Bryan from HVAC School interviews JD Kelly, known as "student of HVAC" on Instagram, about Delta T measurements in HVAC systems. This episode dives into the fundamentals of Delta T, common misconceptions, and proper measurement techniques.

JD explains that Delta T is simply a temperature difference between two points of the same medium, which is often misunderstood in the industry. Many technicians are taught to measure between return grills and supply registers, but this approach can lead to inaccurate readings due to external factors like duct leakage or heat gain from attics. The proper measurement should be taken directly at the equipment to evaluate how the evaporator coil is performing.

Humidity plays a significant role in Delta T measurements, which JD discovered when researching the fundamentals. Bryan elaborates on this point, explaining that in high-humidity environments (like Florida), more energy goes toward removing moisture (latent heat) rather than cooling the air (sensible heat), resulting in lower Delta T readings. This is why a newly repaired unit in a humid house might initially show lower readings but improve as the home dries out. The discussion highlights why the common "20-degree Delta T" rule of thumb isn't universally applicable and requires context.

Key Topics Covered:

• Definition of Delta T: Temperature difference between two points of the same medium
• Difference between Delta T and TD (temperature difference)
• Proper probe placement for accurate Delta T readings
• Impact of humidity on Delta T measurements
• How regional differences affect expected Delta T values
• Relationship between CFM (airflow) per ton and Delta T readings
• Common mistakes: Adjusting equipment based solely on Delta T readings
• Challenges of applying Delta T in heat pump heating mode
• How temperature dead spots can affect readings
• Why Delta T readings must be considered alongside other diagnostic tests
• The danger of making unnecessary adjustments to HVAC systems
• Why high Delta T isn't always good and low Delta T isn't always bad

JD's Delta T tech tip: https://hvacrschool.com/solving-delta-t/ 

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

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In this short podcast episode, Bryan talks about fire sprinklers and how to avoid setting them off on job sites.

Fire sprinklers have an element in the center that expands when exposed to heat (like a TXV sensing bulb) and breaks the glass. When the glass breaks, the fire sprinkler starts pouring out water. In some cases, fire sprinklers are linked to a larger fire suppression system in which several may go off at once, but most of the time, only a single fire sprinkler will go off if bumped or exposed to heat.

If you're using torches or doing any form of hot work in a closet or other location with a fire sprinkler, make sure to keep torches away from the heat-sensitive bulb or at least cover the sprinkler with a wet rag (and follow your company's guidelines). Blunt force is another possible issue, so we want to avoid hitting the sprinklers with lifts, ladders, or building materials like studs. Keep clearances in mind, and watch out for your colleagues.

You can get some specialty-built cages to protect the sprinklers, but awareness is one of the best ways to protect fire sprinklers. If possible, make sure signage is posted or that you alert other people in the area about the fire sprinklers.

If the fire sprinkler does go off, make sure you can quickly reach the person(s) who can access the fire shutoff or direct you to the fire shutoff. While fire sprinklers won't pose much of a personal safety hazard, property damage is a major concern. Training and awareness are the keys to preventing property damage due to fire sprinklers.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

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In this engaging session, David Richardson breaks down the concept of high-performance HVAC, offering a clear roadmap for industry professionals looking to elevate their craft. Richardson argues that the HVAC industry has long been focused on equipment rather than complete systems, leading to widespread inefficiencies. The average system delivers only about 57% of its rated capacity into buildings, while even code-approved systems barely reach 63%. By implementing high-performance HVAC principles, contractors can achieve up to 88% efficiency while improving safety, health, comfort, and energy performance.

Richardson presents a practical framework using the acronym "PATH" - Pressure, Airflow, Temperature, and Heat (BTUs) - as a step-by-step approach to implementing high-performance HVAC. He emphasizes starting with static pressure testing, which he calls "the foundation of airflow" and one of the most misunderstood principles in the industry. Just as doctors check blood pressure as a vital sign during every visit, Richardson advocates for measuring static pressure on every call, or at minimum, when encountering "red flag" issues like repeated equipment failures. From there, professionals can progress to measuring airflow, temperature, and finally BTU delivery to create complete system diagnostics.

The presentation offers a journey-based approach, acknowledging that implementation takes time and requires breaking old habits. Richardson introduces the "one degree principle," suggesting that change happens incrementally, with small improvements eventually leading to breakthrough moments. He urges contractors to apply this methodology not just to equipment, but to extend testing into duct systems and even the building envelope. By making these changes visible through measurement, contractors can prove value to themselves, their teams, and ultimately their customers, transforming the way HVAC work is perceived and delivered.

Key Topics Covered:

• The definition of high-performance HVAC: getting back to craftsmanship, challenging the status quo, and confirming work through measurement
• The industry problem: focusing on equipment instead of complete systems, resulting in just 57% of rated BTU capacity reaching conditioned spaces
• The PATH framework: Pressure, Airflow, Temperature, and Heat as building blocks for system diagnostics
• How to implement static pressure testing as the foundation for airflow diagnostics
• The importance of measuring at both equipment and register/grille locations
• Breaking down implementation into three areas: equipment, ducts, and building envelope
• STEPS approach: Show, Teach, Equip, Promote, with application to yourself, your team, and your customers
• The "one degree principle" for making incremental changes that lead to breakthrough results
• Common obstacles to implementation and how to overcome resistance to change
• How measurements make your work transparent and lead to better performance

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 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

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In this episode of the HVAC School Podcast, host Bryan sits down with Phil, the executive electrical team leader at Kalos who has transitioned into the world of estimating. Phil shares his extensive background in electrical work dating back to 1994, from his high school electrical elective to running his own business for eight years before joining Kalos and eventually establishing their estimation department.

The conversation delves deep into the fundamentals of estimating in the trades, contrasting traditional qualitative approaches with more rigorous quantitative methods. Phil emphasizes that good estimating is about "finding the truth" - understanding the actual costs of materials and labor for a project. They discuss how traditional estimating often relies on heuristics and past experiences with similar jobs, while more detailed estimating involves comprehensive takeoffs and assembly-based counting. The pair explores how estimation isn't just about producing a final number but should provide valuable information that transfers to the production phase.

A highlight of the episode is Phil's introduction of his self-developed estimating software called Unity Build. He explains how his interest in AI technologies led him to learn programming and eventually create this cloud-based solution that integrates AI assistance while maintaining the fundamental tools needed for thorough estimating. The software allows for collaboration between team members, is entirely browser-based, requiring no downloads, and is priced at $125 per month per seat. Bryan emphasizes that this is Phil's own business venture that he's taken an interest in, and they both stress that potential users should buy it for what it currently offers, not future promises, though they are committed to continuous improvement.

Topics Covered:

• Phil's 30+ year journey in electrical work and how he learned estimating
• The difference between qualitative (heuristic-based) and quantitative (detailed takeoff) estimating approaches
• Unit pricing vs. assembly-based takeoffs in estimating
• How good estimating transfers value to the production phase
• The workflow of detailed estimating from information gathering to closeout
• Labor factoring and how it affects cost calculations
• Phil's development of Unity Build estimation software using AI integration
• Cloud-based advantages of the new software, including collaboration capabilities
• How Unity Build facilitates handoff from estimating to production
• Pricing model ($125/month per seat) and target customers (small to mid-sized contractors)
• The importance of estimating honesty and finding the "truth" in project costs

Check out Unity Build Estimation at https://unitybuildestimation.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 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

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In this short podcast, Bryan answers a listener-submitted question about Nylog, oil, and where you put them when you're making flares.

Nylog is a thickened refrigerant oil (which is either POE for Nylog Blue or mineral oil for Nylog Red), and it's miscible with the refrigerant and moves with it through the circuit. You don't want to put excess Nylog on valves, but a small amount won't do harm. There are a lot of concerns about Nylog voiding the warranty, but it doesn't actually do that because it's nearly impossible to prove that Nylog caused the issue.

Like oil, Nylog helps connections fit together (even threaded connections) and prevents galling. However, oil and Nylog also reduce friction, which will affect your torque specs when you use a torque wrench to tighten a connection. You don't need to tighten it as much, as you risk overtightening otherwise.

When you apply Nylog, put a little bit on the front and back face of a flare (and the cone of the flaring block if you wish). You can put a small bead on the threads, but it's not an issue as long as you stay aware of your adjusted torque specs (low range). In our experience at Kalos Services, Nylog is particularly useful under vacuum and has helped us make high-quality flares that last a long time. Remember: Nylog is NOT leak lock, and it's not a traditional thread sealant.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

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In this episode of the HVAC School podcast, Bryan and Jim discuss strategies for growing an HVAC business, focusing on the importance of maintenance contracts, consistent service, and effective branding. Drawing from Jim's 15 years of experience running a successful HVAC company in California, they explore how maintenance contracts not only provide consistent revenue but also create valuable training opportunities for technicians.

The conversation emphasizes that maintenance contracts are fundamental to building company value. Jim shares that when he sold his business, the number of maintenance contracts was a key valuation metric. These contracts tie customers to your company, provide consistent work during shoulder seasons, and offer technicians crucial repetitive practice with equipment. Bryan adds that maintenance provides technicians with opportunities to observe normal equipment operation repeatedly, which builds troubleshooting skills through pattern recognition.

Both hosts stress the importance of consistency in growing a business. They note that large, successful HVAC companies aren't always the most technically excellent, but they deliver consistent service that customers can rely on. Jim introduces the marketing concept of "TOMA" (Top Of Mind Awareness), sharing how he used branded coffee bags as thank-you gifts to keep his company in customers' minds even after service calls were completed. The discussion concludes with an examination of White Rogers' contractor branding program, which allows HVAC companies to put their name and logo on thermostats, creating another touchpoint for customer awareness.

Key topics covered:

• How maintenance contracts increase company valuation and create customer loyalty
• Using maintenance as a training ground for developing technician skills
• The importance of consistent processes and documentation when scaling a business
• Creating "Top Of Mind Awareness" (TOMA) with customers through strategic touchpoints
• White Rogers' contractor branding program for thermostats
• Benefits of Sensi thermostats and their app features, including multiple temperature sensors
• Different pricing strategies for customers with and without maintenance contracts
• The importance of documenting extended warranty information on invoices
• How service departments can weather economic downturns better than installation-focused businesses

Get contractor branding on your Sensi thermostats today at https://hvacrschool.com/contractor-branding. 

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 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

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In this short podcast episode, Bryan answers a listener-submitted question about oversized evaporator coils, particularly when they're half a ton or a full ton larger than the condenser.

The expanded performance data contains the information that'll tell you whether the coil is right for the system. However, when it comes to the specific issue of oversizing, there is a common misconception that coil size affects the saturated suction temperature. The truth is that they're not related; you could fully insulate different-sized coils and move the same amount of refrigerant, but they will behave similarly.

The saturated suction temperature (suction pressure, evap temperature) is driven by the heat entering the system. Coils are designed to handle refrigerant flow rates and airflows, so having a lower airflow over a large coil allows for greater cooling due to the bigger surface area, lower bypass factor, and dwell time. When more heat enters the evaporator coil, the saturated suction temperature increases, but some of that heat enters as latent heat and helps with dehumidification. However, a larger coil also takes longer to get colder, and the superheat settings become more important.

You have to be careful with lower face velocities across the evaporator coil, as laminar flow isn't as good at transferring heat as turbulent flow. That is one of the limitations of using a larger coil with lower airflow. If the expanded performance data has a rated match for a larger coil, then that same data will also contain information about the required airflow. Testing in and testing out is also important.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

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In this episode of the HVAC School podcast, host Bryan sits down with building science expert Allison Bailes to dive deep into the world of Energy Recovery Ventilators (ERVs). The conversation explores the critical role of ventilation in modern homes, highlighting how ERVs have become an essential component of maintaining indoor air quality and energy efficiency. Bailes breaks down the technical nuances of ERVs, explaining how these systems not only bring fresh air into a home but do so while recovering both temperature and moisture energy.

The discussion goes beyond simply explaining what an ERV is, delving into the practical considerations of ventilation strategies. Bailes shares personal experiences, including challenges he faced with over-ventilation in his own home, which led to extremely dry indoor conditions. The podcast explores the complex balance of bringing outdoor air inside while managing humidity, temperature, and air quality. Listeners gain insights into why simply bringing in outdoor air isn't always the best solution, especially in climates with extreme humidity or air quality challenges.

Throughout the episode, Bailes and Bryan emphasize the importance of thoughtful ventilation design. They discuss the evolution of home construction, noting how increasingly airtight buildings have made proper ventilation more crucial than ever. The conversation touches on key considerations for selecting and implementing ERVs, including motor efficiency, boost capabilities, filtration, and the impact of outdoor air conditions. The experts provide practical advice for contractors, technicians, and homeowners looking to improve their understanding of indoor air management.

Key Topics Covered:

• The difference between Energy Recovery Ventilators (ERVs) and Heat Recovery Ventilators (HRVs)
• Moisture transfer and vapor permeability in ventilation systems
• Balanced ventilation strategies and their importance
• Challenges of over-ventilation and indoor air quality
• Filtration considerations for ERV systems
• Impacts of outdoor air quality on home ventilation
• Strategies for different climate zones
• The role of ERVs in managing indoor humidity and temperature

Resources Mentioned:

• Allison Bailes' book: "A House Needs to Breathe... Or Does It?"
• Upcoming online ventilation course from Energy Vanguard (expected May 2025)
• Energy Vanguard website: energyvanguard.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 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

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In this short podcast episode, Bryan answers a listener-submitted question asking whether you can use another surge protector at the disconnect panel with an ICM 493 already in place.

Using multiple surge protectors in the configuration described does NOT count as daisy-chaining. Surge protectors with MOVs (metal oxide varistors) shunt current from high voltage to ground by reducing their resistance. MOVs are sacrificial, so they wear out over time. Surge protectors don't last forever, so installing multiple is a fine idea.

You can have whole-home surge protection with additional surge protectors positioned at the appliances/electronics. While it can be done and doesn't hurt anything, it's not the most cost-effective solution. 

When you install a surge protector, wire it in parallel with the circuit to ground. It should be wired properly with the shortest possible path to ground. In any case, many surge protectors won't hold up against direct lightning strikes, but they will protect the equipment from power surges after power comes back on or constant overvoltage.

Our company, Kalos Services, now uses DITEK's Kool Guard 2 as our surge protector and voltage monitor of choice. They also provide warranties for their products, which have come in handy for customers.

Learn more about the DITEK Kool Guard 2 at https://www.diteksurgeprotection.com/product-series/intelligent-voltage-monitoring/. 

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

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In this podcast episode, HVAC professionals Chris Hughes and Adam Mufich discuss the intricate challenges technicians face when commissioning modern inverter-based heating and cooling systems. Unlike traditional single-stage or two-stage HVAC equipment, inverter systems introduce a new level of complexity that can leave even experienced technicians feeling uncertain about proper installation and startup procedures.

The presentation highlights a fundamental shift in how HVAC systems operate, moving from straightforward single-stage systems to sophisticated inverter-based technologies that modulate compressor, fan, and refrigerant flow dynamically. This technological evolution creates significant challenges for technicians, who previously could rely on simple, consistent commissioning processes. The speakers emphasize that modern inverter systems require a much more nuanced approach, with specific temperature ranges, wait times, and verification methods that are not always clearly documented in manufacturer manuals.

Recognizing the industry-wide need for clarity, Chris and Adam have developed a comprehensive spreadsheet resource that consolidates commissioning information across multiple HVAC brands. Their goal is to empower technicians by providing accessible, standardized guidance for working with these complex systems. By sharing their research and encouraging collaboration, they aim to address what they see as a critical gap in manufacturer support and technical documentation.

The podcast serves as both an educational resource and a call to action for HVAC professionals and manufacturers alike. Chris and Adam argue that the industry needs more transparency, better documentation, and a collective effort to standardize inverter system commissioning practices. Their work represents a significant step towards demystifying these advanced HVAC technologies and ensuring that technicians can confidently and effectively install and service modern heating and cooling equipment.

Key Topics Covered:

• Differences between single-stage, two-stage, and inverter HVAC systems
• Commissioning challenges with modern inverter technologies
• Critical factors in proper system startup, including:
  • Outdoor and indoor temperature requirements
  • Wait times for system stabilization
  • Refrigerant charging methods
  • Airflow measurement and verification
• The importance of precise refrigerant charging (superheat and subcooling)
• Challenges with manufacturer documentation and technical support
• The need for standardized commissioning procedures across HVAC brands
• Strategies for verifying system performance during commissioning
• The speakers' collaborative effort to create a comprehensive inverter system commissioning guide

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 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

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Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android