BACK

Ductless and VRF – Good, Bad, & Ugly #LIVE

By Bryan Orr

Some great live guests join the podcast to discuss the advantages, disadvantages, and challenges of ductless and VRF equipment.

We started off working on ductless equipment with Mitsubishi, especially installing them in lanais. Sunrooms have large amounts of radiant heat coming in, and the heat load often warrants getting an A/C system just for the sunroom/lanai. We even began oversizing them a bit (which was a lesson learned). We also learned that mini-split ductless systems tend to have filthy blower wheels because moisture tends to build up on them. However, bib kits make cleaning the blower wheel in place an easy process.

High-wall ductless systems also work in houses, not just sunrooms. However, they may have issues dehumidifying effectively. To remove more latent heat, you have to ramp down your blower and ramp up your compressor to get your coil colder. Overall, Bryan is not a large fan of using multi-zone ductless units in residential applications UNLESS they are replacing window units.

VRF systems are typically used in commercial applications. The systems typically use cassette-type units or low-static fan coils, unlike high-wall ductless units. Although VRF and high-wall ductless units tend to have different sets of advantages and disadvantages, both of them struggle a bit with humidity and may need supplemental dehumidification.

Overall, while VRF and ductless systems are desirable because they can control sensible capacity, those modulation capabilities can also lead to serious problems in wet climates.

We also discuss:

Condensate pumps
Blower wheel set screw issues
Ductless and VRF filtration
Sensible heat ratio (SHR)
VRF serviceability
Dehumidification vs. efficiency
Regional VRF manufacturing practices
EER vs. SEER
Daikin dry mode
What should HVAC systems really control?
Engineering commercial buildings
VRF refrigerant loss
ICM493 controls

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Comments

What We Learned From NCI Duct / Balancing Training

HVAC Systems for Architects: Making Sense of the Alphabet Soup – Short #273

Sizing Breakers and Conductors (for HVAC) – Have Things Changed?

Absorption Cooling – The Rise and Fall and Rise – Short #272

Combustion Analysis w/ Tony G.

Residential vs. Commercial HVAC Sales

When Ammonia Ruled the World – Short #270

Humidity, Airflow, and Refrigeration

The Finned-Tube Coil – Short #269

Are Two Are Better Than One: Understanding Tandem Compressors

Author:

Bryan Orr

Company: HVAC School

Position: Founder

Check out our most recent video

How to Evacuate an AC system, Full Vacuum Procedure

Our latest Podcast

HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

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.

Search Episodes

What We Learned From NCI Duct / Balancing Training

01/08/2026

Bryan Orr

HVAC Systems for Architects: Making Sense of the Alphabet Soup – Short #273

01/06/2026