HVAC School - For Techs, By Techs

In this engaging and informative episode, Bryan sits down with Elliot to discuss his recent training experience with the National Comfort Institute (NCI), covering two intensive courses on duct system optimization and residential air balancing. The conversation offers valuable insights for HVAC professionals looking to improve their technical skills and provide better service to their customers. With a mix of technical expertise and practical field experience, this episode breaks down complex HVAC concepts into actionable strategies for contractors and technicians. Elliot shares his key takeaways from the NCI training, emphasizing how the courses filled critical knowledge gaps about the "invisible stuff" in HVAC systems—the air itself. The discussion reveals a common industry problem: most HVAC professionals focus heavily on equipment while neglecting proper duct design and air balancing. Elliot explains how he learned to move beyond guesswork in duct design, discovering that flex duct has actual CFM ratings and that proper system design requires understanding static pressure, equivalent length of fittings, and the science behind airflow. The conversation highlights the importance of oversized return air systems—a point both hosts stress repeatedly—and explains why Florida (and possibly the entire nation) suffers from chronically undersized returns. The hosts discuss various duct system approaches, from traditional trunk lines to the flex-and-fitting systems, acknowledging that different markets require different solutions based on climate, building construction, and supply chain availability. Throughout the episode, Bryan and Elliot tackle practical installation challenges that technicians face daily. They discuss the importance of proper flex duct installation, explaining how compressed or sagging ductwork dramatically reduces airflow efficiency. The conversation covers the critical role of balancing dampers in every branch run, the impact of proper duct strapping, and how simple adjustments like straightening kinked flex duct can immediately improve CFM delivery. The hosts also address the limitations of builder-grade installations, noting that most new construction lacks the dampers necessary for proper air balancing. They emphasize a practical, process-based approach to HVAC work that focuses on getting clients measurable results without requiring perfect conditions or unlimited budgets. The episode concludes with a strong endorsement of the National Comfort Institute's training programs and tools, particularly the TrueFlow Grid and measureQuick technologies that simplify complex air balancing calculations. Bryan and Elliot stress the importance of ethical, high-performance contracting that delivers real value to customers rather than just marketing sizzle. They encourage HVAC professionals to invest in training and proper tools, acknowledging that while the initial investment may seem steep, the ability to provide superior service and reduce callbacks makes it worthwhile. The conversation serves as both a technical deep-dive and a call to action for contractors to elevate their skills and focus on the whole system—equipment, ductwork, and building envelope—to truly solve customer comfort problems. Topics Covered NCI Training Experience - Elliot's overview of the duct system optimization and residential air balancing courses, including instructor quality and course relevance to Florida's HVAC market Duct Design Fundamentals - Moving from guesswork to calculated design using CFM ratings, square footage calculations, and proper system output considerations Static Pressure Management - Understanding static pressure drop across coils, the importance of variable speed fans, and strategies to reduce total external static pressure Return Air Systems - Why bigger returns are always better, the critical importance of oversized return grills, and the impact of filter face velocity on system performance Equivalent Length of Fittings - How fittings add "phantom" duct length to runs, techniques to reduce equivalent length, and the dramatic impact of turning vanes on 90-degree turns Flex Duct vs. Trunk Lines - Comparing different duct system approaches across various markets, the pros and cons of metal, duct board, and flex systems, and the flex-and-fitting methodology Proper Flex Installation - The importance of stretching flex duct correctly, proper strapping techniques, and how sagging or compressed flex drastically reduces airflow Air Balancing Techniques - The necessity of balancing dampers in every branch run, methods for achieving proper air distribution, and using velocity comparisons for troubleshooting Throw and Mixing in Rooms - Understanding that grills, not duct size, control air throw and mixing, and the role of Manual T in selecting appropriate terminal devices Practical Installation Tips - Simple improvements technicians can make during service calls, like straightening kinked ductwork and adding straps to reduce sag High-Performance Tools - The TrueFlow Grid, measureQuick app, hot wire anemometers, and other technologies that simplify complex air balancing calculations Building Performance Perspective - Moving beyond equipment-only focus to consider the entire system: ductwork, building envelope, and how they all interact Ethical Contracting - Delivering real value to customers, avoiding the "all sizzle, no steak" approach, and providing solutions that work within real-world budgets and constraints   Learn more about NCI's training opportunities HERE. Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool. Purchase your tickets or learn more about the 7th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.

In this short podcast, Bryan answers a question submitted to HVAC School by an aspiring licensed architect who wanted to learn more about the many different types of HVAC systems. The three main buckets of HVAC systems are air-to-air, water-source, and air-to-water. Air-to-air systems move air around to remove heat from one space, and that heat is rejected to the air somewhere else. Water-source systems move water around the building and use water as the heat rejection medium. Air-water hybrid systems condition the load with water and may use air for ventilation; water or air may be used as the rejection medium. Systems may be direct-exchange (DX) and may transfer heat directly to refrigerant, or they may flow the air or water over a coil with water or glycol, utilizing a secondary fluid. Systems may also have separate indoor and outdoor architecture (split systems), or all components may be rolled into a single box (package unit). Package units include window units, PTACs, and RTUs. When it comes to forced-air systems, constant air volume (CAV) systems maintain the same volume of airflow (though the temperatures will change). Variable air volume (VAV) systems use one stream of cold air in a main duct, and each zone has a VAV box that functions as a damper to control zones individually. Dual duct systems have one cold duct and one warm duct that run parallel to each other and mix at each zone. Packaged rooftop units (RTUs) are self-contained with ducts that run down into the space and are common in retail spaces. Air-to-water systems use fan coil units (FCUs) fed with chilled or hot water. Air moves locally inside the space, so there is less ductwork and good zone control, but there are many units to manage. Chillers make chilled water, and that water is pumped around the building and sent to individual air handler units (AHUs). These are highly efficient and have large amounts of piping. They need mechanical rooms and dedicated personnel to maintain them. Variable refrigerant flow (VRF) systems are DX systems that are becoming more popular and consist of multiple indoor units with one or more outdoor units. Some of these can be used for heat recovery, meaning one space can be cooled while another is heated. Heat pump types include air-source, water-source, and ground-source. Air-source heat pumps absorb heat from the air via one unit and reject it via the other; the outdoor and indoor units can swap functions. Water-source heat pumps are common in commercial applications and have multiple heat pumps tied into a water loop that tries to stay within a given temperature range via boilers and cooling towers. Ground-source or geothermal heat pumps pick up heat from the earth's stable temperature and are highly efficient, but they have high installation costs. Passive systems come in all sorts of varieties and reduce the HVAC system's loads but don't replace HVAC systems in North America. Mechanical systems consist of straight-cool (air conditioner with electric heat), furnaces (gas, propane, or oil combustion), or heat pump (reversible air conditioners) systems.   Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool. Purchase your tickets or learn more about the 7th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.

In this essential episode, Bryan Orr sits down with Elliot, the residential install supervisor at Kalos Services, to unpack a critical issue that's causing confusion among HVAC technicians, electricians, and inspectors alike: the new standards for breaker and conductor sizing on inverter-driven equipment. The conversation was sparked by Elliot's frustrating experience of having two inspectors in the same county fail the same installation for opposite reasons—one for an oversized breaker and another for an undersized breaker. This contradiction led to a deep dive into recent changes in UL standards and how they affect everyday HVAC installations. The heart of the issue stems from the transition to low-GWP refrigerants and the updated UL 60335-2-40 Edition 3 standard, which replaced the 1995 certification approach. This new standard introduced more conservative calculations for electrical characteristics, particularly affecting equipment using A2L refrigerants. The result? Data tags now show higher Minimum Circuit Ampacity (MCA) ratings than before, even though the equipment itself hasn't changed—only the math used to calculate these values has shifted. This has created a puzzling situation where the MCA can be higher than the recommended breaker size, which seems counterintuitive to anyone familiar with traditional electrical principles. Bryan and Elliot clarify the fundamental rule that still applies: size your wire to the MCA and your breaker to the MOCP (Maximum Overcurrent Protector). The confusion arises because manufacturers like Mitsubishi are now including "recommended breaker" sizes on data tags that are lower than the MCA—a courtesy to contractors, not a code requirement. The higher MCA reflects conservative safety margins that account for extreme operating conditions, but in practice, inverter-driven systems have multiple built-in protections that prevent them from ever actually reaching these calculated amperage levels. The key takeaway is that contractors can safely install breakers at the recommended size without safety concerns, as long as the breaker's lugs are rated to accept the wire size required by the MCA. The episode also explores how inverter-driven equipment fundamentally differs from traditional PSC motors, particularly regarding locked rotor amps (now more accurately termed "inverter input") and voltage drop considerations. Unlike conventional motors that simply run slower with reduced voltage, inverter-driven compressors and ECM motors compensate by drawing more current to maintain performance, creating a potential compounding effect with voltage drop that installers need to understand—even though voltage drop itself isn't an enforceable NEC code requirement. Topics Covered: New UL 60335-2-40 Edition 3 standards and their impact on electrical calculations for HVAC equipment The relationship between MCA (Minimum Circuit Ampacity) and MOCP (Maximum Overcurrent Protector) and why they can now seem contradictory Recommended breaker sizes on modern data tags and why they may be lower than the MCA Handling inspector conflicts and failed inspections related to breaker sizing Differences between inverter-driven equipment and traditional PSC motors in electrical behavior The transition from "locked rotor amps" to "inverter input" terminology for modern equipment Voltage drop considerations with inverter-driven systems (NEC 210.19A and 215.2A) Why inverter-driven equipment draws more current at lower voltages compared to traditional motors Proper wire and breaker sizing for A2L refrigerant equipment (454B systems) NEC Section 440 requirements specific to air conditioning and refrigeration equipment Breaker lug ratings and ensuring they can accept the required wire size Practical advice for communicating with inspectors and resolving code disputes   Read the tech tip on this topic HERE. Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool. Purchase your tickets or learn more about the 7th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.

In this short podcast episode, Bryan goes on another history journey, retelling the story of the rise and fall and rise of absorption cooling. Some of the first HVAC/R engineers cooled buildings with fire; they used absorption refrigeration, which ran on heat instead of electricity. In the early 1800s, French scientist Michael Faraday showed that gases like ammonia could absorb heat as they evaporated. Instead of compressing the vapor, engineers looked for a way to absorb the heat from the vapor and drive it back out. In 1859, Ferdinand Carré invented a machine that boiled ammonia, absorbed the vapor into water, and reheated the mixture to desorb the ammonia, creating a self-contained refrigeration machine powered by heat alone (including waste steam from boilers). This ammonia-water absorption machine could freeze water and chill brine, and it became popular in the 1880s. An absorption system has an evaporator that boils refrigerant, which is then absorbed into another liquid and creates a strong solution. Heat drives refrigerant back out of the solution as a vapor, where it is then condensed back to a liquid and metered. However, while they were reliable, they were heavy, expensive, and slow to respond. In the 1920s and 1930s, the rise of practical sealed electric compression systems began replacing absorption refrigeration infrastructure. By the mid-1900s, absorption chillers were replaced in all but a few applications. Absorption didn't completely vanish, in part thanks to Servel, which continued manufacturing absorption refrigeration systems for industrial applications and rural areas with unreliable electricity. By the 1960s, Japan and Europe refined the design with lithium bromide instead of ammonia. Absorption chillers are still present, but their complexity, maintenance demands, and poor efficiency still make them impractical for most refrigeration purposes. However, with concerns about the electrical grid and decarbonization initiatives on the rise, absorption refrigeration in hybrid systems with improved efficiency and a heat source obtained from gas turbines and biomass boilers looks promising.   Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool. Purchase your tickets or learn more about the 7th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.

In this comprehensive training session from the symposium, Tony Gonzalez, Training Director at Fieldpiece, delivers an engaging and practical guide to combustion analysis for HVAC technicians. With 25 years of experience at Fieldpiece—from warehouse worker to training director—Tony brings both technical expertise and real-world application to this 50-minute interactive session focused on the company's CAT 85 combustion analyzer. Tony emphasizes that combustion analysis serves four critical purposes: safety, efficiency, equipment specification verification, and liability protection. He makes a compelling business case for investing in combustion analyzers, noting that preventing just two callbacks or one liability lawsuit can pay for the equipment ten times over. The training walks attendees through the complete process, from properly warming up the analyzer in fresh air (allowing sensors to calibrate to ambient oxygen and zero carbon monoxide) to generating professional PDF reports that can be shared with customers or integrated into work order management systems like ServiceTitan. The session provides detailed guidance on interpreting key measurements, including stack temperature, oxygen percentage, carbon monoxide levels, and draft pressure. Using design parameters from the National Comfort Institute, Tony demonstrates how to diagnose issues by comparing actual readings against acceptable ranges for different furnace types (atmospheric, 80% induced fan, and 90+ percent condensing). He walks through practical troubleshooting scenarios, showing how measurements like high oxygen combined with low stack temperature can point to specific problems like low gas pressure that technicians can then verify and correct. Throughout the presentation, Tony emphasizes proper technique and best practices, from creating test ports at least 12 inches above the inducer fan to the importance of plugging test ports after completion. He also highlights innovative features of Fieldpiece's analyzers, including the hydro cycle pump that eliminates traditional water traps, sensor vault technology that extends sensor life to four years, and built-in wireless connectivity allowing technicians to view measurements on their mobile devices through the Job Link app. Topics Covered: Why perform combustion analysis: Safety verification, efficiency optimization, OEM specification compliance, and liability protection Business benefits: Reducing callbacks, improving OEM relationships, enhancing professional image, and protecting against lawsuits Proper startup procedure: Warming up analyzers in fresh air for accurate oxygen and CO sensor calibration Ambient CO testing: Using combustion analyzers vs. dedicated walk-around detectors for carbon monoxide detection in living spaces Test port installation: Proper placement at least 12 inches above inducer fans and away from 90-degree elbows Key measurements explained: Stack temperature, oxygen percentage, CO PPM, CO air-free, draft pressure, and efficiency calculations Equipment type selection: Choosing correct settings for atmospheric, 80% induced fan, or 90+ percent condensing furnaces Diagnostic interpretation: Using National Comfort Institute parameters to identify issues like excess combustion air or low gas pressure Advanced features: Built-in dual port manometer for gas and static pressure, wireless Job Link app connectivity, and hydro cycle pump technology Report generation: Creating professional PDF reports with company branding for customer documentation and CYA protection Maintenance tips: Checking particle filters, understanding sensor vault technology, and the importance of annual calibration Sensor longevity: Four-year sensor life warranty and field-replaceable sensors without sending equipment for service   Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool. Purchase your tickets or learn more about the 7th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.