Stay Away from Unapproved Flammable R22 Substitutes

At the risk of sounding like a broken record, I am once again talking about the dangers of unapproved, highly flammable R22 substitute refrigerants which are still easily available over the internet to anyone who wants to buy them. A quick Google search for R22 replacement refrigerant will list several places to buy these dangerous mixtures. The manufacturers market these under a variety of names. The EPA has listed many of them as specifically NOT approved for use. They include refrigerant products sold under the names R-22a, 22a, Blue Sky 22a refrigerant, Coolant Express 22a, DURACOOL-22a, EC-22, Ecofreeez EF- 22a, Envirosafe 22a, ES-22a, Frost 22a, HC-22a, Maxi-Fridge, MX-22a, Oz-Chill 22a, Priority Cool, and RED TEK 22a. The main component of all of these is propane.
 
It is true that the EPA has approved some flammable refrigerants for use in new systems with  lot of restrictions. However, the allowed use is for small refrigerators. The total allowable amount is very small, the systems must be new and specifically designed for flammable refrigerant. Refrigeration systems designed for flammable refrigerant meet strict safety standards, including non-sparking controls and labeling.  Class 3 flammable refrigerants are specifically NOT approved for use as a retrofit refrigerant for R22, or any other system designed for non-flammable refrigerant.

Every time a contactor or relay opens or closes they make a spark which is hot enough to ignite a flammable gas. If someone is losing refrigerant, their system has a leak. Continuing to add a flammable refrigerant on top of R22 will eventually create a flammable mixture. More worrying is that the flammable mixture will be leaking out somewhere.

As a practical matter, most recovery units are not designed to handle flammable refrigerants. Master Cool has just come out with one that is  specifically designed to safely handle flammable refrigerant. Even if you did not use any flammable refrigerant, are you certain that someone before did not add one of these flammable substitutes?

Here is a copy of some of the text from the EPA ruling

“ For retrofit residential and light commercial AC and heat pumps— unitary split AC systems and heat pumps, EPA is listing as unacceptable, as of January 3, 2017:
• All refrigerants identified as flammability Class 3 in American National Standards Institute (ANSI)/ American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 34–2013; and
• All refrigerants meeting the criteria for flammability Class 3 in ANSI/ ASHRAE Standard 34–2013. These include, but are not limited to, refrigerant products sold under the names R-22a, 22a, Blue Sky 22a refrigerant, Coolant Express 22a, DURACOOL-22a, EC-22, Ecofreeez EF- 22a, Envirosafe 22a, ES-22a, Frost 22a, HC-22a, Maxi-Fridge, MX-22a, Oz-Chill 22a, Priority Cool, and RED TEK 22a. “

Here is a link to the EPA ruling banning flammable refrigerant as a retrofit refrigerant. https://www.gpo.gov/fdsys/pkg/FR-2016-12-01/pdf/2016-25167.pdf

Alphabet Soup

Daikin just announced the release of R407H and the US EPA has added it to their SNAP list of acceptable refrigerants for both new and retrofit uses. 407H is designed to be a lower GWP refrigerant to replace R404A and R22 in commercial refrigeration applications. I confess, I did not know there was a 407G. I am often asked where all these numbers and letters come from.

The numbers for refrigerants which are mixtures of two or more refrigerants start with either a 4 or a 5. All zeotropic refrigerant numbers start with a 4 while azeotropic refrigerants numbers start with a 5. Zeotropic refrigerants separate when boiling; azeotropic refrigerants do not separate when boiling. The number after the 4 indicates the order that mixture of chemicals was tested by ASHRAE. For example, R401A was the very first. The letter after a zetropic refrigerant designates the order of testing for that specific mix of chemicals. For example, 407A was the first mixture of R32, R125, and R134a to be tested while 407H is the eighth. Please note that the letters for 400 series refrigerants should be upper case.

So what is the difference between 407A, 407C, 407H, and all the other 407 refrigerants? Just the percentage mix of the three ingredients. All eight versions of 407 have slightly different mixtures of the same three constituent refrigerants. A lot of this is done to tweak performance for a specific application or improve a particular characteristic, such as lowering the refrigerant’s GWP. 407H has a GWP of 1500 compared to 404A of 3922.

So what about the other refrigerant numbers, such as 22, or 134a, or (gasp) 1234yf? These describe the chemical construction of the molecules in these refrigerants. These refrigerants all consist of just one chemical compound. Compounds such as R12 or R22 are simple enough to be described without a trailing letter because there is only one way to build them. On the other hand, refrigerants 134a and 1234yf can be built many ways because they have more than one carbon atom. The trailing letters describe how the atom is constructed, which makes a difference in how it behaves. Note that these letters are lower case.

Flammable Refrigernats

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,  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. A refrigerant is classified as highly flammable, Class 3, if  either it requires 3.5% or less less by volume for a flammable mixture or it has a heat of combustion equal to or exceeding 19 kilojoules per gram. Note that EITHER condition will place it in class 3. Class 2 refrigerants require a concentration greater than 3.5% by volume to create a flammable mixture and they must have a heat of combustion less than 19 kilojoules per gram. Note that BOTH conditions must be met in order to be classified as class 2. 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.

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 dor a flammable mixture are less likely to occur.

Auto ignition temperature is the lowest temperature at which it spontaneously ignites in normal atmosphere without an external source of ignition. With the exception of 1234yf, the lower flammability refrigerants have higher auto ignition temperatures than the more flammable refrigerants.

Minimum ignition energy is a bit different than the auto ignition temperature. It is the minimum amount of energy required 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 the 2L refrigerants than a highly flammable refrigerant such as propane. Again, this means that the chance of having the right condition for combustion is much lower for class 2L refrigerants.

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 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 BV 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 lower flammability refrigerants are less likely to burn in the first place and when they do burn, the flames are not as hot and do not spread as quickly as a high flammability refrigerant such as propane.

  

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