HVAC School - For Techs, By Techs

In this short podcast episode, Bryan talks about some building science concepts, including vapor diffusion ports, hygric buoyancy, and... fruit packaging? Much of building science wisdom over the past couple of decades has dealt with air sealing (just seal it tighter!). However, building tightness has a darker side: more difficulty drying. When buildings can't dry, moisture accumulates and leads to rot. Air leaks and vapor diffusion are NOT the same thing. Vapor diffusion refers to water vapor diffusing through surfaces into the home (through the materials of walls, floors, etc.). Air moves much more water than vapor diffusion, so air leaks are a bigger problem in terms of moisture. Therefore, air barriers matter more than vapor barriers... until the air barrier battle has been won. Hygric buoyancy refers to moist air's lower density than dry air, so wet air rises toward the attic (and then the attic peaks). While sealed attics are excellent, moisture can accumulate at the roof deck, especially when the roofing cools at night. The condensation is worsened by using open-cell foam, as open-cell foam is air-closed but vapor-open (whereas closed-cell foam is air-closed AND vapor-closed). Drying isn't needed if you can KEEP the moisture out of closed-cell foam. Open-cell foam requires a place for vapor to go. Vapor diffusion ports are airtight, controlled vapor-open outlets at the highest points of sealed attics. A cap protects them from bulk water, and they consist of a membrane that blocks air but allows vapor to exit. Unlike a ridge vent, ventilation is not the goal of a vapor diffusion port; it is drying by diffusion rather than airflow and acts as a controlled pressure-relief valve for moisture. Vapor diffusion ports have been proven to be effective at drying and preventing roof rot in humid climates (but NOT ALL climates). They do not work against bulk water intrusion, in cold climates, or when used as vents. Vapor diffusion ports work like fruit packaging, which is designed to let oxygen in and CO2 out, while controlling moisture and slowing decay.   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 informative episode, Bryan and Bert dive deep into gas appliance safety and combustion analysis from the unique perspective of Florida HVAC technicians. While they humorously acknowledge that Florida's mild winters mean they don't work on gas furnaces daily, they make a compelling case that this actually makes their training even more critical. When technicians only encounter gas appliances occasionally, the stakes are higher—which is why they've developed rigorous protocols to ensure safety every single time. The conversation covers everything from the basics of gas leak detection to the nuances of carbon monoxide monitoring, combustion air zones, and proper venting. Bryan and Bert share real-world stories of dangerous situations they've encountered, from exploding pool heaters to improperly capped gas lines at vacation rentals. Their approach emphasizes that every gas leak is your problem when you're on site, regardless of why you were originally called out. This episode is packed with practical wisdom for both seasoned professionals working in gas-heavy markets and those who encounter these systems less frequently. Throughout the discussion, the hosts stress fundamental safety principles that apply across all markets: using your nose to detect leaks, understanding the difference between unspent gas and carbon monoxide, ensuring proper combustion air zones, and never ignoring warning signs like delayed ignition or flame rollout. They also tackle common misconceptions about equipment like flexible gas connectors, orphaned water heaters, and the real risks of cracked heat exchangers.  The conversation wraps up with important reminders about company lockout/tagout procedures, the critical importance of low-level carbon monoxide detectors, and the tools every technician should carry. Bryan and Bert's candid, no-nonsense approach makes complex safety topics accessible while never losing sight of how serious the consequences can be when gas work goes wrong. Topics Covered Gas leak detection and response protocols - Why every gas leak on site becomes your responsibility, using your nose as the first line of defense, and never leaving a leak for someone else to fix Carbon monoxide safety and monitoring - Understanding CO as a combustion byproduct, the limitations of standard UL-rated detectors, and the critical importance of low-level CO monitors Combustion air zones and depressurization - Identifying risks from sealed spaces, return air leaks, exhaust fans, and other equipment that can create dangerous negative pressure Delayed ignition and flame rollout - Recognizing warning signs, understanding causes, and why you should never ignore scorched wires or tripped rollout switches Proper gas line assembly and materials - Selecting appropriate materials for different environments, avoiding flexible connector failures, and ensuring proper sizing Combustion analysis fundamentals - Measuring CO levels in the flue, targeting air-free CO under 100 ppm, and understanding when adjustments are needed Natural draft vs. induced draft systems - Differences in safety considerations, orphaned water heaters, and the myth of oversized flue pipes Venting requirements and back drafting - Identifying improper venting, looking for evidence of back draft on water heaters, and ensuring proper flue design Gas pressure testing and adjustment - When to adjust and when not to, reading data tags, and understanding that most flame problems are air-related, not gas pressure Cracked heat exchangers in context - Why they're less common in warm climates, the role of proper airflow, and focusing on actual safety risks vs. edge cases Tools and equipment recommendations - Combustion analyzers, personal protective CO detectors, combustible gas detectors, precision manometers, and low-level CO alarms Lockout/tagout procedures - Following company protocols, communicating clearly with customers, and balancing safety requirements with homeowner autonomy   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 dives a bit into equipment sizing rules of thumb and why square footage does NOT equal tonnage in today's world. Many rules of thumb exist in the industry, and one is a load calculation rule stating that you can size the HVAC for a house at 500 square feet per ton.  Old houses are leaky and poorly insulated compared to new homes, which results in large energy loads but allows the homes to dry themselves out, as moisture could leak out before it could cause trouble indoors. Large loads and leaky envelopes made 500-600 square feet per ton a sensible rule.  Homes built within the last few decades have a lot more insulation and are tighter, and they have smaller sensible heat loads. However, they're a lot more moisture-prone, especially when moisture can't escape via proper ventilation paths. The 500 square-foot rule of thumb overshoots the latent capacity and leads to short cycling due to oversized equipment. Enter ACCA Manual J, which presents a load calculation method that is very good, but it has barriers to entry; it is very rigorous, has a learning curve, and can be a hassle. One thing is clear, though: load management is key, especially latent load management. At this time, we measure energy efficiency in terms of metrics like SEER, but the future is pointing to peak load management as the answer: getting the right power draw at the right moments instead of high general efficiency. Modernizing hot deck-cold deck systems with steady-state, constantly running systems might be the way to go, especially if we utilize energy storage and modern variable-speed technologies. The new rule of thumb is to think like a building scientist and apply new tools to concepts that have stood the test of time. Low peak loads and steady-state operation are often the way to go with high latent loads in homes built to the most recent building codes and standards.   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.

Matthew Taylor delivers an expert-level presentation on EPRs, building on his previous work on parallel rack systems. While his earlier content focused on the similarities between air conditioning and refrigeration, this session explores what makes commercial refrigeration unique—particularly the critical role of EPRs in maintaining optimal operating conditions across multiple evaporators running at different temperatures. This presentation was shared at the 6th Annual HVACR Training Symposium. The discussion begins with a fundamental review of the refrigeration cycle in a typical supermarket setting, where 30 to 80 evaporators may share a common suction line. Matthew explains why EPRs are essential: when multiple cases need to operate at different temperatures (ranging from -13°F for frozen foods to 24°F for fresh products) but all connect to the same compressor rack, EPRs become the solution that makes this possible. Without them, cases would cycle on and off constantly, creating efficiency nightmares, oil management problems, and potential food safety issues. Matthew walks through the mechanical principles of various EPR types, from the high-efficiency Sporlan SORIT valve with its pilot-operated design to the Parker A8 valve that can be installed directly in the store. He also addresses the industry's shift toward electronic EPRs, particularly the CDS modules that offer temperature-based control rather than just pressure regulation. Throughout the presentation, Matthew emphasizes practical considerations: how EPRs affect compressor staging, oil system pressure, defrost cycles, and ultimately, the core product temperatures that determine food safety. The session includes real-world troubleshooting insights and addresses common misconceptions about setting superheat on systems with EPRs. This technical presentation provides HVAC professionals with the knowledge needed to understand, diagnose, and service EPR-equipped refrigeration systems confidently. Matthew's approach demystifies a component that many technicians find intimidating, breaking it down into understandable principles while highlighting the critical role EPRs play in modern commercial refrigeration efficiency and reliability. Topics Covered Basic Refrigeration Cycle in Supermarket Applications – Understanding parallel rack systems with 30-80 evaporators sharing common suction and liquid lines Oil Management Systems – Oil separators, oil reservoirs, oil regulators, and the critical pressure differential required for proper oil flow Compressor Staging and Capacity Control – How parallel rack compressors operate as multi-stage units to match system load efficiently Saturated Suction Temperature (SST) – Why racks are designated by temperature (e.g., "13-degree rack" or "-13 degree rack") and how this relates to the coldest evaporator requirement Temperature Difference (TD) Engineering – The relationship between evaporator temperature and case leaving air temperature, typically 10 degrees in traditional systems EPR Fundamentals – Why EPRs are necessary to maintain different evaporator pressures on cases operating at various temperatures while connected to a single rack Mechanical EPR Types – Comparison of Sporlan SORIT valves (pilot-operated, low pressure drop) versus Parker A8 valves (self-contained, higher pressure drop) Electronic EPR Systems – Modern CDS modules and other electronic controls offering pressure control, temperature control, or hybrid approaches System Stability and Load Management – How proper EPR settings prevent compressor hunting, reduce energy consumption, and protect oil management systems Subcooling Requirements – Why liquid receivers eliminate natural subcooling and how mechanical subcoolers restore it before expansion devices Core Product Temperature – The critical relationship between runtime, EPR settings, and food safety in refrigerated cases Dual-Temperature Applications – Converting medium-temp cases to low-temp operation (like holiday turkey displays) using EPR pilot solenoids Superheat Setting Procedures – Why EPRs must be overridden to 50-100% open position when setting TXV superheat High Glide Refrigerants – Special considerations for setting EPRs with refrigerants that have significant difference between dew point and bubble point temperatures Troubleshooting Philosophy – Understanding EPRs and TXVs as independent systems that don't directly affect each other due to non-critically charged liquid receiver systems Pressure Drop Considerations – How EPR pressure losses (0.5-2 psi depending on type) affect compressor suction setpoints and energy efficiency Electronic Control Integration – Various controller brands and approaches to managing electronic EPRs, from pressure transducers to temperature sensors and PID algorithms   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 covers the history of the great heating debate: furnaces vs. heat pumps or combustion vs. compression. He also gives a breakdown of each other's strengths and gives his two cents on the winner of the debate. Fire kept humans warm for much of history, but engineers developed a way to move heat by manipulating refrigerant pressures. Early heat pumps got a bad rap because they didn't live up to the hype; they had frequent operational issues, didn't heat effectively, and were largely unable to be serviced effectively by technicians. However, heat pumps have evolved and now outperform furnaces in many areas. Ones with COPs between 2 and 5 can be anywhere from 200-500% efficient in terms of watts in, BTUs out. They also have many safety benefits over gas furnaces, including no risk of flame rollout, carbon monoxide poisoning, and gas leaks; removing the gas meter and all its risks entirely is a possibility.  Nevertheless, some people still insist that combustion is king due to its comfort, as furnaces' heat is more intense than that of heat pumps. Furnaces also require little electricity, making them more sensible in markets with weak or dirty electrical grids. Combustion appliances also only need to work part of the year, meaning they run fewer cycles and experience less mechanical wear over the same period of time as heat pumps (thus may have longer lifespans). Dual fuel allows you to get the best of both worlds; it allows the heat pump to handle the cooling and most of the heating for the energy efficiency benefits, and the furnace can step in when more intense heat is needed. Ultimately, the "winner" of this debate, at least to Bryan, is the most sensible solution for energy costs, safety, comfort, and reliability; the real answer will depend on the climate, infrastructure, and other factors.   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 engaging episode of the HVAC School podcast, host Bryan Orr sits down with Leo and Paul Sharkey, a father-son duo of mechanical engineers who made the leap into the HVAC business. Leo and Paul share their remarkable journey of purchasing an HVAC company in September 2020 and quadrupling its revenue within five years. Their engineering backgrounds bring a refreshing, data-driven perspective to an industry that often relies on rules of thumb and outdated practices. The Sharkeys operate in the challenging Northeast market, where homes can date back to the 1600s and 1700s. They discuss the eye-opening discovery that traditional HVAC sizing methods—like the simplistic "one ton per 400 square feet" rule—fail dramatically in older housing stock. Their commitment to running thousands of Manual J calculations has transformed their approach, often resulting in smaller, more efficient systems than competitors propose. The conversation dives deep into the unique challenges of working with centuries-old New England homes, including extreme infiltration rates, non-linear heat loss curves during harsh winters, and the complications of mixing modern additions with ancient construction. Beyond sizing, Leo and Paul tackle the practical realities of heat pump installations in cold climates. They explain why turndown ratio is critical, how they handle homes with heat loads that triple their cooling loads, and when backup heating systems are truly necessary. Their consultative approach rejects the "one-size-fits-all" mentality that has flooded the market with incentive-chasing installations. They candidly discuss the problems created by Massachusetts' generous rebate programs, which have attracted fly-by-night operators who prioritize rebate qualifications over proper design and long-term performance. The episode also explores the balance between ductless and ducted systems, revealing when each approach makes economic and technical sense. The Sharkeys share fascinating case studies, from a 1748 house with the equivalent of a full-size door's worth of air leakage to underground concrete dome homes requiring specialized dehumidification. Their willingness to take on complex projects that other contractors avoid demonstrates how engineering thinking, combined with trade expertise, can solve challenging HVAC problems. This conversation is essential listening for anyone serious about understanding cold climate HVAC design, building science principles, and what it takes to deliver quality comfort solutions in real-world conditions. Topics Covered Engineering background transition to HVAC - How mechanical engineering experience in semiconductors and manufacturing informed their HVAC business approach Manual J calculations and proper sizing - Running 7,000-9,000 Manual J calculations over five years and why they typically specify smaller systems than competitors Old New England housing challenges - Working with homes from the 1600s-1700s, extreme infiltration rates, and heat loss characteristics of ancient construction Heat load vs. cooling load imbalances - Managing homes where heat loads can be triple the cooling loads and how this affects system design Heat pump turndown ratios - Why equipment turndown capability is critical for shoulder seasons and preventing short cycling in cold climates Cold weather performance and derating - Equipment capacity loss at low ambient temperatures and the importance of proper backup heat sizing Ductless vs. ducted system economics - When to choose multi-zone ductless over ducted systems based on home layout, infrastructure, and cost Retrofit complications in mixed construction - Dealing with homes that combine 200-year-old sections with modern additions on the same heating system Massachusetts incentive programs - How Mass Save rebates (up to $25,000 financing + $10,000 rebates) have impacted market quality and contractor behavior Installation challenges at low temperatures - Field issues including undersized ductwork, poor equipment placement, defrost cycle complications, and electric backup heat requirements Building science fundamentals - Blower door testing, weatherization impacts, infiltration effects on heat load, and wind loading considerations Consultative sales approach - Rejecting one-size-fits-all solutions and customizing system recommendations based on home characteristics and homeowner needs Backup heating strategies - When and why fuel-based backup systems are necessary, including power outage considerations and client comfort levels Complex project examples - Case studies including underground concrete dome homes, storage closet air handler installations, and severely under-designed retrofit corrections   Learn more about Leo and Paul's business, Jay Moody HVAC, at https://jaymoodyhvac.com/.  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 listener-submitted question and explains why heat pumps get a bit weird: when it comes to superheat in heat mode. He also explains how we can move heat from outdoors to indoors, even in temperatures below freezing (cold temperatures just have less heat, not zero heat). In order to move heat in very cold conditions, we need very low suction pressures and cold coils, which gives us a high compression ratio. Superheat will be affected by these conditions. Remember: superheat that is too low can cause floodback, and superheat that is too high can cause the compressor to overheat. Superheat is easy to check in cooling mode, but it's harder in heating mode, especially since the suction line is at the outdoor unit. In heating mode, we can only measure superheat between the coil outlet and the reversing valve inlet, which is a very short run of tubing. The superheat will also be less stable in heat mode in cold weather, and it will have a wider range of "normal" values than cooling mode, depending on the conditions. Superheat could even drop to zero with some fixed-orifice metering devices (which would cause floodback). That's why many of these heat pumps have accumulators, which collect liquid refrigerant to protect the compressor. Even though TXVs attempt to maintain superheat, you may still see some variation in heat mode during cold weather. EEVs are common in ductless systems and are highly controllable but maintain relatively low superheats by design; fast metering control, intelligent logic, accumulators, and low refrigerant charges allow them to avoid floodback in low temperatures. In any case, spikes and drops in temperature can cause the superheat to jump or collapse because the load changes (as the outdoor coil is the evaporator). Frost buildup on the coil also inhibits airflow and heat transfer, causing the superheat to change as the evaporator pressure and temperature drop. Defrost also introduces chaos to the equation. All of these should influence your judgment when checking superheat to diagnose or commission a system in heat mode.   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 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.

In this short podcast episode, we go back into the history of the trades, namely the battle over frequency (and how each side had to give until it hertz). The low hum of motors is alternating current: electricity moving back and forth through copper 60x per second (in the USA and Canada, at least). In another version of history, that pulse could be 50x per second instead (as in much of the remainder of the world). The forgotten frequency war is the lesser-known sequel to the war of the currents. Tesla's AC power prevailed over Edison's DC, but different motor and generator companies chose different alternating current frequencies. Westinghouse chose 60 cycles per second, whereas General Electric experimented with 25-40 cycles per second, and Europe-based Siemens and AEG standardized around 50 hertz. These different frequencies set the rhythm for everything that turns or glows, and electric parts that didn't match often failed. Nevertheless, the engineers of the companies defended their own frequencies. In the 1910s, the US began merging electrical grids to set a single standard. Westinghouse had the most dominant technology at the time, and 60 hertz became the norm in the USA. However, across the pond, 50 hertz made more sense for the European infrastructure that was in place and being rebuilt after WWI, and it was solidified by the rebuilding efforts of WWII. As a result, roughly 2/3 of the planet uses a 50-hertz frequency. The two frequencies are incompatible because motors will travel at a different speed than their design while drawing the same current, leading to reduced capacity or overheating. In the 1960s, international companies produced dual-rated compressors and motors, but global trade is still complicated by different frequencies, and moving entirely to a single frequency is impractical due to the infrastructure disruption required. However, modern VFDs and inverter technology can change frequencies as they enter the motor, thus solving the battle over frequency and reminding us that flexibility is the real future.   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 candid conversation, Nathan and Bryan dive deep into the often-misunderstood world of sales in the construction and HVAC trades. Nathan, who has transitioned from fieldwork to spending roughly 60% of his time in sales, offers a unique perspective on why sales professionals are necessary despite the skepticism they face from tradespeople. The discussion tackles head-on the negative perceptions surrounding salespeople while making a compelling case for their essential role in growing and sustaining a trades business. The conversation explores the fundamental differences between residential and commercial sales, revealing insights that anyone in the industry will find valuable. Nathan explains that residential sales requires quick relationship-building, subject matter expertise, and the ability to emotionally connect and disconnect rapidly from customers you may only see every few years. It's essentially retail sales with a technical component. Commercial B2B sales, on the other hand, is far less transactional and much more relational—it's about building confidence, managing accounts effectively, and ensuring clients can focus on their core business while you handle their facility problems seamlessly. One of the most refreshing aspects of this discussion is Nathan's honesty about the unglamorous side of sales. He emphasizes that the job isn't about fancy lunches or golf outings—it's about being the person who answers their phone, follows through on commitments, and doesn't shy away from uncomfortable conversations. The guys share frustrating examples of poor salesmanship, from ghosting potential clients to making promises that can't be kept, illustrating how these failures give the entire profession a bad reputation. Nathan stresses that good sales is fundamentally about managing expectations, delivering on promises, and serving as the crucial liaison between customer needs and production capabilities. The conversation concludes with practical advice for tradespeople considering a move into sales: if you're motivated by the chase, enjoy solving people's problems, and find satisfaction in knowing your work directly impacts the bottom line, sales might be for you. But if you're just looking for an easier path with less physical labor, think again—great salesmanship is mentally demanding work that requires constant follow-through and resilience. Topics Covered: Why tradespeople are often critical of sales and the misconceptions about the profession The difference between "good" and "bad" salespeople and the moral use of sales skills Essential traits for successful residential HVAC salespeople, including product knowledge and emotional agility How commercial B2B sales differs from residential—less transactional, more relational The critical importance of follow-through, responsiveness, and keeping promises in account management Why sales serves as the essential "oil in the machine" that prevents business breakdowns The role of salespeople in managing customer expectations and protecting production teams The unsexy reality of sales work: constant uncomfortable conversations and problem-chasing When entertaining clients (golf, lunches) is appropriate versus when it becomes buying work Advice for tradespeople considering transitioning into sales roles   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 takes us on a history journey back to when ammonia ruled the world. In the mid-1800s, before R-12, many inventors and scientists experimented with vapor-compression refrigeration systems to make ice. They used a variety of refrigerants in their patents, including ether, ethyl ether, carbon dioxide, sulfur dioxide, methyl chloride, and ammonia. Each one had tradeoffs, but ammonia was the favorite because it was inexpensive, very good at moving heat, and useful because its odor made leaks obvious (although it was toxic and irritated the lungs and mucus membranes). Toxic refrigerants, particularly sulfur dioxide and methyl chloride, were common refrigerants but had plenty of negative press due to the many deaths they caused. In response to the public's reservations about toxic refrigerants, Thomas Midgley from General Motors (who developed leaded gasoline) teamed up with Charles Kettering and DuPont to find a refrigerant that was non-toxic, non-flammable, and non-corrosive. In 1930, they announced dichlorodifluoromethane, also known as R-12 (a CFC) and trademarked as Freon. This refrigerant was non-toxic, non-flammable, and had no odor, and it effectively replaced the methyl chloride, sulfur dioxide, and ammonia. However, many decades later, scientists discovered that chlorine-bearing compounds were destroying the ozone layer. To combat the environmental damage, many nations signed the Montreal Protocol in the 1980s, which would effectively phase out R-12, R-11, and other CFC refrigerants. Over time, the regulations have tightened on HCFCs and high-GWP HFCs, leading us to where we are now with lower-GWP A2L HFCs and HFO blends. As with the old refrigerants, each refrigerant had a tradeoff. Meanwhile, this whole time, ammonia never became truly obsolete and quietly remained the lifeblood of industrial refrigeration, and it also had no global warming potential OR ozone-depletion potential. Ammonia systems run with relatively little charge, especially when paired with CO2, and ammonia is still a powerhouse today because of its chemical formula (NH3), good compression ratio, and excellent latent heat of vaporization. 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 episode of the HVAC School podcast, Bryan and Nathan dive deep into the challenges of humidity control in grocery stores and other refrigerated environments. While the conversation takes several entertaining detours (including discussions about morning radio shows, Indian weddings with elephants, and imaginary lava-heated homes), the core content provides valuable insights for HVAC and refrigeration technicians dealing with condensation and moisture issues in commercial refrigeration spaces. The hosts explain why humidity management is critical in grocery environments, where refrigerated cases and displays must maintain cold temperatures while preventing condensation on doors, frames, and floors. They discuss the evolution from traditional solutions—like energy-intensive frame heaters that kept surfaces above dew point—to modern strategies involving dedicated outdoor air systems (DOAS), strategic use of waste heat from refrigeration racks, and various dehumidification approaches. Nathan emphasizes that the key is maintaining proper dew point levels (typically targeting 45% relative humidity at around 72°F) while keeping the building under positive pressure to control moisture infiltration. A significant portion of the discussion focuses on airflow management and its impact on refrigeration equipment. The hosts explain how air curtains in display cases work on Bernoulli's principle to maintain cold temperatures, and why even minor disruptions to airflow patterns can cause product spoilage or increased energy consumption. They stress the importance of understanding building pressure dynamics, especially considering makeup air requirements for exhaust systems in sculleries and loading docks. The episode concludes with practical troubleshooting advice for technicians dealing with sweating cases and humidity problems. Nathan recommends systematically checking building pressure with a manometer, measuring dew point at multiple locations throughout the store, and verifying that door and frame heaters are functioning properly. He also suggests looking for intermittent fresh air sources and exhaust fans that might be disrupting the carefully balanced airflow patterns that keep moisture under control. Topics Covered: Dew Point vs. Relative Humidity: Why focusing on dew point (50-55°F typical target) is more important than relative humidity in grocery environments Condensation Prevention Strategies: Evolution from energy-intensive frame heaters to modern DOAS systems with reheat capabilities Airflow and Air Curtains: How Bernoulli's principle creates invisible barriers in refrigerated display cases and why disrupting these patterns causes problems Reheat Methods: Various approaches, including waste heat from refrigeration racks, electric reheat, and desiccant dehumidification systems Building Pressure Management: Importance of maintaining positive pressure while managing fresh air requirements and exhaust systems Radiant Heat Effects: How surface temperatures, not just air temperature, affect condensation on refrigerated cases Troubleshooting Humidity Issues: Systematic approach to diagnosing moisture problems, including pressure testing, dew point measurement, and identifying intermittent airflow sources Return Air Placement: Benefits of pulling return air from underneath cases to capture the most humid air for dehumidification   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 explores the history of the finned-tube coil, which is what we use for heat exchange in air-source air conditioners and heat pumps. Air-source HVAC systems have copper tubes threaded through thin metal fins. This design was optimized to ensure the greatest possible surface area for heat exchange to occur. However, prior to the finned-tube coil, HVAC coils looked more like plumbing projects with bare copper loops, which were heavy, costly, and inefficient.  In the early 1900s, HVAC was essentially plumbing with higher expectations; capacity was dictated purely by size and charge. In the 1910s and 1920s, early air conditioning pioneers were already attempting to increase surface area with metal discs or pipes, which evolved to continuous sheet fins. The tube would move refrigerant, and the fins would collect heat from the air and pass it into the tube; the finned-tube coil was born. The added weight was minimal, but the contact area was increased by almost 3000%, meaning coils and charges could be smaller with added efficiency. This move was necessary because while we already knew that heat can indeed move without touching molecules (radiant transfer), radiant cooling had a unique challenge: dew point. Finned-tube coils rely on convection and only have temperatures below the dew point in a small area, which allows us to have a small drain pan. Aluminum was also plentiful after WWII, enabling finned-tube technology to evolve to louvered fins and reach the masses. By the 1960s, finned-tube coils were in all sorts of applications. However, it became clear that aluminum was fragile, and we have since innovated to overcome that challenge. There are three barriers that heat transfer must overcome: air-side film resistance (air is a poor conductor), wall conduction through the tube and fins, and refrigerant-side film resistance (oil inside or laminar flow). The fins help with air-side film resistance, so we want to clean and straighten them as much as possible.   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 episode of the HVAC School podcast, host Bryan Orr sits down with three experts from Copeland to demystify tandem and trio compressor systems. Joining him are Gina Kahle (Multiples Engineering Manager with 12+ years at Copeland), Tyler Daniels (Product Management team member), and James Stevenson (Technical Sales veteran with 28 years of field experience). Together, they provide both the engineering perspective and real-world service insights that technicians need to understand these increasingly common systems. The conversation begins with the fundamentals: tandem and trio systems represent an evolution in compression modulation, allowing multiple compressors to work together on a single circuit rather than requiring separate circuits for each compressor. This design philosophy delivers significant advantages, including energy savings through better modulation, simplified system design, reduced costs, and the ability to meet stringent minimum modulation requirements (such as the 25% threshold for units under 60,000 BTUs per hour). The team emphasizes that tandems aren't just about pairing any two compressors together—Copeland engineers carefully consider application requirements, flow characteristics, and stress testing to ensure reliable oil management and system resonance control. A major focus of the discussion centers on practical service considerations that every technician needs to understand. James provides invaluable guidance on identifying whether a failed compressor in a tandem system can be replaced individually or requires replacing the entire tandem assembly. The "rule of thumb" is clear: compressors small enough to fit in residential systems (typically under 10 horsepower or about 7 inches in diameter) generally require full tandem replacement, while larger units may allow single compressor replacement. The distinction between "tandem ready" and non-tandem ready compressors becomes critical here—larger compressors (10+ horsepower) are typically sold tandem ready at wholesalers with the necessary oil equalization ports and sight glass connections, while smaller units are not. The episode also explores advanced topics, including the integration of Enhanced Vapor Injection (EVI) technology with tandem systems, particularly for cold climate heat pump applications. Gina explains how EVI extends the operating envelope down to -40°F, opening new markets and applications. The team discusses the transition to A2L refrigerants and how Copeland continues to innovate despite changing regulatory landscapes. Throughout the conversation, they emphasize the critical importance of proper oil management through oil equalization lines (OEL) and two-phase transfer lines (TPTL), and why maintaining these connections exactly as designed is non-negotiable for system longevity. Key Topics Covered: Tandem and Trio Basics: Definition and benefits, including energy savings, cost reduction, and design simplification Modulation Requirements: Meeting state-mandated minimum modulation thresholds (25% for units under 60,000 BTU/hr) Applications: Data centers, DOAS units, rooftops, chillers, and various commercial spaces Compressor Pairing Options: Fixed speed, digital, variable speed, two-stage, and mixed configurations Oil Management: Critical importance of oil equalization lines (OEL), two-phase transfer lines (TPTL), and gas equalization lines (GEL) Service and Replacement: How to identify tandem-ready vs. non-tandem-ready compressors; when to replace individual compressors vs. full tandem assemblies Visual Identification: Using compressor size (7" vs 9" diameter), port configuration, and horsepower ratings to determine replacement strategy Piping Configurations: Three-pipe vs. four-pipe designs and when each is necessary Installation Considerations: Importance of keeping oil equalization lines level (parallel to ground) and using proper mounting spacers Enhanced Vapor Injection (EVI): How EVI technology extends operating envelopes to -40°F for cold climate heat pump applications Energy Efficiency Standards: Meeting IEER, IPLV, and upcoming IVEC standards through strategic tandem use Copeland Mobile App: Features, including parts lookup, resistance specifications, amperage mapping, AI Scout assistant, and technical bulletins   Learn about the Copeland Mobile app at https://www.copeland.com/en-us/tools-resources/mobile-apps/copeland-mobile.  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 tells the story of the technology that tried to beat the compressor... and still may someday. We associate cooling with refrigerant... and all the things that come with it, including compressor noise, oil, recovery machines and tanks, leaks, superheat, and regulations. However, there is a means of providing cooling with two pieces of metal and several semiconductors; current runs through it, and one side becomes cold, and the other side becomes hot. This technology is called thermoelectric cooling, associated with the Peltier effect. In 1834, French watchmaker and amateur physicist Jean Charles Athanase Peltier was experimenting with electricity and dissimilar metals. When he joined two wires of different materials and ran current through the junction, one got colder, and the other one got hotter. This phenomenon was named the Peltier effect, and it describes how passing electrical current through two dissimilar conductors causes heat to move from one side to the other, like a tiny reversible heat pump. However, it didn't have any practical use at the time. Semiconductors arrived in the mid-1900s, and engineers could make thermoelectric devices strong enough to move meaningful amounts of heat. In the 1960s, NASA even began using the technology in spacecraft for precision temperature control, which was hardy and allowed them to stabilize sensors and electronics in space. We began using them on Earth in some specialized applications, including portable coolers, wine chillers, and CPU coolers in computers. However, this technology didn't replace vapor-compression refrigeration due to efficiency constraints and the need to reject heat. Thermoelectric modules are only 5-10% as efficient as vapor-compression systems, and they need heat sinks or fans to give the heat somewhere to go. We've still been pursuing a comfort cooling use of the Peltier effect, and we've gotten closer, but most applications still have the efficiency block. When efficiency isn't a problem, we encounter difficulties with moisture and latent heat removal. Nevertheless, thermoelectric cooling is still making a difference for sensors and in localized cooling applications.   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 episode, Bryan and Roman dive deep into one of the most challenging topics in modern HVAC: making VRF (Variable Refrigerant Flow) and ductless systems perform effectively in humid climates like Florida. The conversation tackles a common misconception that inverter-driven equipment automatically handles humidity well simply because it can "turn down." Roman emphasizes that successful application of VRF technology in humid environments requires skilled professionals who understand building science, envelope integrity, and proper system sizing. The biggest takeaway? If you're going to err on sizing, undersize rather than oversize - these systems will run longer and maintain better humidity control when properly sized. The hosts explore the three critical factors for dehumidification: runtime, coil temperature, and surface condensation. They explain how traditional inverter systems were programmed for energy efficiency by allowing coils to warm up as they approached the set point, which unfortunately sacrifices latent capacity. Modern systems with active dehumidification capabilities use expansion valve control to "starve" the coil, lowering saturation temperature to around 35-37 degrees while extending runtime. Roman shares his personal experience with a 7,000 BTU unit serving his 700 square foot master bedroom suite, demonstrating how proper application and understanding of equipment capabilities can deliver excellent humidity control without oversizing. The discussion takes a practical turn as Bryan presents a comprehensive troubleshooting checklist for humidity problems, starting with bulk water leaks and progressing through envelope integrity, duct sealing, equipment selection, and pressure balancing. They debunk common "solutions" that actually make problems worse, like adding attic insulation or solar attic fans without addressing root causes. The conversation reveals a counterintuitive truth: reducing sensible load through excessive insulation can worsen humidity problems by reducing equipment runtime. They explain why "active dehumidification" through overcooling isn't true dehumidification, and why another solution - reheat - requires adding sensible heat back to spaces to maintain longer equipment runtime. Topics Covered: VRF and inverter sizing misconceptions - Why undersizing is often better than oversizing in humid climates Three factors of dehumidification - Runtime, coil temperature, and surface condensation explained Active dehumidification technology - How expansion valve control creates longer runtime and colder coils Equipment capacity ratings - Understanding that a "12K" unit may actually perform at 18,000 BTU Latent vs. sensible capacity - Why checking engineering specifications is critical for humid climate applications VRT (Variable Refrigerant Temperature) - When this energy-saving feature should be disabled in humid climates Fan operation strategies - Why continuous fan operation can worsen humidity problems Duct and envelope leakage - How pressure imbalances drive moisture problems Surface condensation - Why vents and ducts sweat and how to prevent it The overcooling trap - Why lowering the set point creates interstitial space moisture problems Humidity sensors in thermostats - Understanding what they do (and don't do) Load diversity and zone control - How multiple smaller units can outperform single large systems Reheat strategies - From electric resistance to passive solar gain Common mistakes - Why attic insulation and solar fans often worsen humidity issues Troubleshooting checklist - A systematic approach from bulk water to equipment selection   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.