HVAC School - For Techs, By Techs

Tersh and Bryan were both techs working for other companies when they started their own businesses. This episode is a look back at what they got right, what they got wrong, and the top things that have worked over the years. In general, there are two types of HVAC business owners: the sales/business type and the technical type. Bryan and Tersh are both of the technical variety. These types of owners may be less familiar with the ownership and business organization side. Many current technicians will find themselves in a similar position if they decide to go into business. The HVAC industry is NOT as profitable as many people imagine it to be, especially in the early years. Tersh recommends that technicians really research the expenses of HVAC business ownership, namely worker's compensation, general liability, licensing, fuel expenses, and advertising. He also recommends that business owners use digital media to assist their business operations. Bryan encourages prospective business owners focus on their financial literacy. You can be excellent with customer service and can draw many customers to your business, but those qualities don't matter if you can't manage your money effectively. Business owners need to understand what profit REALLY is, how margins work, and how to evaluate and nurture a successful business model. Also, business owners should track labor rates and know who to compete with; don't compete with businesses that do bad work or are going out of business. You must also have good people skills if you want to start an HVAC business. If you cannot be empathetic and build relationships, running an HVAC business isn't for you. Bryan and Tersh both agree that the best overall mindset for an HVAC company's business model is "People over profit." That includes service technicians, customers, and all staff.

In this episode, Bryan speaks with Jim Bergmann of Redfish Instruments about his path to being a test instruments business owner. He has also worked with Testo and has teaching experience under his belt. In the past, test instruments were low-resolution and often inaccurate. Many HVAC techs of the past based all of their knowledge on inaccurate measurements. We also didn't use many of the best practices we use today. For example, technicians used tap water for sling psychrometers, not distilled water. As such, technicians of the past had serious issues with wet-bulb enthalpy calculations. Some of these challenges stemmed from issues with the educational system. There was a lack of emphasis on the fundamentals and measurement and an overemphasis on installation, and the poor curriculum still persists in some institutions. Today, Jim sees a large understanding gap between the engineers that develop test instruments and technicians in the field. As a business owner who developed some of those testing technologies, Jim's goal is to close the gap. In the future, Jim believes that the HVAC labor shortage will be a challenge for test instrument developers as the industry moves forward. Due to issues that remain in the HVAC education system, Jim also worries that the people who enter the field will be "parts-changers;" they won't check the system thoroughly for a proper diagnosis. So, Jim has been working on a diagnostic tool called MeasureQuick to help new technicians by educating them on what their readings mean. These technologies are meant to help entry-level techs and aid intermediate and senior techs. Here's a bonus note about measuring with pitot tubes: use longer hoses and an instrument with a very high resolution. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.  

In this podcast, Bryan talks about condensing temperature, condenser split, and subcooling. All three of the values are proportional. If one changes, all three of them will change. Saturation is also a critical concept that relates to all three of those, so we also cover those relationships. As you remember, a condenser rejects heat and turns vapor refrigerant back into a liquid. Condensing temperature is the saturation temperature at which the refrigerant changes from vapor to liquid; it can change depending on ambient temperature. While in the condenser, the refrigerant will be at saturation and be a liquid-vapor mix throughout most of the coil. Subcooling indicates how low a liquid is below liquid-vapor saturation. For example, if you had a condensing temperature of 110°F and took a liquid line measurement of 98°F, you would have 12°F of subcooling (110 - 98 = 12). Although some high-SEER HVAC systems may get their liquid line temperatures pretty close to the ambient temperature, you cannot have a liquid line temperature below the ambient temperature. Otherwise, you probably have a restriction in the line. Many technicians set a charge based on subcooling. Condenser split is a bit trickier to define. You DON'T compare the temperatures of air going into the condenser and air going out. Instead, it is the difference between the condensing temperature and the outdoor temperature. The outdoor temperature MUST be lower than the condensing temperature. Otherwise, heat rejection cannot take place. In general, most manufacturers tend to engineer their HVAC systems to maintain a 15-30°F condensing split. Heat mode has its own set of challenges. For example, subcooling can be difficult to predict in heat mode. However, between 20-30°F of subcooling in heat mode is normal. As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE.

In this episode, Bryan talks a bit about the air side of the system. Understanding airflow is all about seeing the relationship between readings. We cover latent and sensible heat, relative humidity, wet and dry-bulb temperatures, and static pressure. Latent and sensible heat refer to heat that we can feel (sensible) or heat that contributes to a phase change and cannot be felt (latent). Both latent and sensible heat have a major impact on equipment sizing, especially in coastal regions and other areas where humidity is naturally high. When we attempt to control sensible and especially latent heat, we have to look at the airflow over the evaporator coil. When you run the blower more slowly, you pull more moisture (latent heat) at the expense of efficiency and capacity. Therefore, for peak capacity, efficiency, and sensible heat removal, you will want to max out the blower speed. Delta T (or air temperature split) is another important reading. Delta T is the temperature differential from the return to the supply. When you measure delta T with a dry-bulb thermometer, you will only get a sensible heat measurement. You need a wet-bulb temperature reading to account for humidity and latent heat changes. Relative humidity (RH) is the ratio of moisture in the air compared to the maximum at that temperature. Therefore, wet and dry-bulb temperatures are the same at 100% relative humidity. Static pressure is an indicator of airflow, but it isn't airflow. Static pressure is essentially resistance pressure that exerts itself on all surfaces. It is not the force of air flowing through the duct (that's velocity pressure). Also, consider adding a differential manometer to your toolbox. They make measuring TESP a breeze. As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE.

In this first episode of a new series Justin talks about the calls he is doing before and after he does them, giving us a look inside the van of a senior HVAC tech. 

In this episode of the HVAC School Podcast, we talk about some cool technologies and controversial tools. Joe Shearer joins us to talk about hard start kits. Some people believe that hard start kits are only suitable for one-time use, but Joe and Bryan believe that there's a lot more to it than that. If hard start kits are high-quality, then you could leave it on. However, if a unit has a hard-shutoff TXV, then it absolutely needs a hard start kit. Many techs are still hesitant about using hard start kits because they can damage the compressor if the relay doesn't take them out. Some techs feel similarly towards Stay Brite #8. You don't have to flow nitrogen with Stay Brite #8 solder, and some technicians (Bryan included) are suspicious about the quality of the work when you cut out those critical steps. So, many technicians prefer brazing, but Stay Brite #8 and brazing each have their benefits and drawbacks. At AHR, Bryan got a chance to speak with FasTest representatives about CoreMax valve cores. These large cores are great for commercial HVAC applications and help you achieve high flow during evacuation. Your typical core removal tools won't work, but CoreMax core removal tools exist, and the core assembly is also easy to replace. He also got to speak to a Packard representative about motor temperature ratings, especially on OEM vs. aftermarket motors and motor performance in various ambient conditions. Browning shared some information about their notch belts and the temperature ratings of those belts. Also, remember to check that the discharge temperature stays below 220°F. The discharge temperature can tell you a lot about your compressor and your chances of experiencing oil breakdown. As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, Jeremy Smith comes on the podcast to talk about low-ambient controls, headmaster valves, charging, and condenser flooding. If our head pressure drops too much, we won't get enough of a pressure drop across the TXV. Pressures dictate the TXV function, so we need to make sure our systems give that valve what it needs to operate correctly. Three pressures operate a TXV: bulb pressure, spring pressure, and evaporator pressure. However, pressures throughout the system can also affect the pressures that act on a TXV. Condensers are sized for maximum heat rejection at the highest ambient temperatures a unit will experience. Low-ambient controls help get your liquid pressure up by effectively reducing the condenser's capacity. One common thing we can do is use a fan cycle; a pressure control can turn the fan on and off, but you can see large pressure swings. We can also use headmasters, which maintain head pressure by backing up liquid in the condenser; it fills the condenser with liquid and shifts some discharge gas to the receiver to maintain the receiver pressure. Headmasters are NOT adjustable in the field. When diagnosing headmasters, try to look for leaks first; Jeremy thinks many headmaster failures could have been misdiagnosed. Split condensers can shut off parts of themselves to reduce capacity, which can serve as another low-ambient control without bypassing discharge gas or wasting energy. You may also come across some adjustable controls that allow you to adjust your head pressure by setting receiver pressure and other similar values. Jeremy and Bryan also discuss: Balanced-port TXVs Fan cycling in air conditioning Using a clear sight glass to charge refrigeration units Headmaster part numbers Carrier Motormasters Parallel rack systems and remote condensers Inefficiency and bypassing discharge gas   Read the companion tech tip HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Bryan takes a break from the technical talk and tells a quick story about how two brothers fueled an industry and created an empire with raw sibling rivalry. Bryan co-owns a family business, and we understand that many people in this trade work with family, so we hope you'll enjoy this story. Many of us are competitive, and nobody enjoys failing. We especially try to avoid failing in front of our family members. However, the drive to succeed and avoid failure can sometimes get a bit out of hand. In the early twentieth century, two brothers named Adi and Rudy Dassler worked in their father's shoe business. Rudi was the more outgoing older brother; Adi was younger, quieter, and focused on making shoes. Business practices had changed as industrialization occurred across Europe, and many shoes were made in a factory instead of by hand. With all of the innovation going on at the turn of the century, both brothers realized that they, too, could own a factory. After serving in World War I, Adi began making shoes in his mother's laundry room. Rudi talked their parents into helping start up a shoe business. The brothers established their own athletic shoewear company, which became popular with help from the Modern Olympic Games. Adi approached Jesse Owens, a famous African-American track athlete from the United States, to wear his shoes in the Olympics. Jesse wore the shoes to victory, angering many Nazis. Rudi was the more ardent Nazi, and a rift started between the brothers. Rudi was arrested for war crimes during World War II, though historians suspect that Adi may have snitched on him. The sibling rivalry came to a head in 1948 when Rudi officially split from the company and formed Ruda. Adi formed Adidas, which was more successful than Ruda (now Puma).   If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode, we talk with Jeff Nieman about chillers and how they work. For those of you who primarily work in residential or light commercial HVAC, chillers may be unfamiliar at best and terrifying at worst. However, centrifugal chillers' parts are actually quite similar to those of HVAC units. They have an evaporator, compressor, condenser, metering device, and control system, just like the HVAC units we see every day. Jeff believes that breaking a chiller down into its parts is the easiest way to become comfortable with it. Chillers are used for comfort cooling and process cooling. In comfort cooling, chillers discharge cool water (44°F) to the building. From there, air blows over the water to cool the space. For process cooling, chilled water flows through machines that require constant cooling to operate correctly, such as laser-cutting machines and MRIs. As you can see, chillers simply absorb and reject heat, just like standard compression-refrigeration HVAC systems. However, unlike traditional compression-refrigeration units, chillers have an independent oil circuit. Preventive maintenance is a major part of chiller work. You can tell a lot by listening to a chiller and looking for oil or water on it. You also check superheat, subcooling, and water temperatures. Service calls also require technicians to engage their senses. Most issues deal with low water flow, building issues, and dirty strainers in the condenser water piping. Bryan and Jeff also discuss: Two-way and three-way valves Glycol and freeze protection Alarms (float switch, low evaporator pressure, high condenser pressure) Chiller troubleshooting Impellers and inlet guide vanes Suction in negative pressure Fan coils Chiller water Screw chillers   Also, Bert and the Testo 770-3 make an appearance. As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this episode, Bryan and Bert talk about properly stripping cables and leak detection best practices. Bert is a senior technician and self-proclaimed leak detection expert. As a slight aside, Bert CAN'T STAND when technicians strip wires. Basically, his advice is NOT to cut around the wires or use a razor knife. Leak detection starts when you walk up to a unit and confirm that the unit is low on refrigerant. Typically, you hook up gauges and check the five pillars. You will particularly check for low superheat and high subcool. However, your senses are also important during the confirmation process. Use your eyes before even grabbing a leak detector. You can typically spot corrosion on the line set, coil, or pipe fittings. Then, you can perform a bubble test to confirm the leak without a tool. Bert starts with coil and checks for oil spots. He then feels brazing joints for oil (even though that sounds a little suspicious). Most importantly, if Bert suspects a leak, he does his bubble test BEFORE pulling out the electronic leak detector. When Bert uses the leak detector, he turns it on and lets it stabilize for a little bit. He starts LOWER on the coil to get a hit and starts HIGHER to pinpoint the leak. And NEVER put your probe in water! New coils can be tricky. Although they CAN leak, it's improbable. If your leak detector gets a hit on a brand new evaporator coil, it could be caused by the chase. You MUST confirm that the leak is on the coil; it's not good enough to say that there is a leak without knowing exactly where the leak is coming from. As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE.