Decoding HFO Numbering

 Undoubtedly you have seen news articles mentioning HFO refrigerants with names like 1234yf, 1234ze(Z), or 1234ze(E). Although these names look like a secret code, there is method in the madness. The good news is that technicians probably don’t need to know exactly how to read this secret code to do their job. However, telling me I don’t need to know what’s behind the curtain just encourages me to pull the curtain back. So here goes.

What is an HFO

First, you need to understand what an HFO is. An HFO is essentially an HFC with a double bond between two carbon atoms. You might remember from high school chemistry that carbon has a valence of 4. Think of the valence as the number of Velcro tabs on the atom. The carbon atoms in a normal hydrocarbon molecule are joined by single bonds, just one set of Velcro tabs joined between each carbon atom in the chain. They are called saturated because they are connected to largest number of atoms possible. Unsaturated hydrocarbon molecules, like HFOs, have a double bond between two of the carbon atoms. They use two sets of Velcro tabs between two of the carbon atoms. The double bond means there is one less atom in the molecule since two bonds are used between a pair of carbon atoms. Thus the designation as unsaturated.

Secret Code

The first four numbers of the secret refrigerant numbering code identify, in order: the number of double bonds, the number of carbon atoms, the number of hydrogen atoms, and the number of fluorine atoms in the molecule. However, there are many ways those atoms can be arranged, and different arrangements of the same components create different refrigerants with different physical properties. The last two or three letters describe how the atoms are arranged in the molecule.

First Number

The first number in the HFO numbering system describes the number of double bonds. At present, I am not aware of any HFO refrigerants that have more than one double bond. Currently all HFO refrigerants start with the number 1.  The 1 at the start of R1234ze(Z) indicates that the molecule has one double bond.  

Second Number

The second number is equal to the number of carbon atoms minus one.  The 2 in R1234ze(Z) indicates that the molecule has three carbon atoms: (#Carbons (3) - 1 = 2).

Third Number

The third number is equal to the number of hydrogen atoms plus one. The 3 in R1234ze(Z) indicates that the molecule has two hydrogen atoms (#Hydrogens (2) + 1 = 3).

Fourth Number

The fourth number is equal to the number of Fluorine atoms. The 4 in R1234ze(Z) indicates that the molecule has four Fluorine atoms.

First Lower Case Letter

HFO refrigerants are based on propylene, which has three carbon atoms. The first lower case letter identifies the atom connected to the middle carbon atom: x for chlorine, y for fluorine, and z for hydrogen. The lower case z in R1234ze(Z) indicates that the atom bonded to the middle carbon is hydrogen.

Second Lower Case Letter

The way the atoms are arranged on the ends of the molecule can vary. The second lower case letter describes the arrangement of the atoms on the end carbon containing the double bond. The letters are defined as 

a: 2 chlorine atoms

b: 1 chlorine atom and 1 fluorine atom

c: 2 fluorine atoms

d: 1 hydrogen atom and 1 chlorine atom

e: 1 hydrogen atom and 1 fluorine atom

f: 2 hydrogen atoms

The lower case e in R1234ze(Z) indicates that the end carbon with the double bond is connected to 1 hydrogen atom and 1 fluorine atom.

Upper Case Letter in Parenthesis

In some instances, there are two ways to connect the remaining hydrogen atoms. (Z) indicates the hydrogen atoms are on the same side of the double carbon bond. Z stands for zusammen: German for together. (E) indicates the hydrogen atoms are on opposite sides of the double carbon bond. E stands for entgegen: German for opposite. The (Z) on the end of R1234ze(Z) indicates that the two hydrogen atoms are located on the same side of the carbon double bond.

Although R1234yf, R1234ze(E), and R1234ze(Z) are all built out of the exact same type and number of atoms, the difference in how the atoms are arranged makes them three different refrigerants with different physical properties.  

 

 

 

 Diesel Effect Compressor Explosions

There have been a few rare but potentially fatal accidents involving exploding compressors due to an effect known as diesel effect. If the gas mixture being compressed contains enough air, the heat of compression can ignite the refrigeration oil in the cylinder, much the same way diesel oil is ignited in a diesel engine. The heat of compression plus the heat of combustion from the refrigeration oil then ignites the refrigerant in the cylinder, creating a dramatic increase in pressure which blows the compressor apart. Note that this is not just a phenomenon limited to flammable refrigerants, but can happen with A1 rated refrigerants such as 134a or 410A. How? 

Refrigerants are rated for flammability according to ASTM E681 at a temperature of 60°C. Many refrigerants that will not burn under ASTM E681 conditions will burn at higher pressures and temperatures, including R-22, R-134a and R-410A. It is worth noting that in tests where they were trying to create diesel explosions, the University of Tokyo found no significant difference between the behavior of A1 refrigerants (R-22, R-410A) compared to A2L refrigerants (R1234yf, R32). They also found that compressing refrigerant and air mixtures without refrigeration oil did not create a diesel explosion. The refrigeration oil had to be present. 

So how can we avoid compressor diesel effect explosions? Simply put: keep the air out. With no oxygen you cannot have an explosion. Air is never good for any refrigeration system anyway. It should not be news to anyone who has studied refrigeration at all that air does not belong in a refrigeration system. However, you may not realize that leaving air in the system not only hurts system performance and reduces the equipment life, it can create a real hazard to service technicians. Here are a few precautions you can take to avoid the specter of a diesel effect explosion in your refrigeration system. 

• Check new installations for leaks using nitrogen and repair any leaks in the system.

• Never use compressed air or oxygen for leak testing refrigeration systems. 

• Thoroughly evacuate the lines and coil of new split system installations AFTER verifying they don’t leak.

• Never pump a system down into a vacuum. Reducing the low side pressure to a vacuum can suck in air through leaks or incorrectly positioned service valves.

• Never jump out safety controls such a low-pressure switches. Forcing a system to run when it is low on refrigerant creates the possibility of sucking in air through leaks on the low side.

• Don’t simply add charge to systems that are low on refrigerant. This is especially true for systems that are significantly low. You should find and repair the leaks.

You can read more about the research into compressor diesel effect explosions here. https://hpc2017.org/wp-content/uploads/2017/06/o324.pdf

Low Global Warming Potential Refrigerants

You probably have heard that the most popular HFC refrigerants being widely used today are global warming gasses. In fact, some popular HFC refrigerants have higher GWPs than the CFCs and HCFCs they replaced. A refrigerant’s Global warming potential (GWP) compares it to CO², the global warming gas produced by burning hydrocarbons. A GWP of 1 indicates that a gas has the same effect on global warming as CO². The retired popular air conditioning refrigerant, HCFC 22, has a GWP of  1760. HFC 410A that is now widely used in air conditioning applications has a GWP of 1924. It is actually worse! Meanwhile HFC 404A, popular in refrigeration applications, has a GWP of 3943. HFC 134a is popular in domestic refrigerators, commercial refrigeration, and car air conditioning has a GWP of 1300. These high GWP numbers have made HFC refrigerants the target of regulatory efforts to limit their use and replace them with more environmentally friendly refrigerants. Europe has moved aggressively, passing their F-Gas regulations. The ultimate objective of the F-Gas Regulations is to cut the availability of HFCs by 79% between 2015 and 2030. There will also be a servicing ban on HFCs with a GWP >2500 for certain sectors. Here is a link to a quick overview of the F-Gas regulations byMitsubishi.

While the US has not moved nearly as aggressively, there have been attempts by the EPA to regulate refrigerants based on their GWP. Worldwide regulatory restrictions on current HFC refrigerants has spurred development of lower GWP refrigerants. Manufacturers in the HVACR industry have been actively developing lower GWP alternative refrigerants.

HYDROCARBONS

Propane (R290), Isobutane (R600a), and R441A all have very low GWPs of (3, 3,0). They are all non-ozone depleting and non-toxic. Their limitation is their flammability – they are all highly flammable. In the US they are approved only for systems with a charge of 150 grams (5 ounces) or less. In Europe hydrocarbon refrigerants have been used in refrigerators and freezers for years. These refrigerants are now common in residential refrigerator and small commercial refrigeration units in the US. While highly flammable refrigerants are likely to remain a factor in small commercial refrigeration systems, it is unlikely that these refrigerants will be used in larger systems in the US due to our aversion for being sued and the large number of lawyers in the US.

CO² R744

It is interesting that the main global warming culprit, CO², is also a refrigerant with a very low GWP of 1. It does not deplete the ozone, it is non-toxic, non-flammable, and cheap. What’s not to like? Unfortunately, CO² has a critical temperature of 88°F. It cannot condense above 88°F. This means that CO² systems are not “normal” systems. CO² systems must either be transcritical or cascade systems. Transcritical systems operate at very high pressures of 1200 – 1500 psig on the high side. Cascade systems use the evaporator of one system to cool the condenser of another system. Either way, CO² systems are more complicated and expensive than traditional system. One place that CO² has taken root is in large scale commercial refrigeration rack systems. Complexity in large rack refrigeration systems is normal and the extra cost of the transcritcial components is offset by the savings in refrigerant cost. However, in smaller scale systems the cost of a CO² system is prohibitive. For a quick explanation of a transcritical system check out https://www.achrnews.com/articles/94092-co2-as-refrigerant-the-transcritical-cycle

AMMONIA R717

Ammonia refrigeration has been around since the earliest days of refrigeration. Ammonia has always been used in large scale food commercial refrigeration and freezing for food processing because of its efficiency and low cost. Unfortunately, ammonia (R-717) has many application challenges. It is toxic, somewhat flammable, and cannot be used with some metals, such as brass or copper. It will continue to be a mainstay of commercial food processing, but I doubt you will see it expand into other market segments.

LOWER GWP HFCs

There are some HFC refrigerants that have a GWP in the hundreds instead of the thousands. While these refrigerants are probably not long-term solutions, they can provide a way to drastically reduce the GWP footprint of a system without a drastic change in technology or design.

R 32

HFC R-32 has been adopted by many manufacturers in air conditioning systems sold outside of the United States. R-32 is an HFC with a lower GWP of 667. That is still not really low compared to CO2 (GWP 1) or ammonia (GWP 0), but it is considerably lower than R404A, R410A, or R134a. HFC32 has the advantage of being a relatively “normal” refrigerant, making designing systems to use it less challenging than say, CO². However, R-32 is flammable. While not as flammable as propane, it does burn. That precludes its use in most applications in the US, at least right now. The building and safety codes in the US do not allow a flammable refrigerant in systems where the air in the building flows directly over the evaporator. These codes make no distinction between A2L and A3 refrigerants. To them, flammable is flammable.  Manufacturers and code officials in the US are working to determine what new requirements an A2L refrigerant system should have to make it safe for use. The one place you will find R32 in the US is in window air conditioners. The EPA allows use of R32 in limited quantities in window units. Here is a link for more information on R32. 

R466A (Solstice N41)

Honeywell has developed an A1 rated, non-flammable HFC based refrigerant with a GWP of 733. Like R-32, R-466A provides a refrigerant with a much lower GWP than HFC refrigerants currently in use, but not really low. Its big advantage over R32 is that it is non-flammable. R466A achieves this by using a mix of 49% R32, 11.5% R125, and 39.5% R1311. R32 and R125 are the two components found in R410A. R1311 has been previously used as a fire suppressant. This blend performs similarly to R410A, making adoption relatively easy.  Here is a link to more information on R466A. 

HFOs

Hydrofluoroolefins (HFOs) are a special type of HFC. They have at least one carbon double bond, making them less chemically stable than a “normal” HFC which has all single bonds. Because they are less chemically stable, they do not persist in the atmosphere for long, and this reduces their global warming potential. For example, HFO1233zd has a GWP of 0. HFO1233zd is a low pressure refrigerant for chiller applications. It has an A1 safety rating and does not deplete the ozone. HFO1234yf has a GWP less than 1. It has an A2L safety rating – meaning that it is somewhat flammable. HFO1234yf is used in auto air conditioning systems. It has been what most auto manufacturers now use instead of HFC134a. Here is a link to more information on HFOs.

R1234ze

R1233zd

R1234yf 

Lower GWP refrigerants are the future of HVACR. Some old and some new. Understanding how to safely work with these lower GWP refrigerants will be an important part of all technician’s knowledge set going forward.

Chemours (Dupont) Buys ICOR International

I just got an email info blast from ICOR in which it states that ICOR is now a wholly owned subsidiary of Chemours. Tht surpised me, so I looked a littel further into it and found an article on :Cooling Post" dated April 8, 2018 which confrms that Chemours bought ICOR. Here is the link to the Cooling Post artcle
https://www.coolingpost.com/world-news/chemours-buys-refrigerant-supplier-icor/
Here is the link to the info blast that ICOR sent me.
http://www.icorinternational.com/images/C-11673RisksofLow-QualityRefrigerants-ChemoursBranding.pdf

Basically it is warning against cheap refrigerant from unknown sources. As always, if you stick with legitimate supply houses you are pretty safe. If you get it off the back of someone's truck at midnight in the parking lot behind the bar, well you might not be getting what you think you are getting. Even ordering over the internet is risky if you are are buying it from someone outside of the normal distribution chain. There is now counterfeit refrigerant out there, so just because the jog says Honeywell or Chemours does not mean that it really is from that manufacturer. Some of the counterfeit stuff has hydrocarbons in it and could be quite dangerous in a system that is not designed for explosive refrigerant.

New Low GWP Non-Flammable R410A Replacement

This will be a short post because I don't know a lot of details yet. Honeywell is developing a new three part zeotropic refrigerant that can replace R410A. It has a relatively low GWP of 733 compared to 2088 for 410A, and most significantly, is non-flammable. Honeywell's trade name for it is Solstice N41, the ASHRAE number is R466A. It reportedly contains the same two chemicals as in R410A (R32 and R125). A third is added - trifluoroiodomethane (CF3I). This third component is currently used a a fire retardant. It also helps reduce the GWP of the mixture. The new refrigerant is not claimed to be a "drop-in" for R410A, but required design modifications are said to be minimal. The refrigerant is currently undergoing ASHRAE testing, but has received a preliminary A1 rating.  I have now told you all I know, and it did not take very long. Here are links to two articles about this new refrigerant.
https://www.coolingpost.com/world-news/secret-of-honeywells-new-refrigerant/
https://www.coolingpost.com/world-news/honeywell-announces-r410a-breakthrough/
 

Unlocking the Secret Refrigerant Numbering Code

I have wondered why the new HFO refrigerant numbers look like an internet password. In short, the numbering system describes the chemical makeup of the refrigerant. But that is also true of the much simpler numbers, such as HCFC 22. So why does HFO 1233zd(E) look like a secret code? Mainly because the chemical is a bit more complicated. HFC 22 is a methane based molecule, with only one carbon. All that is needed to describe it is a way to determine how many fluorine, chlorine, and hydrogen atoms surround the single carbon atom. There is really only one way to put the molecule together.

HFO refrigerants are decidedly more complicated. They are built around a propene molecule. Propene has three carbon atoms surrounded by hydrogen atoms. Propene is similar to propane, except propane has all single bonds between its atoms while propene has a double bond between two of the carbons atoms.

You can think of each carbon atom as having four Velcro hooks. Molecules like propane only use 1 hook for each bond. This allows each carbon to bond to the most possible other atoms. Molecules constructed this way are referred to as saturated.  Two of the carbon atoms in a propene molecule use two Velcro straps to bond to each other, which reduces the number of other atoms the carbon molecules can bond with. Molecules built this way are referred to as unsaturated.

To unlock the secret code which describes fluorinated hydrocarbon refrigerants, just add 90 to the number, leaving off the leetrs for now. For example, 1233 + 90 = 1323. Working backwards from the right, the first number describes the number of fluorine atoms. In this case it is 3. The second number from the right describes the number of hydrogen atoms. In this case 2. The third number from the right describes the number of carbon atoms. In this case 3. The fourth number from the right lists the number of double bonds in the molecule. In this case 1. Notice the number of chlorine atoms was not addressed. The number of chlorine atoms is found by subtracting the fluorine and hydrogen atoms from the number of bonds. A propene molecule has 6 bonds. 6- 3 -2 = 1. There is one chlorine atom.

So what are the letters at the end of 1233zd(E)? The short answer is that all the letters following the number describe the particular molecular arrangement. We know that 1233zd(E) contains 3 carbons, 3 fluorines, 1 chlorine, and 2 hydrogens. However, even if you know exactly which atoms there are, you must also describe where they are attached because there are now many places to put them.

Each different arrangement of the same atoms produces different properties, so it is important to specify which arrangement the refrigerant is using. These different arrangements are called isomers. The two lower case letters after the number describe the specific arrangement (isomer). But note that this refrigerant number has yet another upper case letter after the two lower case letters. Some isomers have the same arrangement, but differ in spatial orientation. The upper case letter identifies which spatial orientation.

This is about as deep as I feel I should go in a blog post (maybe even a bit too deep). If you want more detail, it is all explained in the ASHRAE Standard 34-2016.

Court Rules Against EPA SNAP Ruling

Two refrigerant manufacturers, Mexichem and Arkema, have successfully sued the EPA over their decision to start phasing out HFC refrigerants because of their global warming effect. The gist of the argument is that the law which established the EPA’s right to regulate refrigerants is specifically about ozone depletion, not global warming. The EPA’s legal right to regulate replacement refrigerants is limited to their effect on ozone depletion. The court ordered the EPA to redo their ruling with this in mind. Below are a couple of direct quotes from the ruling.

“The fundamental problem for EPA is that HFCs are not ozone-depleting substances, as all parties agree. Because HFCs are not ozone-depleting substances, Section 612 would not seem to grant EPA authority to require replacement of HFCs. Indeed, before 2015, EPA itself maintained that Section 612 did not grant authority to require replacement of nonozone-depleting substances such as HFCs.”

“EPA’s novel reading of Section 612 is inconsistent with the statute as written. Section 612 does not require (or give EPA authority to require) manufacturers to replace non-ozone depleting substances such as HFCs. We therefore vacate the 2015 Rule to the extent it requires manufacturers to replace HFCs, and we remand to EPA for further proceedings consistent with this opinion.”

The EPA still has to do their rewrite, and of course it is possible that they might choose to appeal to the supreme court. But for now, the HFC phase down has been phased out.

You can download the ruling and read it for yourself here:

https://www.cadc.uscourts.gov/internet/opinions.nsf/3EDC3D4817D618CF8525817600508EF4/$file/15-1328-1687707.pdf

Below are two links to other articles about this ruling.

http://r744.com/articles/7787/u_s_court_rules_hfcs_cannot_be_limited_by_current_epa_rules?utm_source=mailchimp&utm_medium=email&utm_campaign=Bi-weekly+Newsletter

http://cen.acs.org/articles/95/web/2017/08/Court-strikes-down-US-restrictions-on-HFCs.html

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

Refrigerant Don'ts

With summer now upon us and the price of R22 skyrocketing there are many questions regarding replacement refrigerants. This discussion could fill a book, so I am going to restrict this post to a list of don'ts. The intent is to help people avoid issues that can be caused by improper application of 400 series R22 replacements.

Do NOT use a flammable replacement refrigerant in ANY system originally designed for R22. There are some hydrocarbon (propane) based replacement refrigerants sold online. They are NOT EPA approved and represent an explosive hazard when charged into a system that was not designed for flammable refrigerant.

Do NOT add ANY replacement refrigerant on top of an existing R22 charge. This is an EPA violation. You are essentially creating a “new” refrigerant which has not been tested or approved. There are NO replacement refrigerants which are legal to add in on top of an existing R22 charge. You must first remove ALL of the R22 when doing a conversion.

Do NOT use ANY 400 series refrigerant in a flooded system. Even refrigerants which are advertised to work in systems with mineral oil will still separate in the flooded portions of the system because they are not truly miscible. There is a difference between miscibility and solubility, but that is the subject for another whole article.

Do NOT use ANY replacement refrigerants in ANY system using an electronic expansion valve. This would primarily be older R22 minisplits, multisplits, and VRF systems. Trane hyperion heat pumps can sometimes have an R22 charge. In that specific case, the indoor air handler is designed for both R22 or R410A, so switching to R410A and changing the refrigerant dip switch solves that problem for the indoor air handler. Unfortunately, you will still have to replace the outdoor unit with one designed for R410A.

Do NOT use ANY 400 series replacement refrigerant in systems which were originally designed for R22 and have Trane 3D Scroll compressors. The lubrication system that specific compressor design uses does not work well with HFC refrigerants, including ones advertised as being compatible with mineral oil.

This all come down to one main strategy for replacing R22 in most older systems: it is generally best to replace the whole system. Not only does this avoid application problems, it usually provides a significant efficiency upgrade as well.

What is an HFO?

Hydrofluoroolefins, HFOs, are a relatively new class of low global warming potential refrigerants. They are actually composed of the same chemicals found in an HFC: hydrogen, fluorine, and carbon. If you define an HFC as a chemical containing those three elements, then HFOs are actually HFCs. The difference is in how they are constructed.

Ethane

HFC 134a

 Both HFCs and HFOs start out as a hydrocarbon, containing a chain of carbon atoms surrounded by hydrogen atoms. To make a traditional HFC you replace some of the hydrogen atoms with fluorine atoms. Standard hydrocarbon molecules and traditional HFC molecules are composed exclusively of single atomic bonds. You can think of an atomic bond as a type of Velcro strip holding the atoms together. Carbon has four atomic Velcro strips while hydrogen and fluorine just have one. Single bonds just attach one strip between atoms. Using only single bonds a carbon atom will connect to four other atoms because it has four bonds. Molecules constructed this way are called saturated. They have the maximum number of atoms joined together.

Propane

HFO 1234yf

What makes HFOs different is that they use a double bond between two carbon atoms. These two caron atoms are connected together with two Velcro strips instead of just one. Since carbon atoms only have four connections, using two to connect to each other means that each carbon can only connect to two other atoms besides each other. This reduces the total number of atoms that can be connected together. This type of molecular construction is called unsaturated.

Why does this make a difference? Unsaturated molecules are far less chemically stable and tend to break down easier. Since HFOs are less chemically stable, they do not survive long in the atmosphere – and so they do far less harm than the more stable saturated HFCs. The difference is dramatic. HFC 134a has a GWP of 1430 while HFO-1234yf has a GWP of 4.

However, HFOs have a design challenge to overcome: they are mildly flammable. The very instability that reduces their GWP increases their flammability. At present, building codes in the US generally do not recognize a difference between highly flammable refrigerants and mildly flammable ones. Most building codes do not allow the use of significant amounts of flammable refrigerant inside the building. ASHRAE is working on revising their Safety Standard for Refrigeration Systems,  Standard 15. It is projected to be ready by January 2018. For more information on the work being done on flammable refrigerants check out this article in Contracting Business
http://contractingbusiness.com/refrigeration/codes-preparing-technology-refrigerant-changes

Sorting Out Refrigerant Flammability

Most techs know that ASHRAE Standard 34 originally established three categories of refrigerant flammability: 1,2, and 3. They ranged from 1 – nonflammable, to 3, highly flammable. Category 2 was listed as mildly flammable, or somewhat flammable. Then they added a new category – 2L – for an even lower category of still flammable refrigerant. I admit that I always found that a bit confusing. In my mind, it either burns or it doesn’t.  In order to get a better handle on this I have done some studying.

Two characteristics are used to differentiate category 1 and category 2 refrigerants: the lower flammability limit and the heat of combustion. The lower flammability limit is the lowest percentage concentration of gas in a gas-air mixture that will ignite. Concentrations lower than the lower flammability limit will not burn. Even highly combustible gasses such as gasoline have a lower flammability limit. Refrigerants with a lower flammability limit of 3.5% or less are considered class 3, highly flammable. For comparison the lower flammability limit of gasoline is 1.4%  and propane‘s is 2.1%. Another way for a refrigerant to be considered class 3 is for its heat of combustion to equal or exceed 19 million joules per kilogram. In general terms, it does not take very much class 3 refrigerant to burn and when it does it is very hot.

Class 2  refrigerants have a lower flammability limit greater than 3.5%. It requires more than 3.5% concentration in order to ignite. Class 2 refrigerants do not burn as hot as class 3 refrigerants: their heat of combustion is lower. The lower heat of combustion is important because that is what sets other things on fire. It is possible for a class 2 refrigerant to burn without burning up everything around it.

So where does the 2L come in? Flammability class 2L is really a subclass of 2. Refrigerants with a 2L designation have a burning velocity of 10 centimeters per second or slower. The burning velocity is how fast the flame travels. A burning velocity of 10 cm/s means that the flame will travel about 4 inches in a second. In contrast, the class 2 refrigerant HFC-152a  has a burning velocity of 23 cm/sec.  – a little more than twice as fast.  Propane, a class 3 refrigerant, has a flame velocity of 39 centimeters per second – 4 times as fast.

Why is this important? The flame velocity and heat of combustion are what determine whether or not an explosion can occur. Rapid burning and high heat of combustion expand the air and combustion gasses so rapidly that great pressure is created, blowing things apart. Class 2L refrigerant cannot burn fast enough or hot enough to blow anything up. In many cases, a burning class 2L refrigerant will not even catch other combustible things around it on fire.

To summarize:
Class 3 Refrigerants have a lower flammability ratio of 3.5% or lower and/or a heat of combustion equal to or greater than 19Mj/kg. They burn fast and hot.

Class 2 Refrigerants have a lower flammability ratio exceeding 3.5%. It takes more of them to burn and they do not burn as hot as class 3 refrigerants.

Sub-Class 2L Refrigerants in addition to a lower flammability ratio exceeding 3.5% also have a flame velocity of 10 cm/sec or less. They burn slowly and without releasing as much heat.

Class 1 Refrigerants do not burn.

HFCs not Going Anywhere

HFCs are not going away any time soon. I am sure you have all hear about the push to reduce or eliminate HFC refrigerants because of their global warming potential. This past weekend at Comfortech 2016 I sat in on a very informative session by Rob Yost on refrigerants. One big point was that low GWP replacement candidates for R410A are all rated at 2 or 2L for flammability. The reason is pretty straight forward. To be non-flammable a chemical must be relatively stable. However, that stability means it lasts longer in the atmosphere, which increases its global warming potential. In other words, low flammability and low global warming potential are somewhat opposites in terms of chemical properties.

The newest low GWP blends being developed are actually blends of both HFOs and HFCs. The highest pressure HFO developed at this time is very similar in pressure to 134a. Obviously that won’t replace 410A. However, mixing it with some higher pressure HFC refrigerants yields a much lower global warming potential than 410A at working pressures that are similar to 410A. However, this mixture will be flammable.

The current building codes in the US don’t allow flammable refrigerants inside buildings in most circumstances, so none of the refrigerants presently being studied can be used under the current building codes. The next revision for building codes is due out in 2018. However, the window for incorporating exceptions for lower flammability refrigerants into the 2018 code has already passed – and no exceptions or conditions for the use of 2L flammable refrigerants are in the upcoming 2018 code. That makes 2021 the closest date that flammable refrigerants could possibly be used inside buildings. Even though that is only a little over four years from now, we can be reasonably sure that no mass extinction of HFC refrigerants will occur any time soon.

Before we transition out of 410A to something else, the issue of using lower flammability refrigerants inside buildings will have to be addressed, and even then, it is likely that HFC refrigerants will be some of the components in the next generation of refrigerants.

Refrigerant Cylinder Color

“Hey, grab that Wedge Wood Blue cylinder and let’s go charge this unit. No, that’s the Royal Blue one. There it is, right next to the Medium Blue cylinder. No, that is the Sky Blue cylinder. Gosh, don’t you know your refrigerant colors?”

Back in the good ole days, we just had a few colors to keep up with. Most of us just had to recognize the difference between green, white, and purple.  Now there are so many different shades that not even an interior decorator can keep up with them.

AHRI Guidline N is where the industry normally lists the colors of the different refrigerant cylinders. The latest version lists 46 different colors – the big box of crayons. That is why you should always read the cylinder label, not just go on the color. Guideline N describes four classes of refrigerants and they allow the same color to be used in different refrigerant classes. So it is possible that Sky Blue cylinder could have either R-134a or R-13. The only way you know is to read the label.

PMS 413

In the future you will have an even better reason to read the label – all refrigerant cylinders will be the same color. The 2016 edition of Guideline N specifies that all Refrigerant containers should be painted light green gray (RAL 7044 corresponding with PMS 413) starting in 2020. This is spelled out in section 4.8.

PMS 185

One critical color to recognize is red – PMS 185. Cylinders containing flammable refrigerant should have a red band on the shoulder or top of the container. This is specified in section 4.7. Not only should you read the cylinder label, you should be familiar with the properties of any refrigerant you handle. If you start working with a new refrigerant, you should read the safety data sheet. Most refrigerant manufacturers also have refrigerant properties and handling instructions online. You can download and read the details of Guideline N for yourself  HERE

EPA Warns of Flammable Replacement Refrigerants

As the summer cooling season gets under way it is a good time to reiterate that flammable refrigerants should NOT be used as replacement for R-22 in existing systems. Some people are putting in R-290, which is simply propane.  A few have tried charging their systems with fuel grade propane. Not only is this dangerous, but fuel grade propane has lots of water contaminants and will screw up your systems, that is if it does not blow up. Yes, it is true that the EPA approved flammable refrigerants for a few very specific uses in systems with a very limited charge. However, these are NEW SYSTEMS ONLY! These systems are designed from the outset to handle a flammable refrigerant.

Your R-22 air conditioner of heat pump has many spark creating controls, such as relays and contactors. A leaky system recharged with a flammable refrigerant could have all the components for an explosion: fuel, oxygen, and an ignition source. The EPA has started fining companies for selling non-approved, propane based R-22 replacement refrigerants. Most have “22a” in their name. Unfortunately, there are still plenty of places to buy this stuff over the internet. A few other names include “Frosty Cool” and Eco-Freeze”. You should be wary of anyone that sells refrigerant directly to consumers over the internet.

I don’t believe regular HVACR wholesalers will have any of this stuff, and major refrigerant companies such as Honeywell, DuPont, or Arkema are not selling it either. They do each offer their own R-22 replacement solutions, none of which are flammable. Some legal replacement solutions have very small percentages of hydrocarbon components to improve oil return. Their hydrocarbon components are in such small quantities that they generally pose no threat of flammability. So what is the best thing to put in an R-22 system? R-22. Read more about the EPA actions and warnings here.

What Flavor is Your CO2 System?

If you work in any phase of refrigeration, you undoubtedly have heard about the emergence of CO2 refrigeration systems in commercial refrigeration. I had the pleasure of touring the HillPhoenix Refrigeration plant in Conyers today, and I was impressed by both the number and variety of CO2 systems they are currently building. They had Cascade systems, Trans-critical systems, Glycol systems and Booster Systems all using CO2. These are distinctly different approaches to working with CO2.

The transcritical has probably received the most press. It derives its name from the fact that the high side operates above the critical point while the low side operates below the critical point. The name indicates that the system operates on either side, or across, the critical point of the refrigerant. The critical point is the pressure and temperature at which the refrigerant can no longer condense to a liquid. So the “condenser” is really just a gas cooler. The refrigerant does not condense to a liquid until AFTER the pressure is dropped. The critical temperature of CO2 is 88°F, so any time the high side temperature rises above 88°F, the refrigerant will not condense. The pressures are bit higher than you might be used to – over 1200 psig, so not just any compressor and piping will do. However, in a way, the transcritical systems are a bit simpler than the other flavors.

Cascade systems use two complete refrigeration systems – one system’s job is really to cool the condenser of the other system. If you keep the CO2 cold enough, say 40°F, the pressures are not that high. However, to have a 40° condenser requires a system whose evaporator is in that same temperature range and whose condenser is at the normal operating temperature for an air cooled condenser. This system typically uses HFC refrigerant. So you have a heat exchanger and an HFC system to keep the CO2 system cool. This allows wider range of compressors because the CO2 compressors are not operating at 1200 psig. However, the system operating with the normal temperature condenser (80°F – 100°F) will have a refrigerant OTHER than CO2.

And then there are the booster systems. The booster systems incorporate both low and medium temperature racks into a single unit. The low temp CO2 compressors pump into the suction of the medium temp CO2 compressors, which operates at transcritical temperatures and pressures. This way the low temp compressors don’t have to be heavy duty transcritical compressors, just the medium temp compressors. The system uses only CO2, no HFC refrigerant is required, as in a cascade system.

There are also glycol systems, where the refrigeration system cools glycol, which is pumped through the store to the cases. This reduces the amount of refrigerant in the system and reduces leaks by reducing the amount of piping, fittings, and braze joints. What became apparent in my visit was that there are many ways to solve the same problem, and you can expect to see different solutions at different locations. It also is apparent that in commercial refrigeration, CO2 is here to stay and HFCs are on their way out.      

Caught One!

The lead story of the August 11, 2014 Air conditioning Heating and Refrigeration NEWS is “Man Gets Prison Time for Venting R-22.” In this particular case he was stealing copper – he just did not bother to recover the refrigerant first. The police literally caught him in the act, and knowing what he did was a Federal violation, reported him to the EPA. Now he is serving 31 months in prison. Truthfully, most people who steal copper or vent refrigerant are not caught. However, this case proves that you CAN be caught, and there is a substantial penalty.  Some people do the right thing because that is the way they conduct their lives. Others need some external reinforcement to avoid doing what they know they are not supposed to do.  Without penalties for breaking the rules, these folks will ignore the them. Hopefully this incident will be widely publicized so that other potential thieves in need of external reinforcement will consider another line of work. Or at the very least, steal something that does not involve venting refrigerant.

Here is a link to the story Prison Time for Venting Refrigerant

EPA Proposes Ban on R-404A and Other Refrigerants

You may have heard that the EPA is proposing to ban the use of some common refrigerants  I would like to give a brief overview of things you should know about this proposed ruling. First – at this stage it is still a proposal – not a ruling. Typically the way this works they publish a proposed ruling, allow us to comment on it, revise the ruling based on the comments (if they choose to), and publish the final ruling.  Since this is still a proposed ruling, you have a little time before it will take effect. Second, not all industries are affected by this ruling. Air conditioning caught a break – air conditioning systems are not covered . However, motor vehicle air conditioning IS covered. For motor vehicle air conditioning the big news is that 134a will no longer be acceptable in NEW VEHICLES beginning January 2016. A large number of zeotropes are also banned from use in new vehicles, but most of those are mainly used today as an R12 substitute. That should not have a great effect because they are only banned in NEW vehicles.

Retail refrigeration appliances and vending machines are also covered. The big news here is that R507 and R404A will be considered unacceptable for both new AND retrofit applications in retail refrigeration beginning January 2016. Retail refrigeration would include things such as display cases in grocery stores.

Four areas that are NOT covered by this proposed rule (yet) include cold storage warehouses, ice machines, refrigerated transport, and industrial process  refrigeration. However, the EPA is specifically asking for comments about the possibility of using low GWP refrigerants in these areas as well.
 “EPA requests comment on the use and viability of both low-GWP refrigerants (e.g., R-744, R-717, and HCs) and other HFC-blends (e.g., R-407A and R-407F) and the possibility of listing R-404A, R-507A, and other high-GWP blends unacceptable in any or all of these four end-uses.” I encourage you to do some of your own research into this. Here is a link to the proposed RULING. Here is a link to a FACT SHEET about the ruling. Here is a table summarizing the proposed changes to the auto air conditioning and retail refrigeration refrigerants.

Refrigerant Uses Deemed Unacceptable as of January 1, 2016
End-use	Substitute	Further Information
Retail food refrigeration (new and retrofit)	R-404A	R-404A is a blend, by weight, of 44% HFC-125, 4% HFC-134a, and 52% HFC-143a. It has a high GWP of approximately 3,920. Other substitutes are available for this endues with lower overall risk to human health and the environment.
Retail food refrigeration (new and retrofit)	R-507A	R-507A is a blend, by weight, of 50% HFC-125 and 50% HFC-143a. It has a high GWP of approximately 3,990. Other substitutes are available for this end-use with lower overall risk to human health and the environment.
Retail food refrigeration (condensing units and supermarket systems) (new)	HFC-227ea, R-407B, R-421B, R-422A, R-422C, R-422D, R-428A, R-434A	These refrigerants have GWPs ranging from 2,729 to 3,607. Other substitutes are available for this end use with lower overall risk to human health and the environment.
Retail food refrigeration (condensing units and supermarket systems) (retrofit)	R-407B, R-421B, R-422A, R-422C, R-422D, R-428A, R-434A	These refrigerants have GWPs ranging from 2,729 to 3,607. Other substitutes are available for this end use with lower overall risk to human health and the environment.
Retail food refrigeration (stand alone units only) (new only)	HFC-134a	HFC-134a has a Chemical Abstracts Service Registry Number (CAS Reg. No.) of 811-97-2 and it is also known by the name 1,1,1,2-tetrafluoropropane. HFC-134a has a relatively high GWP of 1,430. Other substitutes are available for this end use with lower overall risk to human health and the environment
Retail food refrigeration (stand alone units only) (new only)	FOR12A, FOR12B, HFC-227ea, IKON B, KDD6, R- 125/290/134a/600a (55.0/1.0/42.5/1.5), R-407A, R-407B, R-407C, R-407F, R-410A, R-410B, R-417A, R-421A, R-421B, R-422A, R-422B, R-422C, R-422D, R-424A, R-426A, R-428A, R-434A, R-437A, R-438A, RS-24 (2002 formulation), RS-44 (2003 formulation), SP34E, THR-03.	These refrigerants have GWPs ranging from approximately 550 to 3,607. Other substitutes are available for this end-use with lower overall risk to human health and the environment.
Vending machines (new and retrofit)	R-404A	R-404A is a blend, by weight, of 44% HFC-125, 4% HFC-134a, and 52% HFC-143a. It has a high GWP of approximately 3,920. Other substitutes are available for this endues with lower overall risk to human health and the environment.
Vending machines (new and retrofit)	R-507A	R-507A is a blend, by weight, of 50% HFC-125 and 50% HFC-143a. It has a high GWP of approximately 3,990. Other substitutes are available for this end-use with lower overall risk to human health and the environment.
Vending machines (new only)	HFC-134a	HFC-134a has a Chemical Abstracts Service Registry Number (CAS Reg. No.) of 811-97-2 and it is also known by the name 1,1,1,2-tetrafluoropropane. HFC-134a has a relatively high GWP of 1,430. Other substitutes are available for this end use with lower overall risk to human health and the environment
Vending machines (new only)	FOR12A, FOR12B, IKON B, KDD6, R- 125/290/134a/600a (55.0/1.0/42.5/1.5), R-407C, R-410A, R-410B, R-417A, R-421A, R-422B, R-422C, R-422D, R-426A, R-437A, R-438A, RS-24 (2002 formulation), SP34E.	These refrigerants have GWPs ranging from approximately 550 to 3,085. Other substitutes are available for this end-use with lower overall risk to human health and the environment.