R-502 ALTERNATIVE
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| Overview: |
R-404A is an EPA Significant New Alternatives Policy (SNAP, Subpart G of 40 CFR Part 82) program approved substitute for R-502. R-502 is a mixture of HCFC-22 and CFC-115 used primarily in large commercial and industrial refrigeration applications, such as cold storage warehouses, commercial ice machines, industrial process refrigeration units and refrigerated transports. R-404A is a near azeotropic mixture of the following refrigerants: HFC-125 (44%), HFC-143a (52%), and HFC-134a (4%). These refrigerants are all hydrofluorocarbons (HFCs), and thus are not on either the Class I or the Class II lists of ozone depleting substances (ODSs). R-404A was developed as a long-term replacement for refrigeration equipment currently using primarily R-502. R-404A provides similar energy efficiencies and capacities, but with a lower discharge temperature and slightly higher discharge pressure. It is acceptable for both new equipment and retrofit equipment; however, triple flushing is sometimes necessary for retrofit equipment so that most (>95% by weight) of the mineral oil lubricant is removed (allowable residual mineral oil is highly dependent on system configuration and operating conditions). Flushing can usually be accomplished after removing and recovering the existing refrigerant by simply draining the existing mineral oil either from an oil drain plug or by removing the compressor and draining from the suction line. In most small systems, 90-95% of the lubricant can be removed from the system in this manner. Larger systems may require multiple drainage points, particularly if there are low spots around the evaporator. In systems with an oil separator, any lubricant in the separator should also be drained. In all cases, measure the volume of lubricant removed and compare to the compressor/system specifications to assure that >95% of the lubricant has been removed. If >95% of the mineral oil lubricant has not been removed, flushing will be required (if the system shows poor heat transfer, the mineral oil residual is typically still too high). Equipment using R-404A requires polyol ester lubricating oil, so flushing consists of selecting a polyol ester lubricant with a viscosity similar to the existing lubricant and charging an amount of polyol ester oil equal to the amount of mineral oil removed. Recharge the system with the recovered R-502 in order to achieve thorough mixing of the two lubricants (48 to 72 hours of operation may be required). Repeat this procedure twice more, but on the last charge of fresh polyol ester oil, recharge the system with R-404A instead of the recovered R-502. Note: Special care should be taken when handling polyol ester lubricants due to their tendency to absorb water; minimize contact with air and keep them in a sealed container. The following precautions regarding R-404A use should also be noted: 1) Because R-404A is a blend, any leaks in the system may allow components of the blend to bleed off at different rates, leaving behind an altered blend that may mask system problems during troubleshooting and failures. Leak detection and prevention should be maintenance priorities, especially when running systems with refrigerant mixtures. 2) Service ports and valves on retrofit systems should be well marked and identified to assure the refrigerant types is known by all service and maintenance personnel. 3) The chemical compatibility of plastics and elastomers should be considered before retrofitting. Gaskets, shaft seals, and o-ring materials should be reviewed with the equipment manufacturer before retrofitting. 4) Use of HFCs is subject to the no-venting prohibition under the Clean Air Act Amendments, Section 608 (c) (2). For most retrofit systems, the optimum charge of R-404A will be 85-90% of the weight of the equipment manufacturers recommended R-502 charge. Other HFC blends that are available as R-502 substitutes include:
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| Compliance Benefit: |
Use of R-404a which is not an ozone-depleting substance will help facilities meet the requirements under 40 CFR 82, Subpart D and Executive Order 12843 requiring Federal agencies to maximize the use of safe alternatives to Class I and Class II ozone depleting substances, to the maximum extent practicable. The compliance benefits listed here are only meant to be used as a general guideline and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g. the amount of workload involved.
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| Materials Compatibility: |
Although refrigerant development has focused on relatively inert and non-toxic compounds, some products are not compatible with certain lubricants, plastics, and elastomers, while others exhibit a moderate degree of toxicity. The chemical compatibility of plastics and elastomers should be considered before retrofitting. Gaskets, shaft seals, and o-ring materials should be reviewed with the equipment manufacturer. Always check with the original equipment manufacturer to verify material compatibility.
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| Safety and Health: |
Overexposure to refrigerant vapors by inhalation may cause temporary nervous system depression with anesthetic effects such as dizziness, headache, confusion, loss of coordination, and loss of consciousness. Higher exposure to the vapors may cause temporary alteration of the heart’s electrical activity with irregular pulse, palpitations, or inadequate circulation; or fatality from gross overexposure. Potential hazards such as room ventilation issues, eye irritation, skin freezing or burning when exposed to escaping refrigerant gas, exposed flame and residual flux issues associated with brazing operations need to be considered. Refrigerants are heavier than air and will displace air in a confined space leading to possible oxygen starvation (asphyxiation) for any technician working in the space. Oxygen starvation is the leading cause of death in accidents involving a refrigerant. Refrigerants tend to be relatively non-toxic; however, see the individual Pollution Prevention Opportunity Data Sheets for more specific information about the acceptable alternatives and their material compatibility concerns. Also, consult your local Industrial Health specialist, your local health and safety personnel, and the appropriate MSDS prior to implementing any of these technologies.
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| Benefits: |
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| Disadvantages: |
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| Economic Analysis: | According
to Mr. Peter Mullenhard form the Shipboard Environmental Information Clearinghouse,
retrofit costs for refrigeration equipment can vary widely depending on
system designs. Cost can range from several hundred dollars to several thousand
dollars. However, in general, the majority of the cost associated with the
retrofit to an HFC refrigerant such as R-404A can be attributed to the labor
hours required conducting multiple lubricant flushes required for use of
POE lubricant.
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| Approving Authority: |
Approval is controlled locally and should be implemented only after engineering approval has been granted. Major claimant approval is not required.
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| NSN/MSDS: |
*There are multiple MSDSs for most NSNs. The MSDS (if shown above) is only meant to serve as an example.
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| Points of Contact: |
Air Force: Navy:
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| Vendors: |
ICI Chemical and
Polymers Ltd. Honeywell DuPont Note: R-407A and R-407B are both manufactured by ICI Chemical and Polymer Ltd. under the tradenames KLEA 407A and KLEA 407B, formerly KLEA 60 and KLEA 61 respectively. R-507 is manufactured by Allied-Signal under the tradename AZ-50. Note: Du Pont tradename for R-404A is SUVA® HP-62.
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| Sources: |
Ms. Alison Chirkis, TinkerAFB, January, 1998 |