Making Connections

Most curriculums, courses, and books are organized in a manner that resembles house construction. You lay the foundation and then add to that foundation as the material gets progressively more complex. The idea is to present the information in an orderly manner so that complex concepts can be understood. I believe that teachers have been using this general scheme for centuries. I also believe teachers have been frustrated for centuries when they discover that the reason the students don’t understand a higher level concept is that they really don’t make the transition from one conceptual level to another. The problem is that learning is really not too much like stacking bricks, but more like wiring circuits. We have to make connections to learn. It is not enough to present material in an orderly and logical fashion, we must also make connections between different pieces of information. Every chance you get, you need to show how one piece of information connects to another. The more mental connections the students make, the more likely they are to remember the information. Students sometimes ask how a particular piece of information is relevant. I believe what they are trying to say is that they don’t have anything to tie the information to. Random, disconnected facts are quite difficult to remember, and are not normally particularly useful. I like the Bing commercials where people blurt out a series of largely unrelated facts that are essentially useless because there is no logical connection between them. To students, I am sure our lectures can sometimes sound like one of these commercials. I try to connect ideas together – showing how one part of a system affects the others, how pressure is related to temperature, how resistance is related to current – you get the picture. Relationships and connections between ideas are just as important as a carefully crafted sequence of information. This is not to suggest that building a foundation of information is wrong, I would just use the analogy of a framework instead. A framework can allow connections in more than one direction. Understanding a few fundamental physics concepts provides a framework for understanding both refrigeration and electricity. Taken by itself, physics can be pretty dry stuff until you realize that it describes the world around us. Once the students start making connections linking concepts together the whole process can go viral – they start finding their own connections and asking their own questions. This can be a bit scary because you no longer have total control of the flow of information or questions, but it produces an energized, lively class. More importantly, when the students start connecting concepts they are taking an active role in their learning and are far more likely to retain the information.

Electric Heater Resistance - A Moving Target

Most people know that inductive loads such as electric motors draw more current when they start. Did you know that this is also true of most electric strip heaters? The resistance of a conductor increases as its temperature increases. This is true of the nichrome wire used in electric heaters. The heater resistance is less when the heating coil is cold than after it heats up. The increase in resistance causes a decrease in current. In short: an electric heater draws a little more current when it starts than after it heats up. The difference for an electric strip heater is nothing like the huge surge that a motor has, but it is measurable. For incandescent light bulbs, the difference is huge because the temperature difference between hot and cold is much greater. An incandescent light is basically a heater that gets white hot and gives off light. Lights don’t work for Ohm’s Law experiments because their resistance hot is around 10 times as high as their resistance cold. Many years ago I tried having students do Ohm’s Law calculations with lights – it just does not work. The readings were so far off, that the results did not make sense.  I tried to put the difference down to measurement error, but the readings were always similar. Screw in cone heaters work better, but if you put enough current through them for them to get red hot, their resistance will increase and your readings will still be a little off. At least they are in the ballpark. It is something of a catch 22. To measure resistance an ohm meter puts a small amount of voltage across a resistance and measures the current, and then determines the resistance based on the amount of current that flows through the resistance. The problem is that the resistance changes when different amounts of current flow through the same device, based on the temperature change of the device.  Remember that the resistance is turning the electricity into heat, and the heat changes the resistance of the device. Fortunately, the relatively small difference we see in electric strip heaters does not create a substantial problem for us, but it does raise questions when trying to demonstrate Ohm’s Law. If you want to reduce the amount of error introduced by the temperature change, just work with lower voltages and current levels. Use a typical electric strip heater, but only put 50 volts through it. The current and voltage are still measureable and the results will be much closer to what Ohm’s Law predicts. I know there are probably many skeptics reading this, so I challenge you to prove it to yourself. Take a heater, a variable voltage source, a voltmeter, and an ammeter. Read the current draw of the heater at several voltages ranging from just enough voltage to get a current reading to the full voltage the heater can take. Then calculate the resistance using Ohm’s Law by dividing the measured current into the measured voltage. You should see that the resistance is higher at higher voltages because the heater is getting hotter. Have Fun! 

Combustion Air - Don't Forget It!

I am re-posting an article from October 2009 when I talked about combustion air because I believe failure to check the combustion air is a common error in performing gas furnace service.

The arrival of fall brings the start of gas and oil fired furnace seasonal checks. An easily overlooked problem with gas and oil furnaces is lack of combustion air. Although most technicians understand the necessity of adequate combustion air, it is easily overlooked if the technician views their job as servicing appliances rather than systems. Most school shops have no combustion air issues because they are typically great big leaky rooms. On the other hand, the newer homes your students are likely to see are typically very tight, requiring installers and service technicians to be conscious of the need for combustion air.  I believe we should stress the consequences of inadequate combustion air. Most students understand that air is required for combustion and that new air must constantly be brought in to replace the air that was just used in the combustion process. They should understand that the carbon and hydrogen in the fuel are combining with the oxygen to make carbon dioxide and water, the normal products of complete combustion.  You can then explain that if there is not enough oxygen, carbon monoxide and unburned carbon will start to form because there is not enough oxygen to complete the combustion process. As the combustion process continues in a room with inadequate combustion air, the pressure in the room becomes negative. This will reduce the effectiveness of the vent. In bad cases the combustion products can start to spill out of the vent. Now you have a scary situation: a combustion process producing carbon monoxide and combustion gasses spilling out into the room! I have heard of cases where smoke from fireplaces in newer homes comes rolling out into the room when the furnace comes on because the house simply does not have enough combustion air for both the fireplace and the furnace. Technicians should look for combustion air grills and vents when servicing furnaces. Typically there should be an opening or grille near the ceiling and another near the floor. If the grille opens directly to the outside the free area of the grille should be at least one square inch for every 4,000 Btuh of combined input rating. If the combustion air must travel through vertical ducts the ducts must also have a free area of at least one square inch for every 4,000 Btuh. If the air must travel through horizontal ducts, the grille and the ducts must be larger. They must have a free area of at least one square inch per 2,000 Btuh. Draft measurements and room pressurization measurements can tip off technicians to combustion air problems. Because a draft gauge measures the vent pressure relative to the room pressure, inadequate combustion air will cause the draft reading to decrease the longer the furnace operates. An absolute pressure reading of the room will show that the room pressure is decreasing as the furnace continues to operate without adequate combustion air. A quick test is to introduce more combustion air near the furnace by opening a window or door to the outside. If the draft increases when the window is opened and decreases again when it is closed, the room needs more combustion air. For more a more detailed discussion of combustion air check out Unit 37 Gas Fired Heating Systems, Unit 40 Gas Furnace Installation, Startup, Checkout and Operation, Unit 41 Troubleshooting Gas Furnaces, and Unit 44 Residential Oil Heating Installation in Fundamentalsof HVAC/R.  

Budget Stretching Ideas

Schools face a serious budget crunch these days created by expanding enrollment and shrinking resources. There are many small things that you can do to stretch your budget and still provide a reasonable level of training for your students. Refurbishing tools that have become shop worn rather than replacing them is one small possible savings. Tools that normally last for years in the field sometimes only last a few semesters in our lab due to the harsh treatment they sometimes receive as well as the constant use. The seals and depressors in hoses are one example. If you have refrigeration hoses that leak, often the leak is in the seal on the end. The seal in most hoses is a small rubber tube that slips into the end of a brass cup in the end of the hose. The core depressor is either held in place by the seal or screws down into it. Replacement seals and depressors are available for most brands of hoses. If the hoses you have are used for connecting to refrigerant cylinders, vacuum pumps, or recovery machines, there is really no reason to have the core depressor. Removing it will speed up all those operations by removing a restriction. A larger savings can come in the type of brazing rod you keep. While I prefer 15% silver, it is now over $100 a pound and we use several pounds a semester. I hate to have students braze any less because brazing is one of those skills that must be practiced. 0% copper-phos is just over $10 a pound and does the same job. No, not as easily, but I can buy a semester’s worth for less than one pound of the 15% silver. Another savings for many programs is to reduce the paper you hand out. I have always been fairly liberal with the handouts, believing that it is important to disseminate information. I still believe that, but I have modified the way I share information. I started by writing a book that had more of what I wanted in it. But there will always be new information you run across that you want to share. Increasingly, I do this electronically by sharing web addresses. Finaly, let the supply houses and contractors in your area know you need help. They can keep their eye out for opportunities to help you. This past year we have received several donations from contractors and supply houses of “stale” stock or equipment with issues. They receive a tax deduction and we receive equipment. A unit with an issue may be a problem for a contractor, but it is an opportunity for my students . We have received two new packaged heat pumps this past year that had leaks on the pilot tubes of the reversing valves. Students patched the leaks and the valves worked. Now we have two new packaged heat pumps.  

Picture Perfect

Several years ago when I was a student in one of my education classes at the University of Georgia, the instructor asked us what should have been a fairly simple question for a group of teachers: “How do you know when learning has taken place?” I don’t remember my response, but I do remember that the question really brought me up short because it was not asking how do you know when the student has mastered a particular knowledge or skill, but how do you know when they have learned something? Well it is a little late, but I received a great answer today: Learning has taken place when the student requests that their picture be taken with their project. We have a flaring project in which students make an assembly of 1/4”, 3/8”, 1/2”, and 5/8” copper all connected together by flare fittings. After it is done, it is tested for leaks with 100 psig of nitrogen and soap bubbles. After completing their project, one student wanted a picture. Then they requested I take a picture of them holding the project. The student’s broad smile gave me the answer to the question posed to me many years ago. Learning has taken place when the student can enjoy the pride of achievement with tangible proof of their accomplishment. In technical education we have a huge advantage of being able to actually produce. The students’ pride is not based on my judgment, it is based on holding something they made that they could not make yesterday. Some people consider trade skills and knowledge as inferior to pursuits that are purely academic. However, I feel that a strong case can be made that technical skills are actually a higher form of learning because the students must actually perform. Reality is the harshest judge of all – either it works or it doesn’t. Our students must not only understand the theory, they must also apply it and pass the performance test. So if I had to list a learning sequence today, it would be: you study, you struggle, you sweat, you smile! 

Brain Building

Your brain is an essential component for all forms of education. One obvious way to improve learning results is to improve students brain capacity. Some forms of teaching are better than others at building brain capacity. I have noticed that frequently, “smart” students actually work harder than “dumb” students. I believe that their study habits and the way they approach life in general not only builds their knowledge, it also builds their brain capacity. Just as hockey players skate and football players run to improve their ability to perform the fundamental movements of their sport, students should exercise their brains to improve their ability to learn. So what types of things build brain capacity? One proven way to build your brain is by learning to play a musical instrument. Playing an instrument uses both halves of your brain simultaneously, requiring better communication to be developed between the right and left hemispheres. A few years ago at my son’s band concert, I realized that the trumpet section was also three fourths of the schools award winning math counts team. Playing an instrument is both incredibly difficult and incredibly rewarding. Looking into this a little, I learned that Einstein played the violin. His brain was perhaps one of the most studied in history. He had grown an extra lump on the right side of his brain, a feature found in autopsies of other proficient violin players. Einstein had to expand his brain capacity to play the violin! Of course it is possible that playing music does not make you smart, but that smart people enjoy playing music. OK, so besides brain building there are some more obvious benefits. For one, you learn self-discipline. You simply cannot learn to play a musical instrument without the self-discipline that comes with practice. Then there is group disciple. The members of orchestras and bands must learn to work together as a group to perform music. The group objectives can only be met by subjugating all their individual egos. As a parent, there are a few other benefits. After half-time we hand out drinks to both bands. I am always impressed by how polite and truly thankful the band members are. They all say thank you and are gracious even if we have run out of cold drinks and are handing out warm water. When I look out over the gathering of the two bands I know I am seeing leaders in every imaginable field and I am positive about the future.   

Looking for a Day On

As we celebrate this Labor Day I am reminded of the many Americans who don’t want a day off, they are looking for a day on. Your job provides you with more than the financial means to support yourself. For most of us, we are identified by our profession. One of the first things people ask when meeting is “what do you do?” Having regular earned income also gives us a way to be more in control of our destiny. With a predictable source of income, you can manage towards improving your lot in life. I truly believe all our political leaders want to help. We would all like for everyone seeking employment to find it. There have been many attempts by government at all levels to pass legislation that would stimulate the economy and create jobs. The problem is that it is very difficult to create truly new jobs, particularly in new and emerging technologies. I believe we would have more success investing our time and money training people for jobs that already exist, particularly in fields where industry growth exceeds the available workforce. HVACR is one such industry. Jobs are available now for skilled HVACR technicians, even with the construction industry operating at historically low levels. Money spent in technical education prepares students for real jobs that we know exist, not jobs that we wished exist. Preparing people for a real job that pays real money makes them a contributing taxpayer. In short, the government gets the money back. Some HVACR students will be successful enough to start their own business. There are several in the Athens area who started as students at Athens Tech. One relatively small business with five employees can gross $500,000. That generates tax revenue of $75,000 at 15%. If those five employees are trained at Athens Tech, the cost of their training is less than one year’s tax revenue. Not all students will generate that kind of return, but even a student earning $12 an hour will likely pay back the cost of training in two years. For people who already have a job in HVACR, education makes them more productive. Increased productivity means a better bottom line for the government – more income to tax. It is not necessary to start new programs with new administrative costs; there are already programs and institutions in place with proven track records of training workers for skilled trades. All we have to do is support them.