Kimberly Thompson
This is a long conversation, but we are going to try and make it short and impactful.
Let us go over some industry terms for background. The Montreal Protocol (the be all, end all for refrigerant and carbon management developed to protect the ozone layer) was developed in the late 1980s to protect the ozone layer. In the 1990s, refrigerants with Ozone Depletion Potential (ODP) started to get phased out. It was theorized, these refrigerant emissions caused depletion of the stratosphere’s ozone layer over the long term. Additionally, it was first contemplated that when greenhouse gases (GHG) are released into the atmosphere; they absorb energy making it harder for the energy to escape Earth. This trapping of heat can lead to global warming. A variety of GHG were identified that are born naturally or through man-made production and the list includes, but is not limited to methane, nitrous oxide, carbon dioxide, and fluorinated gases (refrigerants).
In the HVAC world, GHGs are represented by their associated global warming potential (GWP). GWP measures the global warming impacts of different gases considering an apples-to-apples comparison against carbon dioxide. This is done by measuring the amount of energy from the emissions of one ton of a gas absorbs over a given time period, compared to the emissions produced by one ton of CO2. In 2016, the Kigali amendment to the Montreal Protocol put a plan in place that was ratified by several countries to phase down production and ultimately, consumption of greenhouse gases
The American Innovation and Manufacturing Act (AIM) requires a phasedown of production and consumption of HFCs down to 15% of the baseline values by 2036. This bill authorizes the US EPA to develop rulemaking that follows the phasedown schedule. The EPA must phase down production, consumption, maximize reclamation, and minimize releases from equipment in accordance with the AIM Act. They may ease the transition through sector-based restrictions. Some of these rules include Significant New Alternatives Policy (SNAP) rules 20 and 21. Rule 20 applies to chillers and Rule 21 applies to aerosols, foams, and automobile air conditioning. This does not restrict the use of HFCs in existing equipment.
The EPA proposed a 700 GWP limit for new HVAC equipment. The deadlines are based on domestic manufacturing dates or import dates – January 1, 2025, for most DX systems and Chillers; January 1, 2026, for VRF systems. Several states are adopting one-year earlier phase-down dates – not Texas though.
Refrigerant types
Refrigerants are numbered with an R- followed by the ASHRAE assigned number. Isomers (molecules with the same chemical formula as another molecule but with a different chemical structure) are identified with a lowercase letter after the number. Refrigerant blends having the same pure components but with different compositions are identified with an upper-case letter after the number.
Refrigerants having the form R-4xxx are zeotropic, which is a blend of two or more refrigerants whose liquid phase and vapor phase have different compositions and can separate. In layman’s terms, Zeotropes contain chemical constituents that boil and condense at different temperatures while working in the confines of a refrigeration system/cycle, thus causing a glide in evaporating or condensing temperature and pressure. Refrigerants with the R-5xxx are azeotropes which are blends whose liquid phase and vapor phase have the same compositions at a specific pressure, so they behave like a single-component refrigerant.
ASHRAE Standard 34 – Safety Group Classifications
ASHRAE Standard 34 categorizes refrigerants by two main characteristics – flammability and toxicity. Regulations have moved the industry away from higher toxicity, higher ODP, and higher flammability refrigerants. No refrigerant is “non-toxic,” but rather is referred to as having lower or higher toxicity – category A and B respectively. Flammability has four levels. Most refrigerants in North America have been in Group A1. Class 2L is a new designation given to refrigerants including the leading replacements for R-134a and R-410A. With the lower probability of ignition, 2L refrigerants significantly reduce the potential for flammability versus class “2” refrigerants. Click here for a link to the video.
Upcoming Refrigerant Alternatives
R-410A (a zoetrope with Glide with 50% R-32 composition, developed in the late 1980s and for sale in 1991) is the current leader for high (positive) pressure refrigerants used in scroll and rotary compressor applications such as chillers, commercial DX units, and residential units. However, R-410A will soon be replaced by the following options: R-32 (pure refrigerant, not a blend of several), R-454B (zeotropic blend of 68.9% R-32 / 31.1% R1234yf), and R-452B (zeotropic blend of 67% R-32, 7% R-125, and 26% R-1234yf) depending on which manufacturer you are working with. R-454B is also known as Opteon XL41, Solstice 454B, and Puron Advance. R-452B, also known as Honeywell Solstice®L41y and OpteonTM XL55. It exhibits a small temperature glide between saturated liquid and vapor.
In 2012, specifically, Daikin gave all manufacturers free access to their patent on R-32 for the application in HVAC and refrigeration Equipment. R-32 or Difluoromethane has been around as a single-component virgin refrigerant for over 50 years. R-32 in HVAC equipment has been widely used for years in Japan, China, Australia, and Europe. This patent release by Daikin enabled several manufacturers to utilize this refrigerant developed a long time ago (developed around the time R-12). It has a noticeable efficiency boost and around 10% more capacity than R-410A, depending on the application and system design. R-454B has a slightly lower capacity than R-410A but slightly better efficiency. See attached flyer for differences between R-32 and R-454B.
The primary medium-pressure refrigerant which has served as the workhorse for Centrifugal and Rotary Screw chillers is R-134A. R-134a is being replaced and even offered now with the Azeotrope R-513A, which most manufacturers are utilizing for the time being. It is comprised of 44% R-134a and 56% R-1234yf. There is also R-1234ze which is an A2L refrigerant but has an extremely low GWP.
For low-pressure refrigerants, there are two options. R-1233zd has a low GWP and is an A-1 refrigerant. It has a slightly better capacity than R-123. The other option is R-514A which is a B-1 refrigerant, and it has a slightly worse capacity than R-123.
There are a variety of theories, discussions, and technical bulletins addressing the possibility of “dropping-in” refrigerants to existing working systems. Similar discussions to R-410A and R-22 many of us dealt with. We ask everyone to best educate themselves to make the best decisions. It is important to note, The operating range of R-410 compared to R-22 was over 200 psig higher and there are tens of millions of installations in the world where existing copper line sets were used when residential homeowners, multi-family owners, commercial building owners used R-410A in existing line sets when securing new split systems or just replacing the condensing unit. Thankfully, the new refrigerants do not have that large of a disparity between R-22 and R-410A.
Hold on to your hats because refrigerant-grade Propane or R290 is coming soon! It’s probably already used in your refrigerator or car!
Moving Forward
Something else to consider in the design and operation of systems is the Total Direct and Indirect Warming Impacts (TEWI) and Life Cycle Climate Performance (LCCP). Only a small portion of the greenhouse gas emissions come from direct emissions due to leaking refrigerant, whereas indirect emissions from electric power generation account for the large majority. Total HVAC system energy should be prioritized versus just using a lower GWP refrigerant. This graphic shows where GHGs come from
Moving forward it is important to keep equipment maintained and check for leaks. Assess the health and age of the equipment. And replace older less efficient equipment first or use them only on peak days. Try to conserve energy by installing the most efficient systems you can afford.