Layered Learning

One common problem with teaching and learning HVACR is that there is just so much material to master. It is easy to drown the students in details if you are not careful. When I was using a text which presents enthalpy diagrams in its early chapters on basic refrigeration, students would come up to me and ask for drop slips after reading the chapter. They looked at the PH diagrams and concluded that they just were not smart enough for HVACR. It was just way too much information for them to comprehend while they were still wrestling with refrigerant boiling while it is cold! The real skill in presenting HVACR subject matter is to take inherently complex material and break it down into a series of comprehensible lessons, without leaving out material. Presenting information in stages, at a rate which most students can more easily digest is preferable to feeding them the whole enchilada at once and causing cognitive indigestion. You can still reach the peak, but you have to get to base camp first.

Electricity is a perfect example. We start with the basic concepts of voltage, current, resistance, and simple circuits. If you think of a simple balance beam with voltage in the middle – if resistance goes up, current goes down. Students can in fact understand how current, voltage and resistance are related without using any formulas. Similarly, you don’t have to bring in Ohm’s Law to understand the concepts of source, path, and load. In fact, I believe circuits are best approached at first without discussing Ohm’s Law. Students can build circuits and operate them to get a mental concept of how switches  and loads behave. They can even build series and parallel circuits to see how they differ: all without formulas. Then AFTER the students understand the basic concept of an electrical circuit, you introduce Ohm’s Law as a mathematical description of a circuit. Now they have something real to relate to the parts of the formula and it is less abstract. You can even build circuits with heaters and take measurements to demonstrate how Ohms Law works.

After students have learned to solve Ohm’s Law problems, then we tell them that Ohm’s Law does not work in most AC circuits. At first, we don’t discuss the effects of alternating current, inductive, and capacitive reactance. It is just too much to take in at once. However, since these concepts have far more to do with most air conditioning circuits than Ohm’s Law, we can’t really afford to ignore them. The effect of inductive reactance can be demonstrated by operating a small motor in a circuit and comparing its resistance, current, and voltage. You can have students build circuits that demonstrate the effect of inductive and capacitive reactance and how they relate to each other. Depending on how much AC electricity you teach, you can put an oscilloscope on the circuits to show what happens in capacitive and inductive circuits (the teacher would be doing this.) Finally, you can bring in reactance and impedance calculations, although I must admit we do not have our Air Conditioning classes at Athens Tech doing LCR calculations. It’s a little like boiling a frog – you do it a little at a time. Before the students know it, they have learned some complex subject matter that would have sent them running for the exits if it had been presented all at once.

HVAC/R Language

A little over a year ago I posted an article on acronyms. Today I am expanding on that idea and offering suggestions on how to avoid confusing your students with HVAC/R techno-speak. We have our fair share of acronyms in HVAC/R. Used properly; acronyms speed up communication by reducing long polysyllabic phrases to a few letters. For example, speakers would get a bit winded if they used the phrase “heating, ventilating, air conditioning, and refrigeration” repeatedly in a conversation. The abundance of industry specific acronyms and the use of more than one acronym for the same item can be truly bewildering to students. For example, one major valve manufacturer uses the acronym TEV to represent “Thermostatic Expansion Valve,” while another uses the acronym TXV for the same thing. They do not represent two different types of components, just two different ways to abbreviate the same words.

When introducing a new topic, using acronyms can lead to confusion and misunderstanding. Worse, students can start to pick up the jargon, but use it incorrectly. It can be difficult for teachers who have had years of experience with HVAC/R techno-speak to remember that the acronyms we casually throw around often have no meaning for our students. Imagine listening to a lecture in which every important concept was in Russian! For example: “The evaporator delta T is controlled by the TEV adjustment, the return air wb, and the CFM.” Now I believe that most any air conditioning instructor understands this sentence, but it is essentially unintelligible to many air conditioning students. It might as well be in Russian! Replacing the HVAC/R specific jargon with the wingdings font it looks like “The evaporator delta T is controlled by the TEV adjustment, the return air wb, and the CFM.” THAT is what this sentence looks like to a new student!

In general it is a good idea to resist using an acronym for something until that item or process has been discussed. Otherwise, the acronym will appear to students to be a mysterious grouping of letters used by air conditioning shaman to communicate with each other. The acronyms and jargon become a secret language which they are not familiar with. I believe that acronym free language promotes better understanding.

Of course, students must still learn the HVAC/R language. Having a solid grasp of the terminology is necessary to make use of essential technical literature produced by equipment manufacturers. Once they are understood, acronyms help us communicate. Can you imagine actually writing out or saying positive temperature coefficient thermistor every time we disused PTC devices? However, the acronyms must first be explained and defined before they are used. It is much easier to remember an acronym if you understand what the letters stand for. When using an acronym for the first time make sure and explicitly spell out what the letters represent, this will increase student’s understanding and retention of the term. It also helps for the students to have a good mental picture of the object or process being described. They are far more likely to remember what  Δ T (Delta T) stands for if they have actually measured a temperature difference and you have discussed it in class. That way the abbreviation is not an esoteric piece of jargon attached to something they don’t understand, but a name for something they have done. In Fundamentals of HVAC/R, we always use the complete word or phrase before introducing an acronym. It helps to explain concepts plainly. After introducing the concept, we give the technical terminology that is used to refer to the concept. The students are more likely to remember the terminology if it is logically connected to something they understand.

Fundamentals of HVAC/R has a unique abbreviation and acronym dictionary to help students learn the language of HVAC/R. Students can find out exactly what is meant by a particular acronym or abbreviation in Appendix C which lists the definition of common acronyms and abbreviations used in HVAC/R. The acronym dictionary is very useful when students are reading industry literature and need help with a particular abbreviation or acronym. For definitions of acronyms the students use when texting each other you will have to refer to another reference, acronymfinder.com  


BFN GTG

Managing Large Group Labs

The easiest way to manage your lab is to have one lab instructor for every five students. I have actually taught lab classes where we had this ratio and it was a lot of fun. We were able to spend a lot of time with each student and we were able to do things you just can’t do with larger groups. So what if you have more like 20 students per lab instructor? It is still possible to give them a good lab experience, but a lot more planning and organizing will be required up front, and there will be things that are just not practical. One management technique is to split up large groups into smaller ones and schedule them at different times, effectively making several smaller lab classes. Of course this means you must spend more time than usual since you will be repeating the lab for each group. This may not be an option for everyone depending upon the number of instructors, students, lab equipment, and available lab time. For most of us, there will come a time when we have to work with larger groups in the lab.

A common technique is to have students work in groups. I try to avoid this if possible because it often means a couple of confident students do the work and the rest of the group watches and writes down the results. In group projects, you can see the 80/20 rule at work: 80% of the work is done by 20% of the people. However, this can be managed if you know it is going to occur. Ask every member of the group a question that requires an understanding of the process. For example, if the group is measuring the superheat on an air conditioning system you might ask different students

• What is superheat?
• What measurements are required?
• How did you arrive at the current superheat?
• What readings are necessary to use the manufacturer’s superheat charging chart?
• What does the system charging chart say the superheat should be?
• What does this system's superheat tell us about the system?

If they know they are going to be asked to perform a task or answer a question, they will at least pay more attention to what is going on.

Some skills are so important, every student must perform them for you individually. Lighting an oxy-acetylene torch is one example. An issue with large groups is simply the amount of equipment and tools available. Most of us would be hard pressed to come up with 15 oxyacetylene torch sets so that every student could have their own. Besides, I really do NOT WANT to have more than three rookies working torches at the same time. Once when I had a class of 18 students who needed to learn to braze, I worried about how I was going to teach all of them to handle an oxyacetylene torch safely. What I did was to demonstrate, as I always do and then ask questions to see what people remembered. We then went back over the procedure, paying particular attention to things that I felt they had missed the first time. Finally, I lined them up and had each student turn on the tanks, set the regulators, light the torch, adjust the flame, shut off the flame, and shut down the torch leaving it ready for the next student. If they hesitated, they repeated the process. I noticed that the students got progressively better, which was odd because the most confident students had stepped forward first. When I remarked to one student on how quickly and confidently he performed the task he replied “I saw it done 10 times before I had to do it.” In other words, the students waiting in line learned through the experience of their fellow students. This made me feel less guilty about having everyone wait in line to work with me. This method works well for procedures that can be demonstrated in a few minutes such as lighting torches, soldering, brazing, or installing gauges. If the students use their time wisely and pay attention to what is going on they will learn by watching others and everyone leaves with an important skill they did not have the day before.

Problem Solving

HVAC/R Service is about practical problem solving. All the tools, technology, training, and literature are just there to help us identify and solve problems. The primary skill that any service tech needs is problem solving. The most important tool at your disposal is your mind. I am frequently asked why we make students do BTU calculations of ice turning to steam, series parallel ohms law problems, gas law calculations, or any host of other primarily mental exercises that nearly all HVAC/R students must suffer through. Usually, the students asking are doing the most suffering. Although I can justify all of the above as an endeavor to garner a deeper understanding of the principles which make HVAC/R systems work, I usually tell them that you can’t become a champion weight lifter by lifting marshmallows. Service techs are not paid to connect gauges or take voltage readings, they are paid to solve problems. Obviously techs need to be familiar with all the tools at their disposal, but we should never overlook the fact that their primary tool sits on their shoulders. I am afraid the current focus on standardized testing throughout our educational system has not prepared our students for practical problem solving. Rather, they are used to selecting the best solution from a very limited set of answers. My prescription? Lots of work that requires students to recognize and define the problem, systematically find the cause, and offer a solution. Assign work that requires students to provide written answers. Ask questions whose answers have not been explicitly stated, but require students to put two pieces of information together. If you get an answer that is way off base, try and ask leading questions to help the student work their way through a solution to the problem. The exact answer is not as important as the process. Encouraging students to use their minds to solve problems is crucial. The shop is a great place to work on problem solving because real life problems are never as simple as a, b, c or d. But don’t accept “the part is bad” as an answer. The student should be able to explain what the unit is doing wrong, what is the cause, how they determined the cause of the problem, and what their proposed solution is. Truth be told, I believe this approach could work in a lot of fields besides HVAC/R. The leaders in any field are always people who have recognized and defined problems and then devised solutions.

Dry Out!

Its spring, the weather is warming up, flowers are blooming, and our thoughts turn to dehumidification. In humid climates like the southeast, removing humidity from the air in warm weather is just is just as important to comfort as reducing its temperature. Being warm blooded, our body normally produces more heat than it needs and then regulates our temperature using different cooling mechanisms. The primary cooling mechanism is evaporation of perspiration from our skin. Dry air makes us feel cooler because it accelerates the evaporation from our skin. Humid air makes us feel warmer because the evaporation process is slowed down. Dehumidification can be the difference between being comfortable and being uncomfortable at 78°F. Dehumidification can save energy by reducing the amount of sensible cooling required for comfort. Many people with oversized air conditioning systems essentially over cool their house to be comfortable because their systems do not run long enough in mild weather to reduce humidity, so they do not feel comfortable until they reach temperatures of 70°F in their house. It takes several minutes for most air conditioning coils to get cold enough to sweat. An over sized system will often satisfy the thermostat and shut off shortly after the coil reaches dew pont. A properly sized air conditioning system will run longer, allowing longer operation with an evaporator operating below dew point and removing more water from the air. Systems with ECM blowers and thermidistat controllers have a special dehumidification mode that reduces system airflow for dehumidification. This increases the latent system capacity and decreases its sensible capacity. Two stage cooling systems can help by allowing longer system operation at moderate loads. All of these are a big improvement over the typical oversized single capacity system with a PSC blower. However, an air conditioner is still not a dehumidifier.

If you are really serious about dehumidification you need a dehumidifier. In a nutshell, a dehumidifier is an air conditioner with a single blower that moves air first over the evaporator, and then over the condenser. The air first passes over the evaporator where it is cooled to dew point to remove water, and then the same air passes over the condenser where it is reheated to a temperature slightly above its original temperature. If you have a basement in the southeast you NEED a dehumidifier. My basement stays below 80°F all the time without air conditioning, but it feels warm without my dehumidifier operating. In the past most dehumidifiers have been small console types that are noisy, inconvenient, and typically undersized. Several companies now offer whole house dehumidifiers that can be integrated into a complete comfort system for your house. They have enough capacity for a house, are far quieter, and do not require you to empty a bucket twice a day. Therma-Stor has a good short animation on why basements have high a relative humidity and how a dehumidifier addresses this problem. You will find other articles on their website which help address specific dehumidifier applications. They also have a psychrometric chart in a round format that looks like a ductulator that are great for teaching psychrometrics. To read more about the effect of humidity on comfort, check out Unit 61 Fundamentals of Psychrometrics in Fundamentals of HVAC/R. To download an interactive pschrometric chart for free, go to HandsDown Software.

Promote Active Listening With Questions

I believe that what the students do is just as important as what the teacher does. One of the big problems with traditional lecture is that most of the students are doing very little, the teacher is doing all the work. The teacher talks and the students listen. In the days before whiteboards and powerpoint this was often referred to as “chalk and talk.” I must confess that I can slip into this mode if I am not careful. Delivering a well organized lecture and writing notes as you go is not bad, but keep in mind that just because YOU SAID IT does not mean that the STUDENTS LEARNED IT! It is important to use delivery techniques that keep the students engaged. One simple technique is to ask questions. Three types of questions I use are volunteer responses, shout outs, and directed questions. Note: these are my own labels. Other folks probably have their own descriptive labels for these common methods.

I often open a topic or discussion with volunteer responses. This gives me an idea of what my students know and opens a discussion on the topic in a relatively low stress way because students are not put on the spot. Students that have done their homework or already have knowledge in the topic are the most likely to respond. Volunteer responses are probably the most often used in many class rooms. Two potential hazards of volunteer responses are that the same students tend to do all the answering, and the answers you receive can be wrong. Wrong answers are OK, just try and steer the class in the correct direction without embarrassing the student that offered the incorrect answer. If people are shot down when responding, the responses will stop.

Shout outs (my term) are questions directed at the audience in general where the answer you expect is fairly obvious and several people are likely to shout out the answer. These work to reinforce material, review main points, and provide you with feedback before you go on to another topic. I just have the class finish my sentence. For example, after discussing the states of matter and the properties of each state you might say “So, the three states of matter are … and the class will respond “solid, liquid, and gas.” Then follow with some more specific questions like “The state which has both a definite shape and volume is...”

Both volunteer responses and shout outs suffer from a common flaw: they allow a small core of dominant students to do all the answering while less confident students hide. Directed questions ask a specific student a detailed and specific question. This can be done using homework questions. The idea is to make sure everyone has to answer at least one question. I had a professor in college that was great at this. He would ask a few questions over homework or the previous day’s lecture to start each class. He would ask the question before calling the name of the person who was required to answer. This kept all of us listening to the questions and the answers because you did not know when you would be required to answer. I can tell you this technique is effective at getting lazy students to study the material before class – it certainly worked on me! However, it does also create a fair amount of stress. I use directed questions about once a week when we go over homework. Everyone knows they will be embarrassed if they show up for class without having done their homework. I reduce the stress level by going around the room in order, so students have a good idea when their time will come.

The simple act of asking questions and requiring students to do more than sit quietly improves retention of the material. After all, the goal is not for you to say everything the student needs to know, it is for the students to learn it.

Keep the Discussion on Track

I attended the 2010 HVACR & Plumbing Instructor Workshop at the National Conference Center in Landsdowne, VA this past week. This past couple of weeks has been both tiring and rewarding. I often pick up ideas and teaching tips just by watching other people work. I went to see Wes Davis of ACCA discuss system efficiency and picked up a simple and effective idea for handling questions that could possibly sidetrack the discussion. I am particularly bad about exploring questions and ideas that students pose during my lectures because my lectures are often more discussions than lectures. However, if the discussion gets too far away from the outline, you run the risk of missing important points and losing most of your audience while you are engaging in exploratory oratory. Don’t get me wrong, I believe you should encourage questions. However, it is important to also keep the discussion moving forward in an organized and logical manner. Wes had a large flip chart with the title Parking Lot at the top. Whenever a question came up that did not fit well into the flow of the lecture, he wrote it down in the parking lot. The idea is to acknowledge the question and come back to it, while avoiding a possibly distracting trip down a side alley of thought. I noticed that many of the parking lot questions were eventually answered later on in his presentation. He addressed the ones that were left at the end, and this discussion created more questions and discussion. Putting questions in the parking lot allowed the flow of the presentation to continue while still encouraging questions. Actually writing the questions down insured they would be addressed and showed that he was not just dismissing the questions. Then when the questions were addressed it seemed to get the group’s juices flowing and created lively discussion. There were many good power point presentations that will be put up on the CARE website. You have to be a member of CARE to see many of them, but one good power point presentation is worth the $25 cost of joining CARE. I would recommend that you join CARE and go to the resources they have on their site for their members. The CARE website is http://www.carehvacr.org/

Lab Magic!

Most of us think of labs as a chance for students to practice the practical application of HVAC/R skills: brazing, charging, wiring, or troubleshooting to name a few. Certainly, students must practice their practical skills in the lab. I believe that the lab can also be instrumental in teaching more abstract concepts like gas laws or ohm’s law.

I have found that most HVAC/R students are visual and tactile learners. They learn more by seeing, touching, and doing than by reading, writing, and listening. Frequently the desire “to do” is part of what motivated them to study air conditioning in the first place, as opposed to a more academic pursuit. They arrive at the HVAC/R class excited and ready “to do”, and then we provide them with an opportunity to learn gas law formulas and ohms law. Normally we teach these subjects with an extra helping of mathematical equations. The numbers in the equations are typically all presented as part of a hypothetical example or problem. For those of us with a good understanding of the theory and the concept, the meaning is clear. For students who are still trying to understand the difference between a volt, an amp, and an ohm the problem simply becomes an exercise in math. They are not really interested in math formulas, and telling them the formulas are good for them is a bit like forcing them to take their castor oil. To overcome this, get them in the lab early and use numbers from real objects.

For ohms law, have the students measure the resistance of a strip heater, measure the voltage at the source, and then have them use ohm’s law to predict the amp draw. Next, have them operate the heater and measure its amp draw. The readings won’t be perfect, but they will be close enough to get the point across. Then do the same thing with two heaters in series and then two in parallel. They can read the individual resistance of each heater and then the combined circuit resistance to show how series and parallel resistances work. The key is to have the numbers associated with something real.

Gas behavior also works well. You can talk about the boiling point being tied to the pressure all day long and not really get the point across that boiling does not have to occur at a high temperature. This is because the information contradicts the student’s life experience – the only thing they have seen boil was hot. Put water in a flask, attach the flask to a vacuum pump, and start the vacuum pump. The water will boil at room temperature. Invite the students to touch the flask and ask questions. I have yet to see anyone who does not like this experiment. It is simple, does not take a lot of equipment, and really makes an impact.

There are many other similar labs we run whose purpose is to demonstrate an important concept. Students can quickly learn fundamental electrical circuits in the lab as well. Just make sure students know not to energize any circuits before having an instructor checks them. After the students start to connect the concepts to something that is real, then they will start to ask questions. Now you can start to use hypothetical examples and the students have a mental image of a real device to give the discussion meaning.

For some more ideas about these types of labs, take a look at the Lab Manual by David Skaves. It contains an entire section of labs labeled as Properties labs. These labs teach students about physics properties that make HVAC/R work. Although this Lab Manual is written to accompany Fundamentals of HVAC/R, it works well with any text because it is organized by subject matter with sections on Fundamentals, Properties, Refrigeration, Accessories, Controls, Electricity, Maintenance, Gas Heat, Oil Heat, and Electric Heat. Each section has several labs.

The New 70

Many of the old timers I talk to who are still leery of R-410A want to know what the “new 70” is. They want a target number for the suction pressure of an R-410A air conditioning system. Many service technicians are in the habit of charging to a target number on the suction side. This is frequently 70 psig on R-22 systems. The saturation temperature of R-22 at 68.5 psig is 40°F and for many years the standard evaporator temperature at design conditions has been 40°F. But 70 is a nice round, easy to remember number and close enough for quickie rules of thumb. The problem is that systems seldom operate at design conditions. Another big problem is that conditions other than charge can cause low suction pressure. If a technician is only checking the suction pressure, they are not collecting enough information to recognize other system factors that can contribute to low suction pressure. A common error of inexperienced techs using the “70” method is overcharging systems that have low evaporator airflow. I have gone behind someone using the “70” method who had overcharged the system so severely the compressor stalled at startup and pegged my high side gauge past 500 psig. The customer was told that the compressor was bad. To be fair, most experienced technicians that use the “70” method understand how airflow and system operating conditions affect system pressures, they just don’t want to bother with manufacturer’s charts. They just modify the target up or down as they judge conditions affecting system pressures. These folks can usually get a system cooling; that is why they still have a job. However, the system will often not be performing optimally when they leave. Today’s customers are paying a premium for systems that are more efficient and have less environmental impact than older systems. Beginning January 2010, even the least expensive unit a customer can purchase will be non-ozone depleting and more efficient than the least expensive unit they could purchase just a few years ago. This means everybody is paying for efficiency and reduced environmental impact. However, if technicians don’t charge units properly, customers are not getting what they are paying for. Your students can be the vanguard of a new era that values professionalism. Make sure your students know how to handle new refrigerants like R-410A and know how to read and follow manufacturer’s charging charts. That will put them in a position of leadership early in their career.

Fundamentals of HVAC/R has a detailed discussion of system charging in Unit 27 Refrigerant System Evacuation and Charging. Variables affecting system pressures, common methods of determining the correct charge, and common methods of adding refrigerant are all covered. Charging is also discussed in other units including

• Unit 35 Residential Split system Air conditioning installations
• Unit 36 Troubleshooting Split System Air Conditioning
• Unit 52 Heat Pump Installation
• Unit 53 Troubleshooting Heat Pump Systems
• Unit 83 Troubleshooting Refrigeration Systems
• Unit 84 Installation Techniques
• Unit 85 Planned Maintenance
• Unit 86 Troubleshooting

The Formula To Success

A problem that many students have when beginning their study of air conditioning and refrigeration is that many of the most crucial concepts are traditionally presented primarily through math formulas. Even simple concepts become confusing when they are presented using traditional algebraic formulas that assign constants and variables for each measurement. For many students, algebraic explanations become barriers to learning. Presenting the foundation science conceptually and using analogies to common life experiences helps. If students understand the basic idea, learning the math that represents the idea is easier. That is why Fundamentals of HVAC/R presents science facts conceptually, not just as math formulas.

Take gas laws for example. Relate temperature to the average speed of the molecules: higher temperatures produce faster moving molecules; lower temperatures produce slower moving molecules. Next tell students to imagine gas pressure as the force of the gas molecules colliding with the sides of the container holding them. The more collisions produce higher gas pressure; fewer collisions produce lower gas pressure. Now tie the two concepts together: when a gas is heated the molecules move faster, increasing collisions with the sides of the container which increases the gas pressure. When a gas is cooled the molecules move slower, reducing collisions with the sides of the container which reduces the gas pressure. Discuss this point and ask questions to make sure they understand. After they have grasped the pressure temperature relationship you can introduce the related formula. Understanding the concept first makes the math a little easier to grasp because they have some context to hang it on. Remember it is more important for students to understand the pressure-temperature relationship than it is for them to calculate gas law formulas. Being able to work the gas law formula is not really the goal, understanding the temperature-pressure relationship is.

However, most standardized tests in this filed still rely heavily on manipulating traditional math formulas. So we also discuss common formulas that students are likely to see in HVAC/R literature and standardized tests, like the ICE or NATE. Throughout the book, whenever a formula is introduced, we give detailed examples showing step by step how the formula is used. To make the example formulas are easy to follow they are presented in the most straight forward, uncomplicated way possible. The text also uses practical examples showing the usefulness of the formulas that are introduced. Students are more willing to make an effort learning something that has a demonstrated application. Besides discussing formulas throughout the text whenever they are relevant, Fundamentals of HVAC/R lists many useful formulas in one place: Appendix B Commonly Used HVAC/R Formulas.

A good exercise in preparation for taking an industry standardized test is for the students to look through all the formulas listed in Appendix B and make certain they understand how to apply each formula. The unit in the text where the formula is discussed is listed beside each formula. This shows students where to look for a discussion and an example problem for any particular HVAC/R formula.

It's Called a Compressor Because ..

How often have your students asked for study guides and hints before tests? Tell them that the hints are built into the terminology. In many cases, HVAC/R terms define themselves. The names for most components and processes are not randomly chosen, they are frequently drawn from general vocabulary to describe a component or process. For example, a compressor compresses gas. The word compress means to make smaller. When you squeeze something you make it smaller, or compress it. The compressor raises the pressure and temperature of the gas by squeezing it, making its volume smaller. If the students understand that compress means to squeeze, they should have no trouble remembering what the compressor does.

To truly understand HVAC/R terminology students should not simply memorize a list of attributes for the rather large number of HVAC/R terms, but should connect the function to the name. Making these connections also increases memory retention. The method that a compressor uses to accomplish its work is used to describe the types of compressors. Reciprocate means to go back and forth: a reciprocating compressor uses pistons that go back and forth in a cylinder. A scroll is spiral: scroll compressors use intermeshing spirals or scrolls to compress the gas. A screw compressor uses intermeshing auger shaped screws to compress the gas. Connecting the name to the function will help students get a mental picture of the device and increase both understanding and memory retention.

All the components of the refrigeration cycle have names that either describe their function or describe them physically. The key is for students to understand where the name comes from. If students understand that orifice is simply a three syllable word for hole, they should have not problem remembering what an orifice is. One of the reasons I believe in covering the science behind the refrigeration cycle before trying to discus the refrigeration cycle is so that these connections can be made. If the students already understand the processes of evaporation and condensation, they will have no trouble remembering what evaporators and condensers do. This same technique can be used for many aspects of HVAC/R. In electricity potential difference literally means the difference in electrical potential between two points. The refrigerant terms zeotropic and azeotropic can be better understood if you explain the vocabulary they are built on. For most of us, these words are presented simply as arcane terms for refrigerants that are mixtures of two or more refrigerants. The fact that they differ by a single letter makes remembering the difference between the two difficult. Most students complain that the two terms are “all Greek to me!” In fact they do come from Greek roots. “Zeo” is to boil, “trop” is to turn, so zeotropic refrigerants turn, or change as they boil. Placing the letter “a” in front means “not.” For example: amoral means without morals. Similarly, azeotropic refrigerants do NOT turn or change when they boil. Give a few vocabulary lessons and increase your student’s understanding and memory retention. For more HVAC/R vocabulary tips check out the glossary in Fundamentals of HVAC/R, the largest glossary in any major HVAC/R text.

R22 Phase Out

If you are at all involved in the HVAC/R trade, you know that new equipment may not be manufactured or imported beginning January 1, 2010. This imminent date has most of us at least a little apprehensive about the future. Right now, all the details and rules have not been firmly established. In most people’s minds, the date a unit is “manufactured” is when it is made in the factory. The EPA has proposed a rule change that would set the date of “manufacture” as the date of final charge. For split systems, this would be when the unit is installed. Adopting this rule change would effectively mean that R-22 split systems could not be installed beginning January 1, 2010. This would make inventory of existing R-22 systems essentially worthless on January 1, 2010.

AHRI has launched a site dedicated to monitoring the issues regarding the HCFC phase out and passing on information to the industry: www.phaseoutfacts.org.

Another good web site to keep an eye on is the EPA site devoted to the HCFC phase out: www.epa.gov/ozone/title6/phaseout/hcfcfaqs.html

Although R-22 will continue to be available for servicing existing systems, the amount of new R-22 available will be substantially less than is available this year, see EPA web site for details
www.epa.gov/ozone/title6/phaseout/hcfc.html

R-22 systems will still be with us for some time since the majority of the current installed base of air conditioning systems use R-22. However, R-22 systems represent the past; R-410A air conditioning systems represent the future. All HVAC/R training labs should have a full complement of R-410A systems. We need to prepare our students for the future, not the past. The training materials you use should support training using the refrigerants of the future, including R-410A. Fundamentals of HVAC/R includes extensive coverage of R-410A. We don’t just talk about R-410A in Unit 23 Refrigerants and Their Properties, but throughout the book whenever specific refrigerant pressures and temperatures are mentioned in examples. In Unit 17 Refrigeration System Components and Operation, the refrigeration cycle diagram uses R-410A as the refrigerant. Unit 27 Refrigerant System Evacuation and Charging uses R-410A for many specific examples of charging charts and operating specifications. Specific details of handling zeotropic refrigerants like R-410A are given in Unit 26 Refrigerant Management and the EPA. In all, 14 units have specific examples of working with and using R-410A refrigerant. R-22 has certainly not been left out. There are still plenty of examples and details using R-22. After all, we will be working on R-22 systems for several years to come. If you have not already moved towards incorporating R-410 your curriculum, now is the time to take the first step. If you are looking for materials that will help your students meet the challenges of the future, please take a look at Fundamentals of HVAC/R.

The Language of HVAC/R

Many students find the large number of technical terms used in HVAC/R confusing. To the uninitiated, HVAC/R has its own language of technical jargon that can become a barrier to learning. Confusion over terminology can lead to not clearly understanding crucial concepts. This problem is compounded by the use of acronyms and abbreviations that are frequently used when discussing common topics. For example, one major valve manufacturer uses the acronym TEV to represent “thermostatic expansion valve,” while another uses the acronym TXV for the same thing. In Fundamentals of HVAC/R, we keep technospeak to a minimum, preferring to use common, easily understood language whenever possible. Making a relatively simple concept seem highly technical by using an overabundance of jargon does not help students.

Of course, students must still learn the HVAC/R language. Having a solid grasp of the terminology is necessary to make use of essential technical literature produced by equipment manufacturers. To encourage students to learn the language, we always use the complete word or phrase before introducing an acronym. It helps to explain concepts plainly, and then introduce the technical terminology that is used to refer to the concept. The students are more likely to remember the terminology if it is logically connected to something they understand. For example, I have found that students just starting to learn the operation of the refrigeration cycle often can recite the order of components, but they have not made the connection between the component names and what they do. It is much easier to remember “TEV” if you know that “TEV” is an acronym for “thermostatic expansion valve” and you know that the refrigerant expands as it goes through the thermostatic expansion valve.

We have three resources in the back of the text deigned specifically to help students learn the language of HVAC/R: an acronym dictionary, an English language glossary, and a Spanish language glossary. When a student wonders exactly what is meant by a particular acronym or abbreviation, they can find it in Appendix C which lists the definition of common acronyms and abbreviations used in HVAC/R. The acronym dictionary is also very useful when students are reading industry literature and need help with a particular abbreviation or acronym. Students can use either the English language or Spanish language glossary to look up the definition of common HVAC/R terminology. Fundamentals of HVAC/R has a very complete glossary to help students learn the HVAC/R language. It has the largest number of defined terms of any major HVAC/R text and the terms are fully explained, including multiple definitions of the same term.

I sincerely believe that students and instructors alike will find that Fundamentals of HVAC/R is an invaluable aid in learning the language of HVAC/R.

Laying the Foundation for Success

This is the inaugural post of the blog devoted t0 instructors and students using the text Fundamentals of HVAC/R. I plan to post weekly and I would love to hear from both instructors and students. I especially would like to hear about things you like about the book, things you don't like about the book, things you wished it had, and any particular HVAC/R topic you are particulary interested in. Although the blog is meant specifically to support the text Fundamentals of HVAC/R published by Prentice Hall, I plan to cover topical issues of interest to anyone studying HVAC/R. In this first posting I would like to cover a topic near and dear to my heart: the Science of HVAC/R.

A problem that many students have when beginning their study of the refrigeration cycle is the large number of technical terms and new concepts used to describe what happens in the refrigeration cycle. For many students, grasping all of this information at once is simply information overload. Many students turn to rote memory in order to recite all that happens to the refrigerant in the refrigeration cycle. However, if students don’t really understand the basic science behind the concepts and terminology, the information is just a collection of seemingly random facts that must be memorized, like the multiplication tables. There is no doubt that some memorizing of new terms is necessary, but I believe an understanding of the concepts and terms helps students remember them. Understanding the science behind the cycle also helps them keep the cycle details straight. In Fundamentals of HVAC/R, we promote this understanding by devoting section two of the book to HVAC/R Science. Units 4 through 8 explain the science that makes HVAC/R systems work. Because this is an Air Conditioning text, the principles are presented using plain language with a minimum of mathematical formulas. The practical application of the science concepts to refrigeration is explained when the concepts are introduced. The goal is to give students the conceptual tools they need to really understand the refrigeration cycle.

Unit 4 Properties of Matter explains what matter is, basic atomic structure, and the most important properties of matter. These include the three common states of matter, density and specific gravity, change of state, the effect of pressure on boiling and condensing. Unit 5 Types of Energy and Their Properties explains the relationship between matter, energy, work, and power. Types of energy and conversion from one form to another are discussed. Common units for measuring both power and work in the HVAC/R trade are discussed and compared. Unit 6 Temperature Measurement and Conversion logically follows the unit on energy. The four common temperature scales are discussed along with a discussion of absolute zero and absolute temperature. A brief history of thermometers and temperature measurement adds interest to what can be a dry subject. How to take accurate temperature readings with different types of thermometers is also discussed in detail. Unit 7 Thermodynamics – The Study of Heat explores heat methods of transfer, sensible and latent heat, and specific heat capacity. The way both sensible and latent heat are used in the refrigeration cycle is also discussed. This unit explains how to use PT charts and discusses the difference between saturated mixtures, a superheated gases, and subcooled liquids. Unit 8 Pressure and Vacuum covers what pressure and vacuum are and how they are measured. Atmospheric pressure and the difference between gauge and absolute pressure are discussed in detail. Different pressure measurement systems such as psia, psig, inches of mercury and inches of water are discussed. The unit closes with coverage of the gas laws. Illustrations and examples show graphically how the gas laws work and how they help make the refrigeration cycle work.

Although the concepts are not discussed primarily in terms of math formulas, the most important formulas associated with these concepts are presented. Whenever a formula is introduced, we give detailed examples showing step by step how the formula is used. Students will have no trouble following the formula examples because they are presented in the most straight forward, uncomplicated way possible.

I believe that students save time in the long run by taking time at the beginning to understand the science that makes HVAC/R systems work. By the time students complete units 4 through 8, they have a good grasp of all the concepts necessary to understand the refrigeration cycle.