I have a holiday story to tell that involves pushing people’s buttons and the value of knowledge.
Twas the day after Thanksgiving, and all through the store, frenzied elves were all searching for more. Their buggies were loaded in high rising stacks in hopes that their credit card limits weren't maxed. Their children were manic and running around, in hopes that ipods soon would be found. When up on the roof there arose such a clatter, the manager called me to see what was the matter. His nerves all a-jangle, reason passing away, he requested my services to salvage the day.” I am just sitting down to sup with my kin, first thing in the morning I will gladly begin.” “Please come now” he insisted and pleaded, “this is Black Friday, I’ll pay anything needed. “”I have no boards, no relays or switches. I can’t fix it if more parts are needed.” I quoted a price so round and stout that I thought surely he would wait the day out. When to my wondering ears he replied, “agreed – come quickly before customers fly.” I found a reset, red and protruding, I pushed it to see just what the unit was doing. The dead unit sprang into life and I saw on his face, a look of relief at all the sales saved. I checked to make sure it would run through the night, and promised to return to do it up right. I requested my fee for services rendered, when the manager balked and refused to surrender. “You can’t charge ALL THAT for pushing a button!” “Of course not,” I said, “pushing is free. Knowing which button to push demands the full fee!”

There is nothing wrong with charging for what you know. You have an investment in time and money collecting useful knowledge. It is reasonable and appropriate to charge for it. The customer should know up front what they will be paying and what they will be receiving for their payment.

Disclaimer: This is a fictional holiday tale. No buttons were pushed in the making of this story.

Furnace Ignition Sequence

One of the best ways to prepare for troubleshooting any piece of equipment is to learn it’s normal operating sequence. If you understand what is supposed to happen and the order in which nit is supposed to occur, you can narrow the probable causes by observing the unit operation. By carefully observing the operation of a gas furnace, you can often narrow the possible causes of trouble to just a few items based on how far into the sequence the furnace gets. Most furnaces today use many similar components. This includes hot surface igniters to light the burners, induced draft fans to pull the combustion gasses through the heat exchanger, and draft proving switches to insure the draft.

The first step is to energize the induced draft fan. This is the little fan on the front of the furnace, not the larger indoor blower. The induced draft fan runs for a minute or so to purge the combustion chamber. The draft safety switch should close after the induced draft blower starts. If it does not, the process stops there – often with the daft blower continuing to run indefinitely. If the draft switch senses a proper draft, it closes and the sequence continues.

Next, the hot surface igniter is energized. If it is working, you will see a bright glow.

After a warm up period of 30 seconds to a minute, the gas valve is energized. The gas should ignite when it flows over the hot surface igniter.

A flame rod must sense the presence of flames within a few seconds or the system will close the gas valve and start the process again. After several aborted attempts, the system will lock out and quit trying to ignite.

After the flames are ignited, the control turns off the hot surface igniter and waits for the furnace to warm up before operating the indoor blower.

When faced with a furnace that does not operate properly, pay attention to how far into the sequence it gets before the process stops. That can help you decide where to start your troubleshooting.

Would You Like Some R with your HVAC?

At the recent RSES National Conference, Rusty Walker of Hill-Phoenix noted that many of us in the HVACR business forget about the R – Refrigeration. He noted that during a time of high unemployment, refrigeration contractors cannot get enough skilled help. From his perspective, we spend most of our efforts training HVAC mechanics and too often leave off the R. I must confess that I am guilty as charged. My background is HVAC, my family owns and operates a local air conditioning company, and I have taught Air Conditioning Technology for 35 years. However, we have had many students enter the world of refrigeration and they have done well. 

There are some compelling reasons to consider a career in Commercial Refrigeration, including the ready availability of work and good pay. Every company that owns a refrigeration box, freezer, or ice machine is a potential customer; and these things need to work year round. Commercial refrigeration is undergoing something of a renaissance as companies look to innovative technologies for reducing their carbon footprint, energy use, and operating costs. Getting involved in Commercial Refrigeration now will put you among the first technicians trained for these new systems.

Training is required to become a refrigeration mechanic; it is not something you can just decide to do. This may be discouraging to someone without any training, but it is an advantage for people employed as refrigeration mechanics. Employers cannot simply replace you with someone who is not trained because those folks just cannot do the work, and training them takes time and money. An investment in education will pay off with a career that lasts a lifetime. However, this takes us back to the original problem: there are far too few places to get the training. One solution is to train for air conditioning. The physics and concepts that apply to air conditioning also apply to refrigeration. The basic vapor-compression refrigeration cycle and electrical circuitry are required for both fields. Understanding air conditioning puts you on the road to understanding refrigeration. So how about it. Would you like some R to go with your order of HVAC?

My Heat Pump is on Fire!

Every tech that works on heat pumps will eventually get a service call from a distressed customer who believes their heat pump is on fire because they saw smoke pouring out. Typically, they just happened to catch the end of a defrost cycle and saw steam rising out of the unit as the defrost cycle finishes. They can see that the outdoor fan is no longer turning, yet they can hear the compressor still running. They may also hear loud compressor noises or the refrigerant whoosh as the system reverses at the conclusion of the defrost cycle. If they are near a register inside, they will most likely notice that the air is not very warm. All of this panics the customer into believing something terrible is wrong with their system. Simply telling them that this is all normal may sound like you are not interested in their problem. Or worse, you are hoping they will forget about the problem long enough for the warranty to expire. You should check the unit to see that it operates normally in first stage heat, second stage heat, emergency heat, and defrost. Then, explain the purpose of the defrost cycle. You probably don’t have time to completely explain heat pumps and the defrost cycle, but you can explain that ice buildup occurs as the unit operates and that it must be removed to keep the system operating efficiently. Once they understand that the defrost cycle is intended to heat up the coils to remove frost and ice, it is easy to see why you would not want the fan running while trying to heat up the coils. Heating the outdoor coil also explains the “smoke,” which if course is really steam created as the coil heats up. Finally, the loud compressor and whoosh noises simply signal that the defrost cycle is over as the reversing valve shifts. Taking the time to thoroughly check their system shows the customer that you are indeed interested in their concerns. Taking the time to explain what is happening will help reassure them and save you time down the road. Next time they will know what they are seeing.  

RSES Annual Conference

I just returned from the Annual RSES Conference in Charleston, South Carolina. What a great experience! Of course there were many great speakers on a wide range of current HVACR topics, from Building Envelope Testing to Transcritical CO2 Refrigeration Systems. All the sessions were great. However, the thing that impressed me the most was the level of training and experience demonstrated by the people attending the convention. I often found myself sitting in a whole room full of experts. Because the people attending are practicing industry professionals, the level of questions and discussion in the sessions was quite high. And truth be told, the folks gathered here were not just any industry professionals, but the people that go the extra mile. They invest their time and money in educating themselves about a field in which they are already very well versed. The discussions in the halls while people were just waiting for the next event were both interesting and informative. One of the main reasons for attending an educational conference is to be energized. Talking with other professionals and sharing their enthusiasm for the trade inspires you. You don’t have to wait for the annual meeting to experience this, you can also meet with other highly motivated professionals at a local RSES meeting, because meetings of local RSES chapters occur throughout the year. If you want to be immersed in a professional culture that inspires and elevates its members through education, you belong in RSES.

Thank You!

We have just completed a major national election. Regardless of whether your candidates won, you won. We often take for granted the right to choose our leaders, but this is far from a universal freedom. Recent events in the middle east show us how fortunate we are to be able to hold elections to select our leaders, and how blessed we are that the government by the people, for the people, and of the people continues to function smoothly right through a major election. The loser is not jailed as a dissident, nor do they take to the streets with AK-47s. The biggest election winners were we the people.

Our country and our freedom to choose our own leaders in a democratic process are protected by the men and women that serve in the armed forces. During the last decade, we have asked these men and women to sacrifice a lot for their country and they have delivered. Putting their lives on hold and risking everything to serve their country. Perhaps no single event highlights how important their service is than an election. 

To all who have served in the armed forces – thank you!

Flooded HVACR Equipment

Areas that have experienced flooding from Sandy have a big cleanup job and lots of rebuilding ahead. Make sure your students know to be careful when working on equipment that may have been flooded. Even after drying out, the corrosion and debris left behind can make the controls and motors inoperable. Worse, they can be dangerous. While it is possible that many parts of the system may still function properly, it is really a gamble to operate equipment that has been flooded. Safety controls that have been under water cannot be relied on to work. Silt and debris can create potential shorts or prevent proper mechanical operation. This can turn a normal malfunction into a potentially dangerous situation. For example: a blower motor on a furnace starts, but fails after a few hours of operation. The limit does not shut off the burners because its contacts are shorted together, the furnace overheats and burns the house down.

Another concern is for the health of the building occupants. Flood waters contain all types of things that you really don’t want in your air conditioning system: chemicals, gasoline, dead animals, and sewage to name a few. Coils , equipment cabinets, and insulation will all retain some of these undesirable things even after the water has receded. Technicians may be asked to repair flood damaged equipment, but in most cases the proper repair is more costly than replacing the equipment. It is hard to tell someone who has just lost most of their possessions that you cannot fix their flood damaged equipment, but that is exactly what you should do. Then there is the matter of duct work: obviously a good place to catch things. Again, cleaning may not really be practical.

A danger to technicians working in a previously flooded area is the muck they will often be working in. They will be walking, crouching, crawling, sitting, and laying on this muck when they go in the house to look at the equipment. Again, this is not just mud. This is a combination of nasty stuff that is definitely hazardous to your health. For more information on flood damaged equipment check out the AHRI page on flooded equipment.

75th Annual RSES Conference

The 75th Annual RSES Conference is coming November 14-17 at Isle of Palms South Carolina. RSES has been in the business of training and educating HVACR Technicians longer than most other industry organizations have been in existence. Note that this is the 75th Conference. RSES is really the only national organization whose sole mission is providing training and education for HVACR technicians. The conference has an impressive lineup of speakers and training sessions. If you live on the east coast, this is a chance to attend a major educational conference specifically for HVACR without traveling to Las Vegas or Colorado Springs. There is still time to register. You don't have to be a member of RSES to attend the Conference. However, while you are there, you can join if you like what you see. Click on these links for more information

RSES 75th Annual Conference

Conference Schedule

Educational Sessions

Exhibitors

Service Tech's Secret

Most of the truly outstanding technicians that I have met have one thing in common – they read a lot. Reading is their trade secret. One example of this is Chris Mohalley. He is the Genteq™ Certified Master ECM Trainer. He has created a nationally-recognized ECM training program and he travels the country spreading the ECM gospel. He serves as a NATE Technical Committee SME, a NATE proctor and ARI Chief EPA Examiner. He holds so many NATE Certifications that his shirt looks like a quilt. In short, he knows his shit. So I asked him one time how he became so erudite. His response, he reads a lot! Personally, I try to read something related to my field every day. At least once a week you should find something that peaks your interest and dig a little deeper. Information is now easier than ever to access. Take advantage of it! The amount of information that can be readily accessed on the internet is really staggering. When the EPA “Final Ruling" on ozone depleting substances was published in May of 1993, I had to go to the library at the University of Georgia to view it in the Federal Register. Now you can pull up the Federal Register online anytime you want. If you are not familiar with the Federal Register, it is the official government publication containing all the announcements, pronouncements, and new regulations of all Federal Agencies. This is where they post proposed rulings, and what are called “Final” rulings. Basically, a “Final Ruling" means that now it is law. There will definitely be more rulings to come. If you want to know exactly what the rules really say without any filtering by someone else, you want to read them for yourself at the Federal Register. That said, the Federal Register is some of the most tedious reading I have ever seen. Further, there is a lot of it. The Federal Register is published weekly. In its paper form, it is about the size of a phone book for a city the size of Athens Georgia. In other words, it is might be possible to read ALL of the Federal Register by yourself, but that would be about all you did. Thankfully, search engines let us look for all the juicy parts without reading the entire tedious tome.

Thankfully, there are many outlets for HVACR information which are really interesting, such as the RSES Journal. This month’s Journal has a great article on micro-channel coils and why manufacturers are looking at using micro-channel evaporator coils. You might even pick up a copy of a text, like Fundamentals of HVACR and read it one unit at a time. At one unit a week, you will finish the book in a little over a year and a half – there are 92 Units. You can pick up a lot just by looking at the material posted by manufacturers and distributors online. One caveat on web surfing – realize that the freedom for anyone to publish on the web means that there are products, policies, and procedures espoused that may not be in your best interest to pursue. A case in point: the flammable R-22 replacement refrigerants that are NOT EPA approved. They are mixtures of propane and butane. They absolutely should NOT be used to replace R-22 in an existing system. Remember, nothing in that original system was designed with a flammable refrigerant in mind. Always look to see who is posting the information. If you read a lot you will learn to sort out the fact from fiction. Thanks for reading!

Check the Draft

With the arrival of Fall weather technicians will soon be taking Fall furnace checkup calls. One of the things we should be doing is checking the vent draft pressure to insure that the vent is working properly. While many technicians are careful to check for cracks in heat exchangers, they sometimes neglect the vent. I believe that improper venting occurs far more often than cracked heat exchangers. Further, a vent that is spilling into the house has the potential to release far more vent gasses into the house than a crack in the heat exchanger. Of course it is right to check for cracks in the heat exchanger, just don’t neglect the vent operation. For all Category I furnaces, the vent should be a negative pressure. That is, it should be at a lower pressure than the room the furnace is operating in. Typically we want at least -0.02” wc. In other words, the vent pressure should be 0.02”wc less than the room pressure. This is true even with fan assisted Category I furnaces, which nearly all 80% AFUE furnaces are today. The fan helps pull the combustion gasses through the heat exchanger, it is NOT designed to PUSH vent gasses through the vent. Typical Class B vent is not air tight. If it is pressurized, it will leak out combustion gas.Even with fan assisted furnaces, the vent is supposed to operate at a negative pressure and the vent gasses leave because of their buoyancy compared to the surrounding air.

What can cause a lack of draft in a vent? One of the main culprits is lack of combustion air. The operation of the burners and the vent system can remove air from the room faster than it is being supplied, causing a negative pressure in the room. In older, leakier homes we often relied on infiltration for combustion air. Today, you really should provide outside air to the appliances. I have seen the operation of a furnace pull smoke out of a burning fireplace. There was enough air for the fireplace, but not both the fireplace and the furnace. The room went so negative that the fireplace vent was not lower than the room pressure. If the vent gasses cool off too much in the vent pressure will increase because the gasses are heavier, decreasing the draft. This can be a particular problem when replacing an older furnace with a newer one. Often, the vent is too big for the new furnace, causing the flue gas to cool off too much as it travels through. Another possibility is a plugged vent or vent cap. The flue gasses back up in the vent and then start to spill out of the appliance. 

Although most Category I furnaces with draft inducer fans have draft pressure switches to shut off the burners if the draft pressure is not at the minimum setting for the switch, I have seen furnaces operating with a positive vent pressure continue to run. Draft switches are, after all, switches and can fail. So don’t assume that because the draft switch is closed, the vent pressure is OK – measure it so you know.

Eco-Friendly Cooling

The folks at Greenheat in Australia wrote to remind me that there are ways to keep cool without using so many kilowatts. What follows is a short article from them on keeping cool the Green way.

Eco friendly ways to cool your home

Maintaining a comfortable temperature inside your home during fierce summer heat using eco friendly methods is often viewed as a faintly impossible ask. Many people are still labouring under the false impression that the only way to get proper relief from the heat is by installing a gargantuan, decidedly non eco friendly air conditioning unit. Sorry, environment. We’re too hot to bother with you.

Good news, lovers of cool temperatures and the earth. You can have it both ways. By implementing some of the measures suggested below, you’ll be minimising your impact on the environment without compromising your own comfort during the warmer months. To learn more about eco friendly ways to cool your home, visit Greenheat.

Let’s look at some eco friendly ways to cool your home:

• Keep the heat out! Seems obvious, but by properly insulating your home, ensuring your windows and doors are properly sealed, drawing the blinds at sunrise, and cutting down on your use of household appliances like washing machines, ovens, and stove tops, you’ll significantly reduce the amount of heat within your home.
• Become an Ivy Leaguer- covering your external walls with greenery is an effective and beautiful way to insulate your home from the punishing effects of hot weather. You’d be surprised at just how effective a measure this can be. Green walls can cut the surface temperature of walls by as much as 10 degrees Celsius.  Additionally, they help to filter air pollution.
• External shades and blinds- external blinds and shades are more effective than internal shades and blinds, simply by virtue of the fact that they block the solar energy before it hits your window.
• Split system air conditioning- inverter split system air conditioning units fluctuate according to the air conditioning requirements throughout the day. This makes them an energy efficient air conditioning option, minimising energy consumption by as much as sixty six percent.

NOT COOL

Not too long ago a morning television show did a “sting” type of operation on several HVACR contractors that were called out to service a system that had one simple problem. The good news is that all the technicians found the problem quickly. The bad news is that all the technicians then tried to pad the bill by replacing unnecessary parts. You don’t need to cheat people to make money. In fact, I think that cheating people ultimately ends in losing customers. Most satisfied customers will refer you to friends and family. The HVACR business works best with long term repeat customers, not a long string of patsies.There was once a contractor in Athens who specialized in getting their foot in the door and then condemning equipment. They are no longer in business. They literally ran out of people who would do business with them. When you cheat your customers, you are slitting your own throat. It does not take a high profile television program sting for folks to figure out something is wrong. Eventually, your customers will catch up to you. When they do, everyone they know will know about it.

There is nothing wrong with making a profit, and there is nothing wrong with being paid well for your time, expertise, and investment. So be up front and charge people for your time, expertise and investment, not parts they don’t need. There is also nothing wrong with offering premium services. If you want to sell setback thermostats or other system improvements, you should make your argument based on the increased comfort, energy efficiency, or convenience that the customer will enjoy. We make money by solving problems for people, not creating them.

The Strength Remains

Eleven years ago, I was working in my office at school when a teacher from down the hall came in and said that a plane had flown into one of the World Trade Center Towers. While I was searching for information about the first plane, the second plane hit the other tower. It was only then that I realized we were under attack. I believe the trade center towers were chosen because they became an icon of American strength. Rather than weaken us, the attacks strengthened us in many ways. We proved our mettle immediately following the tragedy. Stories abound about how people rose to the challenge: from police and firemen risking their lives to politicians speaking with one voice as Americans. My favorite story involves St.Paul’s Chapel directly across the street. Somehow St. Paul's survived the shower of debris and was transformed into a round the clock hostel, providing care and support for eight months to the rescue and recovery workers. For months, volunteers came from all over America to work there. So many volunteers came that they had to be scheduled and their time helping was limited to allow everyone a chance to experience the blessing of helping. People cried when their time was up and they had to leave.

The towers came down. The strength remains.

To Stretch Your Budget, Roll Your Own!

Gary Recher is one of a group of instructors who communicate with me regularly, giving me feedback and ideas. In today's tough economy, we are all being asked to do more with less. Rather than focusing on what we don't have, I suggest we focus on what we DO have. Gary sent me this article on how he makes his own trainers. I hope it will stir your creative juices to see how you can use what is at hand to teach effectively in a challenging environment. If you have a favorite idea that you are willing to share, send it in and I will post it!

Electrical Troubleshooting Trainers

We as instructors want to provide our students with as much realistic troubleshooting scenarios as possible. We can use troubleshooting diagnostic software, manufactured trainers, and actual equipment that many times that we have to swap good parts for bad to provide troubleshooting tasks. Each has its place and can provide excellent opportunities for students’ to hone their troubleshooting skills.

Computer software can stimulate the student on various troubleshooting scenarios. This allows the students’ to develop problem solving skills without shorting out equipment or meters. However, it does not allow them to demonstrate those skills on actual systems using test equipment.

Use of manufactured trainers are many times boards that have the same components as an actual system that has trouble switches to simulate problems. The advantage of a trainer is that it allows the student to use their meter in an actual troubleshooting scenario rather than at a computer screen. Giving them the chance to use a meter and interpret their meter readings. The downside of these trainers that many times they are forced to use test points for the meter test prods rather than testing at points one would actually use in troubleshooting such as relay terminals.

Actual equipment allows students to get actual hands on experience. The limitations to using actual equipment is that to create a troubleshooting scenario the instructor or lab assistant will have to remove good components and install defective ones. This method is time consuming as the equipment will have to be set up for the troubleshooting scenario and then repaired at the conclusion of the troubleshooting session. If there is only one student this is ideal as the student can then demonstrate the removal and replacement of the defective component and then accomplish an operational test of the system. If several students have to troubleshoot the same fault there is always the downside of the fault being compromised to students that have not accomplished the troubleshooting task.

As HVAC/R technicians/instructors we are no strangers to solving problems. And there are ways to providing realistic troubleshooting scenarios without having to swap good parts for bad. Here is what our course has done that allows us to change troubleshooting scenarios using toggle switches. One of our troubleshooting stations is a cube air conditioner connected to an air handler with electric heat. On the back of the air handler a large hinged door component box was installed. Which is now becomes troubleshoot control center. Inside are mounted four motor starter rated toggle switches several lower amperage rated toggle switches and a dual run capacitor. Inside the compressor compartment the wires for the compressor and fan windings and wires spliced back to the control center. In the air conditioner’s electrical control box the contactor coil wire is unsoldered from one of the terminals. A 20 gauge stranded wire is soldered to the terminal and a second wire soldered to the coil wire. Both are run back to the control center to a toggle switch. Are you getting the idea now? With a flip of a switch there is a defective contactor. With the flip of a switch there is an open compressor or fan motor overload or run winding. The air handler cube relay was relocated to the control center. A similar relay was disassembled and the coil disabled and wires soldered to the internal terminals a hole drilled to the bottom of the relay and then through the mounting plate, grommet inserted into drilled hole, and back to control center through toggle switches. The thermostat was not immune either to our devilish modifications. By carefully grinding the current path etchings on the terminal board with a Dremel grinder wires can then be soldered to both sides of that break and then run to a toggle switch to the control center.

The downside of this is that you will have to do it yourself, and it does take time to make. The upside to doing this is that the student will be troubleshooting equipment as near world as possible and troubles can be changed with the flick of a switch from a thermostat to a fan relay to a compressor problem, etc..

This same procedure can be accomplished using manufactured demonstrators. By installing faux relays and toggle switches a demonstrator can be turned into a troubleshooting trainer.

The bottom line of this article is to hopefully to inspire you to use your mind, innovate and create the training devices that provide more realistic training situations.

Practicing for Success

"We are what we repeatedly do. Excellence, then, is not an act but a habit." – Aristotle

I would like to propose a slight revision to Aristotle’s line of thought: Success is not a condition, but a habit. Have you ever known someone that is lucky and seems to go from one success to another? It is sometimes difficult not to be envious of their success and wish we were so lucky. If the primary action you take towards becoming successful is to wish for success, chances are you will not find it. People are not successful because they are lucky; they are successful because they prepare for their success through repetitive practice. So the question is: “Are you practicing for success or failure?” You might ask “Who would practice for failure?” However, I have seen many students diligently practicing for their inevitable failure. They practice for failure by not preparing for class, arriving late, and making endlessly creative excuses for their failure to complete their work. Eventually they become expert at failing – eliminating all chances of success. I will not tell you that if you work hard and put your best effort into everything you do that you will always be successful. But I can guarantee that if you do not work at being successful, you will most certainly fail.

A big part of achieving success is preparing for opportunity. Opportunity comes in different forms at different points in everyone’s life. But to take advantage of opportunity when it comes around, you have to be prepared. That is one of the main reasons for going to school – to prepare for your future opportunities. You should practice being successful to prepare for opportunities that are sure to come. Show up to class early, prepare for class by studying the assigned material, ask questions when you don’t understand something, and don’t settle for good enough to get by, always strive to improve. I can not tell you exactly when or where opportunity will present itself in your life, but I do know that you must prepare yourself to take advantage of it when it arrives.

So if you have been practicing for failure, I suggest you reconsider your strategy. Put yourself out there, throw yourself into your studies, and risk being successful.  

Centrifugal Blower Motors

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 with a standard AC inductive motor 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.

Although the noise and increased air velocity make it seem like the fan is actually moving more air, the truth is that it is moving less. The air that it IS moving is traveling at a very high velocity, or speed. This is what makes the increased noise. But since you are effectively making the hole that the air travels through smaller, less air is able to get through, even at higher velocity. This is more difficult to show. To get accurate readings, you really need the air to be moving through some ductwork.

Another point to discuss is the difference between a blower with a traditional PSC motor and one with an EVM blower. The behavior we have been discussing is typical of an AC induction motor, like the PSC motors that come standard on most blowers. However, an ECM blower motor senses the change in work and increases its speed enough to actually overcome the resistance, so that the fan moves the same amount of air even against increased resistance. Since this requires more electrical energy, the amp draw for an ECM blower will increase when the fan is restricted. The ECM technology solves one problem: losing airflow due to increased resistance. But is creates a new one: increased electricl use to overcome the resistance. 

To read more, check out Unit 41 Fundamentals of Psychrometrics and Airflow and Unit 75 Fans and Air Handling Units in Fundamentals of HVACR 2nd edition. You can find the blower labs in the new Lab Manual for Fundamentals of HVACR, 2nd edition. They are labs 75.3 AC Induction Motor Blower Properties and lab 75.4 ECM Blower Properties.

Why 120 + 120 = 208

Have you ever wondered why in a standard three phase system that the leg to leg voltage is a little lower than the two leg voltages added up? Typically, if your two legs are 120 volts to ground, the voltage between them will only be around 208 volts. A system like this uses a transformer arrangement called a wye because it looks something like a wye on paper (page 544 of Fundamentals of HVACR). The three windings are tied together in the middle, and that is where the transformer is grounded. Each leg to ground is around 120 volts, but when you check the voltage between legs, you only get 208 volts. Remember that voltage is a measurement of potential difference – it is measuring the difference in electrical potential from one point to another. That is why if you put both leads on the same point you read 0 volts. That does not mean there is no electrical potential at that point, just that the difference between your two probes is 0. When measuring the voltage between two phases of a 3 phase system, the meter is reading the difference between the two phases. If you were to draw both phases on a graph and plot another curve that represented the difference in the two phases, you would be plotting what the voltmeter reads. This can be represented mathematically by vectors.

A vector has both a direction and a strength. An easy way to understand vectors is to imagine a wagon with a rope pulling it. With one rope, the wagon will go at the same speed and direction as the person pulling the rope. Tie a second rope to the wagon and have two people pulling in different directions, and now the wagon will travel a path somewhere between the two people. Now have one person pull faster than the other, and the wagon will travel a little more in that direction. Adding different AC voltages and currents is done with vectors because vectors can account for differences in strength and direction. If the two legs were 180° apart from each other pulling in completely opposite directions, the voltage would be the sum of the two legs, as in single phase systems. Because the two phases of a wye type 3 phase system are not pulling in completely opposite directions, the difference is not simply the sum of the two voltages. You can see this by looking at a drawing of a Y type transformer, like the one on page 544 of Fundamentals of HVACR.

Zero is Not Nothing!

The other day a technician asked me why there appeared to be refrigerant coming out of a compressor that he was de-brazing. He had recovered the system refrigerant, so where was this refrigerant coming from? First I asked now deep a vacuum he pulled with his recovery machine. He had pulled down to 0 psig. I pointed out that 0 is not nothing. Even though I am from Georgia, “0 is not nothing” is in fact not a double negative. Remember that there is still 14.7 psia worth of pressure in the system at 0 psig, so 0 is really not nothing. Something is still in there. You would have to pull a deep vacuum to get close to nothing. Additionally, the compressor oil holds lots of refrigerant. So if you want to reduce the refrigerant coming out of the system, you need to go lower. For a system that has an operating compressor, operate the system until the compressor gets warm before starting recovery. No recovery machine can pull refrigerant out of the oil as fast as you can by operating the compressor. However, if you are changing the compressor, that probably won’t work. Instead, get out your hair drier and heat up the bottom of the compressor with hot air. While you are at it, heat the accumulator and filter drier as well. If you don’t plan on dining out while the recovery machine operates, use core removal tools to take the Shrader valve cores out to reduce restriction. Trying to recover through a Shrader valve with the core in is like drinking a milkshake through a coffee stirrer –not impossible, but really slow. But back to the 0 is not nothing story. 

I have done an experiment several times now that shows how much refrigerant can be left in the compressor oil. After recovering a 2 ton R22 packaged unit down to approximately 5” hg vacuum, we let it sit to see that it would not rise above 0 psig. Convinced that we had achieved 0, we operated the unit. After a few minutes of operation, the system was operating at 150 psig on the high side and 25 psig on the low side. There was a lot of refrigerant in the compressor oil. Now I must warn you that compressor manufacturers would frown on my experiment – so don’t do this at home – use someone else’s compressor! Operating a compressor on “nothing” is a sure way to kill it. One last safety tip: instead of de-brazing the compressor, try cutting it out. No fumes, no flames, and far safer if you mistakenly left a lot of “not nothing” in the system.

Synthetic Marijuana Kills!

I found out recently what killed a promising student in my program this past year. His heart was stopped by synthetic marijuana. I have no idea why he was using it, I only know that it killed him. He was a promising young man with significant ability that is now lost. He left behind a son that he cared deeply for. One of his motivations for learning a trade was to improve life for his family. I admittedly know very little about this stuff, so I am providing some links to articles about it. Wikipedia Article   National Institute of Health

What I do know is that it makes no sense to inhale any kind of drug laced smoke into your body. Before FDA approved drugs are even tested in limited quantities on people, they are extensively tested in animals for safety. With these designer drugs, the customers are the lab rats. My message is simple: if you use this stuff - stop. If you know someone else who uses it - stop them. It is literally a matter of life and death.

I am pleased to introduce my first guest blogger - Kevin Thompson of Thompson Heating in Louisville, Kentucky. He has contributed an article on what homeowners can do to prolong the life of their equipment, and what they should leave to trained professionals. 


Home comfort technology has come a long way in a very short time. For some it seems like just yesterday our homes were cooled with a box fan in the front window or heated during the winter months with a heap of coal and a trusty stove. While some may still prefer those primitive methods, most of us have evolved into using more complex, electrical contraptions to heat and cool our homes. These modern machines have resulted in safer, long-term, and more efficient options for modern day homeowners, especially when they are treated with their recommended annual maintenance. For most heating and cooling units, changing the air filter every 3 months is critical to its long-term maintenance. Over time dirt, dust, dander, and pollen build up and your filter keeps it from circulating in your home. If the filter is not replaced regularly, it could become clogged and your blower begins to work overtime. When your blower becomes overextended, it results in higher monthly energy costs and it could overheat your unit. Most air filters are inexpensive and can be purchased at your local supermarket or hardware store year round. Staying on top of their air filters is one way homeowners can save money on their comfort system and prolong its use. 


While making sure the air flow in your unit is not obstructed is very important, there are a number of other tasks that should be inspected by a trained HVAC professional. Among the things a service professional should check on a furnace include the burner assembly, gas pressure, carbon monoxide testing, and the indoor blower wheel. For an air conditioner unit, they may inspect the refrigerant charge, capacitors, lubricate moving parts, and clean the condenser coil. Not only is it important to have your comfort systems checked annually, but it is equally as important to have them serviced during the peak of their respective seasons. For example, a furnace should be checked towards the end of the summer months at the beginning of fall. Air conditioning units should be serviced at the beginning of spring. That way your units will operate at their highest level of efficiency during the most important times of the year. All of the abovementioned maintenance should be inspected by a trained professional. Most states require HVAC professionals to complete a specified number of hours per year to remain certified. The training they receive prepares them for the injury risks and technical know-how that is entailed in each service call. Some homeowners erroneously attempt to service their heating and cooling units on their own, deferring to online forums and do-it-yourself (DIY) manuals as opposed to making a simple call to their local HVAC professional. DIY projects are great for many jobs around the home, but HVAC repairs should be left to the professionals. There are too many things that could go wrong to justify servicing a unit on their own. 


Today’s HVAC products are far more complex than the wood or coal-burning stoves and box fans of the past. Making repairs on these primitive commodities could more easily be taken care of by a homeowner or a local handyman with a little welding and some electrical work. These days one would be hard-pressed to find two similar heating or cooling units in two homes on the same street. The wide diversity of products speaks to the crucial importance of having a certified professional perform annual inspections and needed repairs on furnaces and air conditioning units. Proper do-it-yourself maintenance is appropriate for air filter replacements which may help to save on monthly utility payments and could serve to extend the life of a unit. All other repairs and service calls should be taken care of by a certified HVAC professional annually in the beginning of the spring and fall months, depending on the respective unit. Proper annual maintenance by a certified professional will not only ensure the longevity of HVAC units, but may also protect against unnecessary injuries that may occur during DIY projects. As the complexity of home comfort systems evolves, so must the mindset of HVAC consumers as it pertains to proper and safe maintenance for furnaces and air conditioning units.


If you would like to find out more about Kevin or his company, check out their web site at http://www.thompsonheating.net

Is You Refrigerant System Constipated?

I am hearing more stories about systems having problems with refrigerant restrictions. Many are from black scale created inside the pipes by brazing without a nitrogen purge. In the old days we often got away with this if we did not take a long time brazing the joints and did not overheat the pipe. Today, however, the POE lubricant and HFC refrigerants scrub off the oxides and carry them around in the system. This is especially problematic with metering devices of all sorts. TEV screens get plugged, orifice metering devices get plugged, and even filter driers get stopped up. The black oxides can also conduct electricity, so if they build up inside the compressor shell they can cause it to ground out. Prevention is the best remedy – not forming the oxides in the first place. You can do this by purging the lines with nitrogen while you braze. Of course you need to let the nitrogen out as you put it in so the system does not pressurize. You can’t braze up a hole under pressure. There are new flow meters that let a trickle through – just enough to keep the air out, which is all you need. No air means no oxygen to form oxides. The primary symptoms of refrigerant restriction are a low suction pressure, a high superheat, and a high subcooling. The head pressure may anywhere from slightly low to kind of high. If someone has tried to fix the problem by adding charge, the high side may be high. Normally, it will be a little low after a few minutes of operation unless the system has been overcharged. If the restriction is anywhere in the liquid line, like the filter drier, there may be a temperature drop at that point due to liquid flashing off.

If your system is constipated with black scale, ex-lax won’t help. You will need to recover the system refrigerant, disassemble it and flush it out using a solvent made specifically for refrigeration systems, such as Qwik Flush by Mainstream Engineering. Using carburetor cleaner will just add to your problems. Re-assemble it with a new filter-drier, pull a good vacuum, and weigh in the manufacturer’s specified charge. You will have to adjust the charge slightly for line length and the amount of refrigerant the filter holds. I recommend using flare filters because they are easier to change, and you won’t have to worry about making any more scale. For more details on this procedure, check out unit 91 Refrigeration System Cleanup in the 2^nd edtion of Fundamentals of HVACR.  

Desired Air Conditioning Temperature Drop

I was recently asked for a formula to determine the temperature drop between the return air and supply air of an air conditioning system. While it is logical to check the temperature drop, determining exactly what it should be is not as simple as plugging in readily available numbers into a formula. Two operating conditions can have a pronounced effect on the results: the relative humidity of the return air and the amount of airflow. Most air conditioning systems condition the air two ways. They cool the air, referred to as sensible cooling; and they take water out of the air, referred to latent cooling. Only sensible cooling creates a temperature drop. Removing water from the air takes system capacity. The more water the system removes from the air, the less capacity is left for reducing the air temperature. Standard airflow is 400 CFM per ton for most systems, but that does not mean your system is actually operating at 400 CFM per ton. If you move less air across the coil, the air will be cooled a little more. To determine the temperature drop you must know the outdoor ambient temperature, the return air dry bulb, the return air wet bulb, the CFM of airflow, and the system’s sensible cooling capacity at that condition.

Take for example, a system that is removing no water out of the air operating at 100% sensible cooling with a standard 400 CFM per ton of airflow and producing 12,000 Btuh per hour. The temperature difference is calculated as TD = 12000/(400 x 1.08) = 28°F TD. If the airflow is reduced, the TD becomes 12000/(350 x 1.08) = 32°F. Increasing the airflow would make the TD 12000/(450 x 1.08) = 25°F. In humid climates, the latent capacity can easily be as much as one third of the total capacity, reducing the sensible cooling capacity to 8,000 Btuh. These same airflows would then give TDs of: 8000/(400 x 1.08)=19°F, 8000/(350 x 1.08)=21°F,8000/(450 x 1.08)=16°. In reality, these TDs would be a little off because the overall system capacity would be a bit less with the decreased airflow and a bit more with increased airflow. The system capacity will also change depending upon the outdoor ambient. The 12.000 Btuh per ton is a nominal figure based on the AHRI rating condition of 95°F outdoor ambient, 80°F indoor dry bulb and 67°F wet bulb.

You can try to account for duct gain by reducing the expected TD by some amount: say 3°F - 5°F. However, it is really difficult to use TD at the registers because the duct gain from one system to another can vary a lot. Ducts in the attic will pick up more heat than ducts in a crawl space. Duct leakage also has a big effect. If 10% of the air entering the coil comes from a 150°F attic, that obviously will affect the delivered air temperature. The rule of thumb people have used for many years is a TD of 15°F to 20°F across the coil, not at the registers. Looking at the above calculations, you can see where this comes from. However, it is also easy to see how little you actually know if you don’t really know all the operating conditions, the system airflow, and the system capacity at those conditions. If all you do is measure the return and supply air temperatures at the registers, you don’t really know much.

Substitute Refrigerant Safety

As R22 prices increase and R22 availability decreases, many technicians have at least thought about using a substitute refrigerant in place of R22. Usually, we are looking for a drop-in which can be used to charge a system instead of R22. My primary consideration is safety. Of course I want any substitute refrigerant to work well and be environmentally friendly, but most of all, I want it to not hurt me or my customers. The refrigerant manufacturer should be able to show that their refrigerant is listed on the EPA SNAP list of acceptable replacement refrigerants. If they can’t, I would not use it. Another source of safety information is the required MSDS sheet. Any chemical sold in the United States must have an MSDS sheet. If the seller cannot provide an MSDS sheet, I would not consider using the refrigerant. The MSDS sheet will list important information such as toxicity and flammability. One replacement refrigerant that is advertised on the internet has enough information on the MSDS sheet to let me know I don’t want any part of it. The proper shipping name is “Petroleum Gasses Liquified.” Other statements include “Vapor may ignite if exposed to static discharge", and "Flammable vapor may form if allowed to mix with air. Accumulation of gas is an ignition hazard. Vapors are heavier than air and may travel to an ignition source." R22 systems are not built to operate safely with a flammable refrigerant. There is no way I would put this in a system designed for R22. Last year technicians were killed while working on refrigerated shipping containers that exploded.(See post about it). They were R22 systems which had been charged with a flammable substitute refrigerant. Although the EPA has recently approved the use of flammable refrigerant in limited charge applications, it is important to note that there are many requirements a system must meet to be safe with flammable refrigerants. R22 systems meet none of these. For more information on flammable refrigerants, take a look at my previous post on Flammable Refrigerants. For more information on R22, take a look at my previous post on R22 Conversion. A couple of simple rules to follow will help keep you safe. Can you buy the refrigerant at your local wholesaler? If you can only get it over the internet or from a guy at a flea market, you don’t want it. Is the refrigerant listed on the EPA SNAP list for the specific application? If not, you don’t want it. Does it seem too good to be true? If so, you probably should avoid it like the plague.

Establishing Your Lifelines

All indications are that the HVACR Industry wants to help more people become involved in the HVACR trade. Their motivation is not founded in philanthropy, but self-interest. Unions cannot prosper without skilled members, contractors cannot prosper without skilled workers, and everyone needs skilled technicians to keep warm in the winter and cool in the summer (unless they live in Australia where keeping warm in the winter is not a problem). Howard Weiss of the ESCO Group recently sent out an message encouraging everyone involved in HVACR to step up to the plate and contribute to the education efforts in our industry. He points out the Bureau of Labor Statistics projects that 65.6% of HVACR service personnel in the industry in the year 2020 will be people not in the industry today. The whole industry has a stake in education. I believe that one problem is that many of the organizations who are already involved and contributing the HVACR education efforts often have a difficult time getting the word out. Teachers are often busy keeping up day to day and don’t always have the time to investigate instructional materials, scholarships, industry sponsored training, or equipment donations already available. I find that sometimes companies and organizations can’t understand why more schools, teachers, or students don’t respond to their offers. What we have here is a failure to communicate.

Anyone wishing to get instructors involved in their activities needs to plan ahead. Early notice is essential to educators. The educational bureaucracy moves at a slothful pace. The first time I went to the AHRI Instructor’s Workshop, the president of my school had to obtain permission from the state for me to go, even though Pearson was paying my way and I would be speaking at the conference. We have to know months in advance to make things happen.

For manufacturers and trade organizations, you need to market your help the way you market your products and services. One or two e-mails or flyers is just not going to get the job done. You need to make pests of yourselves! It is also a good idea to use more than one method to notify us and to make each promotional piece a little different so that it will be noticed. A good example is the National HVACR Educators and Trainers Conference sponsored by the ESCO Group. They put out e-mails and flyers on a weekly basis months away from the date of their conference. The result is that their conference has sold out two years running in a very tight economy. I know that marketing free or low cost products and services might seem counterintuitive. It is really simply a matter of following a successful model. Persistent marketing works.

As instructors, we need to recognize that we must invest time developing a network of support for our programs. If we wait for the resources we need to just show up, we won't have much to work with. I have several local contractors who donate materials and equipment to my program. A local contractor on my advisory board recently gave our program one of the new Trane Communicating touchscreen thermostats that look like an ipad. What does the contractor get out of the deal? He and most of his employees are graduates of Athens Tech. But all donations do not have to be so elegant. A recent graduate now working in the field brought us a 3 ton ICP heat pump that is less than 2 years old. It was involved in a house fire and was being replaced. Students who needed a job cleaning coils cleaned it up and a student who needed a job installing a split system installed it. I am proud to say that the newest addition to our shop runs great! If you have needs, let someone know. Below is a small list of organizations you can use to start your HVACR support network.

Instructor Networking

• Council of Air Conditioning and Refrigeration Instructors  CARE
• Refrigeration Service Engineers Society RSES

Conferences

• RSES National Conference, November 14-17, 2012
• HVACR & Mechanical Conference, March 11-13, 2013
• National HVACR Educators and Trainers Conference, March 17-20, 2013

Equipment Donations

• AHRI has a program connecting equipment manufacturers to programs with equipment needs. AHRI Equipment Donations
• Appion will donate an Appion recovery unit to your school. Also, if you buy their speed kit, they will donate one of their vacuum pumps. Appion Donations
• AMRAD builds the Turbo 200 multi-capacity replacement capacitors. They will give you one for your class. They will also come to your school and do a class on how to use them. AMRAD donations

Scholarships

• AHRI Rees Scholarship literally has more money than they know what to do with because too few students apply. Let’s change that.
• PHCC Scholorship Foundation gives scholarships each year
• Grainger awards many Tools for Tomorrow scholarships throughout the country which include both financial support and a tool kit

Expensive Top Offs

For years, many technicians and customers have been content to “top off” leaky air conditioning units, feeling the time and expense required to find and repair small leaks exceeded the inexpensive price of adding a few pounds. After all, adding refrigerant is pretty easy, does not take long, and most customers were perfectly happy to have their systems gassed up every so often. With the cost of adding refrigerant steadily rising, the era of cheap “top offs” is coming to an end. Newer units also hold considerably more refrigerant than older models, and the refrigerant is quite costly. A bill of $500 for “topping off” a system is quite possible. At $500, I don’t want to call you back next month for a repeat performance. I want the problem fixed. Customers are going to start demanding that we fix the leaks – not just gas up the units.

The temptation to just add refrigerant is strong. Locating and repairing leaks takes time and there is really not a sure-fire leak test that can prove a charged system has no leaks. We detect the refrigerant coming out to prove a leak. However, not finding any leaks does not necessarily mean there are none – it just proves that you did not find them. Like many things, better tools often yield better results. Everyone should have a good electronic leak detector and good quality soap bubbles that will form micro-bubbles. An ultrasonic detector is also a good idea for detecting leaks using nitrogen. You also need to use the tools enough to feel confident and comfortable using them. A fancy electronic leak detector is not much help if you don't trust it or use it .

Some leaks are really not repairable. Take for an example an evaporator coil with multiple pin-hole leaks. Plug a little hole today and a new one springs up tomorrow. The repair is to replace the coil, which is expensive. However, not replacing the coil is also expensive. Not only is the cost of adding refrigerant quite high, so is the cost of electricity. A system with a leak loses capacity and efficiency from the day it is charged. The unit has to run longer and longer to accomplish less and less, until it simply can’t meet the demand. The combined costs of added refrigerant and increased operational cost can add up to the cost of replacing the coil. Topping the charge off is no longer an easy and inexpensive solution. It is now just the lazy and expensive cop out.

A Father's Perspective

I have a tradition of posting to my blog on father’s day. Typically, I write about what I see from the perspective of a son. This year I am looking from the perspective of a father. I have two children. Both are very talented and have an impressive record of achievement. My daughter just graduated from Vanderbilt which a degree in Biomedical Engineering. My son, a rising junior in high school, was recently accepted to the University of Georgia as a dual enrollment student. He will start taking freshman college classes while he finishes high school. They are both wield more academic prowess than their dad who took 20 years to get his bachelor's degree. 

Music is a family tradition and both my kids are excellent musicians. There is nothing more satisfying than performing with your family. After a recent band concert in which both my son and I played, we took a picture of Grandfather, Dad, Son, and Daughter. A love of music passed from each generation to the next. I believe that my children's musical training has helped them immeasurably in their academic success and their poise. They are both natural leaders – inspiring the people around them to excel. Best of all, they are really nice people. I can't tell you how many times other parents who have had the opportunity to spend time with my kids have told me how impressed they were with them. 

Of course I mention these things to brag, but also to point out that these two outstanding young people are my father’s day gift 24-7. Nothing they can buy can compete with the people they have become. I don’t believe anyone can express in words the emotions, pride, and love a father experiences seeing the babies that he held become an engineer, or rip through a Scott Joplin rag on the piano with gleeful abandon. Although I am in no hurry to be a grandfather, I do hope that my children will both raise children one day. The truth is, you can’t really know how much your parents love you until you are a parent yourself. My children have the intellectual, creative, and interpersonal gifts to make the world a better place for the rest of us. Come to think of it, they already do!

Are You Giving Grades or Recording Them?

I have a sort of electronic life-line to several instructors around the country. They send me ideas, links to helpful information, and point out issues in the book or on MyHVACLab that they would like addressed. One of my e-mail buddies, Gary Reecher at Scott Community College, sends me things from time to time that he believes would help other HVACR Instructors so that I can share them with more folks. Recently he sent a link to an article entitled “Why Some Students Need to Fail” by Melissa Nicolas. If you have been teaching any time at all, you have probably experienced a student who is desperately seeking a lifeline to pull them through the course. The compassionate nature of most teachers tugs at us to help solve the student’s problem. Instructors should work with students who are struggling to help them succeed. However, this help should not extend to giving the student a grade they did not earn. An analogy might be the boat that accompanies a swimmer as they try to swim across the English Channel. The people in the boat can help the swimmer navigate the course, they can provide hydration so that the swimmer stays healthy during the event, they can offer encouragement, and they can rescue the swimmer should it become impossible for the swimmer to continue. What they may not do, is put the swimmer in the boat, deliver them to the opposite shore, and then declare that the swimmer successfully swam the English Channel. Giving a student a passing grade when they have failed is like providing a ride in the boat and then declaring they swam the English Channel. 

In her article, Melissa Nicolas suggests a helpful change of verb for the awarding of a grade. Rather than “giving” grades, you are “recording” grades. In fact, recoding is really a better description. Giving suggests that you are reaching into your bag of goodies and pulling out a gift for each student. Students who receive an inferior grade will naturally feel slighted by their less generous gift. “Oh I am sorry Johnny, I am all out of A’s. How about a nice C+!” They may also see grades as an indication of how much the teacher likes them. Receiving an F not only hurts your grade point average, but also hurts your feelings because the F indicates that the teacher does not like you. Students need to know that their grades are an achievement, not a gift or an entitlement. The instructor is not giving grades, just recording the grades the students have earned. When they make their A, they know that nobody gave it to them, they earned it.

Summer is Capacitor Replacement Season

Any practicing service tech will tell you that service calls involving dead capacitors are common, especially in hot weather. The two most common causes of capacitor death are heat and over voltage. However, there is another less known cause: old age. Many capacitors have a shelf life. I have seen shelf lives listed as little as one year. The oxides on the metalized film break down when the capacitor is not in use, weakening the capacitor. They do tend to self-heal during use. That is why a capacitor which cannot sit on the shelf for longer than a couple of years can last for ten years in use.

Always check the capacitance of any replacement capacitor with a capacitor tester or the capacitance scale on a digital multi-meter before using the capacitor. It may have already died of old age before you install it! A capacitor is a pretty simple device, basically, it is a couple of rolled up sheets of aluminum foil or metalized film with paper or plastic between them. Although a capacitor is a simple device, it is an extremely important part on most air conditioning systems. A bad capacitor can kill a system’s compressor. To protect your reputation and your customer’s equipment, only use capacitors that can pass the EIA-456 Highly Accelerated Life Test. The HALT test subjects a set of capacitors to 125 percent of their rated voltage and 10˚C above their rated temperature for 2,000 hours. For example, a capacitor that is rated at 5uf/440 vac, with an operating temperature of 70˚C, is tested at 550 vac and 80˚C for 2,000 hours.  

Determining which capacitors to stock on your truck is another problem. There are so many sizes of dual capacitors that it is nearly impossible to have all the necessary sizes. American Radionic, AMRAD, has a solution – a multiple capacitor with enough sizes to cover nearly any application. Better yet, they will send instructors sample capacitors to use in your lab. These are great for demonstrating the effect of connecting capacitors in series and parallel. Their web site is AMRAD

Fundamentals of HVAC/R 2nd edition has coverage of capacitors and their effect in circuits in Unit 34 Alternating Current Fundamentals, Unit 37 Electric Motors, and Unit 88 Troubleshooting Refrigeration Systems.

Courage

On this Memorial Day weekend we set aside time to remember the men and women who have given their lives for their country. The bravery and courage of our fallen heroes will be mentioned in speeches, songs, and gatherings all across the country. In a culture steeped in action movies with larger than life characters portrayed by the likes of John Wayne and Sylvester Stallone, it is easy to imagine that the men and women serving in our armed forces are fearless; caring nothing for their personal safety as they conquer the forces of evil in the world. However, courage is not the absence of fear. Courage is fully understanding the peril about you and proceeding anyway to perform your duty. The brave men and women who gave their lives were not cinematic action figures, immune to pain, suffering, or terror. They felt fatigue, pain, anguish, and fear the same as any of us do. Despite all these very human feelings, they found the courage to perform their duty. I hope on this Memorial Day we will also find time to pray for the brave men and women serving around the globe. Every day, fully aware of the peril, they overcome their fatigue, pain, anguish, and fear to perform their duty. That is courage far beyond Rambo. 

Simple Troubleshooting

One of the problems with knowing a lot about possible complex issues is that we tend to look for complex solutions to simple problems. After learning how to measure superheat and adjust expansion valves, we send to see every problem as a problem with the TEV. This is similar to buying a car that you swore you never saw on the road before, and then by next week you notice every other car seems to look like yours. Our brains have a kind of data pre-fetch routine that tries to speed up our recognition of our surroundings that leads us to jump to conclusions. It is just how we are wired. Recognizing this, we need a system to prevent us from confusing ourselves by making incorrect assumptions based on very limited input. This is one of the reasons that systematic troubleshooting saves time in the long run. Having a system helps us avoid the temptation to solve the problem by guessing. Although there are many ways to approach a problem, I try to remember to check easy things first. If you are going to run down a list of things to check first, at least make sure the list includes simple things that don’t take long to check and should normally be checked anyway. For example, it is never wrong to check the air filter. You really should always do this anyway, and trying to check the system operation with a dirty air filter just wastes time. Dirty air filters reduce the airflow, causing a host of other problems such as low superheat, floodback to the compressor, furnaces cycling on the limit, burned heat strips, and generally poor heating and cooling performance. Similarly, it never hurts to take a look at the condenser coil to make sure it is clean. Dirty condenser coils can lead to units tripping on high pressure switches and compressor internal overloads opening. Always check to see that the thermostat is actually set to bring the unit on. Don’t assume that the thermostat is set correctly. Customers often don’t know how to set their thermostats, especially with the newer electronic thermostats. If the thermostat uses batteries, a fresh set of batteries will often cure a thermostat that is acting erratically. While you are at the thermostat, set the fan switch to on. If the fan comes on, you know that you have power to the indoor unit and also control voltage. With digital thermostats that have batteries, seeing a display on the thermostat does not necessarily mean you have control voltage because the display can operate from the batteries alone. If a unit will not operate, you need to check power to the unit first, and then check control voltage. The problem will often become apparent during these initial checks. Even if the problem is not discovered during these preliminary observations, you have eliminated many common problems in a relatively short period of time.