Keeping Up on CFCs and Chillers
CSE: Several alternatives are available for chlorofluorocarbon (CFC) replacement, such as hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs) and ammonia. How does one determine which is best for existing chillers—or whether to install a new chiller? LEADER: If a new chiller is considered, it's best to do a cost analysis that looks at all aspects of chiller replacement, not just...
By Barbara Horwitz-Bennett, Contributing Editor
CSE: Several alternatives are available for chlorofluorocarbon (CFC) replacement, such as hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs) and ammonia. How does one determine which is best for existing chillers—or whether to install a new chiller?
LEADER: If a new chiller is considered, it's best to do a cost analysis that looks at all aspects of chiller replacement, not just efficiency. There are many opportunities to improve overall chilled-water system operation. A chiller's kW per ton is just one piece of the puzzle.
CSE: Can you expound further on that?
LEADER: The recent emphasis on low-flow, high delta-T chilled-water systems is a good example, as it has a big impact on overall economics. These systems affect chilled-water and condenser-water pumping power, cooling-tower fan power and suitability for series vs. parallel chiller pumping arrangements. A colder chilled-water supply temperature and a warmer condenser-leaving water temperature increases the chiller power requirements. However, the pumping and tower fan power requirements will be reduced, generally more than enough to offset the chiller operating cost penalty, particularly on existing piping systems that were originally designed for a "traditional" 10
MANDYCK: But, if an existing chiller with a CFC refrigerant is still in good mechanical condition and has significant service life remaining, a refrigerant containment strategy is usually the most economically attractive option—if proper measures are taken to minimize refrigerant leakage. This can be accomplished, in part, through the installation of additional hardware on the chiller itself, or as part of the system.
LEADER: I'd say the first consideration is the chiller's age. A unit less than 10 years old is probably a good candidate for a retrofit.
Chillers between 10 and 20 years old are borderline, and the decision comes down to a life-cycle cost analysis between refrigerant replacement and a new chiller. However, for a unit that is over 20 years old, replacement may be best.
CSE: How about changing to a different refrigerant?
MANDYCK: That's another option, but an estimate of performance with the new refrigerant must be made. The evaluation must consider anticipated change to the cooling capacity and input power requirements. Various material and compressor aerodynamic changes will undoubtedly be necessary as well, for material compatibility and chiller performance.
Finally, if a chiller is a new addition to the existing chilled-water plant, or is replacing a unit that has reached the end of its service life, the question is which non-CFC refrigerant to use.
CSE: What kind of options are there?
MANDYCK: First and foremost, one should be aware that HCFCs, like CFCs before them, are under a phase-out schedule—the first step being a 35% reduction by 2004, culminating in an end to their production. The Montreal Protocol stipulates that no HCFCs can be used in new equipment in developed countries beyond 2020. By that time, the consumption limit will have been reduced by 99.5% below today's level. The 0.5% remaining is reserved exclusively for servicing and maintenance only. Complete phase-out of all HCFCs is currently scheduled to occur by 2030.
Similarly, the U.S. Clean Air Act calls for an end to HCFC-22 use in new equipment by 2010, and cessation of production of HCFC-22 by 2020. HCFC-123 is permitted for new equipment sales until 2020 with production ending in 2030.
CSE: Does this apply to HFCs as well?
MANDYCK: HFC refrigerants are not scheduled for phase-out, either by the Montreal Protocol or the U.S. Clean Air Act. Further, HFC-134a is used extensively in the commercial centrifugal and screw-chiller market. The efficiency of HFC-134a chillers is often compared to HCFC-123, with the results showing an overlap in their efficiency ranges. If a variable-speed drive is considered in the evaluation, the part-load performance of an HFC-134a chiller often exceeds that of a constant-speed HCFC-123 chiller.
HFC-134a also carries the highest ASHRAE-34 safety rating, while HCFC-123 does not. For smaller capacity systems, HFC-410A is used today as a replacement for HCFC-22, especially in the residential and light commercial markets.
Ammonia is also a good refrigerant in industrial applications, but its use is restricted by codes because of concerns about toxicity and flammability. HFC-410A is currently being used in smaller direct-expansion equipment, but its pressure makes it difficult to use in flooded chillers.
DOOLEY: There just isn't a 'one-size-fits-all solution' for phasing out CFCs. Unfortunately, although CFC production was banned as of the end of 1995, Congress did not adopt a simple tax code change to relieve building owners of the burden of depreciating chillers over a 39-year lifetime. Consequently, the phaseout of CFC chillers has suffered. On the plus side, the payback for replacing a unit can be five years or less, so replacement is a strong option. In fact, by the end of last year there were only 8,697 conversions of CFC chillers compared to 32,492 replacements.
CSE: What about reclaimed refrigerant? Is it a viable option? How much of a market is there for this?
DOOLEY: Refrigerants ranging from CFCs to HCFCs and HFCs are reclaimed to meet ARI Standard 700 and are available throughout the United States. Some refrigerants, such as R-502, appear to be in short supply, and the cost of CFCs increased dramatically compared to 10 years ago. There are many refrigeration uses of CFCs, but non-venting regulations and penalties of up to $25,000 for violations encourage reclamation. Over the past decade, millions of pounds of refrigerants have been recovered and reclaimed. However, due to the vagaries of the CFC supply, building owners and managers simply must have a refrigerant management program if they intend to keep using CFCs. They can re-use their own refrigerants from CFC units taken out of service or make arrangements with refrigerant reclaimers.
LEADER: The U.S. Environmental Protection Agency recently produced a graph entitled 'Reclaimed Refrigerant Amount by Type in the United States-2000.' It shows that R-11 and R-12—1,548,734 lbs. and 1,679,526 lbs., respectively—are a distant second to R-22 at 7,094,995 lbs. ARI has a short list of certified reclaimers—only 13 companies—so my impression is that this isn't a very strong market.
MANDYCK: ARI has several standards that govern the purity, procedures and equipment involved in reclaiming refrigerants, including ARI 700-1999, Specification for Fluorocarbon Refrigerants; ARI 740-1998, Recovery/Recycling Equipment; and ARI Guideline K-1997, Containers for Recovered Fluorocarbon Refrigerants. The Industry Recycling Guide, IRG-2, is also a pertinent document, developed by equipment and refrigerant manufacturers together with the General Services Administration. These standards define the purity and composition of reclaimed refrigerants and establish how and where they can be used once they've been removed from de-commissioned chillers. The use of reclaimed refrigerant certainly becomes more of a factor once production of a particular substance has ceased, since reclamation and recovery then becomes the only legal channel for future procurement. Like anything else, the economics of supply and demand will ultimately determine the market price.
CSE: Do building owners lack sufficient knowledge about CFC phase-out? If so, how can this education gap be filled?
LEADER: Based on one recent experience with a sophisticated client for whom we just finished a study on replacing vs. retrofitting several 30-year-old water chillers, I'd have to agree. For quite some time, the client had been making repairs and replacing leaking R-12, while preferring to use R-134a as a substitute. Our life-cycle cost analysis showed their outdated constant-flow primary/constant-flow secondary pumping system with three-way cooling coil control valves was the real energy consumer. The analysis showed that a simple variable primary flow series chiller arrangement with variable-speed primary pumps was the best choice. This system had a simple payback of 0.4 years and a ROI of 243% when compared with the cost of replacing the existing chillers and pumps with new equipment. In this case, the chillers were air-cooled and efficiencies weren't much better with the new rotary screw compressor chillers than the old reciprocating compressor chillers. However, the major portion of the operating cost savings was in the pumping costs.
As engineers, we need to do a better job of speaking the language of individuals from the corporate and financial world and not use vague, general terms. A comprehensive life-cycle cost analysis and a high ROI is what they understand.
MANDYCK: ARI estimates that 40,000 CFC chillers remain in active service in the U.S. today. There are likely many reasons why this is so: the equipment's useful life; scarce capital for replacement; a 39-year depreciation schedule in the U.S.; and the need to create more awareness of the benefits of CFC replacement.
LEADER: Right now, the weak economy is being blamed for the decline in the rate CFC phase-out.
CSE: Have there been, or do you foresee, any changes in codes or standards that would affect CFC phase-out?
MANDYCK: A depreciation time period, shorter than the current 39 years in the U.S. tax code, could provide for the accelerated replacement of CFC equipment.
LEADER: ASHRAE Standard 90.1-1999, Energy Efficient Design for Buildings Except Low-Rise Residential Buildings, has been adopted now by many state code jurisdictions. The standard was renamed in 1999 and expanded to include coverage of alterations and additions to existing buildings.
The minimum equipment efficiency ratings in the standard indirectly rule out many refrigerant replacements. However, it does not address CFC phase out per se. Unless an existing chiller needs replacement, it can survive as long as there are parts available and a willingness to pay for reclaimed refrigerant.
Edward W. Dooley , Vice President of Communication and Education, The Air-Conditioning and Refrigeration Institute, Arlington, Va.
Phil Leader , P.E., Director of Mechanical Engineering, Albert Kahn Assocs., Inc. Detroit
John Mandyck , Vice President, Goverment and Intl Relations, Carrier Corporation, Syracuse, N.Y.
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