UNEP Ozone SecretariatFactSheetsonHFCsandLow GWP AlternativesUNEP Ozone Secretariat – Background Material on HFC ManagementOctober 2015FACT SHEET 10Water chillers for air-conditioning1. Description of market sectorThis market sector includes water chillers that are used for building air-conditioning and some industrialcooling applications. Many large buildings that require air-conditioning are cooled using pumped chilledwater systems with a central chiller installation. In some countries, relatively small buildings also usewater chillers (in competition with the larger “air-to-air” air-conditioning systems, see Fact Sheet 9).Market sub-sectorsThe sector has been split into two sub-sectorsa) Small and medium sized chillersb) Large sized chillersTypical system designMost chillers systems use a vapour compression cycle. In large buildings, chillers are located in amechanical equipment room. Chilled water is pumped to air handling units or terminal units that deliverconditioned air. Condenser water is pumped to a cooling tower. For smaller buildings, chillers maybe located outdoors and use air cooled condensers. Small and medium sized chillers often use a direct expansion (DX) evaporator and an aircooled condenser. They usually use scroll, reciprocating or small sized screw compressors.Large sized chillers usually use a flooded evaporator, a water cooled condenser and a largescrew or centrifugal compressor.Variable speed drives are a popular addition that improves part load efficiencyAlternative technologiesHeat driven absorption chillers, usually based on a water-lithium bromide system, can be used in placeof electrically driven vapour compression systems. Solid adsorption systems (e.g. water / silica gel) canalso be considered. Sorption systems are only cost effective if there is a suitable source of waste heat,as they are less efficient than vapour compression systems. They might also be used in locationswhere the electricity grid is unreliable or low in capacity.Changes driven by ODS phase outPrior to 1990 this sector used CFC-11 and CFC-12 for large centrifugal chillers and HCFC-22 for smalland medium sized chillers. By 1995 largeCFC-12 chillers were replaced with newdesigns based on HFC-134a; CFC-11 chillersmoved to HCFC-123.From around 2000,small and medium sized chillers moved fromusing HCFC-22 to R-407C and then toR-410A. In non-Article 5 countries HCFC-123has a phase-out date of 2020. As the 2020phase out approaches the market forHCFC-123 chillers is diminishing. New chillersusing HCFC-123 and HCFC-22 are stillavailable in Article 5 countries.Typical small air cooled chiller for outdoor operationFact Sheet 10: Water chillers for air-conditioning1Version 2, October 2015
UNEP Ozone Secretariat – Background Material on HFC ManagementTable 1: Chillers for air-conditioning: summary of characteristics for HFC equipmentMarket sub-sector:Small / medium sized chillers*Large chillers*Typical refrigerant charge20 to 250 kg250 to 6 000 kgTypical cooling duty50 to 750 kW750 to 10 000 kWR-407C (GWP1 1774)HFC refrigerants widely usedTypical refrigeration circuit designManufacture / installationR-410A (GWP 2088)DX evaporator, air cooledcondenserFlooded evaporator, watercooled condenserScroll, reciprocating or smallscrew compressorLarge screw or centrifugalcompressorFactory built, often pre-charged with refrigerant.Some large systems charged with refrigerant during installation.Typical location of equipmentTypical annual leakage rateMachinery room (water cooled) or outdoors (air cooled)2% to 4%2% to 4%Operating leakageOperating leakageNew systems65%50%Maintenance35%50%Main source of HFC emissionsApprox. split ofannual refrigerantdemandHFC-134a (GWP 1430)* The sizes indicated in Table 1 are approximate. Smaller and larger sizes may be available.Typical medium pressure R-134a (left) and low pressure R-123 (right) Centrifugal Chillers1All GWP values are based on the IPCC 4th Assessment ReportFact Sheet 10: Water chillers for air-conditioning2Version 2, October 2015
UNEP Ozone Secretariat – Background Material on HFC Management2. Alternatives to currently used HFC refrigerantsTable 2: Lower GWP alternatives for water rs with centrifugal compressorsHFO-1234ze72LBeing developed for large centrifugal chillers asan alternative to HFC-134a.HFO-1233zdHFO-1336mzz5911New fluids suitable for low pressure centrifugalchillers as an alternative to HCFC-123.HFO-1233zd models are commercially available.R-718 (water)01Water can be used as a refrigerant in chillersystems, but requires very large compressorswept volume.Chillers with positive displacement compressors72LAlready available in a range of small and mediumsized chillers.HFC-326752LHas performance similar to R-410A and issuitable for small and medium sized chillers.R-446AR-447AR-454B4602L2L2LNewly developed blends with properties similar toR-410A. Being considered for small and mediumsized chillers.HFO-1234ze582460R-717 (ammonia)02LSuitable for medium and large sized chillers withscrew compressors. More commonly used forindustrial chillers but can also be applicable forair-conditioning.HC-2903233Suitable for small and medium sized chillers.Available widely in Europe.R-450A601R-513A631R-513B*595111Newly developed blends with properties similar toHFC-134a, suitable for medium sized chillersusing screw compressors.HC-1270There is a range of different low GWP options that are well suited to chillers. Most chillers are locatedin a machinery room or in an outdoors location. This makes it easier to deal with safety issues relatedto both flammability and toxicity, allowing the use of large charges for the refrigerants listed in Table 2.Flammable refrigerants require special safety considerations and compliance with building codes.Some machinery rooms are located in “difficult access” locations such as a basement. The use offlammable and higher toxicity refrigerants in such locations can be more problematic.2Refrigerants and text shown in italics have been added in this latest version of the Fact Sheet* R-numbers marked with an asterisk are awaiting final approval from ASHRAE3Flammability categories based on ISO 817 and ISO 51493 higher flammability; 2 flammable; 2L lower flammability; 1 no flame propagationFact Sheet 10: Water chillers for air-conditioning3Version 2, October 2015
UNEP Ozone Secretariat – Background Material on HFC ManagementTesting of new, lower-GWP refrigerants for chillers started several years ago. Some alternativerefrigerants have been introduced into product ranges, although it is not yet clear which ones may beselected for broader commercialisation. Trade-offs are apparent between GWP, energy efficiency,safety, and installed cost. The product development costs for a full range of compressors and chillerproducts are substantial.3. Discussion of key issuesSafety and practicalityProvided a chiller is located in a machinery room or an outdoors location there are few restrictionson the refrigerant charge that can be used for various suitable refrigerants. This provides chillermanufacturers with a wide range of low GWP options. Safety requirements for the appropriateflammability and toxicity category must be followed.For some refrigerants there could be limitations to applicability in basements and other “difficultaccess” locations.Commercial availabilityVarious designs of chiller using low GWP alternatives are already commercially available, includingHFO-1234ze, HFO-1233zd, HCs and R-717.Many new chiller models with low GWP refrigerants are expected to become available within the nextfew years.CostHFO-1234ze chillers will be of similar or slightly higher cost to HFC-134a chillers.HC chillers are cost competitive with R-410A systems, but site installation cost may be higher due toflammability safety measures.Ammonia chillers are considerably more expensive, especially for smaller capacities. Costs of lowpressure centrifugal chillers using HFO-1233zd or HFO-1336mzz are not yet clear, but are expectedto be competitive with prices for HCFC-123 chillers.Energy efficiencyThere have been excellent improvements in the efficiency of water chillers over the past 10 yearsthrough the introduction of numerous technical improvements. It is expected that good efficiency canbe achieved for all the refrigerants listed in Table 2 if best practice designs are used.Applicability in high ambientSmall / medium chillers: Many smaller chillers are air-cooled and will operate at very highcondensing temperatures in high ambient. HC-290 and HC-1270 chillers can be designed to operatewell at high ambient. HFC-32, R-446A, R-447A and R-454B have a higher critical temperature thanR-410A and can be expected to perform better than R-410A at high ambient but not always as wellas HCFC-22.Fact Sheet 10: Water chillers for air-conditioning4Version 2, October 2015
UNEP Ozone Secretariat – Background Material on HFC ManagementLarge chillers: Most large chillers are water cooled and are relatively easy to use in high ambient ifthe cooling water is evaporatively cooled in a cooling tower. This helps avoid extremely highcondensing temperatures. However, if water is scarce, a cooling tower may not be appropriate. If adry air cooler is used, the condensing temperature will be much higher. Refrigerants such asHFO-1234ze, HFO-1233zd and HFO-1336mzz have high critical temperatures which make themreasonably well suited to high condensing temperatures, although a high compression ratio couldcreate difficulties for some types of centrifugal compressor.Opportunities to retrofit existing equipmentCentrifugal chillers: It is not appropriate to retrofit existing HFC chiller equipment that usescentrifugal compressors.Positive displacement chillers: It is technically feasible to retrofit small and medium sized positivedisplacement chillers. This has been done widely to replace HCFC-22 in water chillers. However,there is currently little or no retrofit activity related to HFC chillers.Technician trainingLower flammability HFCs/ HFOs: Training will be essential for maintenance of chillers with lowerflammability refrigerants. Training is being provided by manufacturers of new models of chillers usingthese refrigerants.HCs: Technicians doing maintenance need training that addresses handling of higher flammabilityrefrigerants. There are established training courses available although only a small proportion of airconditioning technicians have skills to deal with large HC systems.R-717: Technicians doing maintenance need training that addresses handling of R-717, especiallyin relation to use of a higher toxicity refrigerant. There are well established training courses availablefor R-717 technicians in many countries, although not many air-conditioning technicians are familiarwith R-717.Minimising HFC emissions from existing equipmentChiller systems are factory built and have the potential for very low levels of leakage if best practicedesign and maintenance is carried out.Chillers have large refrigerant charge and it is essential that appropriate recovery equipment is usedduring maintenance and at end-of-life.Low pressure chillers (e.g. using HCFC-123 or HCFO-1233zd) may operate with an evaporator atbelow atmospheric pressure. This creates the possibility of air leaking into the refrigerant circuit.Appropriate automatic air-purge equipment should be used to avoid refrigerant emissions when airis removed.Fact Sheet 10: Water chillers for air-conditioning5Version 2, October 2015
Technician training Lower flammability HFCs/ HFOs: Training will be essential for maintenance of chillers with lower flammability refrigerants. Training is being provided by manufacturers of new models of chillers using these refrigerants. HCs: Technicians doing maintenance need training that addresses handling of higher flammability refrigerants.