Hvac School - For Techs, By Techs

In this informative HVAC podcast episode, Bryan and Bert dive deep into the complex world of locked and internal overload compressors, focusing specifically on single-phase residential units. The discussion begins with Bert explaining one of the most common challenges technicians face: diagnosing a locked compressor. He describes how compressors that are locked will typically run for only a second before overheating and stopping, creating a cycle that can be difficult to detect if technicians aren't carefully monitoring at the right moment. The hosts share personal experiences and practical diagnostic techniques, with Bert recounting how he once simulated a locked compressor by cutting the start winding wire and concealing it beneath other wires and zip ties. This demonstration highlights the importance of thorough inspection, including checking terminal connections. Bryan shares a story from his early career when he mistakenly condemned a compressor with damaged terminals, not knowing about terminal repair

In this short podcast episode, Bryan covers some unique electrical cases: when 0v isn't safe. When you measure voltage, you're finding out the electrical potential between two points. Just because there is 0v between one point and another doesn't mean there will be 0v between those points and other points. Non-contact voltage detectors are good tools that measure the flux from the wiring, but they have their limitations. A common mistake is measuring voltage across a switch. When you measure 0v across the switch, that could mean there is 0 potential to ground, neutral, or the other leg, but it could also represent a closed switch where power is actively being passed. You need to measure voltage across a load or with neutral as the other point. You will also measure 0v when one of the legs of 240v power (with a two-pole breaker) stops making contact. You'll measure 0v between the legs, but that's because one of the legs is open. There may still be a complete path on the other leg; therefore, you will want to c

In this episode, Bryan and Bert dive into the often misunderstood world of compressor testing, focusing on common mistakes technicians make when using ohmmeters, compressor testers, and megohm meters. The conversation highlights how diagnostic errors can lead to unnecessarily condemned compressors and wasted time and resources. The hosts begin by discussing fundamental concepts like the difference between "open" and "short" conditions, emphasizing that a path doesn't necessarily indicate a short circuit—it simply means there's a low-resistance path. They explore how many technicians get confused when testing terminals, mistakenly thinking that normal winding-to-winding measurements indicate a problem. Through practical examples from their field experience, they illustrate why understanding normal readings is crucial before taking any measurement. A significant portion of the discussion centers on proper testing techniques for scroll compressors, which often show different measurements to ground compared to ot

In this short podcast episode, Bryan talks about what the ambient rating means on a motor. These ratings can be found on both condensing fan motors and blower motors. They have Cs in their rating, which represents the maximum ambient temperature the motor can handle in degrees Celsius (like 40C or 60C). Heat and overvoltage kill motors, and motors with higher ratings can withstand higher temperatures and last longer in hot conditions. Be careful not to confuse this rating with the insulation class (which is classed by letters and corresponds to temperature limits). You could have a condition where you exceed the insulation's rating but not the ambient rating.  Air over operations (especially in the case of TEAO motors - totally enclosed air over motors) also play a role. The airflow helps cool the motor, and airflow restrictions like dirt and soil can create conditions that cause the motor to exceed its rating.  Motor bearings also matter. Ball bearings tend to last longer and withstand higher temperatures th

In this episode of the HVAC School podcast, host Bryan discusses superheat with guest JD, who recently co-authored an article on the topic with Ty Branaman. The conversation explores the often misunderstood concept of superheat, its importance in HVAC diagnostics, and common misconceptions technicians have when measuring and interpreting it. Bryan begins by sharing how superheat was initially taught to technicians in the late 1990s and early 2000s, primarily as a method for charging fixed metering device systems. He explains how this limited view led to problems, as technicians would often add or remove refrigerant based solely on superheat readings without considering other system factors or giving the system time to stabilize. JD points out how the industry shifted when TXVs (Thermostatic Expansion Valves) became standard, with many technicians abandoning superheat measurements altogether in favor of subcooling measurements, missing crucial diagnostic information in the process. The discussion then evolves

In this short podcast, Bryan talks about how to deal with too much at work and in life. He gives some practical tips to help you when you feel overwhelmed. One of the best ways to get ahead is to wake up early, exercise, get sunlight, stay hydrated, eat healthy, and get enough sleep. Taking care of yourself and giving yourself ample opportunities to set your mind and body up for success can ensure that you have the energy to tackle the challenges at work and in other areas of your life. When you're in the middle of an overwhelming mix of tasks, it helps to take a small break and take some deep breaths. Some people take smoke breaks. Once you have an opportunity to step back and clear your head, try to document all of the things you need to do. You can use a Google Doc with the help of ChatGPT to lay everything out. Once you have all of your tasks in front of you, pick 3-5 things that must get done today and then use your calendar, silence your notifications, and use all the tools at your disposal to focus on

Bryan from HVAC School interviews JD Kelly, known as "student of HVAC" on Instagram, about Delta T measurements in HVAC systems. This episode dives into the fundamentals of Delta T, common misconceptions, and proper measurement techniques. JD explains that Delta T is simply a temperature difference between two points of the same medium, which is often misunderstood in the industry. Many technicians are taught to measure between return grills and supply registers, but this approach can lead to inaccurate readings due to external factors like duct leakage or heat gain from attics. The proper measurement should be taken directly at the equipment to evaluate how the evaporator coil is performing. Humidity plays a significant role in Delta T measurements, which JD discovered when researching the fundamentals. Bryan elaborates on this point, explaining that in high-humidity environments (like Florida), more energy goes toward removing moisture (latent heat) rather than cooling the air (sensible heat), resulting in

In this short podcast episode, Bryan talks about fire sprinklers and how to avoid setting them off on job sites. Fire sprinklers have an element in the center that expands when exposed to heat (like a TXV sensing bulb) and breaks the glass. When the glass breaks, the fire sprinkler starts pouring out water. In some cases, fire sprinklers are linked to a larger fire suppression system in which several may go off at once, but most of the time, only a single fire sprinkler will go off if bumped or exposed to heat. If you're using torches or doing any form of hot work in a closet or other location with a fire sprinkler, make sure to keep torches away from the heat-sensitive bulb or at least cover the sprinkler with a wet rag (and follow your company's guidelines). Blunt force is another possible issue, so we want to avoid hitting the sprinklers with lifts, ladders, or building materials like studs. Keep clearances in mind, and watch out for your colleagues. You can get some specialty-built cages to protect the sp

In this engaging session, David Richardson breaks down the concept of high-performance HVAC, offering a clear roadmap for industry professionals looking to elevate their craft. Richardson argues that the HVAC industry has long been focused on equipment rather than complete systems, leading to widespread inefficiencies. The average system delivers only about 57% of its rated capacity into buildings, while even code-approved systems barely reach 63%. By implementing high-performance HVAC principles, contractors can achieve up to 88% efficiency while improving safety, health, comfort, and energy performance. Richardson presents a practical framework using the acronym "PATH" - Pressure, Airflow, Temperature, and Heat (BTUs) - as a step-by-step approach to implementing high-performance HVAC. He emphasizes starting with static pressure testing, which he calls "the foundation of airflow" and one of the most misunderstood principles in the industry. Just as doctors check blood pressure as a vital sign during every vi

In this episode of the HVAC School Podcast, host Bryan sits down with Phil, the executive electrical team leader at Kalos who has transitioned into the world of estimating. Phil shares his extensive background in electrical work dating back to 1994, from his high school electrical elective to running his own business for eight years before joining Kalos and eventually establishing their estimation department. The conversation delves deep into the fundamentals of estimating in the trades, contrasting traditional qualitative approaches with more rigorous quantitative methods. Phil emphasizes that good estimating is about "finding the truth" - understanding the actual costs of materials and labor for a project. They discuss how traditional estimating often relies on heuristics and past experiences with similar jobs, while more detailed estimating involves comprehensive takeoffs and assembly-based counting. The pair explores how estimation isn't just about producing a final number but should provide valuable info

In this short podcast, Bryan answers a listener-submitted question about Nylog, oil, and where you put them when you're making flares. Nylog is a thickened refrigerant oil (which is either POE for Nylog Blue or mineral oil for Nylog Red), and it's miscible with the refrigerant and moves with it through the circuit. You don't want to put excess Nylog on valves, but a small amount won't do harm. There are a lot of concerns about Nylog voiding the warranty, but it doesn't actually do that because it's nearly impossible to prove that Nylog caused the issue. Like oil, Nylog helps connections fit together (even threaded connections) and prevents galling. However, oil and Nylog also reduce friction, which will affect your torque specs when you use a torque wrench to tighten a connection. You don't need to tighten it as much, as you risk overtightening otherwise. When you apply Nylog, put a little bit on the front and back face of a flare (and the cone of the flaring block if you wish). You can put a small bead on th

In this episode of the HVAC School podcast, Bryan and Jim discuss strategies for growing an HVAC business, focusing on the importance of maintenance contracts, consistent service, and effective branding. Drawing from Jim's 15 years of experience running a successful HVAC company in California, they explore how maintenance contracts not only provide consistent revenue but also create valuable training opportunities for technicians. The conversation emphasizes that maintenance contracts are fundamental to building company value. Jim shares that when he sold his business, the number of maintenance contracts was a key valuation metric. These contracts tie customers to your company, provide consistent work during shoulder seasons, and offer technicians crucial repetitive practice with equipment. Bryan adds that maintenance provides technicians with opportunities to observe normal equipment operation repeatedly, which builds troubleshooting skills through pattern recognition. Both hosts stress the importance of con

In this short podcast episode, Bryan answers a listener-submitted question about oversized evaporator coils, particularly when they're half a ton or a full ton larger than the condenser. The expanded performance data contains the information that'll tell you whether the coil is right for the system. However, when it comes to the specific issue of oversizing, there is a common misconception that coil size affects the saturated suction temperature. The truth is that they're not related; you could fully insulate different-sized coils and move the same amount of refrigerant, but they will behave similarly. The saturated suction temperature (suction pressure, evap temperature) is driven by the heat entering the system. Coils are designed to handle refrigerant flow rates and airflows, so having a lower airflow over a large coil allows for greater cooling due to the bigger surface area, lower bypass factor, and dwell time. When more heat enters the evaporator coil, the saturated suction temperature increases, but so

In this episode of the HVAC School podcast, host Bryan sits down with building science expert Allison Bailes to dive deep into the world of Energy Recovery Ventilators (ERVs). The conversation explores the critical role of ventilation in modern homes, highlighting how ERVs have become an essential component of maintaining indoor air quality and energy efficiency. Bailes breaks down the technical nuances of ERVs, explaining how these systems not only bring fresh air into a home but do so while recovering both temperature and moisture energy. The discussion goes beyond simply explaining what an ERV is, delving into the practical considerations of ventilation strategies. Bailes shares personal experiences, including challenges he faced with over-ventilation in his own home, which led to extremely dry indoor conditions. The podcast explores the complex balance of bringing outdoor air inside while managing humidity, temperature, and air quality. Listeners gain insights into why simply bringing in outdoor air isn't

In this short podcast episode, Bryan answers a listener-submitted question asking whether you can use another surge protector at the disconnect panel with an ICM 493 already in place. Using multiple surge protectors in the configuration described does NOT count as daisy-chaining. Surge protectors with MOVs (metal oxide varistors) shunt current from high voltage to ground by reducing their resistance. MOVs are sacrificial, so they wear out over time. Surge protectors don't last forever, so installing multiple is a fine idea. You can have whole-home surge protection with additional surge protectors positioned at the appliances/electronics. While it can be done and doesn't hurt anything, it's not the most cost-effective solution.  When you install a surge protector, wire it in parallel with the circuit to ground. It should be wired properly with the shortest possible path to ground. In any case, many surge protectors won't hold up against direct lightning strikes, but they will protect the equipment from power s

In this podcast episode, HVAC professionals Chris Hughes and Adam Mufich discuss the intricate challenges technicians face when commissioning modern inverter-based heating and cooling systems. Unlike traditional single-stage or two-stage HVAC equipment, inverter systems introduce a new level of complexity that can leave even experienced technicians feeling uncertain about proper installation and startup procedures. The presentation highlights a fundamental shift in how HVAC systems operate, moving from straightforward single-stage systems to sophisticated inverter-based technologies that modulate compressor, fan, and refrigerant flow dynamically. This technological evolution creates significant challenges for technicians, who previously could rely on simple, consistent commissioning processes. The speakers emphasize that modern inverter systems require a much more nuanced approach, with specific temperature ranges, wait times, and verification methods that are not always clearly documented in manufacturer man

In this short podcast episode, Roman Baugh takes over the HVAC School podcast to answer a listener-submitted question about VRF (or VRV) system evacuation. Evacuation is a critical step of making repairs on VRF systems, which are very diverse and versatile but require a high level of understanding. VRF systems have multiple indoor units per outdoor unit, and they achieve that with the help of several components and accessories down the refrigerant line that can pose issues in evacuation and pressure testing. In heat recovery units, some manufacturers use solenoid valves (or even electronic expansion valves) in branch selector boxes or branch collector boxes. These valves act as little traffic guards, and the system needs to be put in its refrigerant recovery or vacuuming mode. If not, then you won't be able to evacuate all of the refrigerant and non-condensables from the system. Even if the system passes a decay test, contamination is a major concern when the system starts up and the valves open (due to nitro

This podcast episode is of Bryan's session from the HVAC School Symposium, "10 Things I've Learned in the Last 10 Years." Delivered as HVAC School approaches its 10-year milestone and Kalos hits 20 years, Bryan blends technical know-how with personal stories, revealing how his “expertise” is a product of constant learning—often from the very audience he’s addressing. Bryan’s presentation weaves together practical HVAC lessons and relatable anecdotes, offering a glimpse into his growth as a technician, educator, and leader. He tackles wire sizing versus breaker sizing, debunking outdated myths tied to the National Electrical Code and sharing tales of sparring with inspectors over code-compliant innovations. On vent sweating and duct leakage, he provides actionable fixes—like sealing boots and tackling attic moisture—while urging techs to look beyond bandaids. Bryan also dives into coil corrosion, distinguishing formicary from galvanic causes and advocating for field-driven research over manufacturer spin. His

In this short podcast episode, Bryan answers a listener-submitted question about using R-290 as a drop-in refrigerant for R-22 systems. It is NOT safe to use R-290 as a drop-in, but there are some similar properties between the two and some interesting thought experiments within this topic. R-290 is propane, a hydrocarbon that belongs to the family of natural refrigerants. R-22 is an HCFC refrigerant that has undergone a manufacturing/importation phaseout in the USA. They are both single-component refrigerants, not blends. Both of them have similar operating pressures and oil carry. However, the latent heat of vaporization of R-290 is almost double that of R-22, which makes it extremely effective as a refrigerant. The main issue with using R-290 is that it is highly flammable and explosive (A3), and it has very small charges (500 grams). Around 2010, some people started selling R-290 blends as drop-in alternatives for R-22. In theory, that combination would work very well, but it is not a safe or legal option

In this episode of the HVAC School Podcast, host Bryan welcomes Jeff from Copeland to discuss the critical topic of flooding and slugging in compressors. Jeff, calling in from frigid Minnesota (at negative 19°F), explains the differences between these harmful conditions and how they can damage compressor systems. The conversation begins by differentiating between flood back and flooded starts. Flood back occurs during system operation when control of the evaporator is lost, often due to airflow issues. Flooded starts happen after the system has been off, when refrigerant migrates to the compressor oil. Both conditions can lead to slugging - when liquid refrigerant enters the compression chamber, causing immediate damage to valves and internal components. While flood back and flooded starts may cause gradual damage over time, slugging can break compressor components instantly. Jeff emphasizes that proper superheat levels are essential for compressor health, with most Copeland compressors requiring about 20 deg