• Monthly Archives: February 2022

Decoding HFO Refrigerant Numbers

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.

The 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.  

Duck Tape

Like many others, I have assumed for years that the original and proper spelling for the ubiquitous gray cloth tape is duct tape, as in taping duct seams. I was wrong. I just recently learned some of the history of the original invention of Duck Tape by reading about it on a Facebook post by George Lanthier. If you work in oil or gas heat in the northeast, you probably have at least heard of George.  I know he knows what he is talking about, but we are talking about a Facebook post, so I did a little more research. According to Educationalnow.com, the word duck comes from the Dutch word doek, which means linen canvas. According to thoughtco.com, soldiers called it “Duck Tape” because of the way it repelled water. Perhaps both are true. But that is not really the interesting part of the story.

A mom named Vesta Stoudt came up with the original idea for Duck Tape while working in a factory packing ammo boxes. Before the development of Duck Tape, cartridges were packed in heavy cardboard boxes that were taped and dipped in wax to make them waterproof. The box flaps were sealed with thin paper tape, and a tab of tape was left loose so that it could be pulled to release the waterproof wax coating and open the box. The problem was that the thin paper tape wasn’t strong enough, and the tabs frequently tore off when soldiers pulled on them to open the ammo boxes, leaving them frantically scrambling to claw the boxes open while under enemy fire. Vesta developed a prototype cloth tape to solve this problem. She had a personal reason for her concern about the effectiveness of the ammo box sealing method, she had two sons in the Navy.  Unable to convince her supervisors of the merits of her idea, she wrote president Roosevelt. President Roosevelt and his military advisors liked Vesta Stoudt’s idea, and they asked the Industrial Tape Corporation, a division of Johnson & Johnson, to develop and manufacture a cloth-backed, water-resistant tape with a strong adhesive. Duck tape was made with a layer of cotton canvas (doek) coated in waterproof polyethylene, and a layer of strong rubber-based adhesive. Soldiers returning from the war found all sorts of uses for Duck Tape and its usefulness made it popular. Duck tape was not used for duct work until after World War II. Unfortuneately, the original style Duck tape is not actually recommended for use on duct work. It tends to dry up and become brittle. However, there are many other practical uses for general purpose Duck Tape.  Manco, now part of ShurTech Brands,  trademarked the name “Duck Tape” in 1980. Today, any tape actually named “Duck Tape” is from ShurTech. Now there actually is tape designed specifically for sealing ductwork, and it is referred to as “duct tape.”  Tape used with ductwork should have a UL 181 rating. The next time you hear someone mention “Duck Tape,” just realize they are being historically correct.

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