2.15 of [9], then the requirements for a Class IV location shall apply.

NOTE     Requirements for ventilated enclosures are included in [9] and[14].

EXAMPLE     heat pump within a ventilated enclosure

5.3 Classification of access to occupied spaces, machinery rooms, and open air

For the purpose of this document, access classification shall be determined according to Table 4.

The access category is defined according to Table 4 by consideration of the group of occupants who are least familiar with the safety precautions. For example, in a supermarket, department store or transport terminus an unregulated number of customers who are not familiar with the location or its safety precautions can gather. In a general office the number of people in the building is more easily regulated and occasional visitors will be accompanied by a regular occupant who can advise on the safety precautions in the event of an emergency. In a manufacturing facility all of the occupants will be familiar with the safety requirements and access to the workplace will be restricted.

NOTE 1     A complex building can contain several access categories, for example the public areas and the plant rooms in a hospital can be classified as access category a and access category c respectively.

Table 4 — Categories of access

NOTE 2     Access categories can be classified by national requirements.

NOTE 3     Open air locations including roofs, car parks and outdoor equipment compounds are considered to be parts of the building.

Where there is the possibility of more than one access category, the more stringent requirements apply. If occupied spaces are isolated, e.g. by sealed partitions, floors and ceilings, then the requirements of the individual access category apply.

Machinery rooms shall not be considered as an occupied space.

NOTE 4     Attention is drawn to the safety of adjacent premises and occupants in areas adjacent to a refrigerating system. Refrigerants heavier than air can cause oxygen deficient pockets at low level (see molecular mass in [2]).

5.4 Classification of refrigerants

Refrigerants listed in [2] use the designation and safety class specified in [15]. Practical limits values shall be those assigned in prEN 378‑5.

The practical limit for a refrigerant represents the highest concentration level in an occupied space which will not result in any escape impairing (i.e. acute) effects or create a risk of ignition of the refrigerant. It is used to determine the refrigerant quantity safety limit m_sl.

For refrigerants including blends that were commercialised by 2003, the practical limits existing at that time (as set in previous international or national standards) shall be maintained unless, for non-flammable refrigerants, the ATEL/ODL values exceed the practical limit, in which case the ATEL/ODL values shall be used.

The toxicity class of the refrigerant (A or B, the first character of the safety group) shall be according to prEN 378‑5:2024 Table 1, Table 2 and Table 3.

The flammability class of the refrigerant (1, 2L, 2 or 3, being the part of the safety group after the first character) shall be as indicated in prEN 378‑5:2024 Table 1, Table 2 and Table 3.

6 Determining the room volume and floor area used in refrigerant quantity safety limit calculation

6.1 General

The size of an occupied space that leaked refrigerant can enter into shall be determined.

Where parts of a system are installed in, or leaked refrigerant can flow to more than one occupied space, each space needs to be evaluated separately. Connected spaces shall be taken into account in space calculations as required in this Clause 6.

The space size calculation shall only consider the empty volume of a room that is readily available for dispersion of leaked refrigerant. Dimensions of a space shall be determined according to direct physical measurements or according to architects’ or other appropriate drawings.

Where refrigerant-containing parts is located in an air supply duct system serving multiple spaces, refer to 6.3.

For refrigerants of safety class A1 the total volume of all the rooms connected with a common ventilation supply, return or exhaust system not containing the evaporator or the condenser is used as the volume for calculation, if the air supply to each room cannot be restricted below 25 % of its nominal supply. The effect of the air changes may be considered in calculating the volume if the space has a mechanical ventilation system which will be operating during the occupation of the space.

6.2 Connected spaces calculations

Multiple spaces that have permanent openings between the individual spaces shall be treated as a single space.

The total size of all connected rooms can be used for the room size calculation provided

— that an air exchange of above 0,4 per hour among the rooms or the outside is ensured, or

— that rooms are on the same floor and connected by an open passageway between the spaces that is open permanently, that extends to the floor and is intended for people to walk through.

For refrigerating systems using A2 and A3 refrigerants that rely on integral circulation airflow (7.5.6) the space can be considered as a single space based on the size of the space where the refrigerant can leak directly into plus half of the size of the connected space.

6.3 Space size for ducted systems

For refrigeration systems where refrigerant-containing parts are within the main airflow and supply air is directly ducted to the spaces, the applicable room size for refrigerant quantity calculations (7.5) shall be based on the total area of the conditioned space connected by ducts. Where the airflow to spaces can be limited by zoning dampers, those spaces shall not be included in the determination of the total area. Internal volume of ducting may be included in the total space volume.

NOTE     Airflow distributed to rooms by the ducting will mix and dilute the leaking refrigerant before entering any room spaces.

7 Determining the releasable quantity of refrigerant and the refrigerant quantity safety limit

7.1 General

Where the product complies with a product standards for particular types of systems and where these product standards refer to refrigerant quantities limits, such quantities shall overrule the requirements of this document.

National regulations for installing and operation for refrigerant quantity limits shall take precedence in all cases. 

The methods used to minimize hazards to persons and property depend upon combinations of the properties of the refrigerant, the location of the equipment and the control of access to the location of the equipment. 

Systems shall be designed according to the intrinsic design method or the extrinsic design method.

Quantity limits for the intrinsic design method are given in Table 5 and Table 6. However if the tables indicate that there is no refrigerant quantity safety limit, then other methods of ensuring safety shall be employed (extrinsic design method).  Further details of the requirements for these other methods are given in Part 3 of this standard. 

Where hazards are minimised by limiting the quantity of refrigerant that can leak into a space (intrinsic design method) this Clause 7 defines the parameters to be used and the method of calculation.  In these cases, the refrigerating system or heat pump shall be designed to ensure that the refrigerant concentration in air resulting from a leak of refrigerant does not pose an unacceptable level of risk to occupants or risk of damage to the spaces served by the refrigerating system or heat pump.

Where any refrigerant-containing part is located in a space where the releasable quantity in the event of a refrigerant leak can exceed the quantity safety limit, additional mitigation measures shall be applied (extrinsic design method). Additional mitigation measures include reducing the releasable charge, applying enclosures, ventilation, alarms as appropriate for the installation. The quantity limits defined in this Clause 7 may be used as a part of the extrinsic design method, but they are not mandatory.

In the calculation of the releasable quantity limit each space where there is a risk of a refrigerant leak shall be considered, except where there are only site installed piping and permanent joints complying with EN ISO 14903:2017. That part of the system is regarded to be permanently technically tight.  Each space where refrigerant can accumulate to create a dangerous atmosphere shall be considered.

NOTE     Refrigerant can accumulate in spaces which do not contain refrigerating equipment.

The refrigerant quantity safety limit, m_sl sets the maximum amount of refrigerant in kilogram that is allowed in each space if no additional measures are taken. The refrigerant charge m_c may exceed the capped quantity limits in Table 5 and Table 6, if the releasable quantity m_rq complies with the requirements of this clause in each space considered.

The requirements of EN 378‑3 with regard to the design of the installation shall apply in all cases.

7.2 Establishing the releasable quantity of refrigerant, m_rq

The releasable quantity of refrigerant, m_rq, to be considered in the following calculation, for each space that is served by the refrigerating system shall be:

a) the releasable charge, m_rc if determined for that space, otherwise;

b) the installed charge of the refrigerating system m_i.

Annex H describes a method for determining the releasable charge, m_rc. 

The releasable quantity of refrigerant, m_rq shall be lower or equal than the refrigerant quantity safety limit, m_sl for each space that contains the same refrigerating system.

The refrigerant quantity safety limit m_sl for any system or part of a system shall be based on:

— the releasable quantity of refrigerant m_rq,

— the size of that space and the effect that the leak could have on the space or on the occupants of the space.

The minimum space size calculation can be found in 7.5.

There can be more than one system in a room. There can be one system in multiple rooms.  Multiple systems are considered not to leak at the same time.

7.3 Defining factors for toxicity and flammability

The toxicity factor (TF) expressed in kg/m³ for the refrigerant shall be the ATEL/ODL value or the practical limit (see prEN 378‑5), whichever is greater. 

The LFL, expressed in kg/m³, shall be as indicated in prEN 378‑5. 

7.4 Establishing the refrigerant quantity safety limit, m_sl

7.4.1 General

The following method shall be applied to determine the refrigerant quantity safety limit, m_sl:

Procedure to determine the quantity safety limits:

a) determine the appropriate location I, II, III, or IV according to 5.2 and access category a, b or c according to 5.3 for the system;

NOTE     A machinery room can only be access category c according to Table 4 (reconsider the location of this note).

b) determine the toxicity class and toxicity factor of the refrigerant used in the refrigerating system according to 7.3;

c) determine the toxicity quantity limit, m_tl for the space based on toxicity as the greater of:

— toxicity quantity limit, m_tl according to 7.4.2;

— 20 m³ multiplied by the toxicity factor for sealed refrigerating systems;

— 150 g for sealed refrigerating system using toxicity class A refrigerant;

d) determine the flammability class of the refrigerant used in the refrigerating system, and the corresponding LFL according to 7.3. For determination of refrigerant quantity safety limit (m_sl) for refrigerants of flammability class 1, e) is not applicable;

e) determine the flammability quantity limit, m_fl, for the space based on flammability as the greater of:

— flammability quantity limit, m_fl according to 7.4.3;

— 6  m³ x LFL for sealed refrigerating systems using flammability class 2L;

— 4  m³ x LFL for sealed refrigerating systems using flammability class 2 or 3;

— 150 g for sealed refrigerating systems;

f) The refrigerant quantity safety limit, m_sl shall be the lower of toxicity quantity limit, m_tl according to c) and the flammability quantity limit, m_fl according to e).

7.4.2 Quantity limit based on toxicity

The safety of persons or property with respect to leakage of refrigerant shall be ensured by:

— Intrinsic Design Method, where all toxicity mitigation measures are accounted for and implemented at the design stage and installers are required to follow instructions only, or

— Extrinsic Design Method, where additional toxicity mitigation measures are implemented according to the specific conditions of the installation and measures may include worker and area controls.

Where the Intrinsic Design Method is used, the quantity limits accounting for the measures integrated into the equipment design shall follow those in Table 5 and 7.5, such that a hazardous region beyond the equipment is prevented.

Where the Extrinsic Design Method is used, the requirements of prEN 378‑3:2025 Clause 6, Clause 8 and Clause 9 shall apply, accounting for the selected mitigation measures.

Table 5 illustrates the toxicity quantity limit, m_tl in proximity to the relevant space.

Table 5 — Toxicity quantity limit, m_tl, for intrinsic design method

7.4.3 Quantity limit based on flammability

The safety of persons or property with respect to leakage of refrigerant shall be ensured by:

— Intrinsic Design Method, where all flammability mitigation measures are accounted for and implemented at the design stage and installers are required to follow instructions only, or

— Extrinsic Design Method, where additional flammability mitigation measures are implemented according to the specific conditions of the installation and measures may include worker and area controls.

Where the Intrinsic Design Method is used, the quantity limits accounting for the measures integrated into the equipment design shall follow those in Table 6 and 7.5, such that a hazardous region beyond the equipment is prevented.

Where the Extrinsic Design Method is used, hazardous area classification according to EN IEC 60079‑10‑1:2021 shall be carried out, accounting for the selected mitigation measures. The requirements of [14] Clause 6, Clause 8 and Clause 9 provide a method for mitigation measures activated at not more than 20% of LFL on the complete room volume. 

Refrigeration systems ordinarily considered as location class II, where heat exchangers and piping is within a ducted sealed system, without any potential leak points, shall be considered access class ‘c’ and location classification II.

Table 6 defines the releasable quantity limits.

Table 6 — Flammability charge limits m_fl for intrinsic design method

In location class ‘I’, access category ‘a’ sealed systems or permanently technically tight systems are required.

Calculation examples can be found in Annex F.

7.5 Options for calculation of refrigerant quantity safety limits

7.5.1 General

The quantity limits calculated in this clause may be used as a part of the extrinsic design method, but they are not mandatory for the extrinsic design method.

To apply 7.4 for determination of the refrigerant quantity safety limit, m_sl for a given space, the following characteristics shall be determined first:

— refrigerant class according to 5.4,

— system location class according to 5.2,

— mitigation measures applied; e.g. form of airflow (if any),

— the representative height h* according to 7.5.3,

— concentration factor F according to 7.5.2,

— m_tl, if the refrigerant is toxic according to 7.5.4,

— m_fl, if the refrigerant is flammable according to 7.5.5.

If the refrigerant is toxic, m_sl shall be equal to m_tl. If the refrigerant is flammable, m_sl shall be equal to m_fl. If the refrigerant is both, toxic and flammable, m_sl shall be equal to the lower of m_tl or m_sl.

For systems below ground level, see 7.6.

7.5.2 Determination of the concentration factor F

If the refrigerant is heavier than air, the concentration factor shall be determined using Table 7. If the mass of the refrigerant is lower or equal to air, the concentration factor shall be determined using Annex K.

Table 7 provides concentration factors for use with refrigerants having a molar mass greater than air. Concentration factors are provided in accordance with the equipment and installation characteristics. The values in Table 7 are options used to determine the quantity safety limits and as consequence the charge or the releasable charge of the unit. 

If the molar mass of the refrigerant is lower or equal to air, the concentration factor shall be determined by the designer.

If the concentration can exceed 20 % of the LFL it may be necessary to activate mitigation measures.

NOTE     Examples of mitigation measures are in Clause 6 and 8 of [14].

Table 7 — Base values of F and height

7.5.3 Determination of the representative height h*

If the indoor refrigeration equipment is contained in an enclosure and mounted to a specific height in the room, the representative height h* shall be determined according to Annex J.

If the equipment is not contained in an enclosure or not mounted to a specific height, h* shall be the room height.

7.5.4 Determination of toxicity quantity limit m_tl

For system location class I and II based on toxicity the safety limit, m_tl may be calculated from Formula (1) or Formula (2). Formula (1) is used for calculation of the toxicity quantity limit.

or

7.5.5 Determination of m_fl and A_min

The refrigerant flammability safety limit, m_fl may then be calculated from the applicable formula and the appropriate selection of concentration factor in Table 7.

Formula (3) is used for calculation of the flammability quantity limit, m_fl and Formula (4) for calculation of A_min:

F shall depend upon the refrigerant flammability class, the applicable installation and equipment characteristics and mitigation measures applied, according to Table 7.

If refrigerant-containing parts are within an enclosure with openings, the extended calculation option in Annex J can be used as an alternative to Formula (3) and Formula (4).

Systems with a molar mass higher than that of air can use the formulae in Annex K as an alternative.

For refrigerants molar mass less than air, Formula (3) and Formula (4) can be used, but the representative height, h*, is determined relative to the room ceiling instead of the floor.

For example: A system using R717 is installed in a room of 2,5 m high. Refrigerant-containing part is at 1 m above the floor. Therefore, h* = 2,5 m minus 1,0 m = 1,5 m.

Mitigation measures include integral airflow and room ventilation. Other mitigation measures not specifically referred to, may be accounted for by applying 7.5.6 surrounding concentration test.

7.5.6 Surrounding concentration test

The refrigerant quantity safety limit, m_sl shall be determined according to the test detailed in Annex I.

7.5.7 Required air flow rates to justify the increase of concentration factors of Table 7

7.5.7.1 General

The fan circulation shall operate continuously or be turned on by a detection system.

Operation of airflow shall be continuous or initiated by leak detection. If the airflow is regarded as continuous it shall run continuously, other than for short periods for maintenance and service. If the continuous airflow is reduced to below Q_min, the compressor shall be de-energised and a warning signal given to the operator.

If the airflow is activated by leak detection, the operation shall comply with Part 3 and function shall be checked periodically to ensure that at least Q_min is achieved according to the instructions.

7.5.7.2 Minimum airflow rate for circulation airflow

The minimum airflow shall be calculated using Formula (5):

Integrated circulation airflow complying with requirements in IEC 60335‑2‑40:2022 or EN IEC 60335‑2‑89:2022 are deemed compliant.

7.5.7.3 Minimum airflow for ducted systems with circulation airflow

The maximum refrigerant charge is based on the room area for the total conditioned space as determined in Clause 6.

Where a flammable refrigerant is used the minimum airflow shall be:

7.5.8 Quantity limit based on flammability for class IV ventilated enclosure

If the airflow ensures that the concentration of flammable refrigerant leaving the class IV ventilated enclosure during a leak will not exceed 50% of LFL, then the cap to the flammability quantity limit, m_fl in Table 6, is doubled.

7.6 Additional requirements for spaces below ground

This subclause applies to refrigerants with a molecular weight greater than air.

Refrigerating systems using refrigerants of safety class A1 with releasable quantity of refrigerant, m_rq exceeding the values from 7.5.1 and located below ground are only permitted if the room has mechanical ventilation, that is independent of the building ventilation and that exchanges air at a rate of no less than 4 air changes per hour to the outside or to any spaces large enough to ensure that the toxicity factor is not exceeded.

Refrigerating systems using Flammable refrigerants with releasable quantity of refrigerant, m_rq and located in heavily constrained spaces which are below ground level are only permitted if:

— The releasable quantity of refrigerant, m_rq shall be reduced by adjusting the value of downwards by one-third, i.e., 0,67 × F, or

— The room has independent mechanical ventilation that exchanges air at a rate of no less than 4 air changes per hour, in addition to any air changes used to determine in 7.5.2, to the outside or to any spaces of at least the same volume as the room.

7.7 Special requirements for ice rinks

For refrigerating systems for ice rinks the requirements in Annex D shall be met.

Annex A (informative) Equivalent terms in English, French and German

Annex A

(informative)

Equivalent terms in English, French and German

Table A.1 — Equivalent terms in English, French and German

Annex B (informative) Total equivalent warming impact (TEWI)

Annex B

(informative)

Total equivalent warming impact (TEWI)

The total equivalent warming impact (TEWI) is a way of assessing global warming by combining the direct contribution of refrigerant emissions into the atmosphere with the indirect contribution of the carbon dioxide and other gas emissions resulting from the energy required to operate the refrigerating system over its operational life.

TEWI is designed to calculate the total global warming contribution of the use of a refrigerating system. It measures both the direct global warming effect of the refrigerant, if emitted, and the indirect contribution of the energy required to power the unit over its intended operational life. It is only valid for comparing alternative systems or refrigerant options for one application in one location.

For a given system TEWI includes:

— direct global warming effect under certain conditions of refrigerant loss;

— direct global warming effect of greenhouse gases emitted from insulation or other components, if applicable;

— indirect global warming effect from the CO₂ and other gases emitted during generation of the power to run the system and to cover the power losses between energy producer and energy consumer.

It is possible to identify the most effective means to reduce the actual global warming impact of a refrigerating system by using TEWI. The main options are:

— minimize heat load requirements;

— design/selection of the most suitable refrigerating system and refrigerant, to meet the demand of a specific cooling application;

— optimization of the system for best energy efficiency (the best combination and arrangement of components and system use to reduce energy consumption);

— proper maintenance to sustain optimum energy performance and to avoid refrigerant leaks (e.g. all systems will be further improved with correct maintenance and operation);

— recovery and recycling/reclaim of used refrigerant;

— recovery and recycling/reclaim of used insulation.

NOTE 1     Energy efficiency is therefore usually a more significant target for reducing global warming than reduction of system charge. In many cases a more efficient refrigerating system with a refrigerant charge which has a higher GWP potential can be better for the environment than a less efficient refrigerating system with a lower GWP potential refrigerant charge. All the more so if emissions are minimised: no leaks mean no direct global warming

TEWI is calculated relative to a particular refrigerating system and not only to the refrigerant itself. It varies from one system to another and depends on assumptions made relative to important factors like operating time, service life, conversion factor and efficiency. For a given system or application, the most effective use of TEWI is made by determining the relative importance of the direct and indirect effects.

For instance, where the refrigerating system is only an element of a larger system, such as in a secondary circuit/system (e.g. central station air conditioning) then the total energy consumption in use (including the standing and distribution losses of the air conditioning system) shall be taken into account in arriving at a satisfactory comparison of the total equivalent warming impact.

The TEWI factor can be calculated by the following formula where the various areas of impact are correspondingly separated.

NOTE 2     The GWP (en: global warming potential) is an index describing the radiative characteristics of well-mixed greenhouse gases, that represents the combined effects of the differing times these gases remain in the atmosphere and their relative effectiveness in adsorbing outgoing infrared radiation. This index approximates the time integrated warming effect of a given greenhouse gas in today’s atmosphere, relative to CO₂.

NOTE 3     The conversion factor β gives the quantity of CO₂ produced by the generation of 1 kWh. It can vary considerably geographically and in terms of time.

When greenhouse gases may be emitted by insulation or other components in the cooling or heating system the global warming potential of such gases is to be added:

When calculating TEWI it is very important to update GWP CO₂ related and CO₂-emission per kilowatt hour from the latest figures.

Many of the assumptions and factors in this calculation method are usually specific to an application in a particular location.

Comparisons (of results from) between different applications or different locations are therefore unlikely to have much validity.

This calculation is of particular importance at the design stage or when a retrofit decision is to be made.

Annex C (informative) Examples of classification in Clause 5

Annex C

(informative)

Examples of classification in Clause 5

EXAMPLE 1     A condensing unit serving a small chill room is located in the public area of a shop. Although access to the chill room is restricted to shop employees who are familiar with the safety precautions of the establishment the system charge has to be calculated on the basis of system location class I and access category a because the compressor and condenser are located in an occupied space which can be accessed by the general public.

EXAMPLE 2     A chiller providing glycol to supermarket display cases is located in a locked, fenced compound in the supermarket car park. The heat transfer fluid circuit is protected by vent valves which are located in the compound. The refrigerant quantity safety limit is calculated on the basis of system location class III and access category c.

EXAMPLE 3     If the chiller in example 2 was located in the supermarket service yard which is accessible to delivery drivers and other trades then the refrigerant quantity safety limit would be calculated on the basis of system location class III and access category b.

EXAMPLE 4     If the chiller in example 2 was located in the supermarket car park without the fenced compound and was therefore accessible to the general public then the refrigerant quantity safety limit would be calculated on the basis of system location class III and access category a.

EXAMPLE 5     If the supermarket in example 2 was equipped with a direct refrigerant system which had the compressors and condensers located in an unfenced area of the car park then the system charge would be calculated on the basis of system location class II and access category a. The calculation would need to consider the occupied space in the supermarket as the relevant space, since this is a direct releasable system. Putting a locked fence around the outdoor units would not permit a larger refrigerant charge to be used unless measures were taken in accordance with 7.5 to limit the releasable quantity of refrigerant to the relevant space in the event of a leak.

EXAMPLE 6     The refrigerant R717 has safety group B2L according to [16]. The first character indicates the toxicity class is B and the last two characters indicates the flammability class is 2L.

EXAMPLE 7     The refrigerant R410A has safety group A1 according to [16]. The first character indicates the toxicity class is A and the last character indicates the flammability class is 1.

Annex D (normative) Special requirements for ice rinks

Annex D

(normative)

Special requirements for ice rinks

D.1 Indoor ice rinks

Systems containing A1, A2L, B1 and B2L refrigerants may be classified as indirect systems, if refrigerant-containing parts are separated from a space which is categorised as general access according to Table 4 by an adequate, reinforced, tightly sealed concrete floor. In this case the following requirements shall be fulfilled:

— refrigerant receivers shall be provided which can hold the total refrigerant charge;

— pipes and headers shall be welded or brazed without flanges and encased in the concrete floor;

— flow and return pipes shall be arranged in a dedicated pipe trench which is configured so that leaking refrigerant cannot flow to any occupied space and which is vented to the machinery room.

D.2 Outdoor ice rinks and installations for similar sporting activities

All refrigerating equipment, piping and fittings shall be fully protected against tampering and accidental damage and arranged so that they are accessible for inspection. For systems containing B2L refrigerants the following requirements shall be fulfilled:

— refrigerant receivers shall be provided which can hold the total refrigerant charge;

— pipes and headers shall be welded or brazed without flanges and encased in the concrete floor;

— flow and return pipes shall be arranged in a dedicated pipe trench which is configured so that leaking refrigerant cannot flow to any occupied space and which is vented to the machinery room.

Annex E (informative) Potential hazards for refrigerating systems

Annex E

(informative)

Potential hazards for refrigerating systems

Refrigerating system pressure and temperature hazards can be caused by refrigerant in the vapour, liquid or combined phases. Furthermore, the state of the refrigerant and the stresses that it exerts on the various components do not depend solely on the processes and functions inside the equipment, but also on external causes.

The following hazards are noteworthy:

a) from the direct effect of extreme temperature, for example:

1) brittleness of materials at low temperatures;

2) freezing of enclosed liquid;

3) thermal stresses;

4) changes of volume due to temperature changes;

5) injurious effects caused by low temperatures;

6) touchable hot surfaces.

b) from excessive pressure due to, for example:

1) increase in the condensing pressure, caused by inadequate cooling of the condenser or the partial pressure of non-condensable gases or an accumulation of oil or liquid refrigerant in the condenser;

2) increase of the pressure of saturated vapour due to excessive external heating, for example of a liquid cooler, or when defrosting an air cooler or high ambient temperature when the system is at a standstill;

3) hydrostatic thermal expansion of liquid refrigerant in a closed space, caused by a rise in external temperature;

4) fire;

c) from the direct effect of the liquid phase, for example:

1) excessive refrigerant charge or refrigerant flooding of equipment;

2) presence of liquid in compressors, caused by siphoning, or condensation in the compressor;

3) liquid hammer in piping;

4) loss of lubrication due to the emulsification oil;

d) from the escape of refrigerants, for example:

1) fire;

2) explosion;

3) toxicity;

4) caustic effects;

5) freezing of skin;

6) asphyxiation;

7) panic;

8) environmental issues such as depletion of the ozone layer and global warming;

e) from the moving parts of machinery, for example:

1) injury;

2) hearing loss from excessive noise;

3) damage due to vibration.

Annex F (informative) Calculation examples related to 7.5

Annex F

(informative)

Calculation examples related to 7.5

F.1 Example 1 for 7.5

For an air conditioning system which has:

— a refrigerant charge of 300 g of R290;

— LFL of R290 equals 0,038 kg/m³;

— Unit has characteristics such that F = 0.35

The refrigerant charge is greater than 152 g (4 m³ × LFL), so the minimum room size shall be calculated dependent on the installation location.

Table F.1

Installation location — Minimum room volume

F.2 Example 2 for 7.5

For a room with a floor area of 30 m²

— A window mounted air conditioning system using R290.

— Installation height is 1.0 m.

— Unit has characteristics such that F = 0.35.

The refrigerant quantity safety limit of R290 is 399 g.

F.3 Example 4 for 7.5

A system with refrigerant R410A is installed in room volumes as specified in Table F.2.

TF of R410A is 0.44 kg/m³.

The system is a direct system, in location class II.

Table F.2 — Determination of refrigerant quantity safety limit

Annex G (informative) Estimation of leak mass flow rates

Annex G

(informative)

Estimation of leak mass flow rates

G.1 General

This annex provides leak mass flow rates used in the calculation of ventilation rates for location Class IV, for integral airflow, for the specification of leak simulation tests and for the assessment of hazardous areas according to [17].  It can also be used to assess the risks associated with the toxicity of leaked refrigerant and for various other calculations and tests within the standard.

For these purposes the mass flow is assumed to be in the vapour phase and is based on the conditions corresponding to the highest saturation temperature the applicable part of the system will be subjected to under normal operating conditions.

A system that meets the definition of durably technically tight is considered to be free of leaks in normal operation so the assumed hole size for the system is 0,0 mm². Where there is a possibility that the system might not remain technically tight, for example because it cannot be suitably monitored, maintained or supervised over its lifetime, then the calculation given in Clause G.2 shall be used to determine the refrigerant leak mass flow rate that can occur during operation.

G.2 Leakage during operation

The calculation given in Clause G.2 is based on leaks which arise during operation and appear as hairline cracks in metal components, gaps in threaded connections or leaks through gaskets or o-rings.  It is assumed that for these leaks the mass flux is a function of the internal pressure as shown in Formula (G.2) and is independent of the downstream pressure. 

The mass flow rate is determined for the applicable part of the system when it is operating or is in off-mode.

The largest hole size from Table G.1 is selected from all components within the parts of the system that are within a given location. The leak mass flow rate is then calculated using that hole size and the mass flux of the refrigerant at the appropriate conditions as shown in Table G.2 or calculated from Formula (G.2).

Table G.1 — Assumed hole sizes for selected components (mm²)

NOTE     These hole sizes are derived from [17] for release conditions where the opening will not expand, which is considered to be most appropriate for refrigerating systems

For components not listed, applicable literature sources shall be used for a risk assessment to determine the assumed hole size.

The leak mass flow rate is calculated from Formula (G.1):

Choked flow mass flux for selected refrigerants at various conditions can be taken from Table G.2 where the temperatures relate to the refrigerant saturation temperature at the maximum evaporation or condensation pressure.

Table G.2 — Example for the leak mass flux for ammonia

If the system is below atmospheric pressure at the saturation temperature the calculation is invalid.

For other refrigerants or other operating conditions the mass flux is calculated from Formula (G.2):

G.3 Leakage during adverse operating conditions

Where the leak occurs as a result of adverse operating conditions such as externally imposed vibrations, extreme changes in temperature or mechanical damage then the hole size given in Table G.1 might not be applicable.  If adverse conditions are not expected during normal operation then it is not necessary to consider these adverse conditions in the assessment of risk related to refrigerant leakage in normal operation.

G.4 Leakage during maintenance operations

The leak rates calculated from holes sizes assessed in Clause G.2 do not apply to maintenance conditions.  It could be appropriate to add a calculation of leak mass flow rate under adverse operating conditions to the operation and maintenance manual if there is a perceived risk of leakage during maintenance activity.  This could then be used in a risk assessment of the maintenance function. Maintenance shall be conducted in accordance with EN 378‑4:2016 or ISO 5149‑4:2022 using technicians qualified to EN ISO 22712:2023.

Annex H (informative) Test and calculation methods for determining releasable charge m_rc

Annex H

(informative)

Test and calculation methods for determining releasable charge m_rc

H.1 General

The releasable charge m_rc can be determined in each operating state in accordance with this annex.

The operating state to be applied for a refrigerating system which is not a releasable charge limited system is unit powered in standby mode, indoor and outdoor ambient at 23 ⁰C. The crankcase heater, if any, is recommended to be energized.

NOTE 1     It can be necessary to bypass a thermostat to ensure the crankcase heater is energized.

For releasable charge limited system the test conditions of Clause H.6 apply.

For refrigerating systems having releasable charge limited systems using safety shut-off valves, the releasable charge may be determined by Clause H.2, Clause H.3, or Clause H.4.

NOTE 2     The releasable charge can be determined by Clause H.2, Clause H.3, or Clause H.4 by calculation, measurement or a combination, depending on the product and application. For large or complicated refrigerating systems, it is impossible or impractical to execute the test of Clause H.2, due to the large number of configurations or when leaking of the refrigerant into the atmosphere cannot be allowed during testing.

For all other refrigerating systems the releasable charge may be determined by Clause H.2.

Alternatively, for refrigerating systems with refrigerants with high latent heat or a triple point pressure of the refrigerant is greater than 50 kPa, the releasable charge may  be determined by Clause H.7.

H.2 Determination of releasable charge by a simulated leak into a space

H.2.1 Test set-up

The refrigerating system shall be installed within a test facility according to the instructions.

If a refrigerating system can be installed with additional pipework, the pipework shall be installed which results in the largest releasable charge.

NOTE 1     The largest releasable charge is typically at the largest pipe diameter and length specified by the instructions.

The refrigerating system shall be charged to m_D according to the instructions where m_D is the design charge of the system.

If the releasable charge is determined indirectly according to H.2.2.2 the refrigerating system shall be evacuated prior to each test.

The evacuation process is recommended to be sustained for a sufficiently long time to ensure any refrigerant absorbed in the oil has been removed.

If the releasable is determined directly according to H.2.2.3 the refrigerating system shall be mounted on a scale and recharged prior to each test up to the refrigerant charge according to the instructions.

All potential leak points from where leaked refrigerant could then enter an indoor space shall be mounted on a scale and re considered for determining the releasable charge.

Potential leak points are identified in Annex G.

NOTE 2     When safety shut-off valves are installed in an indoor part of the system, both sides of the valve can be potential leak positions.

A leak orifice shall be installed at a location in the refrigerating system that would result in the greatest amount of refrigerant entering the indoor space. A valve to enable opening and closing the orifice shall be installed between the position where a leak could occur and the orifice. The distance from the position where a leak could occur to the orifice is less than 200 mm. The internal diameter of the piping shall be no less than 4 mm.

The test is for the condition where the leak orifice is positioned at the most critical location, being the one that yields the greatest releasable charge.

For a releasable charge limited system, the test shall be repeated with each of the following orifice sizes:

— calculated orifice size according to H.2.3;

— orifice size matching the largest foreseeable leak in operation according to Annex G.

For other refrigerating systems, the test shall be carried out with the large orifice size only.

The length of the orifice bore shall be no longer than 1 mm.

NOTE 3     Small orifice size is based on a 15 g/min leak rate of R290 vapour at saturation pressure corresponding to 10 °C (under choked flow). It is assumed that a system leaking at this flow rate is unlikely to lead to accumulation of dangerous concentrations.

The refrigerating system shall be tested under the relevant operating state and under the conditions which result in the greatest amount of refrigerant charge being released.

H.2.2 Test method

H.2.2.1 General

The refrigerating system shall be operated according to the relevant operating state.

The test shall be repeated at least three times. The releasable charge m_rc shall be 2 standard deviations above the mean of the test results.

The refrigerant shall be released directly into a test room or directly vented to the outside, as appropriate for the test.

The refrigerating system shall be stabilized in the operating state and test conditions for 30 minutes prior to opening the leak orifice. For systems which are not releasable charge limited systems, the system shall be operated in either the heating or cooling mode for at least 30 minutes and then turned off immediately before starting the test.

The leak orifice shall be opened for a duration of 4 hours, after which time the leak orifice valve shall be closed.

The releasable charge can be determined either indirectly according to H.2.2.2 or directly according to H.2.2.3.

H.2.2.2 Indirect determination of releasable charge

The refrigerating system shall be evacuated, and the refrigerant removed shall be measured.

The weight of the refrigerant removed at the end of the test is the retained mass (m_ret). The releasable charge (m_rc) shall then be determined by Formula (H.1):

H.2.2.3 Direct determination of releasable charge

The releasable charge (m_rc) shall be determined by the weight loss of the system during the release

H.2.3 Calculated orifice size

The leak orifice area to within ± 0,1 mm² shall be the smallest of Formula (H.2) or Formula (H.3):

and

The length of the orifice bore shall be no longer than 1 mm.

H.3 Determination of releasable charge by a simulated leak without venting to the atmosphere

H.3.1 Test setup

The refrigerating system, including safety shut-off valves, shall be installed according to the instructions, in a test room with the smallest room size as specified by the instructions, with the setup that will create the largest releasable charge for that room.

NOTE 1     This method is similar to Clause H.2, only modified to allow evaluation of larger systems or systems with refrigerants that cannot be vented into atmosphere.

NOTE 2     Tests set ups that give a larger releasable charge can be considered representative for setups that give a lower releasable charge: A test setup with indoor units with a larger inner volume can be representative for units with a smaller inner volume. A test set up with piping with a larger inner volume can be representative for piping with a smaller inner volume.

NOTE 3     It is possible for the instructions to cover different room sizes for different setups; if so, each setup will be considered separately.

The refrigerating system shall­ be evacuated prior to each test and charged with the refrigerant charge according to the instructions. The evacuation process is recommended to be sustained for a sufficiently long time to ensure any refrigerant absorbed in the oil has been removed.

A calibrated leak opening is installed in the refrigerating system that would result in the greatest amount of refrigerant released in the occupied space. A valve to enable opening and closing of the calibrated leak opening is installed between the refrigerating system and the calibrated leak opening. The calibrated leak is at the point in the circuit that has the highest saturated pressure in the indoor unit during steady state operation.

The calibrated leak opening vents into a volume at atmospheric pressure.

NOTE 4     The volume can be a room or a pressure vessel kept at atmospheric pressure; this to avoid that the refrigerant is released into the atmosphere.

The calibrated opening shall be a capillary or orifice that leaks at ṁ_leak, matching the largest foreseeable leak in normal operation from saturated liquid at a saturated pressure of 63 °C, see Annex G for proposed hole sizes.

H.3.2 Test method

The refrigerating system shall operate according to the operating state until steady state is reached for at least 30 minutes, prior to opening the valve of the calibrated leak opening.

The test shall be repeated at least 3 times and the releasable charge shall be 2 standard deviations above the mean result.

NOTE 1     The calculation of the mean value and the standard deviations apply to each operating state separately.

The refrigerating system shall operate normally for t_r1 time with the calibrated leak open, where t_r1 is the time before leak is detected as determined in Clause H.5.

After the t_r1 time, the refrigerant charge limited system shall simulate a detected leak.

NOTE 2     This can be done by any method, for example putting the refrigerant gas detector in the refrigerant concentration above the alarm set point of the refrigerant gas detector, C_set.

After the safety shut-off valves are closed, the remaining charge m_rm contained in the part of the refrigerating system which is closed by the safety shut-off valves shall be measured.

The releasable charge (kg) is Formula (H.4):

H.4 Determination of releasable charge by calculation and test

H.4.1 General

The releasable refrigerant charge, m_rc, shall be calculated by making the sum of the refrigerant released in the separate stages by the following Formula (H.5):

NOTE     The releasable charge considers the following: Refrigerant release before the leak is detected, refrigerant release between the detection and closing of the safety shut-off valves and, refrigerant release afterwards.

H.4.2 Refrigerant release between detection and closing the safety shut-off valves

The refrigerant amount released between the leak detection system giving an output signal and closing the safety shut-off valves, m_r2, shall be determined as Formula (H.6):

The value of t_cl shall be determined by test.

H.4.3 Determination of m_r3

H.4.3.1 General

To determine the releasable charge after closing the safety shut-off valves, m_r3, which can leak into the occupied space, the releasable charge for each part (unit or piping), m_r3,i, that can leak into the occupied space after closing the safety shut-off valves shall be determined by one of the following methods:

— determine volumetric density, ρ_part,i, by measuring the pressure according to H.4.3.2;

— determine volumetric density, ρ_part,i, by applying default values according to H.4.3.3;

— determine volumetric density, ρ_part,i, according to H.4.3.4;

— determine the masses m_r3,i directly according to H.4.3.5.

NOTE 1     The volumetric density is the total mass of refrigerant in the part being evaluated divided by the total free internal volume of that part.

NOTE 2     These methods can be combined for evaluating each part.

A part can be the piping or the indoor unit between the field connection points.

NOTE 3     The volumetric densities that are determined in a part can be used to calculate the releasable charge after closing the safety shut-off valves for different configurations. For instance, the volumetric density determined in the piping can be used for the calculation with different piping lengths that operate under the same condition.

The releasable charge after closing the safety shut-off valves, m_r3, shall be the sum of the charge of each part that can leak into the occupied space after closing the safety shut-off valves according to Formula (H.7).