Comfortech 2009

I had the pleasure of attending the Comfortech Conference in Nashville, Tennessee this past week. A national convention like Comfortech provides the opportunity to meet and talk with industry leaders from all over the country. I set out to pick as many brains as possible. The people staffing the booths impressed me not only by their level of expertise and experience, but also with their generosity. I found that everyone was very willing to talk with me. When I introduced myself as an air conditioning instructor their faces seemed to visibly brighten. They wanted to talk about what they felt was important to teach. The people in our industry want to help us, because they recognize the importance of education to their own success.

Whenever I attend a national show I always look to pick up ideas for teaching. Many of these companies need to teach their potential customers in order to sell to them. In a trade show they do not have a captive audience, so they must get their point across quickly. I saw a demonstration by the National Comfort Institute on air filters that was compelling, simple, and quick. They had a blower set up with return and supply plenums, an external filter rack, and adjustable manual dampers on the end of both the return and supply plenums. They adjusted the dampers to achieve a total external static pressure across the blower of 0.5” water column, measured with a magnehelic. They measured the pressure drop across the standard 1” disposable filter as 0.05” water column. Then they replaced the filter with a 1” pleated filter and the pressure drop across the filter increased to 0.5” - as high as the entire system pressure drop before! Emerson was showing off their new communicating controls. They had a condensing unit board that handled all controls and power switching, including the compressor. No contactor! A little box about 1 inch square was switching the compressor! Rheem was using these boards in their newest units on display. I have to stop now because if I described all the cool stuff I saw my blog might be as big as my book. There were over 160 exhibitors, each with their own lessons. You can still see a list of the Comfortech exhibitors by going to the site where you can get links to many of the exhibitor’s sites.

I believe each of us should try to attend at least one national level convention a year. Most national conventions have a showcase event for vendors to display their latest and greatest. These are typically either inexpensive or free. There you can see the latest equipment, tools, and technology and ask questions face to face. If you missed Comfortech, don’t despair, there are several others coming up soon. RSES has its Annual National Conference coming up October 27-31. The grand-daddy of all HVAC/R conferences, the AHR Expo, will be in Orlando January 25-27 2010. The AHR Expo is a joint venture of ASHRAE and AHRI. There are two conferences aimed at HVAC/R instructors: HVAC Excellence National Educator's Conference March 14-16 2010 in Las Vegas and AHRI Instructor’s Workshop in March 24-26 in Landsdowne Maryland at the National Convention Center. Although each of these shows targets a slightly different audience, they are all very applicable to what we do. If you come to either of the instructor’s conferences you might see me. I will be there.

R22 Conversion

Most HVAC/R programs have a large number of R22 air conditioning systems in their shop. The ban on the use of R22 in new equipment begins January 1, 2010 – only a few months away. Although R22 will be available for servicing existing equipment, the amount of new R22 available is scheduled to be reduced by 75% in 2010. The EPA and many people in the industry believe that this will create a shortage of R22 in 2010. What this all means is that R22 will become more expensive and harder to get. I began exploring for an R22 replacement refrigerant to keep our shop equipment operating when R22 is either not available or not affordable. I would like to share a few things to consider when examining potential R22 replacement refrigerants.

Whenever possible check with the equipment manufacturer. Chances are they have some insight into what works, and more importantly, what does not work. Copeland has a six page service bulletin that discusses conversion from R22 to R422A and R422D in commercial refrigeration systems.

Copeland 422 Conversion

Tecumseh offers five service bulletins that discuss R22 refrigerant conversion. They are available at

Tecumseh Service Bulletins

There are a number of replacement refrigerants offered to replace R22 in existing systems. However, even if the system operates and cools, there are some potential negative outcomes that you should be aware of before proceeding.

Make sure that any refrigerant you propose to use has been approved for use by the EPA. You can check the SNAP list to see if the refrigerant is listed.

EPA SNAP List

There are many hydrocarbon based replacement refrigerants for sale on the internet which are NOT approved by the EPA for use in the US. Some are even manufactured in the US, but they may not be used in the US.

For the most part, most manufacturers do not endorse refrigerant conversions. Just because the EPA approves a particular refrigerant does not mean that the manufacturers must approve its use. Using a replacement refrigerant that is not approved by the manufacturer usually means any warranty is voided.

Systems may lose their UL approval since the UL testing was done with the original refrigerant. Many alternate refrigerants have been tested and classified by UL, but many have not. Consult UL or the refrigerant manufacturer to find out if the refrigerant is UL classified.

Zeotropic refrigerants (400 series blends) should never be used for flooded chillers. The refrigerant will separate in the evaporator. Since nearly all replacement refrigerants are 400 series blends there are very few acceptable non-ozone depleting replacement refrigerants for flooded chillers.

Finally, the refrigerant manufacturers will help. Even if you decide to proceed without the equipment manufacturer’s help you are not entirely on your own. The refrigerant manufacturer also bears responsibility for the application of their product. All refrigerant manufacturers offer application bulletins and guidelines for the use of their products. A few are:

Dupont

Forane

Honeywell

Smaller companies that primarily manufacture replacement refrigerants obviously have an incentive to help. ICOR has one of the most interesting support ideas – a toll free telephone number which you can call to talk to an experienced service technician.

ICOR Help

For more detailed information on refrigerants check out Unit 23 Refrigerants and Their Properties in Fundamentals of HVAC/R. For specific details on complying with EPA refrigerant regulations check out Unit 26 Refrigerant Management and the EPA in Fundamentals of HVAC/R.

Teaching Green Technology

I am sure by now everyone has heard about the green revolution. Chances are, you have been asked what you are doing to teach Green Technology? You might feel that you are not doing anything about teaching Green Technology, but I bet you are teaching Green Technology without realizing it. First, your students are already ahead because they are in school. They will be more likely to read and follow instructions than someone who is just “doing it the way we have been doing it for 20 years.” New installation and service techniques develop along with new equipment and technology. Installing a 20 SEER air conditioner incorrectly effectively erases its efficiency advantage. Therefore, the first and foremast Green Technology we should be teaching is correct system installation. Chances are the text you are already using discusses Green Technology. Fundamentals of HVAC/R includes 13 Units that include information relevant to Green Technology. Unit 54 Basic Building Construction , has a section on Green construction.The idea is the Green Technology is more than a separate device or product, but is a new way of thinking and doing things. These 13 Green Technology units are identified in the table of contents with a green asterisk after the unit title. If you are looking for a text that is specifically Green, take a look at Pearson’s Your Role in the Green Environment, or Green Building Fundamentals, or Sustainable Construction and Design. To read more about these texts visit pearsonhighered.com

http://www.pearsonhighered.com/educator/product/Your-Role-in-the-Green-Environment/9780136065968.page

http://www.pearsonhighered.com/educator/product/Green-Building-Fundamentals/9780135028391.page

http://www.pearsonhighered.com/educator/product/Sustainable-Construction-and-Design/9780135027288.page

I hear you saying “but they want me to buy a GREEN trainer!” No problem. I have two suggestions. One, get an ECM blower demo from thedealertoolbox.xom. It allows you to play with an ECM blower and measure the results. Not only will this help teach your students about Green Technology. it will help teach them about airflow. You can read more about it at http://secure.thedealertoolbox.com/p-20-ecm-blower-demo.aspx

Another obviously Green HVAC/R product is the new Lennox Solar Assisted Heat Pump. They are selling a heat pump with a solar panel that produces part of the electricity the heat pump uses. You can see more about it at http://www.lennox.com/pdfs/brochures/Lennox%20XPG20%20Heat%20Pump.pdf

If you are exploring Green Educational programs there are several alternatives ranging from a simple Green Awareness program to offering instruction in fields like Testing and Balancing or building Commissioning. If you would like to offer a Green Awareness program and certification you might check out ESCO’s Green Awareness program http://escoinst.com/GreenawerenessCertification.htm

Testing and Balancing and Building Commissioning are professional fields requiring specific training and credentialing, but if your school is serious about being Green, they are areas to look into. Without testing and balancing and commissioning, you really don’t know if the building and systems are performing as designed. You can get more information on Testing and Balancing at http://www.nebb.org or http://www.tabbcertified.org/ For building commissioning check out the Building Commissioning Association http://www.bcxa.org/ or the “Whole Building Design Guide” by the National Institute of Building Sciences http://www.wbdg.org/project/buildingcomm.php

The big mac daddy of Green right now would have to be the LEED program designed by the US Green Building Council. Buildings are certified as meeting the LEED standards by earning points in a variety of areas from energy efficiency, materials used, recycled content, and waste disposal to name a few. LEED buildings must be inspected by a LEED certified inspector. This offers another training opportunity. To read more about USGBC and LEED go to http://www.usgbc.org/

Again, I firmly believe that the HVAC/R field can be considered a Green Field when done correctly. After all, the Greenest design on paper turns brown if it is not properly installed.

Teaching Ohm's Law for Parallel Circuits

Many students have a hard time understanding why the total resistance of a parallel circuit decreases as loads are added in parallel. Comparing lanes on a highway to loads in a parallel circuit is an analogy that works for many people. Adding another load in a parallel circuit is like adding another lane on a highway. The more lanes you have, the more traffic you can move. So as lanes are added, the resistance to traffic flow decreases. In parallel circuits, the more loads you have in parallel, the more current you can move. So adding loads in parallel decreases resistance to current flow. The total resistance in a parallel circuit is difficult to calculate because it cannot simply be added as in a series circuit. However, the total current flow in a parallel circuit is easy to calculate. It is simply the sum of the currents for all the individual loads. The famous parallel formula for resistances in parallel uses this concept. Dividing the resistance of each load into 1 calculates the current draw for each load at 1 volt. Adding these fractions gives the total current draw of the entire circuit at 1 volt. Since resistance can be calculated by dividing current into voltage, dividing the total circuit current at 1 volt into 1 volt gives the total resistance. I confess that I have used and taught this formula for many years without knowing why it works. Once I understood the reason behind the formula, it seemed far more logical and less imposing.If you want to have some fun, take a parallel circuit calculation and use a number other than one, say 5. Divide each resistance into 5 to get the current for each load at 5 volts. Add all the individual currents up. Finally divide this total current into 5 to get the total resistance. You get the same answer as when you use 1! To prove it to yourself, do the same set of resistances with several voltages. If you don’t stumble on the math, the answer is always the same regardless of the number you start with.

Understanding Centrifugal Fan Motor Performance

Since air is what we work with it makes sense to insure that our students understand airflow and fan performance. Fan motor performance is one of the most often misunderstood aspects air conditioning systems. The amp draw on a centrifugal fan goes down as resistance to airflow is increased. For most people this seems counterintuitive. It is easy to picture the fan motor pushing harder to overcome the resistance and increasing in amp draw. However, this is exactly backwards. Centrifugal fans move air by throwing the air outwards through centrifugal force. The amount of air the fan is moving decreases as the resistance to airflow increases. If the fan blades are moving less air, they can actually spin easier because there is less air to sling. This causes the motor RPM to increase and the motor amp draw to decrease.

The most convincing way to teach this concept is to have students figure it out for themselves using a centrifugal blower. Have them operate a centrifugal blower in free air with no restriction and measure both the amp draw and the fan RPM. Note that most centrifugal blowers cannot operate in free air for an extended time without overheating, so try and keep the free air operating time to a minimum. Next have them block one side of the air intake with a piece of cardboard and recheck the amp draw and RPM. Typically the increase in RPM is immediately obvious, but measurements prove the point. Have them slide the cardboard to block the intake only half way while watching the amp draw. A few minutes of experimentation will convince the students that blocking the intake actually causes an increase in RPM and a decrease in the motor amp draw. Next have them partially block the fan outlet while checking the amp draw. Once again, the amp draw will decrease. Allow them a few minutes of play time to convince themselves. This experiment does more to explain centrifugal blower motor performance than a week’s worth of lectures.

Now that you have them hooked, refer them to Unit 56 Fans and Airflow inFundamentals of HVAC/R where they can read about the characteristics of different type of fans used in the industry and the basic principles of airflow. There the students can see examples of the different types of fans and read about their performance characteristics. Unit 56 Fans and Airflow wraps up with a discussion of the fan laws and using fan perfromance tables and curves. As always, examples show in detail how to apply each of these concepts.

Note that what I have been discussing assumes a "regular" PSC blower motor. ECM blower motors behave differently because they are programmed to adjust their output according to the resistance they are working against, but that is an entirely new discussion which I will save for another article.

Safety note: If you are not sure all of your students understand that it will hurt to put their hands into a moving fan blade, you should put a wire gaurd over the intake and exhaust to keep hands and fingers out. For a more polished trainer build sliding sheet metal baffles for both the intake and exhaust and mount the blower to a stand.

To see all my posts be sure to vist hvacrfundamentals.blogspot.com

Teaching Residential Design

One of the challenges that all HVAC/R educators face is convincing future contractors to ignore all the quick and easy rules of thumb for system sizing and duct layout and use design methods based on research. The problem with the ACCA standard design methods for sizing equipment and designing systems is that a considerable amount of time must be invested to understand how to use them. The first few systems someone does with Manual J and Manual D seem to take forever. Even using a computer design program requires the user to learn how to use the program. These methods appear overly difficult when compared to simple square feet per ton rules, or air changes rules. Still, the question really comes down to “do you just want an easy answer, or do you want a correct answer?” If you think from the customer’s perspective, they really want and need a correct answer. I believe that it is also in the contractor’s long term best interest to get correct answers as well. Avoiding a gaggle of unhappy customers that got the quick, easy, and wrong answer can be more time consuming than taking the time to get it right the first time.

I don’t think every Air Conditioning Technician needs to be able to whip out a Manual J load study, but I do think all technicians should be familiar with the overall concepts and general procedures used. Sometimes, the first step to learning is understanding how much you don’t know. Introducing technicians to the proper way to do a load study can be the light in the darkness that illuminates the path to greater understanding.

The truth is that the procedures are really not that difficult once you understand them. They will still take more time then dividing the square footage by a magic number, but an accurate load study on a typical residential home generally takes less than 30 minutes for someone who understands the process. It is true that you will have to invest hours of your time to get to that point, but that is really no different than any other skill that is required to perform HVAC/R work. The fact that time and effort are required to develop the skills and knowledge required to perform the job is part of what makes HVAR/R jobs valuable. The job is not as simple as memorizing a handful of rules of thumb.

Section 7 in Fundamentals of HVAC/R gives students the information they need to understand residential air conditioning application and system design with several unique features not found in other major air conditioning texts. The System Design, Sizing, and Layout section begins with Unit 54 which describes how buildings are constructed. It is important for students to understand how the air conditioning system fits into the building. Decisions about unit location, duct location, general duct design, and register placement are all very much affected by the building construction. Unit 55 shows students how to read and interpret drawings. Often, the first “look” an air conditioning technician has at a building will be in the form of a drawing. Teaching students how to interpret blueprints allows them to understand the building construction, even before the building is built. Unit 64 takes the students step by step through a manual J8 load calculation. Fundamentals of HVAC/R is the only major text to discuss the use of Manual J8, the latest version of ACCA Manual J, the ANSI standard for residential load studies. Unit 57 shows students the types the different types of duct systems available and how they fit different types of building construction. Unit 58 shows how to install duct systems and how to use friction charts and the ACCA Duct Calculator to design duct systems.

Education Requires Participation

The most consistently successful teaching methods are those that require students to be an active participant in learning. Very few people can sit passively through a lecture and remember most of what was discussed at the end. Actively listening improves their retention. This could include asking questions, answering questions, or taking notes. I remember one class in college in which the professor would ask a handful of students to answer questions at the beginning of class. These questions covered homework and the previous day’s lecture. He made notations in his grade book to keep track of how often you answered correctly and incorrectly. You could not relax even if someone else was on the spot because if they answered incorrectly, he would ask someone else. He quizzed every student at least once a week. This enforced active listening, but at the expense of great student anxiety. However, we paid very close attention to what he had to say. I prefer a dialogue. Ask leading questions to the group and get the students comfortable with answering. They will soon start asking questions, and you can directly address the areas where they need the most help. Reading retention can be improved by asking the students to answer questions. This requires them to look at the text carefully enough to pick out specific pieces of information. Better yet, ask questions that are not directly addressed in the text which require the students to use the information they have read to come to a conclusion. Well done interactive computer programs draw students in. The satisfaction of immediate feedback and reinforcement is extremely powerful and effective. Even without the high end graphics and sound effects, interactive programming hooks students because they receive immediate feedback and reinforcement. But I believe shop work is the gold standard. Nothing teaches students how to build circuits like building circuits. If a picture is worth a thousand words, a shop project is worth a thousand pictures. Labs do not have to be complex to be effective. A simple circuit consisting of a power cord, light switch, and light will show the student how a basic circuit works and how switches work in relation to loads. The circuit can be expanded by adding switches in series or loads in parallel. Now you are teaching series and parallel as well as circuits. If the students build simple circuits with heaters they can measure the resistance, voltage, and current to illustrate the principles of ohms law in series and parallel circuits. Keep in mind that many of your students have never wired anything. To them, wiring a few lights is exciting. I have seen students who could not wire a switch and light at the beginning of the week wire a heat-cool thermostat to a transformer, three relays, and three lights by the end of the week. Because I believe that students must be active participants in order to learn, I really prefer that each student do their own project. Often, if five students are assigned to wire a circuit, only one does the actual work and the other four write down the answers. In other words, one student does all the learning. If students must work in teams, make an effort to insure every student gets their hands on the project. The least confident students will stand back. However, they are the very ones that need the most hands on work.

When planning lessons, keep in mind that what the students do will have more impact on their learning than what you do. No matter how wonderful your powerpoint presentation is, if the students just watch it passively they will not get a lot out of it. For ideas on active lessons, check out the MyHVACLab online companion to Fundamentals of HVAC/R. Besides an e-book copy of Fundamentals of HVAC/R , animations, and a powerpoint presentation for each unit, MyHVACLab includes interactive activities and questions to insure that students are actively involved in the learning. A companion lab manual is also available that complements the Fundamentals of HVAC/R text. Among the unique labs included are labs illustrating the physics principles that the refrigeration cycle is based on. Heating and cooling a refrigerant cylinder while measuring its pressure and temperature helps students understand the pressure-temperature relationship and P-T charts better than a week of lectures will.