HVAC School - For Techs, By Techs

In this short podcast episode, Bryan responds to a comment we received about cracked heat exchangers and how they were characterized in a recent combustion safety podcast episode.
In reality, heat exchanger cracks counter the effects of the inducer motor.  The inducer pulls air through the heat exchanger, but a crack causes the inducer to pull the air from elsewhere, especially once the blower motor comes on. That is a cause of flame rollout and a higher CO measurement.
Induced draft (80%) furnace venting is under negative pressure near the equipment (WRT the air in the room around it).  The inducer fan pulls the air through the single heat exchanger, but air isn't "pushed" out of the flue. That's because the draft in the flue is greater than the inducer itself. 
80% furnaces are also open-combustion units that pull combustion air in from the air around the furnace, and they require access to fresh air. When you have gaps and cracks in the ductwork, the blower comes on and may cause the combustion analysis readings to change briefly. In a 90%+ sealed combustion furnace, the change is very minimal and doesn't last long; if the numbers vary a lot and are sustained, then that's an indicator of a cracked heat exchanger.
In any case, if you suspect a cracked heat exchanger and want to quote it, you must be able to find it. Proper combustion analysis and combustion analyzer use and care also matter for accurate cracked heat exchanger diagnosis.
 
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.
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In this live episode recorded at the AHR Expo 2026 Podcast Pavilion in Las Vegas, host Bryan sits down with longtime friend and industry expert Nikki Krueger of Santa Fe and AprilAire. Nikki brings over 15 years of experience in indoor air quality and whole-home dehumidification to the conversation, having started her career with AprilAire before moving to Santa Fe (formerly Ultra Aire) — and now coming full circle as the two brands have integrated under the AprilAire umbrella as of January 1st of this year. The episode dives deep into a topic close to both hosts' hearts: how to properly manage indoor humidity, and what role a whole-home ventilating dehumidifier plays in a comprehensive HVAC system strategy.
Bryan and Nikki lay out a holistic framework for tackling moisture problems, emphasizing that a dehumidifier should be the last tool added — not the first. Before reaching for dedicated dehumidification equipment, contractors need to assess the building envelope for air leaks, evaluate whether the air conditioning system is properly sized (oversizing is a major contributor to poor latent removal), confirm that the AC is set up with the right airflow and sensible heat ratio, and take into account the ventilation strategy and occupant behavior. The pair discuss real-world scenarios ranging from elderly residents in Florida who keep their thermostats at 80°F, to a project in Barbados where overcooling caused interstitial condensation in walls and ceilings. The message is clear: humidity control is a systems problem, not a single-product fix.
A significant portion of the episode is dedicated to proper installation practices for whole-home dehumidifiers. Nikki explains why Santa Fe recommends pulling from a dedicated return and discharging into the supply side of the AC duct — rather than tying into the return side — because the heat generated by dehumidification (roughly 1,054 BTUs per pint of water removed) can warm the AC evaporator coil and reduce its latent removal capacity. Bryan adds nuance around dew point management when routing outdoor air ducts, and both hosts agree that fan operation strategy (continuous low-speed vs. intermittent) matters more in tight, low-load homes where mixing is harder to achieve naturally. They also clarify a common misconception: a ventilating dehumidifier is not a dedicated outdoor air system (DOAS) and does not automatically condition incoming ventilation air before it enters the home.
The conversation wraps up with an exciting look at Santa Fe's newly launched Ultra V Series, which features an upgraded 8-inch ventilation duct (up from 6 inches), a more powerful fan for handling higher static pressure in retrofit applications, a new digital control panel, and a wired remote humidity sensor that can be placed in the living space for more accurate readings. Nikki and Bryan also field audience questions on topics like short-cycling risks from oversized dehumidifiers and why Santa Fe chose a wired sensor over wireless (accuracy, reliability, and fewer callback headaches). Bryan closes by noting that rising dew points across most U.S. markets over the last 20 years make whole-home dehumidification more relevant than ever — and that any region where you can see green grass outside is a candidate for a more advanced moisture control strategy.
Topics Covered
Introduction to Nikki Krueger and the merger of Santa Fe and AprilAire under one brand
The purpose of whole-home ventilating dehumidifiers and how they fit into an overall HVAC system strategy
Latent vs. sensible heat loads explained — and why both matter for comfort and moisture control
Geographic reach of humidity problems — why dehumidification isn't just a Florida or Gulf Coast issue
Ken Gehring ("Teddy Bear"), inventor of the whole-house ventilating dehumidifier, and his framework for diagnosing moisture problems
The four-factor checklist before deploying a dehumidifier: building envelope, AC sizing, AC setup/airflow, and ventilation strategy
How occupant behavior (thermostat preferences, activity levels, large households) creates latent load variability
The dangers of overcooling — how setting thermostat too low can cause interstitial condensation in walls, ceilings, and attics
Sensible heat ratio (SHR) and its role in a system's ability to remove moisture — targeting ~350 CFM per ton in humid climates
Why dehumidifiers should connect to a dedicated return and discharge into the supply — not tie into the AC return side
How dehumidifier heat output (~1,054 BTUs per pint) can reduce AC coil efficiency when ducted incorrectly
Fan-on strategy debate: when running continuous low-speed circulation helps vs. hurts humidity control
Tighter homes, smaller systems, and the importance of air mixing strategies (including ceiling fans)
 Ventilating dehumidifiers vs. dedicated outdoor air systems (DOAS) — clearing up a common misconception about how ventilation air is conditioned
Dew point management for outdoor air ducts — preventing condensation inside duct runs
Using dehumidifiers to address sweating ductwork in multi-story homes
Rising dew points over the past 20 years and what "green grass climates" means for dehumidification demand
Heat pump oversizing challenges in colder climates and the downstream impact on AC latent removal
Santa Fe's new Ultra V Series: 8-inch ventilation duct, stronger fan, digital controls, and wired remote humidity sensor
Why proper dehumidifier sizing matters: short-cycling risks, moisture reservoir release, and uneven RH throughout the home
Why Santa Fe chose a wired humidity sensor — accuracy, reliability, and reducing contractor callbacks
Audience Q&A: oversizing consequences, short-cycling mechanics, and sensor placement best practices
 
Learn more about Santa Fe Dehumidifiers at santafeproducts.com. 
Connect with Nikki Krueger on LinkedIn or Instagram @nikkikruegerIAQ.
Check out the work of Ken Gehring ("Teddy Bear") or ask him a question on the HVAC Talk Forum: hvac-talk.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 episode from AHR Expo 2026, Bryan sits down with John Pastorello for a discussion about the latter's lifetime of HVAC/R. John was a chemist and an HVAC technician before founding Refrigeration Technologies in 1987, and he received the HVAC Tactical Lifetime Achievement Award in 2026.
Prior to entering the trade, John was a chemist in a lab. He applied for and was hired by an HVAC company when he realized the financial opportunity in the trade. He eventually owned a contracting business, but he didn't truly make his HVAC/R chemistry debut until 1987 with Big Blu. When he noticed problems with existing liquid leak reactants and inaccurate electronic leak detectors, John developed Big Blu in his kitchen (with the help of his local library and patent office for research) and tested it in the field. 
Big Blu was the first Refrigeration Technologies product, and it was the only one for a while. He then developed Nylog in the early 1990s while developing a different product. After falling down research rabbit holes and doing lots of trial and error, he eventually realized the product's potential as an assembly lubricant, and Nylog became an official Refrigeration Technologies product.
Even as Refrigeration Technologies continues to grow and has received several purchase offers, it remains a family business. John's son, Mike, became a mechanic but eventually decided to return to the business, and he runs it to this day. John's career culminated with the HVAC Tactical Lifetime Achievement Award, which is a testament to the service, education, and mentorship he has shared with the HVAC/R industry.
 
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 live episode from the AHR 2026 Podcast Pavilion, Bryan sits down with Copeland's Josh Souders (Manager of Commercial Unitary Product Management) and Jeff Kukert (Compression Senior Technical Trainer) to dive deep into Enhanced Vapor Injection (EVI) technology and its transformative impact on HVAC systems. This conversation offers both technical professionals and industry newcomers a comprehensive look at how vapor injection is revolutionizing heat pump performance, particularly in challenging climate conditions.
The discussion centers on how EVI technology addresses one of the industry's most persistent challenges: maintaining high heat pump capacity in extremely low-temperature conditions. Josh and Jeff explain that vapor injection can deliver up to 20% added capacity and 10% improved efficiency while simultaneously enhancing compressor reliability. This technology, which has been a staple in refrigeration applications for years, is now becoming increasingly prevalent in commercial and residential HVAC systems, especially as cold climate heat pumps gain traction across North America. The guests make the complex topic accessible by breaking down how the system works—taking liquid refrigerant from the condensing line, running it through an expansion device and brazed plate heat exchanger (economizer), and injecting the cooled vapor directly back into the compressor scroll at a specific intermediate point.
What makes this episode particularly valuable is the practical guidance offered for field technicians. The conversation moves beyond theoretical explanations to address real-world implementation challenges and troubleshooting strategies. Josh and Jeff emphasize the importance of understanding operating envelopes, pulse-width modulated (PWM) valves, pressure transducers, and modern control systems. They introduce Copeland's latest product developments, including the YAW variable speed vapor injection platform (1.5 to 25 tons) and the upcoming YAB two-stage vapor injection system launching later in 2026. The discussion also touches on applications beyond traditional HVAC, including commercial water heating and boiler replacement systems where high discharge temperatures are crucial.
Throughout the episode, the guests maintain an encouraging tone toward technicians who may feel intimidated by these advancing technologies. They stress that while EVI systems may appear complex with additional tubing, heat exchangers, valves, and sensors, the underlying thermodynamic principles remain the same. The key is familiarizing oneself with new components like PWM valves and modern controllers, and leveraging tools like Copeland Mobile to verify system performance against operating envelopes. This episode serves as both an educational resource and a call to action for HVAC professionals to embrace these emerging technologies that are rapidly becoming industry standard.
Topics Covered
Enhanced Vapor Injection (EVI) fundamentals – How EVI works, its history in refrigeration, and why it's now critical for commercial and residential HVAC applications
Capacity and efficiency benefits – Achieving up to 20% capacity boost and 10% efficiency improvement, particularly in low-ambient heating conditions
Compressor reliability improvements – How injecting cooled vapor into the scroll set manages discharge temperatures and extends compressor life under high compression ratios
Operating envelope management – Understanding compressor operational limits and using tools like Copeland Mobile to verify field conditions stay within safe parameters
Cold climate heat pump technology – Meeting DOE's Cold Climate Heat Pump Challenge requirements for 100% capacity at 5°F ambient conditions
System architecture and components – Detailed explanation of economizers (brazed plate heat exchangers), pulse-width modulated (PWM) valves, pressure transducers, and advanced controllers
Compression ratio challenges – Managing the increased work required when outdoor temperatures drop while indoor condensing temperatures remain constant
New Copeland product platforms – Introduction to YAW variable speed vapor injection (1.5-25 tons), YAB two-stage vapor injection (launching 2026), and tandem variable speed configurations
Applications beyond traditional HVAC – Water heating systems, commercial boiler replacement, and managing high discharge temperatures for Legionella protection
Technician training and tools – Practical advice on learning PWM valves, thermistors, transducers, and system controllers; emphasis on using Copeland Mobile for dynamic performance analysis
Market trends and adoption – How vapor injection is becoming standard in premium residential systems and increasingly common across commercial rooftop units and dedicated outdoor air systems
Installation and service considerations – Proper system design to avoid oversizing, humidity control in hot-humid climates, and troubleshooting techniques for complex control 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 short podcast episode, Bryan breaks down the differences between a thermostatic expansion valve (TXV) and an electronic expansion valve (EEV). He highlights their strengths and weaknesses.
In the basic refrigerant circuit, the metering device drops the pressure. TXVs and EEVs are both metering devices that cause the liquid refrigerant to drop in pressure and become a liquid-vapor mixture; they control evaporator feeding and maintain a constant superheat.
TXVs achieve this by mechanical means; the bulb responds to suction line temperature and evaporator pressure at the valve. They are self-contained and easy to diagnose with basic refrigeration measurements. However, they are prone to mechanical failures, including clogged orifices and screens, cracked capillary tubes, and powerhead leaks. Installation errors are also easy to make, and TXVs can hunt in low-load conditions. Overall, failures are often mechanical and refrigerant-related. They win in the simplicity department.
EEVs receive inputs from sensors and modulate in response to those digital signals. They have a wider modulation range and maintain stable control in low-superheat applications, and they do well in conditions with highly variable loads or where coordination across multiple coils is required. EEVs come in two types: stepper motor (small, discrete steps) and PWM (controlled solenoid valves). Stepper-style EEVs excel at fine positioning, and PWM-style EEVs are in applications that require a more robust valve (like CO2 refrigeration). EEV failures are often electromechanical or related to sensor control. They win in the controllability department.
There is no "best" metering device; they merely have different strengths that make them better suited to different applications. However, EEVs are the future due to the greater degree of controllability we will need in newer equipment. Commissioning and airflow are also crucial for getting the most out of both metering device types in terms of longevity and reliability.
 
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.