The phase down of HFCs began in earnest this year, as refrigerant manufacturers were required to cut production by 10% in 2022. This reduction is a result of the 2020 American Innovation in Manufacturing (AIM) Act, which gave the Environmental Protection Agency (EPA) the authority to phase down the consumption and production of high-GWP HFC refrigerants in the U.S. by 85% over the next 15 years. This includes R-410A, which is found in just about every type of residential and commercial air conditioning equipment in the U.S.

While R-410A is a nonflammable (A1) refrigerant, its replacements include R-32 and R-454B, both of which are mildly flammable (A2L) refrigerants. In order to install or service equipment containing these new refrigerants, additional safety measures will need to be followed by HVAC contractors and technicians. These were outlined at a seminar given by Jason Obrzut, director of industry standards and relations at ESCO Institute, at the recent AHR Expo in Las Vegas, Nevada.

Installation

When it comes to installing an A2L system, there aren’t too many differences when compared to an A1 system, provided the technician is already employing best practices, said Obrzut. In fact, when comparing installation and service practices between the two, he said there are only three requirements for an A2L installation that are not required for A1 systems.

“These requirements are to purge the circuit with an inert gas, evacuate, and leak test the unit,” he said. “However, based on industry best practices, most would agree that these requirements were things that should have been done with an A1 installation as well. Technicians and contractors employing industry-accepted best practices will notice little or no change at all in their service practices or their installation practices.”

One of the biggest differences between installing an A2L and an A1 system involves evaluating the installation site and determining where the unit can be placed.

“For new construction, we can design a space, and the building can accommodate the requirements for the unit,” said Obrzut. “The biggest headache will be with swap outs, where we're taking the unit out of a closet and putting in a new one that is charged with an A2L.”

In that situation, it will be necessary to consult the installation manual, which will contain the details regarding where a unit may be placed. The “beefed up” installation manual will be one of three manuals that will come with the equipment, as mandated by the UL 60335-2-40 standard, which is the product safety standard for comfort cooling applications, said Obrzut.

“The manuals will be very, very specific to the model and include charging information, use application, use restrictions, etc., and it will have easy-to-read charts,” he said. “However, it is important to always defer to the local authority, because different areas use various versions of the building code.”

A2L units will also come with some type of refrigerant mitigation strategy, which is necessary in the case of a leak. Should a leak occur and a sensor embedded in the equipment detects that the refrigerant concentration has passed the predefined threshold, mitigation actions will be initiated, such as turning on fans and blowers to dilute the refrigerant concentration and maintain a concentration below the lower flammability limit (LFL).

“We're going to have active sensors that will turn things on or off and lock things out, and all of this is going to be onboard the unit for the most part. It's not going to be up to the technician to install or calibrate the sensors or do anything with them, because they will already be in the unit,” said Obrzut.

Labels and Tools

A2L systems will also be labeled differently, so it will be apparent to technicians that they are working on a system that contains a mildly flammable refrigerant. The ISO triangle warning sign with the flame symbol will be affixed to the unit, as will another label containing information filled out by the installing technician.

“The installing technician must use a permanent marker to fill out the label with information such as the final charge, final test pressure, final evacuation level, etc.” said Obrzut. “Many manufacturers are going to tie this into commissioning, so technicians will have to fill out this label, take a picture of it, and send it in.”

As for tools, those that don't touch the refrigerant circuit – such as scales – can usually be used for both A1 and A2L systems. Other tools, such as recovery machines, leak detectors, and vacuum pumps must be rated for use with flammable refrigerants, said Obrzut, adding that these are already readily available from many different manufacturers.

Charging and Recovery

When charging an A2L system, the process is essentially the same, so zeotropic and near-zeotropic refrigerant blends must still be charged as a liquid, said Obrzut. One big difference is that charging with an A2L refrigerant must be done carefully to ensure that the maximum allowable charge is not exceeded. And, the maximum allowable charge will be different for every system installation.

“It's going to be specific to the size capacity of the unit, as well as the air space that the system is servicing, so what works for one area may not work for another,” said Obrzut. “It's not going to be a universal number. It's going to be determined by the charging chart that manufacturers are going to provide based on the cubic volume of air and the location and capacity of the unit. Technicians won’t need to calculate it.”

When evacuating an A2L system, technicians should make sure the recovery machine is rated for use with A2Ls; otherwise, the process is virtually the same as for A1 systems, said Obrzut. Best practices for recovery of both types of refrigerants include:

• Maintaining a vacuum on empty cylinders to help ensure refrigerant purity when filled with refrigerant;
• Properly labeling recovery cylinders by refrigerant type contained within the cylinder;
• Never tampering with relief valves;
• Ensuring that scales are accurate (all refrigerants have different liquid densities, and fill weights will vary by product); and
• Returning full recovery cylinders to the proper source for reclamation.

The color of all refrigerant cylinders is changing to gray-green, but A2L cylinders will also have a red stripe on them. It is expected that A2L refrigerant cylinders will have left-hand threading, while A1 cylinders will maintain right-hand threading, but that has yet to be determined, said Obrzut.

“Another difference is that A2L tanks will have a pressure relief valve that can open, vent a little bit, lower the pressure, and then close back up,” he said. “This is unlike R-410A cylinders, which lose their whole charge if the rupture disc bursts.”

Obrzut concluded his presentation by noting that the HFC phasedown has started and that contractors and technicians should not wait to obtain the training necessary to install and service A2L systems. “There are R-32 systems already on the market in several states,” he said. “Don't wait until 2024 to take the training and buy the right tools. Start now.”