HVAC School - For Techs, By Techs

• Are Two Are Better Than One: Understanding Tandem Compressors

  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.

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• The Tech That Tried to Beat the Compressor - Short #268

  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.

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• VRF, Ductless and Humidity Control w/ Roman

  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.

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• The History of the Thermostat - Short #267

  In this short podcast, Bryan gives another history lesson and goes over the history of the thermostat. Before 1883, automatic temperature control simply did not exist; we shoveled fuel into the furnace and opened windows. If a room got too hot in a commercial building, the janitor would go downstairs to choke the draft damper; this person was responsible for manually controlling comfort. Warren S. Johnson, a Milwaukee-based college professor, sought to do something about his classroom's sweltering heat. He created a pneumatic thermostat that mounted to the wall, sensed temperature, and used air pressure and mechanical systems to control dampers. This invention grew in popularity, and he founded Johnson Controls. Compressed air ran entire HVAC networks by adjusting dampers and valves before electricity went mainstream. Engineers experimented with bi-metallic strips, which could open or close an electrical circuit based on temperature changes, which made thermostats smaller and cheaper. Honeywell came on the scene by hiring industrial designer Henry Dreyfuss, who invented the mercury thermostat: the T87 round thermostat. When the bimetal coil tilted, mercury rolled from one end to the other to complete or open the circuit. These thermostats had a heat anticipator, which kept them from overshooting the temperature. Unfortunately, when these thermostats were disposed of, the mercury polluted the environment and affected the central nervous system. The digital thermostat came on the scene to replace the mercury thermostat, which led to the development of the Nest smart thermostat. However, all this time, comfort has been associated with the number on the thermostat; smart comfort controls that learn our routines and monitor dew point, relative humidity, and IAQ are the next step to create true comfort and health.   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.

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• Tech Support Highs and Woes w/ Roman

  In this candid and comprehensive episode, Bryan sits down with Roman to tackle one of the most frustrating yet crucial aspects of the HVAC industry: technical support. What starts as a conversation about their own tech support nightmares quickly evolves into a deep dive examining the entire ecosystem—from manufacturers and distributors to technicians and sales reps—and how each player can improve the support experience. Roman opens up about his recent tech support struggles, including having to search Russian websites just to find service manuals for major brand equipment. This leads to a broader discussion about the fundamental problem: as HVAC equipment becomes increasingly complex with proprietary controls and advanced technology, manufacturers have simultaneously made it harder to access the information needed to service that equipment. The conversation highlights how the old "I never called tech support" mentality of veteran technicians is no longer viable when you're dealing with VRF systems, building automation, and equipment-specific protocols that require specialized knowledge. The hosts emphasize that good documentation isn't just helpful—it's essential, and manufacturers who hide behind "brand protection" are actually damaging their reputation in the long run. The episode doesn't just complain about problems; it offers real solutions. Bryan and Roman discuss what technicians need to do before calling tech support (hint: know your superheat, subcooling, and basic electrical readings), what makes great tech support personnel, and why investing in these roles pays dividends. They share inspiring examples of distributors and reps who go above and beyond, like the Johnstone team in Louisiana who actively seek out field experts when manufacturers can't provide answers. The conversation also touches on why tech support and education roles are chronically underpaid, and how properly compensating and supporting these positions could transform the industry. Perhaps most importantly, the hosts emphasize that everyone in the HVAC ecosystem is working toward the same goal: keeping end clients comfortable and satisfied. When manufacturers, distributors, reps, contractors, and technicians recognize this shared objective and work collaboratively rather than defensively, everyone wins. The episode concludes with practical advice for sales professionals, including the importance of ride-alongs and adopting the "I got it" mentality that turns good salespeople into indispensable partners. Topics Covered Service Manual Accessibility: The critical need for manufacturers to make documentation easily searchable and available online, not hidden behind outdated processes Manufacturer Responsibilities: Why "protecting the brand" often backfires and how transparency builds loyalty Technician Preparation: What basic measurements and troubleshooting steps should be completed before calling tech support Tech Support Personnel: The importance of properly compensating and supporting tech support staff to reduce burnout and turnover Distributor and Rep Excellence: How the best wholesalers and reps go beyond just forwarding emails to actively solve problems The "I Got It" Sales Approach: Why taking ownership of customer problems is the key to building lasting relationships Cross-Brand Part Referencing: The need for universal parts cross-referencing across sister brands and product lines Field Ride-Alongs: Why B2B sales professionals should spend at least one day per month in the field with technicians Legacy Product Support: The frustration when manufacturer partnerships dissolve and orphaned equipment becomes unsupportable AI in Tech Support: Why throwing technology at support problems without understanding the root issues is a waste of money   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.

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