Hvac School - For Techs, By Techs

In this short podcast episode, Bryan talks about compression ratio and efficiency, particularly how floating or fixed suction and head pressure affect those things. Compression ratio (absolute head pressure divided by absolute suction pressure) closely correlates to efficiency in all sorts of compression-refrigeration HVAC/R systems; the most efficient systems have high mass flow with less compressor work. High compression ratios indicate a greater differential between the head and suction pressures. A lower compression ratio is desirable, but the number has to be realistic; a compression ratio of 1 indicates that the system is off. Medium-temp refrigeration compression ratios are typically around 3:1, whereas low-temp refrigeration can have higher compression ratios (6:1). In commercial refrigeration applications, we can help control the compression ratio with floating suction and head strategies. Floating the suction and head pressures allow the equipment to achieve lower compression ratios and higher equip

This podcast episode is Nikki Krueger (Santa Fe Dehumidifiers) and Bryan's 2023 HVACR Training Symposium session about how we can optimize dehumidification and efficiency to create an HVAC design and humidity utopia. While we attempt to achieve comfort and high indoor air quality in humid climates, we may find challenges integrating these with the HVAC system and getting customers to understand the need for proper dehumidification. Older homes that are built "leaky" allow for uncontrolled infiltration and exfiltration, but newer constructions are a lot tighter and rely on mechanical ventilation to control where the outdoor air comes from and make sure it is properly filtered and distributed. We deal with both sensible and latent BTUs in a home, and we can't treat them as though they're all equal. Many high-efficiency systems have high sensible heat ratios (SHRs) and are designed to remove sensible BTUs very efficiently, but they're not adequate at removing latent BTUs. Ideally, we would rely on an A/C system

This is the episode for you if you've ever asked, "What the flux?" In this short podcast, Bryan explains the basics of flux in soldering and brazing, as well as magnetism. Flux means "flow." In HVAC, "flux" may have two meanings. It may refer to the substance that helps the molten alloy flow and bond to base metals more effectively when you're soldering or brazing. However, flux may also refer to magnetic flux, which is the lines of force that emanate from a magnet; this concept is important in inductive loads like transformers. In soldering, brazing, and welding, flux is a powder-paste or liquid that you apply to the base metal. You usually apply it directly to the male side of the base metal, or it may be embedded in the brazing alloy. Flux prevents oxides (like rust or the black flakes, cupric oxide) from forming on the surface you're brazing, which commonly happens at higher temperatures. Flux helps you create a proper bond, but it doesn't eliminate the need to clean the base metal before brazing. You typ

Steve Rogers from The Energy Conservatory (TEC) returns to the podcast to discuss the impacts of duct leakage on occupant comfort and HVAC system performance. Duct leakage has more significant negative effects in heat pump systems than in furnace systems, especially in climates with high heating, cooling, or latent loads, due to pressure imbalances and moisture problems. You can measure duct leakage by masking off all supply and return registers, attaching a calibrated fan, and running the duct blaster to pressurize the duct work to 25 Pascals.  Exhaust-only ventilation presents many of the same problems as duct leakage, particularly in the humid South. The duct leakage allowable by code (in Florida) is almost equivalent to a 50-CFM bathroom fan. Leakage often happens on the supply side, and it is important to determine whether the leakage is happening on the supply or return side; you may lose significant capacity on the supply side, and you may lose a little less capacity if the leakage is primarily on the

Tom Lorenz from Sensi joins the podcast to talk about the launch of the Sensi Touch 2 thermostat. The Sensi Touch 2 smart thermostat is compatible with room sensors, which makes it an efficient and effective thermostat. Smart thermostats are becoming more common in homes, especially as we focus on HVAC efficiency. Designers are aiming to make smart thermostats user-friendly, aesthetically pleasing, easy to install, and driven by data (via sensors). Installation is easy for contractors, as it relies on push terminals and cleanly covers up the previous thermostat's installation site. The Sensi Touch 2 requires a common wire, but it has easy-to-use push terminals that allow wires to click into place. It also has dedicated accessory terminals for add-on equipment like dehumidifiers. You can also pair the Sensi Touch 2 with its respective app to program the thermostat. Smart maintenance automatically alerts homeowners about poor performance or efficiency. These sorts of alerts can offer peace of mind for the homeo

Eugene Silberstein from ESCO Group returns to the podcast to discuss why and how to create an internal training program for your HVAC/R company. HVAC/R has so many niches, and information and practices are always evolving, so lifelong learning is necessary for the industry. In-house training is a form of education that can come with many benefits, including control over scheduling, building community within the organization, and convenience. However, creating an in-house training program also comes with many challenges, including time and money expenses. For an internal training program to work, there needs to be a clear commitment to lifelong education that is ingrained in the culture. That could include bringing in other educators, setting up mentorship programs, and partnering with local trade schools. Unlike an external training program, an in-house training program also allows you to tailor education to your technicians' goals and needs. A good in-house training program creates an environment of psycholo

In this short podcast, Bryan talks about the times when subcooling is meaningless. It is important to understand subcooling fully before using it as a charging or diagnostic method, particularly in refrigeration systems. When we need to charge TXV systems in residential HVAC, many technicians rely on subcooling to set the charge. However, refrigeration systems don't quite work the same way; charging a refrigeration system by subcooling may lead you to overcharge the system. We take subcooling on the liquid line between the condenser and the metering device. The condenser takes superheated vapor and rejects heat. This process turns the superheated vapor refrigerant into a liquid-vapor mixture midway through and subcools the liquid refrigerant at the bottom of the condenser. That liquid "stacks" at the bottom of the condenser. Adding more refrigerant will cause more liquid refrigerant to stack up at the end of the condenser and increase subcooling. These conditions can cause an increase in head pressure. Howeve

Craig M (AC Service Tech) returns to the podcast to talk about solving work-life imbalance, especially for HVAC/R technicians who have children and families of their own. Our actions tend to be driven by our priorities, which vary at different stages of our lives. Someone's work-life balance could also vary depending on different parts of the year. When we let the right people into our lives and are surrounded by supportive communities, we can reconfigure our personal and career trajectories to keep them in line with our priorities. To create a healthy work-life balance, we must be open to investing in others and letting others invest in us. "Balance" implies a constant state of evenness, but for people who work many hours, own a business, or have a family, their time may not be perfectly balanced at all times. That sort of variety presents a challenge, but it also presents opportunities for us to invite wise counsel and maintain communication to make sure we're on the same page as the important people in our

In this short podcast, Bryan explains how rules of thumb (ROT) can cause duct issues. He talks about the role of friction rate in duct design as well as its intent and limitations. Friction rate is a value located on duct calculation tools, including Ductulators. We use friction rate to predict the operating static pressure of the system, but it is often misapplied when people design their ductwork around rules of thumb. The friction rate is expressed in inches of water column ("WC), which we also use to measure static pressure. However, the operational static pressure and friction rate are NOT the same things. Ductulators provide information about friction rate based on 100 feet of straight ductwork in the size selected, which we almost never see in the field; fittings and turns add effective length (EL), so the total effective length (TEL) is often more than 100 feet. When duct designers apply rules of thumb, like a 0.1" friction rate, and apply it to the CFM, they don't consider the actual length of the du

Craig Migliaccio (AC Service Tech) returns to the podcast to talk about what it means to have the heart of a teacher. Craig discovered his passion for teaching while instructing apprentices on the job, and he went into institutionalized teaching from there. He chose to overcome several administrative obstacles to become eligible as a teacher at technical schools, and that perseverance is one aspect of the "heart of a teacher." One of the most rewarding aspects of teaching is the investment in others. For Craig, HVAC is a tool for supporting someone's family, and a teacher can find a sense of purpose in helping people be better HVAC practitioners. When good teachers invest in their students or apprentices, they give those people a reason to take pride in their work. The job of a teacher isn't to give students the answer, which can be frustrating for students and the teachers of those frustrated students. People who have the heart of a teacher allow students to learn things themselves and be frustrated when the

In this short podcast episode, Bryan explains why saturation can be CONFUSING and clears up some common misconceptions. Saturation applies to dehumidification and refrigerant inside the system. Generally, saturation is the state at which a substance can no longer hold or absorb any more of another substance. When air is saturated with water vapor and can hold no more, it is at the dew point or 100% relative humidity; it will condense on any surface below the air temperature. Air isn't like a sponge that absorbs water vapor; saturation deals with vapor pressure, particularly the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases in a closed system.  Dehumidification is the process by which we remove moisture from the air; this process improves comfort across a significant portion of North America during the summer months, and it prevents fungal growth inside the home. Air in a dehumidifier or an HVAC system in cool mode makes contact with a surface at a temperature below the dew

Kevin Hart from HAVEN returns to the podcast to talk about ventilation in humid climates and some best practices for working on systems that focus on the V in HVAC. HAVEN focuses on IAQ management with the use of software technology. HAVEN started off with its central air monitor, and the company then developed a central air controller to help customers make their homes healthier. Fresh-air ventilation is one IAQ, but humid climates make it tricky to bring that air in; dumping “fresh” air into the structure without taking extra precautions can lead to high indoor humidity and even microbial growth.  ERVs, HRVs, and ventilating dehumidifiers are some traditional ventilation strategies for various climates; exhaust ventilation is also quite common but can pull hot, humid air through the building envelope. HAVEN is creating a more templated approach to ventilation; HAVEN uses whole-home in-duct monitoring and local weather data to get ideas of the conditions inside and outside the home to tailor fresh-air ventil

Dominick Guarino from NCI joins the podcast to talk about the High-Performance HVAC Summit, an upcoming event hosted by NCI from April 17–20. The National Comfort Institute (NCI) is a training organization that helps technicians learn crucial skills and succeed through high-performance contracting. High-performance contracting is based on the mindset of “don’t just promise performance; prove it.” To maximize technicians’ potential, NCI teaches technicians how to test equipment properly and monetize their skills. Techs can then use their knowledge to teach the homeowner about the system and solve problems with sales; they can earn money while being solutions-oriented. NCI’s High-Performance HVAC Summit is a training event geared toward HVAC business owners and contractors. It started as a membership conference for education and networking, and it has since expanded to include like-minded HVAC professionals from all walks of life. Workshops are led by a mix of contractors and NCI staff, and there are breakout s

In this podcast from AHR 2023, Tony Gonzalez from Fieldpiece joins Bryan to talk about training, combustion, and more. Fieldpiece has a new combustion analyzer that reduces the cost of tool ownership and maximizes the tool's uptime, namely by using a long-lasting sensor. The combustion analyzer's oxygen and CO sensors seal up when the combustion analyzer is turned off, which pauses degradation. The sensors are also field-replaceable and come with a 4-year warranty. The CAT85 also has a built-in dual-port manometer (which can measure static pressure) and can measure a live draft pressure during combustion analysis. Some common misconceptions exist around combustion analyzer sensor lifespans and calibration. The sensor life refers to how long a sensor can output a signal to generate a reading; it doesn't refer to the accuracy of the sensor at the end of its life. Calibration keeps the sensors accurate, especially because sensor accuracy tends to degrade over time. To get the most out of your sensor, yearly cali

In this podcast from AHR 2023, Brandon Marshall from Chemours and Chris Forth from JCI talk about the future of refrigerants and Opteon XL41 (R-454B). Refrigerant regulations are changing to pave the way for lower-GWP refrigerants, but M1 is also in full swing. M1 refers to the U.S. Department of Energy's implementation of the new efficiency standards for A/C units and heat pumps (SEER2, EER2, etc.). These standards changed the equipment testing procedure to match field conditions more closely. Opteon is the next-generation portfolio of low-GWP refrigerants for Chemours as a successor to the legacy refrigerants in the Freon product line. These refrigerants are a response to the HFC phasedown outlined in the AIM Act. JCI chose to use Opteon XL41, an HFO, for its equipment due to Opteon XL41's low GWP compared to R-32 and because of the similar operating pressures and temperatures to R-410A. A2Ls are a permanent change in the industry, and their safety considerations and best practices are here to stay. However

In this podcast from AHR 2023, Jim Bergmann and Joe Medosch talk about measureQuick and the ways it's EXPLODING with growth and new features. They also talk about heat pumps, electrification, and other hot topics in the industry. Jim Bergmann recently released an open letter about heat pumps on LinkedIn; he addressed the shortcomings of the industry from a skill standpoint. The lack of training and standards may be mitigated with proper training (and an understanding of building science fundamentals) or by embracing hybrid systems. Heat pumps may also perform relatively poorly during extreme weather events and may not manage temperature swings well. MeasureQuick has recently been working with ACCA and formed other partnerships to allow for standardization (for companies and the industry as a whole). More companies are also integrating with measureQuick, especially TEC and their TrueFlow Grid; accuracy across brands tends to be pretty consistent, and measureQuick allows you to mix and match tools. The customer

Genry Garcia returns to the podcast to talk about pressures in the building envelope, namely the infiltration skeletons behind closed doors. When doing load calculations (Manual J), we need to know how much of the heat load, especially the latent heat load, comes from leakage in the building envelope and the ducts. Opening/closing doors and windows can also worsen the issues that stem from infiltration due to upsetting the balance of pressures in the home. Smoke pencils and other similar tools can give you an idea of the pressure in a home and how it could change when doors open or close. Since there is a lot of room for inaccuracy in extreme climates (especially those with high latent loads), many HVAC systems are oversized and underperform. Some building design features also exacerbate problems presented by oversized HVAC systems. To get the data we need to design systems that mitigate those issues, we need to do a blower door test. Downsizing the tonnage in retrofits or replacements usually has advantages,

In this episode recorded live at AHR Expo 2023, Nick from INFICON joins Bryan to talk about leak detectors and how we can improve our understanding of them. Some leak detectors, including the INFICON Stratus, measure concentrations in PPM (parts per million). When measuring PPM, we have to keep in mind that it doesn't indicate the size of the leak or leak rate, but it does help us pinpoint the leak location. In some cases, we also have to watch for automatic zeroing capabilities. Leak detectors come in many varieties, including heated-diode, ultrasonic, and infrared; each type has unique maintenance needs. Heated-diode leak detectors are sensitive, but their sensors wear off with frequent use and will require replacement. Infrared leak detectors use infrared absorption and don't degrade over time the way heated-diode leak detectors do. An ultrasonic leak detector picks up the sound of refrigerant and air leaking out of a hole to pinpoint the leak. It's a good idea to approach leak detection with a plan, inclu

In this episode recorded live at AHR Expo 2023, Dustin and Jim from Copeland/White-Rodgers join Bryan to talk about the use of heat pumps in cold climates. They talk about the history of heat pump innovation and talk about changes to come. Variable-speed and two-stage compressors, as well as advanced controls, make it easier for contractors to control sizing and for heat pumps to perform to acceptable standards in cooler climates. Contractors in cold climates also rely on dual-fuel models that use electric and gas heat, which makes it easier for the system to move the desired amount of heat. Variable-speed and two-stage compressors help the system deal with different heating and cooling capacities; in cooling mode, these technologies can also help with latent removal if the blower is also able to vary with the compressor.  Advanced controls, especially universal controls, also help with defrost management, a key component of heat pump performance. When defrost is managed effectively, customers can yield energ

In this episode recorded live at AHR Expo 2023, Matthew from JCI (Johnson Controls) joins Bryan to talk about rooftop unit (RTU) retrofit facts and considerations. When doing an RTU retrofit, you want to make sure you know the budget before anything else; larger budgets will allow you to implement things like VFDs and even VAV technology. In many cases, you may consider adding an economizer for "free" cooling and energy savings. You also want to know what you will get out of a retrofit in terms of value, especially when it comes to system efficiency and longevity. Some common IAQ upgrades for RTUs include improved filtration, especially with MERV 13 filters. Economizers also allow you to control the amount of outside air with the help of an exhaust system or even barometric relief. UV lighting can also be used in light commercial RTUs. When doing a retrofit, you'll want to pay attention to the existing equipment's footprint. Sticking to that footprint will make the replacement aspect easier. The utility and e