• Tag Archives: R32

New Refrigerants Transitional

The American Innovation and Manufacturing Act of 2020, or AIM was passed as part of the 2021 appropriation bill, passed on December 27, 2020. Although you probably would not know it from the title, the AIM Act is about phasing down HFCs. This is a phasedown, not a phase out. This table shows the phasedown schedule. Noite, we started the 60% of baseline period this year.  

AIM Act HFC Phasedown Schedule
Date% of Production Baseline% of Consumption Baseline
2020 – 202390%90%
2024 – 202860%60%
2029 – 203330%30%
2034 – 203520%20%
2036 –15%15%

Allowances

Because this is a phasedown and not a phaseout, some HFCs will still be available for a long time. However, ALL HFCs will not necessarily be available. The phasedown is regulated by assigning allocations for production and/or importing HFCs to producers and distributors. How quickly a company uses up their allocation is calculated by multiplying the quantity of HFC produced or used times its exchange value, which is basically its AR4 GWP. For example, R410A has an exchange value of 2088, R32 has an exchange value of 675, and R454B has an exchange value of 465. This means that a company can make 3 times as much R32 as 410A, or almost 4.5 times as much R454B as 410A.

Still Using HFCs?

One interesting situation is that the “new” refrigerants which will be replacing the current high GWP HFC refrigerants also contain HFCs. R32 is an HFC and it is on the list of refrigerants being phased down. Other alternatives being studied, such as R454B, are blends that contain R32. Phasing down R32 will eventually make both R32 and R454B not practical for equipment manufacturers. They will probably be replaced in ten years or less.

Making the Switch

HFC allowances are currently 60% of the baseline. If manufacturers continue to make exactly the same equipment with the same HFC refrigerants that they have been using, they will run out of their HFC refrigerant allowance before the end of the year. I believe most manufacturers will start producing R32 and R454B equipment this year. Just by switching from R410A to R32 a manufacturer can triple the amount of refrigerant they can use. Doing the math 60% x 3 = 180%. Suppose they used up half of their allowance on R410A before switching, that would be 30% x 3 = 90%. This means they could actually increase their overall production. The math is even better for R454B. 60% x 4.5 = 270%, or 135% if you had already used up half your allocation on R410A.

Down the Road 2029

Things get a bit tighter down the road in 2029 when HFCs are restricted to 30% of baseline. Now the R32 calculation is 30% x 3 = 90%, meaning you are restricted to less than the baseline for your entire production. The manufacturer will either have to use a refrigerant with a lower GWP or figure out a way to reduce the charge of the systems they produce. R454B looks a bit better with 30% x 4.5 = 135%, so you are still in business assuming you have not increased production a great deal and you are not using your HFC allocation for anything else.

Down the Road 2034

By 2034 manufacturers will definitely need to have more answers because the allocation drops to 20% of baseline. Now the R32 calculation is 20% x 3 = 60% and the R454B calculation is 20% x 4.5 = 90%: both fall short, and that is before accounting for any growth or using your HFC allocation for any other purpose.

Crystal Ball

In ten years or less I believe we will see systems using other refrigerants start to take over. At this point, I think the manufacturers are thinking HFOs. They are already widely used in car air conditioning and have very low GWPs. What remains to be seen is whether they will be widely accepted. The European Union is pushing back against fluorochemicals in general. They want “natural” refrigerants such as propane or carbon dioxide. Europe seems more comfortable with R290 in larger systems than we are in the US. I don’t think the added fire risk of R-290 is going to be accepted in larger systems in the US. I don’t believe CO2 is practical in smaller systems the size of residential air conditioners and heat pumps. Whatever the form, I believe in ten years we will be looking at very different equipment.  

What Does Mildly Flammable Mean?

I confess that I have always thought of flammability as an either or question: it either burns or it doesn’t. So the concept of different levels of flammability was a hard one for me to grasp. I wondered: what is the difference between 3,2, and 2L refrigerant designations? What follows is a somewhat lengthy discussion of what I learned.

First off, I found that it is not all that simple. There are several flammability characteristics that can be compared: lower flammability limit, upper flammability limit, auto ignition temperature, minimum ignition energy, heat of combustion, and flame velocity. The table at the bottom of the article shows these different specifications for a small selection of flammable refrigerants. Note that pressure and temperature also play a part. For the ASHRAE safety tests, a temperature of 140°F at atmospheric pressure is specified. You get different results when applying higher pressures and temperatures.

The original three classifications (1,2,3) were determined by the lower flammability limit and the heat of combustion. Later, ASHRAE added a 2L category for refrigerants with burning velocities less than 10 centimeters per second. The table below summarizes the different flammability classifications.

Classification Lower Flammability Limit % by volume Heat of Combustion Burning Velocity
1 Does not support combustion at atmospheric pressure
2L Greater than 3.5% Less than 19 kj/g 10 cm/s or less
2 Greater than 3.5% Less than 19 kj/g Greater than 10 cm/s
3 3.5% or less 19 kj/g or more NA

Lower flammability limit (LFL) is the minimum percentage required in air to be combustible. For example propane (R290) has an LFL of 2.1% by volume while ammonia (R717) has an LFL of 15%. Notice that propane only requires 2.1% while ammonia requires 15%. So that is one difference – the amount that must build up before it can burn.

The upper flammability limit (UFL) describes the maximum concentration which will still burn. If the concentration of flammable vapors exceeds the UFL, it will not ignite. It is more difficult to draw a straight line comparison using the UFL. However, you can say that refrigerants whose LFL and UFL are closer together are generally a bit safer simply because the conditions for a flammable mixture are less likely to occur.

The auto ignition temperature is the temperature which the flammable mixture will ignite. With the exception of 1234yf, refrigerants with a lower flammability have higher auto ignition temperatures than the more flammable refrigerants.

The minimum ignition energy is a bit different than the auto ignition temperature. It is the amount of energy that must be used to ignite a flammable mixture, measured in megajoules. Note that in this case R1234yf stands out because the minimum ignition energy is so high compared to the other refrigerants. Also note that the class 2L refrigerants all have minimum ignition energy ratings in the hundreds of megajoules or higher while propane’s minimum ignition energy is a very small 0.25 megajoules. Basically, this means it takes a lot more energy to ignite a class 2L refrigerant than a highly flammable class 3 refrigerant such as propane. Again, this means that the chance of having the right condition for combustion is much lower for class 2L refrigerants.

The heat of combustion is a measure of the amount of heat created when the refrigerant burns. Note that the class 2L and class 2 refrigerants have a heat of combustion in the single digits per gram while propane jumps to 46 kilojoules per gram. This means that the heat produced by combustion of a class 2L or class 2 refrigerant is far less than a class 3 refrigerant. Indeed, it would be possible for a class 2L refrigerant to burn and not ignite other nearby flammable materials.

Burning velocity is the characteristic which distinguishes class 2 and 2L refrigerants. It is the speed with which the flame advances. Note that the 2L class refrigerants have a burning velocity in the single digits while 152a, a class 2 refrigerant, has a burning velocity of 23 cm/sec. Propane’s burning velocity is twice that of 152a. The take home point here is that the flames from higher flammability refrigerants spread faster.

So wrapping it up, my general impression is that

1. Lower flammability refrigerants (2L) are less likely to burn in the first place.

2. When class 2L refrigerants do burn, the flames are not as hot as higher flammability class 3 refrigerants.

3. The flames from burning  2L refrigerant do not spread as quickly as the flames from higher flammability class 3 refrigerants.

Refrigerant R1234yf R32 717 Ammonia 152a 290 Propane
Safety Group A2L A2L B2L A2 A3
Lower Flammability LImit 6.5% 14.4% 15% 3.9% 2.1%
Upper Flammability Limit 12.3% 33.3% 28% 16.9% 10%
Auto Ignition Temperature 405°C 648°C 651°C 440°C 455°C
Minimum Ignition Energy 5,000 – 10,000 mJ 30 – 100 mJ 100 – 300 mJ 0.38 mJ 0.25 mJ
Heat of Combustion 9.5 kJ/g 9 kJ/g 22.5 kJ/g 6.3 kJ/g 46.3 kj/g
Burning Velocity 1.5 cm/sec 6.7 cm/sec 7.2 cm/sec 23 cm/sec 46 cm/sec
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