A2L Refrigerant Change Guide

New equipment with R-410A refrigerant will be completely phased out in January of 2025 in the United States. Globally, the goal is for countries to reach 15 to 20% of their individual original baseline for HFCs and remain there by 2036. More information on the phasedown of HFCs can be found at the EPA link below:

A2L is a refrigerant safety category determined by the EPA for substances that have lower flammability and toxicity compared to other classifications - making it the second safest refrigerant category. A = Non-toxic. 2 = Flammable. L = Low burning velocity. See below for more information:

The A2L subgroup, as categorized by ASHRAE Standard 34, is a class of mildly flammable refrigerants, but are considered safe. All refrigerants, if properly handled, contained, and stored, are safe. Following standard best industry practices and procedures is the best way to reduce the possibility of a mishap or injury.

A2L refrigerants with low global warming potential can increase system efficiency, lowering emissions through reduced energy consumption. They also have very low flammability, making them safer to use in a broad range of applications.

Mildly flammable refrigerants such as R-454B cannot be used in existing R-410A or R-22 systems. Compressors must be upgraded. Systems designed for R-454B will require less of a charge than today's R-410A systems and will be approximately 5% more efficient than current R-410A systems. There are no “drop-in” refrigerants to replace R-410A.

R-410A split systems will have to be replaced with R-454B split systems.

If a customer purchased a new system that uses R-410A refrigerant, they will still receive service from contractors, and any parts necessary for needed repairs from Bosch for the foreseeable future.

Yes. Bosch will provide training.

Bosch partners must become knowledgeable on the HFC phasedown and the move to A2L refrigerant. They must be able to recognize R-454B cylinders, as well as to read and understand the R-454B refrigerant Safety Data Sheets (SDS) and Bosch literature before handling the refrigerant.

Contractors and technicians must be EPA-certified to handle refrigerants. For more information on the certification process for EPA 608 certifications, and other important certification information, please visit the EPA website below:

Industry organizations such as ESCO Institute are curently offering additional recommended A2L/Low-GWP refrigerant training and certification in anticipation of future regulatory requirements.

No. Only certified technicians can use non-exempt refrigerants to service AC equipment. Technicians must comply with the new certification for ozone-depleting and non-exempt substitute refrigerants.

HFO stands for hydrofluoroolefin. The chemical is made of hydrogen, fluorine, and carbon. However, unlike HFCs, HFOs have zero ODP (Ozone Depletion Potential) and low GWP, making them a more environmentally friendly option than HFCs. HFOs don't trap heat in the atmosphere and don't contribute to global warming.

R-454B is a blend of single component R-32 refrigerant and R-1234yf refrigerant, giving some unique advantages. R-454B refrigerant has an ozone depletion rating of 0 (ODP = 0) and has a low GWP value of 466, which is 78% less than R-410A.

The change should have no impact on homeowners who have purchased Bosch equipment using R-454B refrigerant, provided that the installation was conducted by a trained and qualified contractor.

Most residential and light commercial A2L, R-454B, systems look no different than R-410A systems, except for system labeling (flammable refrigerant).

Although all manufacturers are required to phase out R-410A refrigerants, not all will necessarily use R-454B specifically.

If an R-410A needs more refrigerant for proper operation, it’s because there’s a leak somewhere in the system. The leak may be fixable, but it’s at this point that the decline of the system will likely begin to cost more than it’s worth, especially relative to a new, more efficient system that doesn’t use R-410A.

Installation and service procedures for both A1 and A2L systems are similar. For A2L systems, pre-installation safety precautions must be considered that primarily involve site evaluation. The space must be large enough, and have enough air, to keep the refrigerant at or below a percentage of the lower flammability limit (LFL) of the refrigerant, should the entire refrigerant charge (vapor) leak into the space.

Repair of Bosch equipment must use original Bosch components designed for potentially flammable atmospheres.

The refrigerant to be used for Bosch Home Comfort products will be R-454B. This refrigerant is a blend of R-32 and R-1234yf, with a composition of 68.9% R-32, and 31.1% R1234yf.

R-454B refrigerant contributes significantly less harm to the environment than R-410A refrigerant and other blends. and offers better compliance with HFC phasedown initiatives under the Montreal Protocol. R-454B refrigerant has ZERO ODP ensuring no contribution to Ozone layer degradation, and a shorter tropospheric lifetime of approximately 12 years in the atmosphere, compared to R-410A refrigerant with approximately 30 years tropospheric lifetime.

Before beginning the installation of a system that is charged with an A2L refrigerant always verify that all the components being installed are designed for use with A2L refrigerants. Also always make sure the system is properly grounded before installing the equipment.

Upon completion of an A2L system installation the Bosch specification documents must be kept on file by the contractor performing the installation.

A2L is a refrigerant safety category determined by the EPA for substances that have lower flammability and toxicity compared to other classifications. R-454B refrigerant used in new Bosch heat pumps is classified as A2L. This is a low GWP refrigerant that will result in service personnel noticing that there are some significant differences with regards to the handling, charging, and labeling, and the systems that contain them. Safe work practices utilized with R-410A refrigerant, an A1 classification with no flame propagation and no toxicity, are still relevant when working with R-454B. An additional focus on safety has been added to lower the probability of an accident or ignition occurrence.

Installation and service of A2L equipment should not differ much from equipment containing A1 refrigerant, such as R-410A. By following a few new procedures as well as best practices, that should be utilized for every installation, technicians can feel safe and secure when working on the new Bosch A2L R-454B refrigerant system.

If an R-454B cylinder gets too hot, a cylinder-installed pressure relief valve will open when the pressure exceeds 600PSI, releasing refrigerant until the pressure drops below the relief point. The entire cylinder contents will not be released, prohibiting the refrigerant lower flammability limit (LFL) being reached, which is needed for an ignition to occur.

R-454B is classified as a zoetrope and has a low temperature glide so low that topping-off the charge can be done without recovery in many instances to solve the current issue for proper system operation. However, standard industry best practice indicates that adding more refrigerant only temporarily solves the problem and does not prohibit it from reoccurrence. Subsequently, recovery and leak detection/repair/recharging are always recommended.

Many hand tools used daily will not change. Recovery, reclamation, and leak detection tools must be A2L-approved.

R-454B refrigerant can only be used in new equipment designed for A2L refrigerant. Components in the new system redesigned for R-454B refrigerant will include the compressor, expansion valve, and electrical components. Additionally, refrigerant charge level will change. There is no “drop-in” replacement refrigerant for R-410A.

All new refrigerant cylinders will be gray with the refrigerant number stamped on the tank. All A2L R-454B refrigerant cylinders will have a red band near the top of the tank signifying low flammability. Empty cylinders must have any residual refrigerant removed/recovered before disposal and rendered useless. Per standard industry best practices, empty flammable refrigerant cylinders should be punctured with a non-sparking pick for disposal. Never puncture the relief valve on these cylinders.

A2L R-454B cylinders will now have left-handed threads, and a ¼ A2L tank adapter will be required to connect refrigerant manifold hoses. Tanks under 50 lbs. will require a CGA 164 fitting, and tanks containing over 50 lbs. will require a CGA 670 fitting.

Existing R-410A split system line sets can be reused if they are properly sized, flushed and completely purged with dry nitrogen before making any final connections. This flushing removes oil, debris, and any residual R-410A refrigerant. Then the line set must be pressure-tested to Bosch requirements, be leak-free, and in compliance with all local and national codes. Following the flush, always set the regulator to braze setting. Following this process, installation of a properly sized liquid line filter drier is recommended per Bosch specifications.

If the Bosch system is not already pre-charged, the system should be field charged with refrigerant as a liquid. Prior to this, and after installation, the refrigerant piping for an A2L system must be pressurized with dry nitrogen to perform a leak test. Disposable R-454B refrigerant cylinders should be inverted, and reusable cylinders will utilize a dip tube, connect to the high (liquid) fitting. A liquid charge adapter should be used to avoid compressor slugging, and the refrigerant charge should be weighed-in according to Bosch specifications. Charge should be adjusted by determining operating subcooling and superheat values compared to Bosch specifications. The maximum allowable charge is not a universal figure and will vary from one system installation to the next. Variables that can affect the allowable system charge include the system design and capacity, the length and size of the refrigerant piping, the indoor cubic volume, and the occupancy classification of the structure.

Please refer to your Installation and Operations Manual for more information.

Like other refrigerants, A2L systems must be evacuated prior to being charged, but the vacuum pump used must be rated for use with A2L refrigerants for best results, triple evacuation of the system is recommended. You should always use a micron gauge to determine the proper evacuation level has been met. A compound gauge cannot be used to determine the effectiveness of the evacuation.

Please refer to your Installation and Operations Manual for more information on triple evacuation.

To recover A2L R-454B refrigerant, the recovery machine and tank must be certified for use with A2L refrigerant. Contractors/technicians should be EPA Section 608 Certified. A2L R-454B refrigerant recovery tanks will be identified with a red stripe around them and will have left-handed threads to differentiate them from R-410A recovery tanks. Never fill A2L R-454B recovery tanks more than 80% by volume to prevent build-up of hydrostatic pressure and possible tank rupture.

A nitrogen sweep should be done to remove any residual refrigerant vapor.

There are many types of leak detectors available on the market, but infrared detectors (IR) and heated diode (HD) are typically the most used with A2L refrigerant. Always ensure you are using a leak detector that is A2L refrigerant compatible. Always refer to the Bosch specifications for verification.

The Air Conditioning, Heating, and Refrigeration Institute (AHRI) concluded infrared detectors (IR) are the most practical option available. Always check with leak detection vendors for proper device training and use. Never use an open flame, such as a Halide Torch, as a leak detector, with A2L refrigerant.

Leak detection sensors will be used for all Bosch air source heat pump indoor units, and for all Bosch water source units pre-charged with over 64 ounces (4 pounds) of R-454B refrigerant. These sensors may vary between manufacturers, and could include infrared sensors, or thermal conductivity sensors. Sensors will be installed near the indoor coils in these larger Bosch units and are designed to detect R-454B refrigerant vapor. If detecting more than a specific amount of vapor from a leak, the sensors will disengage the compressor and energize constant blower operation to prevent buildup of refrigerant vapor within the space. Factory-installed sensors will typically be shipped in larger vertical Bosch heat pumps, and field-conversion will be required for horizontal models. The standard Bosch Unit Protection Module (UPM) electronic control board will have a new A2L Sensor connection feature for use as necessary for all Bosch water source heat pumps with more than 64 ounces of R-454B.

NFPA 704 hazard placards must be placed in visible locations around the perimeter of the jobsite. The refrigerant tubing should be pressurized with air to stabilize the inner walls. The system charge must be vented to the atmosphere before beginning.

The Refrigerant Concentration Limits (RCL) should be known, which is a rating for R-454B refrigerant which indicates the allowable refrigerant weight per cubic foot of room volume, or pounds per foot cubed to determine the maximum concentration limit allowed in an occupied space of R-454B refrigerant gas. This concentration limit for the cubic feet of air space served by the equipment, is intended to reduce the risks of toxicity, asphyxiation, and flammability.

Date that the pressure test and evacuation was completed.

Bosch A2L R-454B refrigerant systems will be designed with electrical components that are called intrinsically safe (IS), meaning components such as the contactor or capacitor will be enclosed, isolating the electrical contacts from the atmosphere. Systems can then be worked on while energized within a flammable atmosphere without concern of electrical component issues.

To help our customers with comparing our outgoing R-410A water source heat pump models with our new R-454B models, we have created this crossover guide.

Yes, all HVAC units with R-454B, regardless of size, are prohibited from air transport per Federal Regulations.

In the event a customer requires air transport, the refrigerant will be vaccummed out and the unit charged with Nitrogen, prior to shipment. Note: this will require the end customer to charge the unit in the field.