EN378: 2016 CHANGES AND CHALLENGES

Transcription

1 EN378: 2016 CHANGES AND CHALLENGES Andy PEARSON Star Refrigeration Ltd., Thornliebank Glasgow, G46 8JW, UK F: E: ABSTRACT This paper starts with a discussion of what EN378 is and equally importantly, what it is not. It describes the process used to develop the standard and reviews the significant changes introduced since the last version was published. The paper concludes with an appraisal of the difficulties that may be encountered in using EN378 and the benefits that accrue from persevering with it. 1. INTRODUCTION EN378 is a safety and environmental standard, published by CEN, the European Committee for Standards (Comité Européen de Normalisation). It provides guidance for companies who design, construct, install, operate, maintain and use vapour compression systems for refrigeration, air-conditioning, heat pumps, chillers and other similar systems. It is published in four parts, which respectively cover definitions, design (including manufacturing), installation (including commissioning) and operation (including maintenance requirements). In total, the four parts are about 180 pages long, with parts 3 and 4 each about half the length of parts 1 and 2. The text of the standard is produced by a Working Group, a sub-committee of the Technical Committee of CEN responsible for all standards related to refrigerating systems. In shorthand this is WG6 of TC182. The technical committee members are nominated representatives of national standards bodies (NSB) and the committee business is conducted by ballot, with votes cast by the head of delegation from each country on behalf of their NSB. In contrast the members of a WG are nominated experts who do not represent a country or NSB and who do not need to be members of the TC. Membership of the Technical Committee is open to representatives of all CEN member countries (the 28 member states of the European Union, 3 members of the European Free Trade Association (Iceland, Norway and Switzerland), Macedonia and Turkey). EN378 was originally published in 2000 and superseded the British Standard BS4434 which had been the reference for refrigeration safety in the United Kingdom (and many places overseas) since the 1960s. It took eight years to produce the second edition, published in 2008 and has taken a further eight years to bring the third edition to the point of issuing a final draft for national votes. This length of time is unusual for European Standards, and stretches the rules on timing for a revision to the limit. Usually the process is expected to be completed in about five years and is not normally permitted to run beyond an eight year period. The length of time taken to revise EN378 in both cases is due to the complexity of the topic, the breadth of material covered by the standard and the extensive changes happening in the industry during the change period. EN378 provides a means of proving conformity with some relevant European directives. All four parts of the first edition (2000) were harmonized with European Directive 97/23/EC (The Pressure Equipment Directive ) however when the standard was revised in 2008 it was concluded that it was only appropriate to harmonize part 2 ( Design, construction, testing, marking and documentation ) with the PED. Part 2 was also harmonized at that time with European Directive 98/37/EC (The Machinery Directive ). Harmonization means that, once the link between the directive and the standard has been cited in the Official Journal of the European Union and at least one member state has implemented it as their national standard, compliance with specific clauses can be presumed to indicate conformity with the equivalent essential safety requirements of the directive. EN378 is not, however, a legal requirement in its own right. It is possible to install a system in compliance with all relevant regulations, including PED and MD, without following the requirements of EN378. It is also

2 not a complete design guide for refrigerating systems. It only addresses topics that are not fully covered elsewhere. For example it does not give complete guidance on electrical safety, only on aspects which are relevant to refrigeration and which are not adequately addressed elsewhere. It does not provide presumption of conformity with all relevant European directives, only those which are specifically mentioned in Annex Z in each of the four parts. At present this means that conformity can only be presumed with respect to design, construction, testing, marking and documentation requirements for the PED and the MD, not for any other directives and not for any other aspects of the directives. In particular compliance with EN378 gives no presumption of conformity with directive 99/92/EC (The ATEX Workplace directive ) or directive 2006/95/EC (The Low Voltage directive ). Any system using a dangerous substance as defined in DSEAR (2002) is required to meet the requirements of those regulations. Following the requirements of EN378 in full does not provide a presumption of conformity with regard to flammability. In parallel with the maintenance of EN378 the International Standards Organisation (ISO) has developed and published two standards, ISO817:2014 and ISO5149:2014 (parts 1 to 4). A key objective of the task handed from TC182 to WG6 was that the revised version of EN378 should as far as possible be aligned with the text of ISO817 and ISO5149, however since it was desired to retain harmonization with the European Directives it was clear from the outset that the two families would never be an exact match. 2. CURRENT STATUS The CEN standards preparation process comprises several defined stages requiring alternate input from NSBs and Working Group members. A committee draft is prepared by the WG and circulated to NSBs for comment. The comments received are resolved to the best of the WG s ability in discussion, within a concensus process and the resultant draft standard is sent to the NSB s for vote. The rules for voting are complex but clearly defined in CEN rules. The standard is only accepted if several criteria are met. If an NSB votes for approval of the draft standard it is permitted to submit editorial comments to the text but it is not allowed to propose any technical changes. In general a technical comment is one which would alter the meaning of the standard, whereas an editorial change is one which clarifies the previously intended meaning in cases where the text was obscure, ambiguous or simply ungrammatical or inelegant. In some cases, particularly if a large number of comments are received to the draft standard, the text will go back to the working group for review and will then be recirculated as a second draft. Once the text has been refined the standard will be reissued as a final draft for vote by the NSB s. If the votes meet the CEN criteria then the text will proceed to publication. The TC responsible for the standard may choose after the first ballot on the draft standard to proceed directly to the final draft rather than repeating the enquiry stage. The current status of EN378 (in December 2015) is that it has passed the first enquiry stage, but with a significant number of technical and editorial comments. These have all been addressed by the Working Group and in November 2015 the NSBs were asked to decide whether the revised text should be sent out for a second enquiry (repeating the draft standard stage) or should proceed to the final vote. It was agreed unanimously to proceed to the final stage. In the first enquiry stage the four parts received 490, 488, 320 and 150 comments respectively. Some of these comments were simple editorial suggestions. Others were complex technical points running to several pages, requiring detailed technical analysis and often a direct contradiction of other received comments. The working group met many times over the period and many more subgroup meetings were held in person and by teleconference to resolve specific issues or to deal with general principles. It is not surprising that the revised standard, currently out to vote on the final draft, is in some respects very different to the previous edition. 3. WHAT S NEW IN EN378 The main task of the working group, as noted above, was the alignment of EN378 with ISO5149. This included introduction of an additional flammability class, 2L, to the method of charge calculation based on refrigerant classification and the addition of two new alternative methods of charge calculation. Most of this change is contained in part 1. In part 2 there have been some detailed changes to the flowcharts used for determination of protective device requirements and the PED and MD references have been updated to 2014/68/EU and 2006/42/EU respectively. Part 3 includes changes to the requirements for machinery rooms, in particular addressing the anomaly of equipment which is not in a machinery room but is not in an occupied space. The

3 changes to part 4 were less significant, comprising mainly the alignment with ISO5149 and the addition of requirements for moisture tests and a procedure for evacuation of a system. Several informative annexes were also introduced, on stress corrosion cracking, leak simulation, commissioning and ignition sources (part 2) and special provisions for handling ammonia vapour during maintenance or decommissioning (part 4, within the existing Annex C). 3.1 Changes to Part 1 There are some changes to the vocabulary used; for example the special machinery room is now called the separate refrigeration machinery room in recognition of the fact that the only thing that differentiated it from any other machinery room is that it was used solely for the refrigeration machinery. The occupancy category used to determine allowable charge limits has been changed to access category since it is based on consideration of the type of people who are given access to the area in which the equipment is located. The classification of systems according to location and access has been formalised by the introduction of Roman numerals for location (eg I, II, III and IV) and lower case letters for access (eg a, b or c). In some cases the terms have not changed but there is a better understanding of the underlying implications. For example Location Class III (all equipment in a machinery room or the open air) is not incompatible with Access Category a (general access) because a chiller or a condensing unit could be located outdoors in a place which is accessible to the general public. The most significant change is the addition of flammability class 2L and the implications for the design of systems using the new class of low GWP fluorocarbons, often known as HFO refrigerants. However it was already possible to use HFOs in conformity with EN378:2008 and although the charge restrictions look different in the new standard the calculation produces the same result; it is only the format of the equation that has changed. For example in EN378:2008 part 1 the amount of refrigerant of type A2 permitted in a human occupied space for refrigeration was max. charge = practical limit x room vol. and not exceeding 38 x LFL. For R-1234yf, listed in Annex E as an A2 refrigerant, the LFL is kg m -3 so the upper limit of charge was 11.36kg. In FprEN378:2016 the amount of refrigerant permitted for a refrigeration application is 20 % x LFL Room volume and not more than m 2 1,5. The factor m 2 is given as 26m 3 LFL and the LFL listed in Annex E for R-1234yf has been updated to kg m -3 so the upper limit of charge is 11.27kg. In this case the previous version of the standard not only permitted the use of an HFO, it allowed slightly more of it to be used than the revised standard (about 90 g more, or 0.8%). The situation for systems for human comfort is slightly more complicated because there are additional calculation methods and even more have been added. The term for human comfort is hotly debated within both EN378 and ISO5149 working groups because in reality there is no rational justification for discrimination between a split air-conditioner used to keep office occupants comfortable and one which is used to keep IT equipment, process machinery or laboratory animals at a desired temperature. Despite this discussion the current version of ISO5149 and the proposed text of EN378 still maintain the distinction and allow alternative methods of charge calculation to be used. In the 2008 edition there was one additional calculation method which was only used for human comfort and applied to all flammable refrigerants. An equation based on empirical studies of leakage is used to calculate the maximum permissible charge (m max), using the LFL, the area of the room (A m 2 ) and a factor representing the type of installation (h 0 m). The equation is m =2,5 LFL / h A / (1) There was a lower limit of applicability for the equation, of 4 LFL and no upper limit to its use. Below the lower limit the requirements of IEC would apply to this equipment, so it was not covered by EN378. The basic methodology for human comfort is retained in the 2016 edition, but the lower limit has been increased to 6 LFL for 2L refrigerants (while remaining at 4 LFL for other flammable refrigerants). More importantly an upper limit of 39 LFL for 2L and 26 LFL (or 1.5kg, whichever is greater) for other flammable refrigerants has been introduced. This places a significant cap on the amount of refrigerant that can

4 be used for human comfort. The effect of the change from the second edition to the third edition is shown for R-32 and R-290 in Figures 1a and 1b. The thinner lines are the 2008 result. Note that in 2008 there was no upper limit for this method. Figures 1a and 1b Charge limits for human comfort according to EN 378 Part 1 Annex C.2 The slight changes in the R-32 figures are the result of a small change to the LFL figure and the increase in the lower limit is due to the change from 4 LFL to 6 LFL for 2L refrigerants. The R-290 figures have not changed from 2008 to 2016, except that the introduction of the upper cap limits the maximum charge to 1.5 kg. This limit is not in the text of paragraph C.2 but it is implicit in Table C.2 which says According to C.2 and not more than the greater of m 2 or 1,5 kg. In the case of R-290 m 2 is kg so the limit is 1.5 kg. The 2016 edition also introduces (in clause C.3) an additional method of managing risk in occupied spaces under certain circumstances. The circumstances are quite tightly defined and only apply to A1 and A2L refrigerants where the charge is not more than 150kg, is not more than 195 LFL (which is 60 kg for R-32), where the system is a multi-split system in location class II, where the indoor unit is protected against various types of damage and alternative provisions to ensure safety (such as additional ventilation or safety shut off valves triggered by a refrigerant detector) are provided. This additional method applies to all refrigerating systems, not only those that are for human comfort. The scope and definitions of the standard make it clear that this also applies to heat pumps. It is less clear, but equally valid to say that it also applies to airconditioning systems. There are actually two approaches embodied in clause C.3. If there is a gap under the door of the room in which the indoor unit is fitted then an alternative to the Refrigerant Concentration Limit (RCL) is permitted. This alternative is called quantity limit with minimum ventilation (QLMV). In general for A2L refrigerants QLMV is only very slightly higher than RCL, for example for R-32 RCL is kg m -3 and QLMV is kg m -3, so the allowable charge is only 3.3% higher. If additional measures are employed (additional ventilation or safety shut off valves) then a further increase in the limit is permitted. This is termed quantity limit with additional ventilation (QLAV), even though it was pointed out during the committee discussion that additional ventilation is not the only measure permitted the name had stuck, so QLAV it is. For R-32 QLAV is based on 50% of LFL and is therefore much higher than RCL (which is based on 20% of LFL), so a calculation value of QLAV of 0.15 kg m -3 applies. In general for 2L refrigerants the QLMV values are almost the same as the RCLs and QLAV (with additional safety measures) raises the upper limit on refrigerant charge by a factor of about 2.5 A more subtle shift of emphasis with the introduction of QLMV and QLAV is that in 2008 the designer had to use equation (1) for a human comfort application and had to use the practical limit x the room volume for other applications. Now the designer is free to choose for human comfort whether to use equation (1) with a stricter upper limit or to add additional safety measures and use a larger charge. The other major change in Part 1 is that the tables of refrigerants in Annex E have been updated as far as possible, including the correction of some errors in previous versions. The tables should now be aligned with ISO817:2014, but it should be noted that we are back into a period of rapid generation of new blends so the

5 list is regularly extended. As a result of the corrections and adjustments it is recommended that calculations are always done with the most up to date version of the tables. 3.2 Changes to Part 2 A lot of work has been done on the alignment of part 2 with the Pressure Equipment Directive and the Machinery Directive. The intention of these changes was to make the standard simpler to apply, but, while well-meaning, there is a concern that the process has perhaps been over-simplified. The flow charts in section have been retained but streamlined and they are generally an improvement over the old charts. The table of relative pressures (this was Table 3 in the 2008 standard) has been removed and the content is described in paragraph , immediately before the flowcharts. This is a more logical place for the information, but the removal of the chart, which was originally introduced many years ago in BS4434, is regrettable as it was a very handy way to explain the relative positions of the various pressures. The chart s days have been numbered ever since the PED was originally introduced in 1997 because the directive used PS ( Pression Service ) for both components and systems, whereas in the original chart there was a clear distinction between design pressure for components and maximum working pressure for systems. Once that distinction was removed the chart became more misleading and less useful. Four additional annexes have been added; on stress corrosion cracking, leak simulation test, commissioning procedure and ignition sources. There is a case that this information does not belong in a safety and environment standard, but it helps in the implementation and since all four new annexes are informative it seems like a positive step to make the information readily available. 3.3 Changes to Part 3 The changes to part 3 are not as significant as for parts 1 and 2, and primarily relate to the introduction of flammability class 2L and the change of name of the special machinery room. This term caused a lot of confusion because the room was not special (the requirements are exactly the same as for a regular machinery room) and neither is the machinery. The term was coined as a translation of the German Besondere Maschinraum and while besondere can be translated as special, it is in the sense of reserved exclusively for or dedicated. After a lot of discussion the term separate refrigeration machinery room was adopted as a more accurate translation of the German, reflecting the fact that this is a room which only contains refrigeration machinery and other types of machinery are not permitted in the room. Some additional text was added at clause 4.5 regarding the installation of equipment in a space which is neither an occupied space nor a machinery room. A typical example, which caused some difficulty in application of the previous wording, is the installation of defrost valve stations in an unoccupied roof void. There was a lot of discussion about the prohibition of water sprinkler systems in ammonia machinery rooms, with high level lobbying from the fire protection sector to have the ban lifted. There is however a real concern about the adverse effects of adding water to liquid ammonia or aerosol clouds because the heat in the water would cause very rapid boiling of the liquid ammonia. So sprinklers were permitted only on condition that they cannot be manually over-ridden and they can only be activated by heat. 3.4 Changes to Part 4 There are fewer changes to part 4 and they are mainly concerned with the addition of procedures for evacuating gas from a system (usually air and water vapour) before charging with refrigerant and for testing halocarbons for moisture. 4. FLAMMABILITY CONSIDERATIONS As mentioned in the introduction, compliance with all the requirements of EN378 does not ensure that the requirements of the Dangerous Substances and Explosive Atmosphere Regulations are covered. Almost all of the refrigerants in flammability classes 2L, 2 and 3 are included in the definition of dangerous substances in the 2002 regulations because they have a hazard statement under the Globally Harmonized System of Classification and Labelling of Chemicals, published by the UN and adopted in the EU by the CLP regulations (EC/1272/2008). The one exception at present is R-1234ze(E) because while it meets the criteria for classification as flammable in ISO817:2014 it is not considered flammable under the CLP regulation. It is

6 therefore subject to all of the requirements of a 2L fluid in EN378, including charge restrictions, but it is not necessary to complete a hazard analysis in line with DSEAR. It is recommended for this anomaly that the hazard analysis should be conducted anyway and stored with the rest of the system design information. For all other class 2L, 2 and 3 refrigerants the requirements of DSEAR must be followed. This will usually be the completion of a risk assessment and hazard analysis for the plant in question to identify and quantify the risks associated with ignition of the dangerous substance. This assessment needs to be conducted for the whole installation not just the occupied space or the machinery room. There has been significant discussion during the development of FprEN378:2016 of the relevance of many years of safe working with ammonia but we should be wary of extrapolating that experience too far or too carelessly. Similarities are that ammonia, like HFOs, has a low burning velocity and is difficult to ignite. Differences are that ammonia has a smell and small, persistent leaks are obvious. It is lighter than air, unlike all of the A2L refrigerants, so it will not accumulate in low lying areas. When ammonia burns it produces nitrogen and water all HFOs produce (among other things) hydrofluoric acid which is far more toxic than ammonia. Due to its toxicity ammonia is not used in access category a or b installations in small systems, so the good safety experience has been in the context of use in an industrial environment (access category c). It does not follow that the same rules can be used when less well informed people are in close proximity to the refrigerant. It can readily be seen that there are more differences than similarities; the charge limits in EN378 for A2L refrigerants are consequently quite stringent (although there is an argument that they should be even more so). It will take several years of experience, risk assessment and further negotiation before these limits can be further relaxed and it is likely that they will never be as generous as those for A1 refrigerants, where the charge limit is based on toxicity, not flammability. 5. CONCLUSIONS After seven years of discussion and debate the process for the updating of EN378 is nearly complete. This length of time is difficult to defend in a time when refrigerant requirements are changing very rapidly, but the task is complex and requires the balancing of numerous competing requests for change (or in some cases no change). It is difficult to see how the process could be significantly shortened without significantly upsetting at least some of the interested parties. The current version is still too complicated and is not 100% suitable for all circumstances. In particular the increased use of flammable refrigerants, whether they are class A3 hydrocarbons or class A2L HFOs, will result in further refinements to the standard as real-world experience of implementation is gained. In some cases some stringent guidelines may be relaxed or simplified and in other ways it may be necessary to tighten up some requirements. Expect to see extension of strategies currently only permitted for human comfort to other systems and a general rationalisation of the requirements. In particular wider use of A2Ls in supermarkets, chillers and other small to medium-sized systems will require further work to make the standard easy to use while still ensuring safety. The way in which companies do their system design will not fundamentally change with this revision of EN378 but if they choose to use mildly flammable refrigerants they must follow all of the legal and safety standard requirements associated with flammability. This goes beyond the scope of EN378, which is not harmonized with those regulations. It does not mean that all electrical equipment needs to be flameproof of the type found in petrochemical plant, but it does mean that if the safety data sheet for the refrigerant has the hazard phrase H220 or H221 then a risk assessment conforming to the requirements of DSEAR must be completed and must cover maintenance and service activity as well as normal operation and standstill. The main issues with this revision of the European safety standard do not lie with the text of the standard itself, but in the other regulations which will apply if companies are encouraged by the introduction of the new flammability class to adopt the new lower flammability refrigerants. This does not make their use impossible, but it is an extra layer of difficulty to be overcome.