UL White Paper - Revisiting Flammable Refrigerants


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UL White Paper - Revisiting Flammable Refrigerants

  1. 1. White Paper:Revisiting FlammableRefrigerants
  2. 2. White Paper:Revisiting Flammable RefrigerantsIntroductionSince the 1989 Montreal Protocol and its successor agreements, the world ofrefrigerants has been marked by change. In the search for more environmen-tally-preferable refrigerants, technology has moved from chlorofluorocarbonsto a host of alternative substances. Many of these substances are serving asinterim measures, until the phase-out of ozone-depleting and global-warmingrefrigerants meets the targets set by the U.S. Clean Air Act. The journey towardcompliance has caused the HVAC equipment and appliance industries to revisit thepotential use of substances that have good environmental and thermodynamicproperties as refrigerants, but which are also, unfortunately, flammable.This paper explores the ongoing efforts of freezing a simple pail of water, a robustby those who are anticipating the vapor compression refrigeration industrymore widespread use of flammable was developed.1 Today, ice making alonerefrigerants in HVAC equipment and is a nearly one billion-dollar industryappliances, with the principle focus on in the U.S. Along the way, scientists,the use of hydrocarbons as refrigerants. engineers and probably more than aIt is hoped that this paper will initiate few tinkerers2 have experimented witha dialog among stakeholders, and numerous potential refrigerants.increase the likelihood that the more Ammonia (R717) was an early choice forwidespread use of flammable refrigerants breweries and continues to be a populardoes not result in a decline in safety. refrigerant in industrial applications, including food processing, pharmaceuticalAnticipating the Increased and, even today, breweries.3 Noxious but non-flammable sulphur dioxide (R764)Use of Flammable became popular for small refrigeratingRefrigerants in the U.S. systems, and was in widespread use inIt may be surprising to learn that the first the U.S. into the 1940s.4 Methyl chloridecommercial refrigerant was a flammable (R40) experienced brief popularity, butrefrigerant. In 1850, an ethyl ether vapor its flammability and potential toxicitycompression system for ice making was ultimately made it unsuitable as adeveloped. From that humble beginning refrigerant. Propane (R290) was touted aspage 2
  3. 3. White Paper: Revisiting Flammable Refrigerantsa replacement for ammonia refrigerantin the 1920s.5 Isobutane (R600a) was first UL is involved in HVAC and appliance standards developmentused as a refrigerant for small systems in worldwide. It has technical staff participating in leadership andthe 1920s but, as with other flammable expert roles on national and international committees.refrigerants (except ammonia), it Mr. Thomas Blewitt, PE is the Technical Advisor for the TC61 US TAG for householdquickly fell out of use when chloro- and similar electrical appliances. He is UL’s Principal representative to the USfluorocarbon (CFC) refrigerants were National Electrical Code Panel 17 that covers appliances. He also is a member ofintroduced for commercial use in 1931.6 IEC TC61 Maintenance Team for temperature limits for insulation and resistanceCFCs had a 60 year run as the refrigerants to heat and fire.of choice until they were identified in the Mr. Randall Haseman, PE is the Technical Advisor for the SC61Clate 1970s as ozone depleting substances. US TAG for household appliances for refrigeration.The phase-out of CFC refrigerantsbegan a little over 10 years later. Mr. Brian Rodgers is the Convener of the IEC61C Maintenance Team (MT 1) for motor compressors. He is also a member of ASHRAE Standing Standard Project CommitteeA mature safety system had evolved 15 that maintains ASHRAE 15, the Safety Standard for Refrigeration Systems.over the decades, as various industriessettled upon refrigerants which were Mr. Barry Karnes, PE is UL’s Alternate representative to the USgenerally non-toxic and non-flammable, National Electrical Code Panel 11 that covers air conditioners.which provided consistent performance, Mr. Scott MacLeod is a member of ASHRAE Standing Standard Project Committeeand which were relatively inexpensive.7 34 that maintains ASHRAE 34, the Standard for DesignationHousehold refrigerators used the CFC and Safety Classification of Refrigerants.R12. Larger commercial refrigeratorsused another CFC, R502, while air Mr. Robert Wozniak, PE is a member of the Technical Committee of theconditioners used R11 (CFC) and R22 National Fuel Gas Code, NFPA 54/ANSI Z223.1 and the Accredited Standards(HCFC). Manufacturers ensured that their Committee Z21/83 on Performance and Installation of Gas-Burning Appliancesequipment was appropriately designed and Related Accessories.and constructed using well-establishedcriteria and standards, chose the correct The Challenges Posed by this, they used tubing, vessels and otherrefrigerant for the application, and then Flammable Refrigerants components with sufficient mechanicalsold the equipment for installation and Vapor compression refrigeration in strength to handle the developeduse in accordance with equally well- appliances is a closed system that pressures under expected normal andestablished standards and codes. circulates a volume of refrigerant and abnormal operating conditions.However, beginning with the phase-out lubricant under pressure. This system Because the typical HVAC and applianceof CFCs, the choice of refrigerant has typically operates under variable refrigerant gas (excluding ammonia)increasingly become a complicating environmental conditions, and often was non-toxic in the volumes usedfactor in equipment design, construction, must be capable of adjustment to and non-flammable, the potentialinstallation and use. In the U.S., the more meet the end use application. From for gas leakage or explosion was notwidespread use of pure hydrocarbon a traditional electrical equipment considered to be a safety concern, exceptrefrigerants, flammable hydrocarbon safety perspective (electric shock, under fire conditions. In such cases, therefrigerant blends, or halo-hydrocarbon fire and casualty hazards), appliance refrigerant system was required to haveblends with flammable hydrocarbons designers have sought to reliably a means for the controlled venting ofhas further complicated matters. contain the refrigerant. To accomplishpage 3
  4. 4. White Paper: Revisiting Flammable Refrigerantsrefrigerant, before pressure build-up blend additionally depends upon the Smaller equipment such as householdcould cause an explosion hazard. properties of the blended gasses, and refrigerators can also leak. Improved whether they separate into individual containment over non-flammableAside from locations where large component gasses (fractionate). 12 refrigerant systems is also appropriate,quantities of refrigerant might be found but mechanical ventilation or other(e.g., large commercial / industrial Small quantities of flammable refrigerant means to disperse the refrigerant mayfacilities), there has been limited concern discharged into an open area may not be practical for such appliances.for the safety of refrigerant-containing disperse at a rate that ensures that Equipment designers must then lookappliances in all manner of occupancies.8 the LFL is not achieved or is achieved to avoid placing potential ignitionThis would include locations where a for a very brief time period. However, sources in locations (e.g., a storagenumber of appliances are stored or used for larger quantities of refrigerant, compartment, hollow in a wall, etc.)(e.g., warehouses, retail locations)’9 or or in situations in which the leaked that could yield a flammable gas andhow the appliances are transported, refrigerant is contained in a smaller air mixture in the event of a leak. Theserviced or disposed of. However, if a volume space or in which the leaked designer, of course, can often do littleflammable refrigerant were to be used in refrigerant accumulates (e.g., heavier about other possible ignition sourcesthese appliances, it cannot be assumed than air refrigerant), it is more likely that in the installed environment.that safety is adequately assured. the LFL can be reached and sustained. All equipment is serviced and, ultimately,Hydrocarbon refrigerants (HCs) present Supermarket refrigerated cases and disposed of. These activities also offera risk of fire and explosion hazard if building air conditioning systems opportunity for leakage. The equipmentthere is a refrigerant leak. The vapor typically have larger quantities of design must minimize the risk of firewithin the closed refrigeration system is refrigerant. Because these systems or explosion during servicing, andnot flammable until oxygen is present are often assembled on-site, they are service personnel must have sufficientat the location of the leak, or in the more often subject to leaks.13 Indeed, knowledge to safely do their job.location(s) where the hydrocarbon gas leakage is assumed for field-assembled Upon disposal, the refrigerant shouldtravels after leaking from the system. equipment. The Clean Air Act now be recovered, though relatively smallIf the gas and air mixture is within the requires refrigerant leaks to be repaired propane or isobutane refrigerantupper and lower flammability limits (UFL for systems containing over 50 pounds of charges could conceivably be releasedand LFL respectively)10 for the particular refrigerant if the leakage is determined to the air in a controlled manner.15refrigerant, the mixture is flammable to be 35% or greater in a 12 month period Parties involved in the disposal of HVACin the presence of an ignition source. for commercial refrigeration, and 15% for equipment and appliances should alsoHot surfaces11 and electrical arcs, such comfort cooling and other appliances.14 have sufficient knowledge to performas those present at the contacts of Therefore, the use of a flammable their job safely, and should be able toelectrical switching contacts (switches, refrigerant in such equipment would identify equipment with a flammabletemperature and humidity controls, require improved containment features refrigerant charge. For their part,etc.), are the principle potential ignition over those found in non-flammable equipment designers must anticipatesources in HVAC and appliances. refrigerant systems. It would also the need to evacuate the refrigerant require mechanical ventilation and otherThe same concerns hold true for from equipment upon disposal and to mitigation procedures at the installationother flammable refrigerants, as well facilitate identification of locations on the site to avoid the presence of a flammableas for refrigerant blends containing equipment intended for this purpose. gas and air mixture at potential ignitionflammable refrigerant components. sources, either on the equipment or Most appliances, room HVAC equipmentThe presence of a flammable gas and in the installation environment. and split systems are factory charged,air mixture from a leaking refrigerantpage 4
  5. 5. White Paper: Revisiting Flammable Refrigerantsand subsequently transported with the These and similar such concerns involve manufacturers to expand the use ofcharge present, and may be transported a number of potential stakeholders hydrochlorofluorocarbons (HCFCs) wheremultiple additional times throughout the who individually and collectively have a they could, and to use hydrofluorocarbonsproduct’s useful life. Vehicle transport key role in ensuring the safety of HVAC (HFCs) in applications as diverse ascan jar or vibrate the parts containing equipment and appliances containing household refrigerators and automotiverefrigerant, increasing the risk of leakage. flammable refrigerants. As the publisher air conditioning. Manufacturers began toDesigners must account for these of equipment safety standards for use hydrocarbons (HCs) as well aroundconcerns in the equipment design, as HVAC equipment and appliances, this time.well as the equipment packaging. Underwriters Laboratories Inc. (UL) has As noted earlier, isobutane (R600a) had identified stakeholder interests thatIf an individual appliance has a small long ago been used as a refrigerant. it believes to be relevant to the totalrefrigerant charge, but there are many With the phase out of CFCs, isobutane safety system, in which safety standardssuch appliances at a given location was reintroduced as a refrigerant for are an essential element. These areas(e.g., a warehouse or tractor-trailer), household refrigerators and freezers of interest are depicted in Figure 1.the aggregate amount of flammable in Japan16 and Europe, and foundrefrigerant may be relatively large. Stakeholder identification is just a widespread use and acceptance.17Though it is unlikely under normal first step in undertaking a unified and Though ANSI/UL 250, the U.S. safetycircumstance that all of the appliances coordinated review of the potential standard for household refrigerators,might simultaneously leak, a warehouse impact of the wider use of flammable anticipated as early as the 1990s thefire or transportation accident refrigerants in HVAC equipment possible use of flammable refrigerantscould lead to the leakage of large and appliances. Gaps in codes and in the U.S., they were not introducedvolumes of flammable refrigerant. standards for installation and use, in U.S. appliances until 2008. including the applicable equipmentWhile the risk conditions noted above An interim solution, HCFCs are also safety standards, need to be identifiedcan often be anticipated in the design ozone-depleting substances and were and addressed. Education and trainingprocess, it is much more difficult to subject to a longer-term phase out for installers, service personnel,anticipate the abuse of equipment in use, than CFCs. In September 2007, the operators of storage and retailand to design appropriate safety features signatories of the Montreal Protocol facilities, fire fighters and inspectionto mitigate that risk. For example, agreed to a more aggressive phase-out professionals will also be important.vending machines are checked for the of HCFCs. Table 1 describes the phase-outrisk of overturning in cases where the The remainder of this paper will explore timetable under the U.S. Clean Air Act.equipment is rocked back and forth to the most important factors that The imminent HCFC phase-out, coupleddislodge a vended product. But what type are expected to result in flammable with recent efforts to improve energyof rocking test would adequately assess refrigerant HVAC equipment and efficiency of certain appliances as wellthe risk involving a vending machine with appliances, the current state of safety as experience outside of the U.S. market,flammable refrigerant? It can also be a standards, and some near-term has substantially renewed interest inchallenge to ensure that an installation activities to address gaps. the U.S. toward flammable refrigerants,site doesn’t pose an unacceptable risk. isobutane and propane in particular,For example, how can local building U.S. Federal Regulatory along with blends using these substances.authorities anticipate and address the Environment Finally, in September 2008, ice-creampotential risk posed by having multiple CFC and HCFC Phase Out maker Ben and Jerry’s introduced aappliances containing flammable commercial ice cream case into therefrigerant in a single-family residence The phase-out of CFCs began in 1991, a U.S. market, representing the first U.S.or in a children’s play area or classroom? change that drove equipmentpage 5
  6. 6. White Paper: Revisiting Flammable RefrigerantsFigure 1 — Stakeholder Interest Areas Mobile Industrial Flammable Servicing 2L Refrigerant Refrigerants (Retailer, Independent – (ACS, Bulk Suppliers, NATE…, Vendors, Local Suppliers…) ASHRAE 34 Owner…) Regulations Regulations EPA SNAP DOT Other? Other? Channel Installation (Retailers, (home, office, Appliances Disposal Distributors – convenience / grocery (AHAM, AHRI, MAFSI…, Designers stores, restaurants, (transfer, landfill, NAMA, NAFEM…) – FCSI… , cold storage, schools, recycler…) Shippers…) institutional…) Regulations EPA State / Local Codes NFPA 70 Product Safety Standards NFPA 58 UL 250 (60335-2-24) Fire Service Mechanical ASHRAE 15 UL 471 NFPA 90A/90B UL 984 (60335-2-34) (Fire Departments, NFPA, ICC, Fire Marshals…) Officials IMC, UMC, UL 484 (60335-2-40) IFC, NFPA 1 UL 541 other? UL 474 (60335-2-40) UL 1995 (60335-2-40) Regulations UL 921 OSHA UL 1258 State / Local UL 399 CPSC (future?) otherTable 1 — Phase-out of HCFC’s in US US Scheduled Phase-out of HCFCs18 Year % Reduction Consumption Implementation of HCFC Phase-out Per Clean Air Act and Production# 2010 75.0% No production or importing of HCFC 142b and HCFC 22, except for use in equipment manufactured before 2010. 2015 90.0% No production or importing of any HCFCs, except for use in equipment manufactured before 2020. 2020 99.5% No production or importing of HCFC 142b and HCFC 22. 2030 100.0% No production or importing of any HCFCs. # Using prior cap as baselinepage 6
  7. 7. White Paper: Revisiting Flammable Refrigerantsuse of a hydrocarbon refrigerant in a Table 2 — Comparison of Refrigerant GWP and ODP 22conventional commercial food serving Refrigerant Global Warming Ozone Depletingand display application in over 50 years. Potential (GWP) Potential (ODP)The self-contained freezer case, made by R 134a 1430 0Unilever,19 was of a cold wall constructionthat used propane refrigerant. R290 3.3 0 R600 3 0Notwithstanding the movementtoward HC refrigerants, HFCs currently R600a 3 0remain the predominant choice to R1234 yf 4 0replace HCFCs. However, under the R717 0 0European Climate Change Programme(ECCP), a 2006 regulation for all F-gases(fluorinated gases) “makes it mandatory See Table 2 for some examples of the flammable refrigerants in refrigerationto contain via the control of systems GWP for flammable refrigerants. equipment and air conditioners may alsovia leakage detection systems that lead to its use in other appliances. For Over time, these various initiatives canare regularly checked, to recover and example, a storage tank water heater be expected to contribute to a reductionrecycle, to monitor and archive, to could potentially be more efficient if in use of HFCs as an alternative to HCFCs,label, to train and certificate servicing a reverse-cycle (heat pump) system and lead to increased use of HCs.personnel, to restrict marketing of with a relatively small flammableF-gases for emissive uses, etc.”20 Energy Efficiency refrigerant charge were used instead of a large resistance-heating elementAutomobile manufacturers selling In addition to being affected by to maintain the temperature of thein the European market must also the phase-out of ozone-depleting water. A similar technology could becontend with the EU’s directive relating refrigerants, HVAC equipment and used in a clothes dryer to dehumidifyto emissions from air-conditioning appliances employing refrigerants are clothing, instead of drying solely bysystems in motor vehicles (2006/40/ subject to a variety of regulations in resistance heat or heat of combustion.EC), also known as the MAC Directive.21 the U.S. Such equipment must meetThe MAC Directive will eliminate the the appropriate electrical, mechanical, U.S. EPA SNAPmajor mobile air conditioning market fire and public health requirements offor the popular HFC 134a, and has led It is only logical that the transition state and local jurisdictions. Increasingly,manufacturers to explore a “lower toward more environmentally preferable such equipment must also meet stateflammability” refrigerant (HFO 1234 refrigerants and energy savings has and federal energy efficiency goals (e.g.,yf), as well as CO2 and other options. renewed interest in HC refrigerants Energy Policy and Conservation Act23) in appliances. And arguably the mostSomewhat related is the move toward that can be expected to drive the search significant regulation affecting the use“natural refrigerants.” Looking to avoid for new and more efficient technologies, of flammable refrigerants in appliancesaltogether the transition to HFCs, which including the types of refrigerant used. is the Clean Air Act, administered byhave high global warming potential As recently of September 2010, the U.S. the U.S. Environmental Protection(GWP), a consortia of equipment Department of Energy has proposed Agency (EPA), under its Significantmanufacturers and retailers have standards for residential refrigerators New Alternatives Policy (SNAP).included HC refrigerants in their and freezers that are expected to lowerplans to meet energy regulations. According to the EPA, the purpose energy use by as much as twenty-five of its SNAP program is ”to allow a percent.24 The energy efficiency appeal ofpage 7
  8. 8. White Paper: Revisiting Flammable Refrigerants safe, smooth transition away from Vapor Compression Refrigeration and Air Conditioning ozone-depleting compounds by End-Uses# identifying substitutes that offer lower overall risks to human health and • Chillers typically cool water, which is use, e.g., in hotels, restaurants, the environment.”25 SNAP specifically then circulated to provide comfort and convenience stores. identifies the use of refrigerants used cooling throughout a building • Household refrigerators and freezers in HVAC equipment and appliances or other location. Chillers can be are intended primarily for residential as a focus of the policy, including classified by compressor type, use, although they may be used chillers, cold storage warehouses, including centrifugal, reciprocating, outside the home. Household retail food refrigeration, vending scroll, screw and rotary. freezers only offer storage space machines, water coolers, commercial • Cold storage warehouses are at freezing temperatures, unlike ice machines, household refrigerators used to store meat, produce, dairy household refrigerators. Products and freezers, residential dehumidifiers products and other perishable with both a refrigerator and freezer and residential and light commercial goods. The majority of cold storage in a single unit are most common. air conditioning and heat pumps. warehouses in the United States • Residential dehumidifiers are EPA’s SNAP has authorized HCs use ammonia as the refrigerant in a primarily used to remove water (propane, butane and blends) as vapor compression cycle, although vapor from ambient air for comfort alternative refrigerants for industrial some rely on other refrigerants. or material preservation purposes. process refrigeration only. For all other • Retail Food Refrigeration includes all While air conditioning systems applications, such refrigerants are not yet cold storage cases designed to chill often combine cooling and de- authorized as substitutes for refrigerants food for commercial sale. In addition humidification, this application employed today.26 However, there are to grocery cases, the end-use includes serves only the latter purpose. exemptions to this restriction for small convenience store reach-in cases and volume producers of substitutes, and • Residential and light commercial restaurant walk-in refrigerators. in cases where end-use equipment air conditioning and heat pumps is being test-marketed or deployed • Vending machines are self-contained includes central air conditioners for research and development.27 units that dispense goods that (unitary equipment), window must be kept cold or frozen. air conditioners, and other In response to the increased interest in products. Blended HFC 410A has HC refrigerants, the EPA issued a Notice of • Water coolers are self-contained units supplanted HCFC-22, a class II Proposed Rulemaking (NPRM) in the U.S. providing chilled water for drinking. substance, as the most common Federal Register in May 2010. The NPRM They may or may not feature refrigerant for this application. recommends that “isobutane, propane, detachable containers of water. HCR–188C28 and HCR–188C1 be acceptable, Table content extracted from EPA # • Commercial ice machines are used subject to use conditions, as substitutes web content: http://www.epa.gov/ in commercial establishments for R–12 and R–22 in household ozone/snap/refrigerants/index.html to produce ice for consumer refrigerators, freezers, and combination refrigerator and freezers and commercial refrigeration (retail food refrigerators and freezers—stand-alone units only”).29 The NRPM also references product safety standards ANSI/UL 250 and ANSI/UL 471,page 8
  9. 9. White Paper: Revisiting Flammable Refrigerants associated with workplace handling of Disposal# LP-Gas, thoroughly cover transportation of flammable gas in cylinders. “Refrigeration and air-conditioning that refrigerant is recovered from equipment that is typically dismantled equipment before the final disposal of HVAC equipment and appliances on-site before disposal (e.g., retail food the equipment. If the final person in containing flammable refrigerant could refrigeration, central residential air the disposal chain accepts appliances be identified as hazardous material conditioning, chillers, and industrial that no longer hold a refrigerant cargo due to the presence of flammable process refrigeration) has to have the charge, that person is responsible gas. 49 CFR Part 177.834 (Packages refrigerant recovered in accordance for maintaining a signed statement secured in a motor vehicle) states: with EPA’s requirements for servicing from whom the appliance/s is being “Any package containing any prior to their disposal. However, accepted. The signed statement hazardous material, not permanently equipment that typically enters the must include the name and address attached to a motor vehicle, must be waste stream with the charge intact of the person who recovered the secured against shifting, including (e.g., motor vehicle air conditioners, refrigerant, and the date that the relative motion between packages, household refrigerators and freezers, refrigerant was recovered, or a copy of within the vehicle on which it is and room air conditioners) are subject a contract stating that the refrigerant being transported, under conditions to special safe disposal requirements. will be removed prior to delivery.” normally incident to transportation. Under these requirements, the final Content taken from EPA web site # Packages having valves or other person in the disposal chain (e.g., fact sheet: http://www.epa.gov/ fittings must be loaded in a manner a scrap metal recycler or landfill ozone/title6/608/608fact.html to minimize the likelihood of owner) is responsible for ensuring damage during transportation.” Fortunately, the Federal Motor Carrier Safety Administration (an agency of theindicating that equipment must meet containing these refrigerants” to DOT) reports that “crashes involvingthe requirements of these standards minimize the risk of fire.30 large trucks-those with a gross vehicleto use one of the specified flammable U.S. DOT weight rating of more than 10,000refrigerants. The proposal also specifies pounds-carrying hazardous materialsthat hoses and piping be color coded The U.S. Department of Transportation (hazmat) are relatively rare.”32to identify the presence of flammable (DOT) publishes requirements forrefrigerants in these appliances, and “packaging”31 which apply to cylinders U.S. OSHAthat unique fittings and service ports be that may contain liquefied petroleum gas OSHA publishes regulations intendedprovided to avoid accidental connection (LP-Gas). These requirements describe to protect the safety or health of thoseof inappropriate service equipment while the types and sizes, construction, employees working in federally-regu-facilitating recovery of refrigerant during testing, inspection and markings of lated workplaces. National consensusservice or disposal of the appliances. these cylinders, often simply referred standards are frequently referenced for to as “DOT cylinders.” The requirementsFinally, the NPRM proposes that this purpose and, in accordance with are well established for the transporttechnicians working with equipment 29 CFR 1910.7(c), ANSI/UL standards for of LP-Gas cylinders for combustionusing flammable refrigerants be refrigerators and freezers, heating and equipment and, together with regulations“specifically trained in handling air conditioning equipment, associated from the U.S. Occupational Safetyflammable refrigerants service or components and appliances fulfill the and Health Administration (OSHA)dispose of refrigerators and freezers requirements. Such products, oncepage 9
  10. 10. White Paper: Revisiting Flammable Refrigerantslisted by a nationally recognized testing safety. UL standards are part of an standards and codes relevant tolaboratory (NRTL) using the accepted overall safety system of coordinated flammable refrigerants, as follows:standards, may be used in the workplace. standards and codes to facilitate safe • ANSI/ASHRAE Standard 34, Designation installation and use of equipment. TheyOSHA regulations addressing storage and and Safety Classification of Refrigerants complement the electrical installationhandling of LP-Gases are documented requirements of the National Fire • ANSI/UL 2182, Standard forin 29 CFR 1910.110. While these Protection Association (NFPA), notably the Safety for Refrigerantsregulations do not anticipate LP-Gas National Electrical Code (NFPA 70), and ® • ANSI/NFPA 58, Liquefiedrefrigerants, they do cite compliance mechanical refrigeration requirements Petroleum Gas Codewith DOT container requirements and 33 of the American Society of Heating,location of containers in buildings. • ANSI/ASHRAE Standard 15, Safety Refrigerating and Air-ConditioningOf particular relevance for the servicing Engineers (ASHRAE), Standards 15 and 34. Standard for Refrigeration Systemsof HVAC equipment and appliances • ANSI/UL 207, Standard for Safety for Installation codes for HVAC andin-place is 1910.110 c) 5, which states Refrigerant-Containing Components refrigeration equipment are publishedthat “when operational requirements and Accessories, Nonelectrical by International Codes Council (ICCmake portable use of containers International Mechanical Code, • ANSI/UL 250, Standard for Safety fornecessary and their location outside of Chapter 11) and the International Household Refrigerators and Freezersbuildings or structure is impracticable, Association of Plumbing and Mechanicalcontainers and equipment are permitted • ANSI/UL 471, Standard for Safety for Officials (IAPMO Uniform Mechanicalto be used inside of buildings or Commercial Refrigerators and Freezers Code, Chapter 11). Both mechanicalstructures….” There are also caveats to codes reference ASHRAE 15 and 34, • ANSI/UL 1995, Standard for Safety forthis allowance and they are comparable with additional requirements. Heating and Cooling Equipmentto the requirements of NFPA 58(Liquefied Petroleum Gas Code). In addition, requirements for the storage, • ANSI/UL 484, Standard for Safety for use and handling of refrigerants are Heating and Cooling EquipmentInstallation Requirements published by ICC (International Fire • ANSI/UL 474, Standard for Safety forand Equipment Safety Code, Section 606) and the NFPA (NFPA Heating and Cooling EquipmentStandards Environment 1, Chapter 53). These model fire codes impose safety requirements for occupancy • UL 984, Standard for Safety forFulfilling government regulations is based on the volume and safety group Refrigerant Motor Compressorsonly part of the compliance landscape of the refrigerant. As with any of the • ANSI/UL 60335-2-34, Standard forfor HVAC equipment and appliance model codes (electrical, mechanical, fire, Household and Similar Electricalmanufacturers. Equipment must also etc.), local jurisdictions can implement Appliances, Part 2: Particularcomply with safety standards in order to variations and additional requirements Requirements for Motor-Compressorsbe installed in a workplace or (depending for equipment, and may elect to do soupon the local jurisdiction) in other for HVAC equipment and appliances The first three standards listed aboveoccupancies. Retailers, insurers and employing flammable refrigerants, are applicable to refrigerants, whileother parties may also require evidence especially in densely populated areas. the remainder are applicable toof compliance with safety standards. equipment and components. These The remainder of this paper summarizesIn the U.S., UL is the principal standards and other standards also address the current status of many of thedeveloper addressing electrical ammonia, but that refrigerant isappliance and HVAC equipment outside the scope of this paper.page 10
  11. 11. White Paper: Revisiting Flammable RefrigerantsRefrigerant Standards Table 3 — Refrigerant Safety GroupsANSI/ASHRAE Standard 34, Designation Refrigerant Safety Groups (ASHRAE 34 and ISO 817)and Safety Classification of Refrigerants Lower Toxicity Higher Toxicity#According to the standard, “ASHRAE No Flame Propagation a1 B1 (includes R123)Standard 34-2010 is intended to 2L a2L (includes HfO 1234 yf) B2L (includes ammonia)establish a simple means of referringto common refrigerants instead of Lower Flammability a2 B2using the chemical name, formula, or Higher Flammability a3 (includes hydrocarbons) B3trade name. It establishes a uniform # Except for ammonia, refrigerants classified as Bx are not permitted in appliances.system for assigning reference numbers,safety classifications, and refrigerantconcentration limits to refrigerants.”34 ANSI/UL 2182, Standard for cycle equipment does not includeMost notable in the context of this Safety for Refrigerants the storage of LP-Gas, which wouldpaper is the ASHRAE 34 designation This standard contains test procedures include gas in cylinders such as mayof HC refrigerants as A3 – high and methods to evaluate refrigerants be used by service personnel. For smallflammability, lower toxicity (see Table 3 and to authoritatively mark containers HVAC and appliances, the cylindersfor illustration of classification scheme). according to the extent of the are likely to be DOT cylinders.37 refrigerant’s flammability. The refrigerantsA significant inclusion in the latest It would seem likely that the well- covered in this standard are those usededition (Clause 6.1.3) is the optional 2L established practice for handling LP-Gas as components of air-conditioning andsubclass added to the existing Class 2 cylinders used in barbeques and similar refrigeration equipment.35 The standardflammability classification, signifying applications would be appropriate for was created in 1994 as a supplementClass 2 refrigerants with a burning the filling, transport and storage of to ASHRAE 34, and is for intended forvelocity less than or equal to 10 cm/s. cylinders used for servicing household use in conjunction with end productClass 2L refrigerants include R32 and and smaller commercial HVAC equipment appliance standards. It enables the char-the newer HFO 1234 yf, which is being and appliances. However, NFPA 58 does acterization of flammable refrigerantspromoted for use in motor vehicles. not specifically anticipate refrigerant (blends in particular) with respect to recovery/recharge in clause 6.2.2, where itThe potential market for 2L refrigerants fractionalization, flammability and lists applications where containers may bein HVAC equipment and appliances auto-ignition. The requirements do not brought into buildings, nor in clause 6.19is currently unknown and further yet address the additional characteriza- where specific uses are cited. Temporaryequipment standards development is tion needed for Type 2L refrigerants. use for training and demonstrationneeded. Otherwise, a 2L refrigerant will ANSI/NFPA 58, Liquefied purposes (clause 6.19.9) is limited to 20simply be handled as a Class 2 (e.g., A2) Petroleum Gas Code lbs. of propane in a cylinder, althoughrefrigerant. Proprietary studies done to This code applies to the storage, the cylinder may have a larger capacity.date have suggested that equipment andinstallation requirements that result in handling, transportation and use of Equipment Standardsignition sources being kept a distance LP-Gas. It indicates that “refrigerationabove the floor (or not directly below cycle equipment and LP-Gas used as a ANSI/ASHRAE Standard 15, Safety refrigerant in a closed cycle” is outside Standard for Refrigeration Systemswall mounted equipment) may facilitateintroduction of such refrigerants. the scope of the code.36 However, the ASHRAE Standard 15-2010 is directed 2008 Handbook for NFPA 58 states toward the safety of persons and that the scope exclusion for refrigerant property on or near the premises wherepage 11
  12. 12. White Paper: Revisiting Flammable Refrigerantsrefrigeration facilities are located.38 While air conditioners employing flammable Code®, ANSI/NFPA 70.42 Supplementthe standard covers installations involving refrigerants to A2 and A3 refrigerants.] SA of the standard documents thethe full range of potential refrigerant requirements for refrigerators (freezers, The ASHRAE committee responsiblecharges in equipment, it defers to the for Standard 15 (SSPC15) continuously etc.) having flammable refrigerants.listing of equipment complying with maintains the standard and has formed It addresses concerns regarding theappliance safety standards for charges an Ad Hoc group to address the new 2L flammability of the refrigerant byof less than 3 kg, with some restrictions. refrigerant sub-class created by SSPC34 limiting the amount of charge accordingFor example, institutional occupancies (committee responsible for ASHRAE 34). to auto-ignition temperature or heat ofare permitted only up to 50% of the combustion, and controlling for design ANSI/UL 207, Standard for Safety forrefrigerant concentration limit (RCL) 39 and construction variables that can Refrigerant-Containing Componentspermitted for other occupancies. and Accessories, Nonelectrical contribute to the risk of fire. See Table 5 for a summary of the requirements.Group A3 and B3 refrigerants are not These requirements cover non-electrical,permitted except where approved by refrigerant-containing components and ANSI/UL 250 will be superseded inthe authority having jurisdiction. One accessories (e.g., accumulators, driers, 2016 by ANSI/UL 60335-2-24, theexception to the restriction is “listed evaporators, condensers, etc.), intended Standard for Household and Similarportable-unit systems containing no for field installation in accordance Electrical Appliances, Part 2: Particularmore than 0.331 lb. (150 g) of Group A3 with ASHRAE 15 in refrigeration Requirements for Refrigeratingrefrigerant, provided that the equipment systems, air conditioning equipment, Appliances, Ice-Cream Appliances andis installed in accordance with the listing or both, charged with the refrigerants Ice-Makers.43 With respect to flammableand the manufacturer’s installation identified for use in the component refrigerants, the IEC requirements areinstructions.” This requirement 40 or accessory. The requirements also modified or replaced such that theeffectively means that self-contained, apply to components and accessories requirements are effectively the samepermanently installed (not “portable”) intended for use by manufacturers in as the current ANSI/UL 250 standard.commercial and large household factory-assembled systems or units, in The scope of ANSI/UL 60335-2-24 is notrefrigerators and freezers may employ which case the component or accessory identical to that of ANSI/UL 250. ANSI/A3 refrigerants only with permission. is also judged under the requirements UL 60335-2-24 also includes ice makersTypical household refrigerators, for the individual system or unit.41 and household ice cream makers, whichdehumidifiers and other cord and plug Primarily addressing strength of materials are covered by ANSI/UL 563 (Ice Makers)connected appliances meeting the and mechanical assembly, the standard and ANSI/UL 621 (Ice Cream Makers).charge restriction would be permitted. includes consideration of flammable Should such appliances use flammableASHRAE 15 includes a general prohibition refrigerants. ANSI/UL 207 Table 11 specifies refrigerants, ANSI/UL 60335-2-24 would beon the use of Group A2, A3, B1, B2 and the minimum design pressures for applicable for that aspect of their design.B3 refrigerants for comfort cooling common refrigerants. Data for flammable ANSI/UL 471, Standard for Safety for(Clause 7.5.2). There is an exception refrigerants is excerpted from that Commercial Refrigerators and Freezersfor sealed absorption (ammonia) table and reproduced here in Table 4. These requirements cover unitary (self-systems and unit systems (e.g., window ANSI/UL 250, Standard for Safety for contained) and remote commercialair conditioner), provided that the Household Refrigerators and Freezers refrigerators and freezers intendedrefrigerant quantity is no more than 3 kg This standard applies to self-contained for connection to circuits rated notor 10 kg for residential and commercial household refrigerators and freezers greater than 600 volts AC. Commercialoccupancies, respectively. [Note that for use in residential occupancies in refrigerators and freezers includeANSI/UL 484 is expected to restrict room accordance with the National Electrical equipment such as display cases, reach-inpage 12
  13. 13. White Paper: Revisiting Flammable RefrigerantsTable 4 — Minimum Design Pressures for Selected Flammable Refrigerants Minimum design pressures pounds per square inch gauge (kPa) Refrigerant Groupa Name Low side High side Water or evaporatively cooled Air cooled R-30 B2 Methylene 15 (103) 15 (103) 15 (103) Chloride R-40 B2 Methyl chloride 72 (496) 112 (772) 151 (1041) R-170 a3 Ethane 616 (4247) 709 (4888) 709 (4888) R-290 a3 Propane 129 (889) 188 (1296) 244 (1682) R-600 a3 N-Butane 23 (159) 42 (290) 61 (421) R-600a a3 Isobutane 39 (269) 63 (434) 88 (607) R-611 B2 Methyl Formate 15 (103) 15 (103) 15 (103) R-717 B2 Ammonia 139 (958) 215 (1482) 293 (2020) R-764 B1 Sulfur Dioxide 45 (310) 78 (538) 115 (793) R-1150 a3 Ethylene 732 (5047) 732 (5047) 732 (5047) a Classification in accordance with ASHRAE 34.cabinets, meat cases, frozen food and • 150 grams (5.3 oz) - ASHRAE 34 Class units, heat pump water heaters andmerchandising cabinets, beverage 3 “Higher Flammability” refrigerant. fan coil units.46 Currently, the standardcoolers, beverage cooler-dispensers, food Has limits of flammability and does not address the subject ofservice carts, ice cream cabinets, soda heat of combustion greater than flammable refrigerants, which shouldfountain units, door panel assemblies 19,000 kj/kg (8,174 Btu/lb.). be construed to mean that flammableand processing water coolers.45 refrigerants (aside from ammonia47 ) The current standard further indicates are not permitted, an interpretationFlammable refrigerant requirements that, when the leaked amount of consistent with ASHRAE Standard 15.of this standard (Supplement SB) are refrigerant during leak scenario testingvirtually identical to those of ANSI/ of the refrigerating system does There is an active, tri-nationalUL 250, with the notable exception not exceed the 225 or 150 g value, a harmonization effort being conductedof a higher allowable refrigerant larger amount of charge would not under the auspices of the Council forcharge and the particulars of required be prohibited from being used. the Harmonization of Electrotechnicalmarkings and instructions. Clause Standards of the Nations of the Americas ANSI/UL 1995, Standard for Safety forSB3.3 of the standard limits flammable (CANENA)48 to update parts of ANSI/ Heating and Cooling Equipmentrefrigerant charge as follows: UL 1995 (and completely replace UL 484 The standard is applicable to stationary and UL 474) with a standard based on• 225 grams (8.0 oz) - ASHRAE 34 Class equipment for use in nonhazardous IEC 60335-2-40, Standard for Household 2 “Lower Flammability” refrigerant. locations rated 7200 V or less, single- or and Similar Electrical Appliances, Part 2: Has limits of flammability, and 3- phase, and remote control assemblies Particular Requirements for Electrical Heat heat of combustion less than for such equipment. Cooling equipment Pumps, Air Conditioners and Dehumidifiers. 19,000 kj/kg (8,174 Btu/lb.). examples include heat pumps, air Draft UL 60335-2-40 deals with the safety conditioners, liquid chillers, condensing of electric heat pumps, including sanitarypage 13
  14. 14. White Paper: Revisiting Flammable RefrigerantsTable 5 — Summary of Additional Requirements for Household Refrigerators and Freezers Employing Flammable Refrigerants Charge The charge size for refrigerators or freezers shall be as follows for the kind of refrigerant used: • No charge limit - Has no limits of flammability, has either an auto-ignition temperature less than or equal to 750°C (1382°F) or no auto-ignition temperature. • No charge limit - When the blend (does not fractionate). • 225 grams (8.0 oz.) - Has limits of flammability, and heat of combustion less than 19,000 kj/kg (8,174 Btu/ lb). When the leaked amount of refrigerant during leak scenario testing of the refrigerating system, does not exceed 225 grams (8.0 oz.), a larger amount of charge is not prohibited from being used. • 50 grams (1.7 oz.) - Has limits of flammability and heat of combustion greater than 19,000 kj/kg (8,174 Btu/ lb). When the leaked amount of refrigerant during leak scenario testing of the refrigerating system does not exceed 50 grams (1.7 oz.), a larger amount of charge is not prohibited from being used. Construction The requirements distinguish between protected and unprotected cooling systems, the difference largely based on the level of access the user has to refrigerant containing components via the refrigerated storage area. • No dead spaces anywhere within the appliance where flammable gas mixture can accumulate. • Refrigerant tubing must be protected or enclosed to avoid mechanical damage. • No quick-connect refrigeration fittings or packed-stem valves. • Refrigeration joints shall be brazed or welded and protected from mechanical damage. • Refrigeration circuit shall be protected from corrosion. Leakage For a protected cooling system, refrigerant leakage simulation at most critical point in system, which would be one of the joints in the refrigeration circuit. • 80% of the refrigerant charge, or quantity capable of being discharged in a prescribed way within 1 hr., is leaked in a controlled manner at a joint. • For an unprotected cooling system, refrigerant leakage simulation at prescribed location in food storage compartment • 80% of refrigerant charge is discharged within 10 min. • Where accumulation of refrigerant may occur outside the food storage area, leakage simulation at that location. • 80% of refrigerant charge is discharged at a constant rate over a period of 1 hr. • For each of the simulations, the refrigerant air mixture shall not exceed 75% of the lower flammable limit (LFL) for the flammable gas at any time and not exceed 50% of the LFL for a period exceeding 5 min. Ignition If exposed to the refrigerant during the leakage testing, electrical switching components are tested to determine whether they are capable of igniting the flammable refrigerant / air mixture. • Tested in accordance with ASTM E681-98 (Standard Test Method for concentration Limits of Flammability of Chemicals (Vapors and Gases)) at room ambient and again at 50oC Temperature Surface temperature of parts that may be exposed to a leaked refrigerant shall not exceed the ignition temperature of the refrigerant reduced by 100 oC. • R290 (Propane) – ignition temperature: 470 oC, LFL 2.1% • R600 (n-Butane) – ignition temperature 365 oC, LFL 1.5% • R600a (Isobutane) – ignition temperature 460 oC, LFL 1.8% Scratch Accessible surfaces of protected cooling system components are scratched in a prescribed way as preconditioning of the Strength Test applicable to all refrigerant pressure containing systems. [Typical strength test pressures are comparable to those of CFC’s] Markings and Permanent markings on the appliance are required: Instructions •  “DANGER - Risk Of Fire or Explosion. Flammable Refrigerant Used. Do Not Use Mechanical  Devices To Defrost Refrigerator. Do Not Puncture Refrigerant Tubing”. •  “DANGER - Risk Of Fire Or Explosion. Flammable Refrigerant Used. To Be Repaired Only  By Trained Service Personnel. Do Not Puncture Refrigerant Tubing”. •  “CAUTION - Risk Of Fire Or Explosion. Flammable Refrigerant Used. Consult Repair Manual/Owner’s  Guide Before Attempting To Service This Product. All Safety Precautions Must be Followed”. •  “CAUTION - Risk Of Fire Or Explosion. Dispose Of Property In Accordance With  Federal Or Local Regulations. Flammable Refrigerant Used”. •  “CAUTION - Risk Of Fire Or Explosion Due To Puncture Of Refrigerant Tubing; Follow  Handling Instructions Carefully. Flammable Refrigerant Used”. The refrigeration system processing tubes shall be color-coded to indicate the refrigerant used.44 Cautionary statements shall be repeated in the instructions and packaging. They shall emphasize that servicing shall be done by factory authorized service personnel.page 14
  15. 15. White Paper: Revisiting Flammable Refrigerantshot water heat pumps, air-conditioners, Figure 2and dehumidifiers incorporating motor-compressors and hydronic room fan coils.Though the IEC standard also addresseselectric heat pumps, air conditioners anddehumidifiers containing flammablerefrigerant, the Standards TechnicalPanel developing the draft standardhas not itself addressed flammablerefrigerants in its work. For this reason,the draft UL standard has a U.S. nationaldeviation that would currently precludeuse of flammable refrigerants.IEC 60335-2-40 uses the ASHRAE 34 For more than these amounts (e.g. 152 < maximum charge is correlated to the sizerefrigerant classification system (also g ≤ 988 propane), the equipment must of the room in which the air conditionerused in ISO equivalent standard, ISO be marked with a minimum room size, is intended to be installed. However,817). For mechanical strength of the calculated in accordance with Annex GG they do not include an allowance forrefrigeration system, the standard of the standard (see Figure 2 for example larger amounts of flammable refrigerantrefers to ISO 5149 requirements.49 Many results). This requirement will typically when there is mechanical ventilation.of the construction requirements for affect portable air conditioners. Larger ANSI/UL 474, Standard for Safety forequipment employing flammable amounts (up to 4.94 kg) of refrigerant will Heating and Cooling Equipmentrefrigerants are similar to those described require mechanical ventilation operated This standard details requirements forfor ANSI/UL 250, with the addition of by a leak detector/sensor. These amounts movable, household, self-containedspecific construction requirements for are limited to fixed equipment only. dehumidifiers employing hermeticequipment charged at the installation Equipment having very large amounts refrigerant motor-compressors,site, and of requirements addressing of refrigerant is not covered by IEC and intended for connection totransport, storage and service operations. 60335-2-40, which states that national single-phase, alternating-currentThe most significant difference standards shall apply (e.g., ASHRAE 15). circuits rated not more than 20 A, 125between the standards involves how V or 15 A, 208 or 230 V. The situationcharge limits are determined. ANSI/UL 484, Standard for Safety for Heating and Cooling Equipment relative to flammable refrigerants isRather than a fixed charge limit, IEC identical to that of ANSI/UL 484. These requirements cover room air60335-2-40 correlates refrigerant charge, conditioners rated not more than 600 Vac. UL 984, Standard for Safety forvolume of the space (room) for equipment Room air conditioners include packaged Refrigerant Motor Compressorsinstalled indoors, and installation height terminals (PTACs), special purpose and This is the legacy standard applicable to(floor, wall, window, ceiling). Smaller recreational vehicle type air conditioners. hermetic refrigerant motor-compressorsamounts (e.g., ≤152 g propane) of Flammable refrigerant requirements have rated 7200 V or less, for use in air-condi-flammable refrigerant in products such as recently achieved consensus in the UL tioning and refrigerating equipment thatportable dehumidifiers are addressed in 484 Standards Technical Panel and will comply with the standards applicablea manner similar to that of a refrigerator be published shortly. These requirements to such equipment.50 It distinguishes(minimum room size not specified, are similar to the requirements described between refrigerants primarily by theirmechanical ventilation not required). above for IEC 60335-2-40, in that thepage 15
  16. 16. White Paper: Revisiting Flammable Refrigerantsthermodynamic properties, and by It apples to motor-compressors tested for Refrigerating Units, ANSI/UL 427, tothe strength of materials necessary to separately, under the most severe be a general source for refrigerationcontain the refrigerants under normal and conditions which may be expected circuits employed in appliances whereabnormal conditions. Specific reference to to occur in normal use, their rated the relevant appliance standard doesflammable refrigerants is not made in the voltage being not more than 250 V for not already include such requirements.standard; instead, it defers to ASHRAE 15. single-phase motor-compressors and 480 V for other motor-compressors.”51 ConclusionThe basic requirements are the samefor all types of refrigerants, except There is no difference between ANSI/ In the 1990s the U.S. market was notthat leakage around gaskets and seals UL 60335-2-34 and UL 984 with regard ready for the introduction of flammableis not permitted during Strength to how refrigerants are handled. refrigerants in many HVAC and applianceTesting of compressors intended for applications when CFC phase-out beganrefrigerants other than A1 (or A1/A1 Other Appliance Standards to take effect. However much experienceblends). The flammable refrigerant, with equipment using HC refrigerants Other standards potentially affectedlubrication and the compressor motor has been gained around the world by the introduction of flammableelectrical insulating system must also in the intervening years. As the drive refrigerants are ANSI/UL 412, Standardbe compatible. The standard prescribes toward more environmentally-friendly for Safety for Refrigeration Unita test to establish compatibility, though refrigerants and greater energy efficiency Coolers, ANSI/UL 399, Standard forthere are alternative means to do so. continues, it’s time to revisit the use Safety for Drinking Water Coolers,52 of flammable refrigerants in the U.S. and ANSI/UL 541, Standard for SafetyGoing forward, UL 984 will only cover Anticipating that these refrigerants can for Refrigerated Vending Machines.motor-compressors that are outside very quickly attain more widespread use,the scope of ANSI/UL 60335-2-34. “Reverse-cycle” heating, long the it is important that the stakeholders of staple of heat pumps, is also making an the U.S. safety system take a holistic lookANSI/UL 60335-2-34, Standard forHousehold and Similar Electrical appearance in products such as clothes at the potential impact of such use, andAppliances, Part 2: Particular dryers and water heaters. With their take the necessary steps to ensure theRequirements for Motor-Compressors experience in the use of HC refrigerants continued safety track record of HVACIn late 2009, revisions to the previously in household refrigerators and freezers, equipment and appliances. UL believespublished UL 60335-2-34 were European manufacturers have expanded that raising awareness and facilitatingcompleted so that the standard could the application to these newer energy dialogue among stakeholders is anbe declared as harmonized with UL 984. saving technologies (e.g., clothes dryers53). important first step in this direction.Designation as an American National The water heater application isStandard (ANS) was then transferred currently covered by ANSI/UL 1995 for For information about the “Revisitingfrom UL 984 to UL 60335-2-34. conventional refrigerants. There is no Flammable Refrigerants in HVACANSI/UL60335-2-34 is based on IEC current mechanism within that standard Equipment and Appliances” white60335-2-34 whose scope “deals with to address a flammable refrigerant. paper, please contact Thomas Blewitt,the safety of sealed (hermetic and Similarly, clothes dryer requirements Director of Primary Designatedsemi-hermetic type) motor-compressors, (ANSI/UL 2158, Standard for Electric Engineers, Underwriters Laboratoriestheir protection and control systems, Clothes Dryers) do not anticipate the at Thomas.V.Blewitt@us.ul.com.if any, which are intended for use in heat pump technology (conventionalequipment for household and similar or flammable refrigerants). For thispurposes and which conform with the reason, there is an effort underway atstandards applicable to such equipment. UL to re-purpose an existing Standardpage 16