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 13148
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 general guidelines 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. | ||||||||||||||||||||
| 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 hearts 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. | ||||||||||||||||||||
| Benefits: |
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| Disadvantages: |
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| Economic Analysis: | According to Mr. Peter Mullenhard from 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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| NSN/MSDS: |
*There are multiple MSDSs for most NSNs. The MSDS is only meant to serve as an example. To return from the MSDS, click the Back arrow on the Tool Bar. | ||||||||||||||||||||
| Approving Authority: |
Appropriate authority for making process changes should
always be sought and obtained prior to procuring or implementing any of the technology identified herein.
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| Points of Contact: | For more information | ||||||||||||||||||||
| Vendors: |
This is not meant to be a complete list, as there may be
other suppliers of this type of equipment. United Refrigeration, Inc. Refron, Inc.
Honeywell DuPont ATOFINA Chemicals, Inc.
Note: R-407A and R-407B are both manufactured by INEOS Fluor under the tradenames KLEAŽ 407A and KLEAŽ 407B, formerly KLEAŽ 60 and KLEAŽ 61 respectively. R-507 is manufactured by Honeywell, DuPont, and ATOFINA under the tradenames GenetronŽ AZ-50, SUVAŽ 507, and ForaneŽ 507, respectively. Note: Du Pont tradename for R-404A is SUVAŽ HP-62. | ||||||||||||||||||||
| Related Links: |
None
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| Sources: |
Ms. Alison Chirkis, Tinker AFB, January 1998. Mr. Pete Mullenhard, Shipboard Environmental Information Clearinghouse, June 2002. Du Pont Fluorochemicals, vendor communications, August 1998. PA Technical Inquiries: 2065, 2984, and 3136. Allied-Signal fluorocarbon product information. |