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.  

 

 

 

History of 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. Unfortunately, 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.

Chalk and Talk 

Several years ago a fellow HVAC instructor told me he had been strongly encouraged by his immediate supervisor to do more lecturing. To the academically trained supervisor, working with students in the lab didn’t look like teaching, it looked like training. In the supervisor’s mind, training was a lower level pursuit – akin to monkey see monkey do. The school had just transitioned from a Technical School to a Technical Collage and they wanted to look like a college. 

The instructor was asking for any help I could offer, especially along the lines of “chalk and talk”, his description of what he felt was being asked of him. I think that phrase perfectly embodies why so many students really don’t get a lot out of lectures – they are just observers, not participants. The instructor is writing stuff on the board and talking while the students are just passive observers.  In the days of chalk boards, the instructor was not even facing the class when they were writing. It sometimes seemed like the teacher was engrossed in their own thoughts while they stare at the board and talk to no one in particular. 

We have advanced a bit since then. At least with Powerpoint presentations we are usually facing the class, even if we are staring at our computer monitor most of the time. However, it is possible to lecture and still rise above the mind-numbing norm of a monologue delivered to a captive audience of passive observers.  

Begin by facing your audience and making eye contact with people long enough so they feel you are speaking to them personally. If you are using a Powerpoint presentation, be familiar enough with the presentation and the material that you don’t have to read the notes while looking at the screen. It is OK to look at the screen occasionally, but if your discussion is just straight out reading the notes it will be boring no matter how good the presentation is.

Use voice inflection and hand motion to convey personal interest in your subject matter. How do you expect your class to maintain interest if YOU think the talk is boring.

Stop and take a breath. One dead give away of a nervous speaker is someone who has rehearsed their speech so much that all the words come out in a rapid-fire regurgitation that indicates they are just repeating memorized phrases, not really thinking about they are saying.

Whenever possible, involve your audience. People learn more if they do more. Ways to involve the class could include group questions, prompts for input, or even direct questions to individual students if you know them well enough. Be careful with the last suggestion, the goal is to include the students, not intimidate or embarrass them.

Use visual aids. This is pretty easy to do today. Just be careful not to overdo the videos and pictures you share. You should not be handing your class over to professor YouTube, just showing snippets that enhance and reinforce your talk.

When using online material, make sure and watch it yourself first. Even though you are not the person in the video, if you show it to your class you are in effect endorsing it. There are some things online that you don’t want to be associated with. 

Finally, this is an HVACR class. It is perfectly OK to have gauges, meters, gas valves, compressors, or any other tools or parts you want as visual aids. If you are talking about meters, every student should have one in their hands. You can even do some small exercises during the lesson. Remember, people learn by doing, so have the students do something. No, this is not your typical college class – it is a hell of a lot more interesting.

 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

Human Search Engine

 Instructors worry about not knowing all the answers. I know that I do. Let me put you at ease. You don’t have to know all the answers to be an effective instructor. In fact, I feel that anyone who knows all the answers hasn’t asked enough questions. Our job as instructors is not to be a human search engine, but to teach students how to search for answers on their own. In short, to help students become more proficient at the learning process, specifically applied to our field of HVACR. To be clear, I am not suggesting that instructors do not need to be competent in HVACR. Nor am I saying you shouldn’t want to know as many answers as possible. Just that knowing every answer a student might ask is not necessary. Discomfort with areas where you don’t know the answers can sometimes cause instructors to cling to the specific areas of information they already know and refuse to broaden their scope. This is particularly true when it comes to new technology and industry developments. I believe this is an unconscious effort to “know everything” by limiting the scope of knowledge you expose yourself and your students to. Venturing into areas of new development can be uncomfortable because you don’t have as many answers at the ready. However, it is perfectly OK to tell a student that you don’t know the answer to a question they ask. Help them by directing them to resources where they might find answers. They are going to need research skills when they enter the field. Teaching students to learn on their own is probably the most important thing you can possibly teach them. On those many occasions when you DO know the answer, it can be more helpful to guide them through a search process than to simply hand them the answer. People tend to remember things they discover on their own more than things that people tell them. It takes discipline to do this. Providing the answer immediately basically concludes the interaction with the student. Asking leading questions or discussing relevant informative resources makes the interaction more of a dialogue and requires more student participation. It definitely takes a little longer, but provides a better long-term result. Remember, students learn more by what THEY DO, than by what you do.  

Gigabit vs Dialup

 

When lecturing, you should be more interested in ensuring the students understand what you are saying than covering a specific amount of material. Even if you manage to vocalize every important piece of information about a particular subject, it is largely a wasted effort if the students are not receiving the information. Your job is not to state all relevant facts, but to communicate them to the students. It is easy for us to transmit data faster than the students can absorb it. Remember, you have seen all this information before, probably said it all before, many times. You are not having to mentally connect the facts into a logical framework because you have already done that. However, the students who are hearing it for the first time have to comprehend each statement and then tie the different statements together in some logical manner in order to really understand what they are hearing. Help them comprehend the information by including analogies, similes, and connecting statements. One of the most powerful teaching techniques is to introduce new concepts and ideas using things people already know and understand. For example, “the refrigeration system moves heat from one place to another, much like a sponge can absorb water in one place and then release it in another when you squeeze it.” Like all analogies, it is imperfect, but it starts the process of thinking about absorbing heat in one place and releasing it somewhere else. Once you get that point across you can start talking about what the refrigerant does to absorb heat. Maybe boil some water in a flask. Learning is not just collecting data, it is making mental connections between the data points to develop new concepts. This takes time. If you are talking at gigabit speed while your students are listening on dial-up, most of the information will be lost. I have been guilty of this. I can recall asking students questions at the end of a one hour lecture only to discover that they did not really understand something that I said 15 minutes into my lecture. So although I discharged my duty to cover everything, really, I just wasted everyone’s time – including mine! So when lecturing, take some time along the way to ask a few questions and engage in some dialogue with the students to make sure your message is being received. Remember, the idea is not to demonstrate your knowledge, but to help the students increase theirs.

Teach the Process

A common problem that many students have across all levels of education is a failure to gain a thorough understanding of the subject matter being taught. I believe that the primary culprit is our over reliance on standardized, multiple-choice tests.  Information is presented as a disjointed collection of individual facts to memorize so they can be recalled on a test. Think of these facts as data points. People make poor data storage devices. Computers do a much better job. Now that everyone carries a computer in their pocket that is connected via the internet to supercomputers all over the world, there is very little reason for people to spend much time practicing personal data storage by memorizing and recalling facts. Instead, we should focus on what we are better at: understanding. By studying relationships and processes in addition to data, we gain an understanding of subject matter that is far deeper and more consequential. This level of learning exceeds what is possible by simply storing “facts” in our imperfect personal data storage units. 

It takes very little to make our collection of facts useless. A few years ago I was asked to write some technical literature for schools teaching HVAC in Georgia. I readily agreed, after all, I live in Georgia. After agreeing I found out the literature was to be for the Republic of Georgia, the one next to Russia! They don’t measure things in BTUs, CFM, tons of cooling, pounds, Fahrenheit, or any of the other thousand factoids I have rattling around in my head. Things like “400 CFM per ton” instantly became useless. Memorized snippets of code nearly as useless – I had to look up their laws and codes. Most every “fact” that I thought I knew became irrelevant. 

Fortunately, the principles that make the refrigeration cycle work are still the same. Although pressure is measured in kilopascals, temperature in Celsius, heating and cooling capacity in kilowatts, the processes and relationships are the same no matter which Georgia you are working in. While most of us will not have to worry about working in the “other” Georgia, we will have to adapt to technical advancements and changes which can make our set of “facts” just as useless. Take “400 CFM per ton”. Most new equipment does not come set for 400 CFM per ton out of the box anymore. New refrigerants are going to bring a whole new set of PT charts, so those saturated pressures at 45° and 100° are going to change. It is far easier to adapt to tomorrow’s technology if you truly understand today’s technology. Teach the processes, not an assortment of facts. 

Leaking Money

Done regularly, system inspections, leak checks, and system repairs save money. Yes, they cost money up front, but you save money in the long run. Finding and repairing leaks as soon as possible avoids wasting refrigerant and energy. A system operating undercharged loses capacity and efficiency – which ultimately costs the building owner in the form of higher utility bills. Neglecting system repairs can also shorten the equipment life. The problem is that these avoided costs feel a bit hypothetical: this is what could happen if.... 

So, the EPA has come up with a more tangible cost as an extra incentive: fines. If saving on the cost of refrigerant, energy, and system repairs is not enough incentive, consider the recent case of Southeastern Grocers. They recently agreed to a $300,000 civil penalty and to spend to $4.2 million over the next three years to reduce refrigerant leaks and improve company-wide compliance of EPA regulations. But Southeastern Grocers is certainly not alone. Safeway agreed to a $600,000 civil penalty and $4.1 million in system remediation costs, COSTCO agreed to $335,000 civil penalty and $2 million in system remediation costs, and Trader Joe’s agreed to $500,000 civil penalty and $2 million in system remediation costs. So I thought now might be a good time to review some of the basics in terms of what is expected.

As of January, 2019

Leaks in industrial process refrigeration (IPR), commercial refrigeration, and comfort cooling appliances containing 50 pounds or more of refrigerant must be repaired within 30 days if they exceed the EPA established leak rate. The trigger rates are 30% for IPR, 20% for commercial refrigeration, and 10% for comfort cooling. Note that this is a leak rate – you don’t get to wait until 30% of your refrigerant has leaked out. The leak rate must be calculated every time refrigerant is added to a system.

Verification Tests

After repairing the leak, you are required to perform an initial and follow up test to verify that the leaks have in fact been fixed and the system is operating below the established leak rate. The initial verification is done before adding refrigerant and the follow-up is done after the system has been in service.  The verification tests must demonstrate that leaks were successfully repaired. You may conduct as many additional repairs and verification tests as needed within the 30 day repair period. Note- you don’t get another 30 days every time you figure out it still leaks. The process must be completed within 30 days.

Leak Inspections

You are required to perform regular leak inspections on systems that have exceeded the applicable leak rate until the calculated leak rates found during the inspection indicate the leak rate is below the EPA trigger rate. Commercial Refrigeration and Industrial Process Refrigeration equipment that holds more than 500 lbs of refrigerant must be checked every three months.  Commercial Refrigeration and Industrial Process Refrigeration equipment holding between 50 and 500 pounds of refrigerant must be checked annually. Comfort cooling equipment must also be checked annually.

For more details, check out the EPA fact sheet here

https://www.epa.gov/sites/production/files/2016-09/documents/608_fact_sheet_supermarkets_property_managers_0.pdf

What is Vacuum Hose Conductance?

You may have heard or read the term “conductance” in reference to vacuum hoses and fittings. According to VAC AERO, conductance is volumetric flow rate divided by pressure drop, expressed as liters per second. Simplified, the conductance of a vacuum hose means its ability to allow gas to flow through it. The really important point is that no matter how big your vacuum pump is, it cannot move gas through a hose any faster than that hose’s conductance. Vac Aero

Hose conductance is not fixed, but varies with the type of gas, pressure, temperature, geometry of the passageway, hose diameter, and hose length. Duniway Stockroom Corp offers this formula: Conductance = 75 x Diameter³/Length. Note this formula calculates the conductance through a smooth tube in liters per second for dry air at 75°F and very low vacuums (under 50 microns). It won’t really calculate the conductance of a hose removing water vapor or refrigerant at atmospheric pressure. However, we can use it to get some general idea of the effect of diameter and length on hose conductance. Duniway

For example, the conductance of a ¼” diameter, 60” hose would be 75 x 0.25³ /60 = 75 x .015625/60 = 0.0195 liters per second. Turning that into cubic feet per minute (CFM) we get 0.0414 CFM. Suppose we shorten the hose to 36 inches. Now the conductance is 75 x 0.15625/36 = 0.03255 liters per second. That translates to 0.069 CFM. More than a 50% increase just by switching from a 60” hose to a 36” hose. What about changing the diameter? Using a 3/8” hose that is 60 inches long, the conductance becomes 75 x 0.375³/60 = 75 x 0.0527/60 = 0.066 liters per second. Translated into CFM, that is 0.14 CFM. We get over three times the conductance by increasing the diameter to 3/8”. Using similar calculations for ½” and ¾” we get 0.33 CFM and 1.12 CFM respectfully. So comparing different diameter hoses using this formula we see that a 3/8” hose has over three times the conductance of a ¼” hose, a ½” hose has more than twice the conductance of a 3/8” hose, and a ¾” hose has more than three times the conductance of a ½” hose. All together, a ¾” hose has 27 times the conductance of a ¼” hose. Large diameter hoses really do make a difference in the time it takes t pull a vacuum. However, there are other restrictions that must be addressed before the hose size matters: the Schrader valve cores. We’ll talk about them next time.

Wiring Communicating Controls

In some ways, communicating controls are easier to wire than conventional 24 volt control systems. There are fewer wires, and generally speaking, everything connects letter to letter. Still, it seems technicians keep figuring out ways to incorrectly wire four wires.

Wire Type

Early communicating systems used shielded cables that looked like computer cables – because that is what they were. You did not connect bare wires to anything, you plugged in the connector to the socket on the control board. Besides being somewhat expensive, these proved to be less robust than was needed for equipment installed outside. Most communicating control systems for traditional split systems and packaged units work fine with traditional thermostat wire: 18 gauge. In fact, the connections are designed expecting that type of wire.  Do not use anything smaller than 18 gauge. The control wire is generally not shielded. The control wire should not be run parallel to power wire to avoid interference. If you have to cross a power wire, it is best to do it at right angles. As with any installation, the control wire and power wire should not be run in the same conduit. It is fine to tape the wire to the line-set.

Mini-Splits

Nearly all mini-splits and multi-splits use communicating controls. Their wiring breaks all the rules discussed above. Typically, they use 14-4 cables. These cables contain four #14 gauge, stranded wires. Two wires in the cable are for powering the indoor unit and two provide communication. Sometimes this cable is shielded. If you do use shielded cable it is important to only ground one end, not both. I prefer grounding the end at the outdoor unit because you are closest to the power supply and the equipment ground. The connectors on mini-split and multi-split units are made to use stranded wire. Although there are only four connections, it is important that the same wire used to connect to each outdoor terminal connects to a similarly labeled indoor terminal. Sounds simple, but it is amazingly easy to cross up even just four wires. After connecting the outdoor wires, take a picture with your phone so you can verify that you are connecting them to the correct terminals inside.

Multi-Splits

Most multi-split units have terminal connections for each head at the outdoor unit. A 14-4 wire runs from the outdoor unit to each head. A crucial detail is to insure that the wires for each head correspond to the correct set of refrigerant lines. Although this seems simple, it is very easy to screw up. One way to avoid getting wires and lines crossed is to tape the 14-4 cable for each head to the line-set for each head.

Read and Follow Instructions

When it comes right down to it, most installation issues could be avoided by actually reading and following the instructions. Most manufacturers provide specific instructions for wiring their equipment, even if it is as simple as connecting four labeled terminals to four other similarly labeled terminals. There is not really an industry standard for the terminal labels. However, that is not important if you follow the manufacturer’s instructions. Most of the time, whatever label is used outside it also used inside.  

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.

Refrigerant Flammability Safety Rating

This is a re-post of an article I posted earlier. Flammable refrigerants are now really a fact of life, and so it is important that technicians understand the different classifications regarding refrigerant flammability. In particular, it is helpful to understand the difference between class 3 highly flammable refrigerants and class 2L, lower flammability refrigerants. 

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, the lower flammability refrigerants 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 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.

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 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 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

Appliances with Flammable Refrigerant Are In Stores Now

The EPA has approved limited use of flammable refrigerants in appliances. Specifically, R32, R290, R600a, and R441a. They are only approved for appliances with a limited charge, and the appliances must have warning labels to tell anyone working on the equipment that the refrigerant is flammable. However, the manufacturers have not gone out of their way to make sure the end consumer is aware that the refrigerant inside the appliance is flammable. R32 is an HFC with an ASHRAE Safety rating of A2L, which means it is low in toxicity but moderately flammable. You already use it without knowing it. 

R32 is used in many newer HFC zeotropic blends, including R-410A. These blends are generally rated A1 (low toxicity and non-flammable) because the mixture will not burn with the concentrations of R32 in them. R32 can be found at your local big-box store in window units and portable air conditioners. You have to look pretty hard to find it, but somewhere in the information they will tell you what refrigerant is in the unit. 

The other flammables are all hydrocarbons. They are all rated A3 – low toxicity but highly flammable. R290 is propane, R600a is isobutane, and R441a is a hydrocarbon blend. I have seen freezers and refrigerator-freezers at big box stores with R600a (isobutane) for refrigerant. 

Appliances using these highly flammable refrigerants have the required flammable refrigerant warning labels, but they are usually on the back of the appliance where the service access is. If you want to know if that shiny new refrigerator has explosive refrigerant in it you need to look at the back. I noticed that one refrigerator with R600a refrigerant also had a paper stating that using the appliance meant you agreed to binding arbitration as your sole legal remedy for any problems with the appliance. I don’t know if that manufacturer now makes this same disclaimer on all of their appliances, but it is worth asking about before purchasing. 

R290 (propane) is used on many small and medium sized commercial refrigeration refrigerators and freezers. R441a is used in some vending machines and smaller commercial refrigeration machines. I will talk some more in subsequent posts about flammable refrigerants, safe use, and safe service practices.

Tripped Rollout Switch

Anytime you have to reset a rollout switch on a furnace, warning alarms should go off in your head. The switch is not the problem, it is a symptom of a very serious problem. Just resetting the switch and going on is like turning off a fire alarm and leaving the fire burning. You need to find out why the rollout tripped. Rollout switches trip because flames are burning back where they are not supposed to be. Possible causes include a stopped up vent, a stopped up heat exchanger, low gas pressure, or a cracked heat exchanger. All of these conditions are very serious and have the potential to do great harm. Figure 1 shows a common rollout switch.

Figure 1 Rollout Switch

In the case of the plugged vent or heat exchanger. The flue gas cannot exit quickly enough, builds up and pushes the flames out of the heat exchanger into the area where normally there is only secondary combustion air. Although 80% gas furnace heat exchangers seldom become restricted, the condensing, secondary heat exchangers on 90% furnaces often become restricted. Either way, you must have a clear heat exchanger and vent to operate the furnace safely.

A cracked heat exchanger  can also lead to tripped rollout switches. A cracked heat exchanger can allow positive pressure air from the blower into the heat exchanger and reduce the draft. If the hole is big enough, the pressure in that cell of the heat exchanger can become positive, and push the flames out of the heat exchanger into the area where normally there is only secondary combustion air. Figure 2 shows an example of this. Look carefully at the burner on the left. See that there is no bright inner cone. That is because the flames are coming back out of the tube. The burner to the right of it looks normal.

Figure 2 Flames rolling out (left burner)

Low gas pressure can cause the flame to retreat from the burner port, back into the burner body, often all the way to the orifice. Figure 3 shows an example of flames burning back at the orifice due to low gas pressure.

Figure 3 Flames burning back at orifice

Whenever you find a furnace with a tripped rollout switch, you need to determine why the rollout switch has tripped. I know no professional would ever jump out a safety device, such as a rollout switch. But just to make certain – NEVER “fix” a furnace by jumping out a rollout switch. The switch is not the problem – it may be the reason nobody died.

EPA Proposes NEW Rules Change

I am a little late getting this out. On October 1, 2018, the EPA proposed a rules change that would effectively wipe out all regulations on non-ozone depleting refrigerants.

Really, the only ozone depleting refrigerant that is widely in service now is R-22, which will be pretty much extinct in a few years. For all of today’s refrigerants, such as HFCs and HFOs, this rule change would mean anyone could purchase refrigerant, no certification would be required to handle refrigerant, no refrigerant recovery would be required, no mandatory leak checks, pretty much no regulations. This would put technicians following best industry practices at an economic disadvantage compared to folks who don’t both purchasing things like recovery machines. It would open up the path for Home Depot and Lowes to sell systems to the public, since purchasers would no longer be required to be certified. I believe it would lead to more mangled equipment, as well as mangled DIY folks who watched a You-Tube video on how to change their own compressor. I urge you to write in to the EPA and tell them that you want to keep the current regulations, passed on November 18, 2016. All comments must be received by November 15, 2018.

Here is a link to the full text of the proposed rule changes

https://www.federalregister.gov/documents/2018/10/01/2018-21084/protection-of-stratospheric-ozone-revisions-to-the-refrigerant-management-programs-extension-to#addresses

Here are the instructions for submitting a comment

Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2017-0629, at www.regulations.gov. You will need to copy and paste the Docket ID 

Bristol Compressors Closing

It is sad whenever a company in HVACR cannot make a go of it. Bristol Compressors has announced that they are closing after more than 40 years in business. They developed some innovative products, such as the Inertia Compressors with suction valves built into pistons that separated allowing suction gas to travel through the piston head, or the Twin-Single compressors that had a unique crankshaft which moved both pistons up and down in one direction and only one piston in the other direction.  More details on the closing here https://www.coolingpost.com/world-news/bristol-compressors-announces-closure/ 

https://www.youtube.com/watch?v=vChfXCWq9oM

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.