The Difference Between A2L and A1 Cylinders

Tools, equipment, building codes, and even construction practices? What hasn’t changed this year? We cannot deny that all of the recent HVACR regulation changes can be challenging especially understanding how to handle A2Ls and which refrigerants we will still be working with. (For a quick review of what an A2L is, visit our Tech Tip about flammability.)  

One thing is for certain, A2Ls are here to stay. In this article, we will explain the difference between A2L and A1 cylinders. 

What are the main differences between A2L cylinders and A1 cylinders? 

There are 3 differences between A2L cylinders and A1 cylinders that you will notice– valves, pressure relief device and the colors. 

1. Valves: Good news! The valves on A2L cylinders look and operate the same way as previous cylinders. The main difference is in the threaded port which went from a right-handed thread (CGA 165) to a left-handed thread of the same size (CGA 166).  Are you scratching you head wondering why the industry made this change? It was to avoid cross contamination of A1 and A2L refrigerants. Now you know! 
2. Pressure relief device: Cylinders that contained A1 refrigerants used a rupture disk, a metal device that would break open within a pressure range well below the burst pressure of the cylinder, to protect the cylinder from over-pressure. The disk would experience a controlled rupture and that would release pressure from the cylinder, preventing it from bursting. While effective the major drawback was that once a rupture device opened, it would remain open and the entire contents of the cylinder would be vented. Cylinders for A2Ls have pressure relief devices instead of rupture discs.  These devices have a pre-calibrated spring that would allow the valve to open within a pressure range below the burst pressure. Why is a pressure relief device special? Once the overpressure is released, it will reclose. Now, in an ideal situation, only the necessary amount of refrigerant needed to relieve the excess pressure will be vented, instead of the entire cylinder.  A major improvement! 
3. Appearance/Colors: While the cylinders for A2Ls or A1s will look similar visually, A2L cylinders will have a painted red band, or in some cases, the entire top will be red (Canada especially).  This is a US-DOT requirement for transportation of cylinders containing A2L or other flammable refrigerants.  In addition, the industry continues to follow Guideline N from AHRI which recommends that all cylinders be painted in gray.  We have been used to seeing a variety of colors for each refrigerant like the green for R-22 and light blue for R-134a.  That trend is coming to an end and most cylinders of any type will be gray. So, no more rainbows of refrigerants. 

A2Ls cylinders will have some significant modifications designed to enhance their safety and suitability.  Please note that while the A2L and A1 cylinders themselves have a lot in common, the rules of how they are handled and transported are changing. Users need to keep that in mind. Look out for our next few tips where we take on some of these issues. 

Until then, stay safe and always read your manufacturers instructions when handling HVACR equipment!