Hvac School - For Techs, By Techs

Amrit Robbins of Axiom comes on the podcast to discuss how we can use data science to transform grocery and cold storage.   Axiom Cloud uses cloud analytics and AI to map data and analyze trends on refrigeration racks. It can be particularly useful to keep track of readings all the time because it’s impractical to rely on a human to take and record readings 24/7.   Grocery stores are unique because they have so much product at stake and are relatively inflexible in their usage of energy. If something goes wrong on a rack, thousands of dollars worth of products may be lost.    If we could collect and review data at our fingertips, we could spot potential problems before the store loses money. These systems may also have alarms for case temperature problems, floodback conditions, and even some less immediate issues, such as a lack of floating suction.   Axiom Cloud also monitors when systems go into defrost, so you can assess the cycles of case groups and figure out if they correspond to any issues.    When you

In this short podcast, Bryan goes over the basics of superheat and explains why it matters to us.   Superheat is the temperature increase above a substance’s saturation temperature or boiling point. When a substance is superheated, that means it is 100% vapor; there is no liquid at all. We can look at our superheat to determine how much refrigerant is feeding our evaporator coil.   A lower superheat indicates that our evaporator is more full of refrigerant than a high superheat, meaning that the refrigerant is feeding the evaporator coil well. Generally, a lower superheat value will be more efficient, but if the superheat gets too low, we can get liquid in the suction line and compressor.   An evaporator can maintain roughly the same temperature throughout the bulk of the coil because the temperature stays the same during a phase change. As the refrigerant boils off from its liquid state, it remains at the boiling point. You generally want to see no less than 6 degrees of superheat, especially at the compress

In this podcast episode, Bryan and Eric Mele talk about sight glasses, the significance of subcooling in refrigeration, and liquid quality.   While we measure subcooling quite often in HVAC work, we rely on sight glasses and liquid line receivers far more often in refrigeration. You need a sight glass to determine the liquid quality in a refrigeration system. Subcooling is one way to assure liquid quality without a sight glass or a receiver.    Subcooling refers to the temperature drop below liquid saturation. Head pressure can dictate subcooling, and several other factors can dictate the condensing temperature, including stacking. We use sight glasses because a clear sight glass can tell us that we have a full column of liquid (therefore subcooling) without hooking up gauges.    In HVAC, we care about having a certain level of subcooling because we want to make sure the refrigerant is fully liquid when it reaches the metering device; no bubbles should be present by the time it reaches the metering device. Li

In this short podcast, Bryan explains the basics of repairing aluminum, such as on coils or tubing. Repairing aluminum can save lots of time on mission-critical calls and can help stop refrigerant leaks that lead to ozone layer depletion or global warming. Soldering makes almost all of the aluminum repair work we will do. (Brazing is possible, as aluminum has a melting point of 1200 degrees, but that’s still a bit too close to the brazing threshold.)  When working with aluminum, we need to recognize that it melts at a lower temperature than brass, steel, and copper, and it doesn’t change color. Aluminum is also thinner and almost fades away under excess heat. First, you’ll want to figure out how to get the base temperature to the right temperature, usually with a flux. (Some fluxes require cleaning, some don’t; either way, we recommend cleaning.) The powder flux should go clear, and then you’ll be ready to apply the rod. In many cases, indirect heating can be difficult if not impossible. After you choose your

In this short podcast, Bryan goes over energy transfer and heat, specifically specific heat. BTUs per ton is a common measurement; a BTU (British thermal unit) is the amount of heat it takes to raise the temperature of one pound of water by one degree Fahrenheit. 12,000 BTUs per hour is equal to one ton in heating or cooling technology. It takes one “ton” of heat to melt a ton of ice, but we kept the measurement and terminology as we moved away from using ice in industrial refrigeration. When it comes to specific heat, we have to remember that one BTU has a different heating or cooling impact on different substances. Most fluids have a specific heat lower than water, meaning that one BTU of heat will result in more heat transfer in that substance than water. Air is one such fluid that has a lower specific heat than water (0.24 vs. 1); it’s easier to heat air than water. However, the specific heat of vapors can change with temperature and pressure. When we change a refrigerant from a liquid to a vapor in the e

In this podcast, Steve Rogers from The Energy Conservatory explains some pro tips for pressure measurement.   There are three common types of pressure measurements: absolute, gauge, and differential. Absolute pressure is the pressure in a particular space in reference to a complete vacuum. (All absolute measurements use the zero point as a reference.) Gauge pressure uses atmospheric pressure as a reference point (which varies with altitude and location). Differential pressure relies on two connections (one of them is a reference point to the other).   The Energy Conservatory recently designed a manometer (DG-8) that differs from the standard manometers. The purpose of that manometer is to make pressure measurements in a more cost-effective way. Most manometers have similar sensors (diaphragms move with pressure, and the measurement read is the resulting difference in resistance). However, the DG-8’s methodology can help it yield much more accurate measurements.    When dealing with small pressure measurements

Trevor Matthews from Emerson and Refrigeration Mentor comes on the podcast to talk about Copeland reciprocating CS compressors. He and Bryan cover Bulletin AE4-1433 (found HERE) as they look at the operating envelopes for the CS compressor.   The CS compressors are hermetic reciprocating compressors that can work with some of the newer refrigerants. You will likely see these compressors in applications with smaller tonnages.    You’ll usually want to charge these compressors with liquid refrigerant. If you have more than 6 pounds of charge in the system, using an accumulator is recommended. Under those charge conditions, the system also needs a check valve between the receiver and the condenser.   Suction line pressure drop is one of the most important things to pay attention to in the system. Make sure the suction line is of an appropriate size, that filter-driers don’t have restrictions, and that accumulators aren’t clogged. Overall, many manufacturers recommend removing the duction driers to keep the pres

In this short podcast episode, Bryan explains the science behind adiabatic cooling. Adiabatic cooling occurs in specific HVAC/R applications and in our environment as air temperatures and pressures change.   When we think of cooling, we refer to the loss of heat; we are either referring to the change in the total BTU content of the air mass or the temperature change. Adiabatic cooling takes sensible heat and transforms it into latent heat.   The most simple forms of adiabatic cooling can be seen in cooling towers and swamp coolers. In evaporative or swamp coolers, you have a pad saturated with water, and air moves over it. When air moves over the media, some of the energy helps evaporate the moisture on the pads, so the air loses sensible heat and becomes cooler. The thermal enthalpy (total heat content) stays the same, but some of the sensible heat has transferred to latent heat.    Air that goes through a swamp cooler goes in with higher temperature and lower humidity, and it leaves with a lower temperature

In this short podcast episode, Bryan shares his top tips for fighting boredom at work. You can use these tips to help you get out of a rut if you don’t feel productive or get bored easily.   The first tip is to see the art or creativity in your work. Even in the HVAC industry, there are plenty of opportunities for artisan skills and craftsmanship. When you see your work as an art that you need to refine, especially in terms of duct strapping and brazing, it’s easier to get engaged in your work and feel proud of it.   Another way to stop from getting bored is to do more things that challenge you. Being constantly challenged and being out of your comfort zone keeps you interested and can even spark a new passion.   Pursuing mastery allows you to focus on one particular skill or subject to become an expert. When you master a skill, you also become a marketable job candidate and can carve out a niche within your organization. Mastery is about going deep rather than wide, and more people will feel enriched by work

In this podcast episode, Bryan goes through the addendum to the book Review of Vacuum for Service Engineers. He and Jim Bergmann had the honor of revising the latest edition in 2020. You can get the latest edition of Review of Vacuum for Service Engineers from TruTech Tools HERE.   Pulling a Schrader core before evacuation makes a big difference in the speed of the evacuation. You can use a core remover tool to pull the cores when the system is NOT pressurized.    There are three common types of ports to access the system: the Schrader core, high-flow core (CoreMax), and the multi-position service valve. You can mid-seat the multi-position service valve for high flow, but you need to remove or depress cores on the other two port types. (You must use a special CoreMax CRT to remove high-flow cores.)   Three factors limit the speed of evacuation: the conductance speed of the pump, of the connecting hoses, and of the system. The hoses and manifold can severely impact evacuation. TXV and piston metering devices

In today’s short podcast, Bryan discusses electric heat, how we use it in our work, and what it does.   Also called heat strips or heat elements, electric heat is a supplemental heat source that we usually see on heat pumps. We generally see them in fan coils within a cartridge or a kit at the top of an air handler. However, not all systems have backup heat.   We want to avoid running electric heat as much as possible because it is inefficient. There is almost nothing we can do to make heat strips more efficient; they will usually yield around 3.41 BTUs per watt.    We usually only run electric heat when a heating system can’t keep up with the heat loss. However, the electric heat often runs more often than it should, which can cause inefficient conditions. You can avoid inefficient conditions by programming the thermostat properly.   If you reduce the voltage on the heat strips, the less heat they will produce. Current ratings also differ between 208v or 240v applications. When you have more voltage, you’ll

Trevor Matthews comes on the podcast to discuss his newest project, Refrigeration Mentor. Refrigeration Mentor uses Trevor’s experience as a trainer and field technician to guide others in their careers.   Trevor’s goal is to help commercial refrigeration technicians grow and become more confident in their skills. He wants them to become the best technician they can be, and he believes that mentorship is one of the things that make our industry great. Mentorship can help people advance their careers, sharpen their skills, and ease their anxiety about work.   When we share knowledge, we bring value to the technicians. That value extends to the customer when technicians are more confident in their work and do better jobs. A good mentor has a commitment to doing quality work within the trade but will make their mentees feel comfortable to admit what they don’t know.   Mentors can also help their mentees develop a solid work-life balance that helps mentees be present to their jobs and their families. The mentor’s

In this podcast, Ben from HAVEN IAQ, Kaleb, and Bryan discuss how to control indoor air quality and take meaningful, accurate measurements.   HAVEN is a platform that offers hardware and software delivered to a homeowner through an HVAC professional. HAVEN’s goal is to give its customers a healthier, more comfortable home using IAQ solutions.    The hardware (controls, etc.) works with the HAVEN software to give customers and contractors data about IAQ and the performance of the HVAC equipment. Right now, you may install up to two HAVEN controllers and one monitor per zone to help control equipment and monitor the air content.    Air sampling occurs every hour, whether the HVAC system is running or not. Customers can learn to control their ventilation habits to address acute events (e.g., a spike in humidity from cooking), which only result in short-term IAQ problems. However, contractors can use the air sampling data to develop solutions for chronic events (e.g., constant high humidity).   Solutions, even si

Ryan Gorman comes on the podcast to discuss the differences between a college education and early career opportunities in the skilled trades.    Many parents feel pressured to send their children to college and encourage them to get a four-year degree. Despite what society may lead us to believe, there is no shame in thinking that college may not be suitable for you or your child; the skilled trades have many opportunities for people to learn throughout their lives and make a good living.   In many cases, parents may see college as “a ticket to the starting line.” Unfortunately, college tuition has skyrocketed over the years, and a good ROI is not guaranteed. Instead, a career in the skilled trades can allow a person to develop hard skills and land a well-paying job at a young age. As the skills gap widens, young people who learn skills make themselves attractive to employers and increase their earning potential.   Children and teenagers who want to become engineers may actually prefer a trades career where t

Jason Obrzut comes on the podcast to discuss A2L refrigerant facts. Jason is a member of AHRI’s Safe Refrigerant Transition Task Force and author of the RACT manual.   ASHRAE designates refrigerants into categories based on toxicity (A or B) and flammability (traditionally 1, 2, and 3). So, the new A2L designation indicates that a refrigerant is relatively non-toxic but has a flammability value between 1 (low) and 2 (moderate). While propane (R-290) is a good refrigerant because it is natural and has low toxicity, it is very flammable (A3).    Future refrigerants will likely fall under the A2L designation; the mild flammability will probably be the tradeoff for efficient, low-toxicity refrigerant with a low environmental impact. However, A2L refrigerants cannot be vented, even despite their low GWP. We also cannot use these refrigerants in retrofits.   A2L refrigerants will likely become much more prevalent around 2023 as HFC refrigerants phase down. The phase-down period will be specified shortly, and it wil

In today’s podcast, Bryan and some Kalos employees discuss how to deal with difficult bosses and coworkers in HVAC/R work.   Whether your coworkers have anger issues, are careless, or are miserable people, you don’t want that negativity to affect your job satisfaction. Addressing the behavior may likely help, but you don’t want to attack the other person. The key to dealing with difficult coworkers is to communicate boundaries respectfully with the goal of improving the work environment. Boundaries are also important when dealing with sarcastic people or those who make inappropriate remarks.   Any work environment with lots of people is bound to have cliques and tribes. You’re best off not getting involved in any of that drama; the best thing you can do is be kind whenever you have the opportunity. Nepotism may also fall under tribal behaviors, and it may cause you to rethink your future with a company.   On the leadership side, micromanagers can be frustrating—doubly so if your boss also happens to be condes

In today’s podcast, Ed Janowiak comes onto the podcast to talk about the ACCA manuals. Ed started off in the field and has recently become the new Manager of Design Education at ACCA. You can follow him on Snapchat (skinnyed).   ACCA (Air Conditioning Contractors of America) is responsible for publishing and setting the standards in all of the books we use for residential and light commercial HVAC work. (Residential work typically encompasses Manuals J, S, D, and T).   The manuals can be very math-heavy. Many software programs have come on the scene to help automate the math to some degree, but the manuals will still remain relevant for years to come. The ACCA manuals offer guidelines for predictable results, and much of a technician’s success will come down to how well they understand the order of operations.   In our trade, we have developed rules of thumb that help us with sizing and load calculations. However, those won’t work all the time, and the predictability element is lost. The ACCA manuals exist so

In today’s podcast, Bryan and Jesse talk about how technicians can talk about finances and money in the HVAC business.    The first step for any successful business is to provide customers/clients with a product or service of value. However, there must be a balance between providing something of value to customers and providing excellent customer service.   When starting an HVAC business, one of the biggest mistakes is making money the top priority. Money can only become a factor after a business establishes the value of its services and communicates its value to its customers. There is no hard line for fair pricing, so the contractor and customer must communicate to establish a price tag and the expectations for the work performed.    That same mistake applies to employees who want raises or promotions. Employees may feel as though they are owed more for their work, but they must establish their value before they get a raise. Again, the goal is to avoid unmet expectations.   Profitability and value are not j

In today’s short podcast, Bryan explains the differences between sleeve and ball bearings. Techs often make some avoidable mistakes because they either don’t know the difference between the two or don’t notice the bearing type on their equipment.   On a basic sensory level, ball bearings tend to be louder than sleeve bearings. So, if you replace a sleeve bearing motor with a ball bearing motor, then excess noise may not indicate any problems after all. Lubrication is usually more consistent with ball bearings, and those bearings have a far smaller contact area than sleeve bearings.   Sleeve bearings don’t usually last as long as ball bearings; they have a larger contact area and can burn out quickly, so they are more common on smaller equipment where they will experience less intense axial forces. Those sleeve bearings also aren’t as effective as ball bearings in variable-speed equipment. When techs put in a motor speed control and don’t pay attention to the bearing type, they may end up burning up the motor

In today’s podcast, Trevor Matthews from Emerson talks about horizontal scroll compressors. Throughout the podcast, we refer to Bulletin AE4-1338 (R3). You can find that bulletin HERE.   Horizontal scroll compressors are common in mobile applications, like buses and trains. They’re shorter in height than other compressors, so they fit into tighter spaces and are ideal for transport refrigeration.   Scroll compressors are particularly susceptible to overheating, and you need some controls to protect your compressor from damage. To prevent overheating, scroll compressors require pressure relief controls. You can typically use an OEM high-pressure control to protect the system. A low-pressure cutout installed in the suction line can help prevent TXV failure and a wide range of restrictions.   Accumulators are especially important for horizontal scrolls in heat-pump applications. However, accumulators have a fine mesh screen that can become clogged easily. So, we highly recommend replacing your accumulator in th