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25
Jun
When technicians and property owners ask what kind of refrigerant is comparable with R438A, the most relevant options are usually R422B, R422D, R427A, and R407C. However, the best comparison depends on whether the original equipment is used for air conditioning, heat pumps, or medium- and low-temperature refrigeration.
R438A, commonly marketed as MO99, was designed as a retrofit refrigerant for many direct-expansion R22 systems. It is compatible with mineral oil, alkylbenzene oil, and POE lubricant in many applications, which can make an R22 conversion less complicated. Other retrofit refrigerants may serve similar purposes, but they do not have identical composition, pressure-temperature behavior, capacity, temperature glide, or oil requirements.
Most importantly, comparable does not mean interchangeable. R438A should never be mixed with R22, R422B, R422D, R427A, R407C, or another refrigerant. The existing charge must be properly recovered before a system is converted and recommissioned by a qualified technician. Chemours’ official MO99 guidance confirms that R438A is intended for properly executed R22 retrofits rather than topping off an existing R22 charge.
What Is R438A and Why Are Other Refrigerants Compared With It?
Before answering what kind of refrigerant is comparable with R438A, it helps to understand the role R438A plays.
R438A is primarily a service refrigerant used to extend the operating life of compatible legacy R22 equipment.
R438A Is an R22 Retrofit Refrigerant
R438A is used in certain direct-expansion residential and commercial air-conditioning systems, split systems, packaged units, direct-expansion chillers, and medium- or low-temperature refrigeration equipment originally designed for R22. It was formulated to offer capacity and efficiency reasonably close to R22 while operating at a lower compressor discharge temperature in many applications.
Royal Refrigerants provides additional application details through its guide to R438A MO99 refrigerant, including the reasons it is commonly selected for older R22 systems.
Its Oil Compatibility Is a Major Advantage
One reason technicians choose R438A is its compatibility with traditional mineral oil and alkylbenzene lubricant, as well as POE oil. In many straightforward retrofits, a complete oil conversion is not necessary. Complex systems with difficult oil-return conditions may still require adding POE or making other adjustments.
This oil flexibility is important when comparing R438A with options such as R407C, which generally requires POE lubricant when replacing R22 in a mineral-oil system.
Is R422B Comparable With R438A?
When considering what kind of refrigerant is comparable with R438A for residential or commercial air conditioning, R422B is one of the closest practical alternatives. Both are non-ozone-depleting R22 retrofit blends designed to work with traditional lubricants in many systems.
R422B Is Mainly Focused on Air Conditioning
R422B, commonly marketed as NU-22B, is used primarily in residential and commercial air-conditioning systems originally designed for R22. It operates at pressures similar to R22 and can often be used without a complete mineral-oil-to-POE conversion. Chemours states that properly converted R422B systems generally experience a relatively small capacity reduction compared with R22.
Technicians comparing the two can review Royal Refrigerants’ R422B refrigerant options alongside its R438A MO99 collection.
R438A Offers a Broader Application Range
R438A is often considered more versatile because it is intended for both air-conditioning and medium- or low-temperature refrigeration applications. R422B is more closely associated with comfort cooling, although suitability still depends on the equipment and retrofit guidance.
Both refrigerants have an A1 safety classification, but they are separate products and must never be mixed. Chemours specifically states that R438A and R422B should not be combined in the same system.
Is R422D Comparable With R438A?
R422D is another reasonable answer to what kind of refrigerant is comparable with R438A, particularly when the equipment involves direct-expansion refrigeration. It has some of the same retrofit advantages, but its application emphasis and operating characteristics differ.
R422D Is Common in Direct-Expansion Refrigeration
R422D, commonly known as MO29, is a non-ozone-depleting HFC blend used as an R22 alternative in certain refrigeration and air-conditioning applications. Like R438A, it can operate with mineral, alkylbenzene, and POE lubricants in many systems, potentially avoiding a complete lubricant conversion.
Royal Refrigerants carries R422D refrigerant for legacy equipment, giving qualified technicians a relevant option when the equipment and manufacturer guidance support its use.
Capacity and Flow Characteristics Are Not Identical
Although R422D and R438A can both replace R22 in certain systems, they have different compositions, pressure-temperature charts, mass-flow requirements, and expected capacities. Expansion-device adjustments may be needed after either conversion.
The final selection should be based on the application, evaporator temperature, equipment layout, compressor type, lubricant, and expected load. R422D is not a product that should simply be substituted for an existing R438A charge.
Is R427A Comparable With R438A?
For technicians asking what kind of refrigerant is comparable with R438A across a broad range of R22 applications, R427A is another important option.
It is used in air conditioning, heat pumps, and medium- or low-temperature refrigeration, but its oil-management requirements deserve close attention.
R427A Closely Matches R22 Performance
Arkema describes R427A as offering capacity, efficiency, mass-flow rate, and operating pressures relatively close to R22. It may work in a broad range of positive-displacement, direct-expansion equipment without requiring major changes to expansion valves or line sets. Arkema’s official R22 retrofit guidance identifies R427A as a general-purpose option for air-conditioning and refrigeration conversions.
R427A may therefore be functionally comparable with R438A, but the two blends have different compositions and cannot be mixed.
Oil Return Must Be Evaluated Carefully
R427A has been used in systems containing mineral oil, alkylbenzene oil, or POE. However, system layout affects whether the original lubricant provides sufficient oil return. Long piping runs, receivers, vertical risers, and compressors positioned above the evaporator may increase the need for POE lubricant.
R438A was specifically formulated as a no-oil-change option for many common systems, which may make it more convenient when preserving the original lubricant is a priority.
Is R407C Comparable With R438A?
R407C is often included in discussions about what kind of refrigerant is comparable with R438A because both can serve as alternatives to R22 in air-conditioning equipment. The major difference is lubricant compatibility.
R407C Closely Matches R22 Capacity in Air Conditioning
R407C can provide capacity and efficiency close to R22 in many air-conditioning applications. Arkema identifies it as one of the closest capacity matches for R22 comfort-cooling equipment. It can be used in certain positive-displacement, direct-expansion systems after a properly planned retrofit.
Qualified professionals can review R407C refrigerant products when evaluating alternatives for equipment approved for that refrigerant.
R407C Usually Requires POE Oil
The primary difference is that R407C generally requires POE lubricant to achieve reliable oil return in equipment originally operating with R22 and mineral oil. This can require one or more oil changes and additional labor. R438A was developed to function with the existing mineral or alkylbenzene lubricant in many systems.
R407C can be an excellent performance match in air conditioning, but it is not necessarily the simplest retrofit. R438A may be more practical when minimizing lubricant conversion work is a key objective.
Which Refrigerant Is Most Comparable With R438A by Application?
The best answer to what kind of refrigerant is comparable with R438A changes according to the application. No single retrofit blend is automatically best for every R22 system.
For Residential and Commercial Air Conditioning
R422B is one of the most directly comparable no-oil-change options for comfort-cooling systems. R427A also offers broad air-conditioning suitability and close operating characteristics, while R407C can provide a particularly close capacity match when a POE oil conversion is acceptable.
R438A remains a versatile choice for contractors who want one product that can cover many direct-expansion air-conditioning and refrigeration applications while retaining traditional lubricant in suitable systems.
For Medium- and Low-Temperature Refrigeration
R422D and R427A may be considered for some medium- and low-temperature systems, while R407A is often associated with commercial refrigeration. The operating temperature, compressor, expansion device, piping configuration, oil return, and load profile must all be reviewed before selecting a retrofit refrigerant.
Property owners and service companies should avoid selecting a refrigerant solely from a comparison chart. Actual suitability requires equipment-specific technical evaluation.
Why R410A Is Not Comparable With R438A for Retrofitting
When asking what kind of refrigerant is comparable with R438A, some people assume R410A is a possible alternative because it is widely used in air conditioning.
It is not an appropriate retrofit refrigerant for R22 or R438A equipment.
R410A Operates at Much Higher Pressure
R410A operates at substantially higher pressures than R22 and the retrofit blends designed around R22 equipment. Older R22 compressors, coils, piping, valves, and controls were not built for R410A operating conditions.
Using R410A in an R22 system can cause poor performance, equipment damage, or unsafe operating conditions. Arkema’s R22 retrofit guidance explicitly states that R410A should only be used in equipment designed for it.
Newer Refrigerants Are Also Not Automatic Alternatives
New-equipment refrigerants such as R454B and R32 are not substitutes for R438A in existing R22 systems. They have different pressure, safety, and equipment-design requirements. R454B and R32 should only be used in equipment specifically engineered and labeled for them.
Aging R22 equipment that is no longer a good retrofit candidate may be better replaced with a complete modern system rather than converted to an unrelated new-equipment refrigerant.
Oil Compatibility Can Determine the Best Comparison
Oil requirements are central to what kind of refrigerant is comparable with R438A because the refrigerant must help return lubricant to the compressor. Poor oil return can reduce lubrication and shorten compressor life.
No-Oil-Change Alternatives
R438A, R422B, and R422D are formulated to operate with mineral, alkylbenzene, and POE lubricants in many common applications. These options may reduce conversion time and cost when the existing system has a straightforward layout and good oil return.
The phrase “no oil change” should not be treated as an unconditional guarantee. A complex system may still need some POE added, particularly when it includes long line sets, receivers, low-pressure vessels, or difficult vertical piping.
POE-Based Alternatives
R407C generally requires POE oil in a system that previously used R22 with mineral oil. R427A may also benefit from partial or complete POE conversion when the system layout does not support adequate mineral-oil return.
The existing oil should be identified before conversion, and its condition should be checked. Burnt, acidic, or contaminated lubricant should not be retained merely to reduce labor.
Two Additional Factors to Review Before Selecting an Alternative
Beyond pressures and oil compatibility, what kind of refrigerant is comparable with R438A also depends on the equipment’s condition and the long-term economic value of the retrofit.
Age and Mechanical Condition of the System
A refrigerant conversion may be worthwhile when the compressor, coils, piping, motors, controls, and cabinet remain in sound condition. Retrofitting equipment with a severely leaking coil, failing compressor, poor efficiency, or repeated electrical problems may only delay an unavoidable replacement.
Technicians should document baseline pressures, temperatures, airflow, superheat, subcooling, and compressor amperage before recovering the original charge. That information provides a target for evaluating performance after conversion.
Availability and Regulatory Conditions
R438A and many comparable R22 retrofit refrigerants are higher-GWP HFC blends. Their availability and permitted use may change according to federal, state, and regional regulations. Contractors should confirm current rules before committing customers to a long-term service strategy.
Purchasing refrigerants for stationary HVAC equipment in the United States is generally restricted to properly certified technicians or qualifying businesses. The EPA refrigerant sales restriction explains the applicable Section 608 purchasing requirements.
How to Convert a System From R438A to Another Refrigerant
Determining what kind of refrigerant is comparable with R438A does not mean one product can be poured on top of another. Changing refrigerant requires complete recovery, system evaluation, and recommissioning.
Recover the Existing R438A Charge
The full R438A charge should be recovered into an appropriate recovery cylinder. It should not be intentionally vented or mixed with recovered R22, R422B, R422D, R407C, or another refrigerant. EPA regulations prohibit intentional venting of covered refrigerants during maintenance, service, repair, and disposal.
Once recovered, the refrigerant should be labeled and handled through an appropriate recycling, reclamation, or disposal channel.
Repair, Evacuate, Recharge, and Label
Before adding the chosen refrigerant, the technician should repair leaks, replace the filter-drier, inspect critical elastomeric seals, evaluate oil condition, pressure-test the system, and evacuate it properly. The replacement blend should generally be removed from its cylinder as liquid and charged by weight according to its specific retrofit instructions.
After the system stabilizes, the technician should adjust the charge or expansion device as instructed, document operating measurements, and label the equipment with the new refrigerant and lubricant information.
FAQ
What Refrigerant Is Closest to R438A?
R422B is one of the closest practical comparisons for no-oil-change residential and commercial air-conditioning retrofits. R422D, R427A, and R407C may be comparable in other applications.
Can R422B Be Added to a System Containing R438A?
No. R422B and R438A must not be mixed. The existing charge should be completely recovered before a different refrigerant is introduced.
Is R407C Better Than R438A?
R407C may provide a close R22 capacity match in air-conditioning systems, but it generally requires POE oil. R438A is often easier when retaining mineral or alkylbenzene oil is important.
Can R438A Be Replaced With R410A?
No. R410A operates at much higher pressures and is not a retrofit refrigerant for R22 or R438A equipment.
Are R438A and MO99 the Same?
Yes. R438A is the ASHRAE refrigerant designation, while MO99 is a widely recognized trade name for the product.
Does Changing From R438A Require an Oil Change?
It depends on the replacement refrigerant and system design. R422B and R422D may work with existing mineral oil in many systems, while R407C generally requires POE lubricant.
Conclusion
The answer to what kind of refrigerant is comparable with R438A depends on the equipment and its application. R422B is a close comparison for many air-conditioning systems, R422D is relevant to certain direct-expansion refrigeration applications, R427A covers a broad range of R22 equipment, and R407C can closely match R22 capacity when a POE oil conversion is practical. None of these refrigerants can be mixed with R438A or used without a proper professional conversion.
Royal Refrigerants supplies application-specific products for legacy HVAC systems, modern cooling equipment, and automotive air-conditioning service. Qualified professionals evaluating an R22 retrofit or servicing equipment already converted to MO99 can explore Royal Refrigerants’ R438A refrigerant collection, compare available R422B alternatives, or browse the complete HVAC refrigerant range to source the correct product for each approved application.
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