Hvac School - For Techs, By Techs

In today’s short podcast, Bryan discusses buck-boost (auto) transformers and what they do.   Autotransformers are not automatic; the “auto” prefix comes from the fact that autotransformers only have one inductive winding. That winding is shared by the primary and the secondary, so it is not an isolation-type transformer. These transformers run current through the same winding used for induction.    Buck-boost transformers rise or decrease voltage. When the transformer “bucks,” it decreases voltage from primary to secondary, and a “boost” increases the voltage from primary to secondary. In other words, a “boost” is a step up, and a “buck” is a step down on a small scale.   You can only wire these transformers if you use the manufacturer literature. There are many types of autotransformers, and you need to know the exact setup for your transformer’s specific design. Generic diagrams will usually not suffice.   When sizing a buck-boost transformer, you must keep your start load in mind as well. As technicians, w

In today’s podcast, John Ellis joins Bryan to talk about indoor air quality (IAQ). He also explains the ideal process for providing IAQ solutions. John has a lot of experience work as a consultant for people who have respiratory issues.   The HVAC and IAQ fields intersect in the areas of thermal comfort, humidity, building pressures, ventilation, filtration, and source control (which pollutants are present, where they come from, and how we can remove them).   John does not believe in throwing IAQ products at a problem. He believes in a thorough analysis of the structure to present the customer with solutions tailored to their home and needs. Ideally, John would like to see technicians take a process-oriented approach to indoor air quality: investigate, analyze, and quote. He believes in the power of slow, complete diagnosis, including listening to customers’ complaints. Remember, they’ve been living in the structure and can tell you about the issues they’ve noticed in their home and their health concerns.   W

In today’s podcast, Scott Krasman from TZOA, Andrew Greaves, and Kaleb Saleeby join Bryan for a conversation about mental health in the trades. We have a greater awareness of mental health than we ever did before, and although some of us may make fun of the topic, it is something we should focus on as HVAC technicians and business owners.   “Toxic” is a common buzzword these days, but it’s relevant here. A work environment with toxic traits will wear you down over time as you are exposed to disillusioned or selfish journeymen or senior techs at work who disregard your wellbeing and development. Sadly, these behaviors often come from low morale and projection.   HVAC industry leaders can take strides by promoting a culture of inclusiveness and encouraging conversations about mental health. There is also an element of personal responsibility within techs to acknowledge if something is wrong and to have honest conversations with their leaders. As techs, we need to know when to ask for help if we need it. Leaders

In today’s podcast, Jim Bergmann talks about troubleshooting the entire system. He takes a holistic approach to the art of troubleshooting, NOT just an equipment-centered one.   According to NIST, the most common HVAC system problems are duct leakage, refrigerant undercharge, and oversized equipment (often for undersized ducts).   Duct leakage heavily affects the envelope; the equipment only plays a part in conditioning a space. As such, you will want to seal up holes that lead to unconditioned spaces, such as behind the thermostat, to avoid creating negative pressure. When there is that negative pressure, especially close to the thermostat, the home could be at risk of over-cooling.   We check that the filter is clean, but we rarely ever question if the filter is good enough for the home. If the filter does not do a good job of improving air quality, you may consider changing the filter type or reducing the air velocity.   Even though we take temperature and pressure readings from the outdoor units, we somet

In today’s podcast, Steven Rogers joins Bryan to talk about measuring total system airflow.   Fluid measurement is NOT restricted to liquids; a fluid is anything that flows, including liquids and gases. In HVAC, we deal with both of them, but airflow is strictly limited to the flow of gas. The airflow we experience in HVAC is exclusively turbulent flow, NOT truly laminar flow.   Total system airflow is difficult to measure directly; we can use flow hoods, but they have their limitations, especially on systems that have multiple returns. So, we measure pressures that give us clues about the airflow tendencies.   One of the most recognizable measurements is static pressure. Many factors can contribute to poor static pressure, including dirty filters and poorly designed supply and return plenums.    All measurements that you use to calculate static pressure will require an average. You take readings at multiple points of the duct, so you need to calculate an average value, whether you’re using static pressure ti

In today’s short podcast, Bryan explains how growth happens in an HVAC/R career. He also gives tips to get “unstuck” if you feel like you aren’t moving forward.   You won’t move forward if you haven’t set a goal to move forward. Making a “vision board” helps you determine what matters in your life, and it helps you clarify what you’ll need to do in order to achieve your life goals. That way, you can use your career to help achieve those goals and see whose support you need.   Having a growth mindset and a lifelong learning mindset is essential for success. The growth mindset will help you deal with the “growing pains” of advancement (such as occasional failures). People with positive attitudes also tend to see more possibilities for their future careers. On the other hand, negative people are likely to idle in their careers.   You also want to surround yourself with people who will bring out your best. It’s great to be around people who challenge you, have positive outlooks, and are happy for you when you mak

In today’s podcast, Bryan and a team of Mitsubishi Electric Trane HVAC US (METUS) managers (Mike Schaefer, Charles Miltiades, and Sly Grimm) discuss mini-split controls strategies.   Some contractors misunderstand what mini-splits are. Mini-splits CAN be ductless, but not all of them are ductless. Mini-split systems also have handheld controls, but those are not the only control options for mini-splits. Mini-split controls also come in wi-fi, wall-mounted, and wired varieties.   Another common misconception about mini-splits is that they do not work in the cold. While that used to be accurate, modern mini-splits can function well as heat pumps that integrate backup heat. That is especially when it is also tied into a ducted system.   A lot of thought goes into sensor placement, and contractors have many options as to where they can be placed. You can put wireless sensors in discreet locations, such as under the air return in the basement.   Lately, there has been a market shift towards a preference for multiz

In today’s short podcast, Bryan discusses the key factors for system performance WITHOUT doing a deep dive into system commissioning. “Performance” refers to system efficiency, capacity, air filtration/cleanliness, longevity, and the ability to match the latent and sensible loads of a space.   System airflow is the main performance factor to consider. To determine proper airflow (CFM), consult Manuals S, J, and D to perform calculations. In general, the absolute lowest limit is around 275 CFM (in extreme dehumidification mode), and the highest limit should be around 525 CFM (in arid climates or at altitude).    You can determine your CFM target after you set up your ECM motor in the design. Then, you can also check airflow indicators: total external static pressure and pressure drop across the filter. The best way to improve airflow is to reduce pressure drop across the filter and build a better return plenum. For improving overall system performance, make sure the ducts are appropriately sized.    System cha

In today’s podcast, Trevor and Bryan discuss Copeland Scroll Compressor Multiples for Air Conditioning. “Multiples” refer to equipment setups with multiple compressors that have connected suction and discharge lines; they resemble parallel rack refrigeration setups. Multiples typically come in tandem (2) or trio (3) sets. Compared to having a single giant compressor, multiples are more efficient, more reliable, and have the ability to keep running in case if there’s a compressor failure. We often use multiples in rooftop units, makeup air units, and chillers. When you’re working on multiples or troubleshooting multiples, it’s okay to have sight glasses that indicate different oil levels. If you shut the compressors down and restart them, they should equalize. If you have a single compressor failure on a set of multiples, you may have to replace both compressors in a tandem set; the manufacturer does not make single replacements for some tandem models. Check the Application Engineering (AE) bulletin to determi

In today’s short podcast, Bryan clears up the differences between markup and profit margins in HVAC businesses.   The number one mistake that people make in business is confusing markup and gross margin. For example, you can double the price of a $50-part and sell it for $100. That would be a 100% markup. However, your gross margin is NOT 100%; your gross margin is only 50%; you only made a 50% profit on the total sale.    In the same case you have above, you have a 50% cost of goods sold (COGS). COGS is the direct cost of the expenses you paid to sell your service or product. The opposite of COGS is overhead. Overhead includes anything that doesn’t directly bring money to your business (rent, utility bills, etc.). Let’s say that your overhead costs total $30. You’re left with $20 of net profit.   Typically, 10-20% net profit is a good (if slightly idealistic) goal. Net profit can contribute to business growth if you put it into your business. For example, you can use that money for advertising, buying vans,

In today’s podcast, Eric Mele and Bryan explain the planning, layout, and execution of HVAC projects. They mostly cover commercial ductwork but also touch on piping and some residential projects.   Planning   The first step is to review the construction plan WITH a site visit. It is best to see how a plan works within the space; plans may be feasible on paper but may not work out as planned in the actual space.    During the site visit, you also want to establish solid communication with everyone else on the project. As such, it is best practice to have a coordination meeting with the general contractor and other trades (such as drywallers) to communicate potential areas of conflict. (When building ducts in commercial structures, you will want to watch out for conflicts with trusses, joists, fire sprinklers, and plumbing/drains. In residential structures, you will have to watch out for ventilation paths, such as dryer vents and kitchen exhaust vents.)    Before deciding to alter the design, be sure to communi

In today’s short podcast, Bryan explores the differences between startup and commissioning.   Startups typically involve going in during the construction phase after the drywall has been sealed up. (Vents, ducts, and copper piping typically go in before the drywall.) A technician can then perform a startup. The startup includes testing the drain line, checking the charge, checking for leaks, and seeing if the equipment performs its most basic function. (Does the gas furnace make flame? Does the A/C unit blow cold air?)    The startup’s goal is to get the equipment working. A startup does NOT focus on peak performance. A good startup will typically suffice for a cookie-cutter residential construction.    Conversely, the goal of commissioning is to optimize the equipment and test the advanced functions. Combustion analysis, airflow tests, and dehumidification tests all fall under the “commissioning” umbrella. Commissioning is where we use Manual S and Manual J to see if the equipment is appropriate for the home

In today’s podcast, Eric Kaiser and Bryan talk about mentorship in the HVAC industry. They discuss what it means to be a good mentor, how to find a good mentor, and what it means to be mentored.    Mentorship is an organic process. Most mentees don’t go up to someone they respect and formally ask that person to be their mentor. Respect is the foundation of the mentor-mentee relationship; formal mentorship often resembles friendship in many ways.    However, mentorship can take more forms than the traditional mentor-mentee relationship. In the digital age, podcasts and YouTube channels that readily share information about a skill are resources that can fulfill the same role as a traditional mentor.   A good mentor has a willingness to explain the how and why behind a question or process; they don’t give simple answers. Good mentors must also be able to provide resources for their mentees; they know the limits of their knowledge and are willing to find those answers with their mentees. Often, the better mentors

In today’s podcast, Bryan explores the upsides of choosing a career in the skilled trades instead of going to college. He also covers ways to prepare your child for a trades education and career while they are still deciding what to do with their lives.   When we think about what we want for our kids, the following goals come up quite often: purpose, financial upside and reward, freedom from debt, and joy. The trades can offer a lifestyle that covers all of these bases. However, the opinions of our friends and the fear of failing as a parent may prevent us from encouraging our children to enter the trades.    Going to college has plenty of downsides, such as saddling students with debt and not guaranteeing opportunities to move forward in a career.   Alternative career paths include the HVAC/R trades, electricians, off-grid solar technicians, and so on. Your child will learn hard skills on these career paths that are easily transferable. These trades also generally have plenty of apprenticeship opportunities.

In today’s short podcast, Bryan explores triple evacuation. Many people believe that we don’t like triple evac, but that’s simply NOT true. We’re here to set the record straight.   If the manufacturer tells you to follow triple evacuation processes, then it’s a good idea to do a triple evacuation. We won’t argue with that. However, our argument is that triple evacuation can be more time-consuming than it’s worth when it’s NOT necessary.   Deep vacuum technically counts as a vacuum pulled below 500 microns (in residential, that target is usually 200-300 microns). Most modern micron gauges and tools make it easy to achieve a deep vacuum. In a triple evacuation, you pull the vacuum three times (instead of once). Between pulling vacuums, you break with nitrogen before pulling the vacuum back down.   Triple evacuation originated in a time when micron gauges and vacuum pumps were less reliable. We did not take deep vacuum very seriously, especially since mineral oil (MO) typically did not break down inside the syst

In today’s podcast, Bryan explains how he teaches physics. He believes that teaching physics is about continuously building a mental model, and he covers the methods and mindsets that facilitate that learning style.    The basic Wikipedia definition of physics states that it is a science that deals with matter, energy, and their interactions. Even then, we can simplify “matter” to “stuff.” Simplifications like these help students feel more familiar with the subject and NOT feel intimidated by the material. Students learn best when they feel like they can grasp the topics out of the gate. That is why the math-based approaches of traditional education might turn students away from physics. Some students who don’t like math might feel out of their depth when teachers approach topics with a mathematical approach.    Instead, effective teaching is about attaching experiences to a concept. Teachers can take stock of what students already know and build on that. They can also attach experiences to a concept, such as

In today’s short podcast, Bryan explores the dangers of cold tanks during refrigerant recovery.   Whenever you have a recovery tank, you only want to fill it to 80% capacity in the liquid state. The same goes for all sorts of vessels (coils, etc.).    However, capacity isn’t the only factor to consider for safety. We need to know what our maximum temperature will be. You will be in greater danger of overfilling a tank when it is cold because higher temperatures increase the pressure. High pressure in a closed space may lead to explosions. When you fill a tank to 80% under cold conditions, normal temperature conditions could put you in the danger zone (let alone temperatures above 100°F).   So, it’s better to determine your tank fill based on densities at the MAXIMUM temperatures you will encounter, NOT for the measurements at artificial cooling conditions (such as when you put the tank in ice water during recovery).   In the end, just be careful when you’re recovering into a cold tank or using tanks when it’s

In today’s podcast, Nikki and Bryan discuss dehumidification. They cover the relationship between cooling and dehumidification, humidity control, and dehumidifier installation practices.   If the A/C unit is the king, the dehumidifier is the queen. The A/C unit controls cooling and humidity, but it can only do so much. A dehumidifier helps the A/C manage comfort under more demanding conditions. Many factors contribute to comfort, including sensible heat ratio (SHR), relative humidity (RH), and ventilation. Dehumidification reaches all of those factors.   Humidity control requires a holistic approach. Band-aid fixes DO NOT work. Dehumidifiers should work with the A/C system and building design to keep RH in the 50-55% range. Proper installation is vital. For example, tying into the HVAC supply is a recommended practice. Returns are the opposite; dedicated returns are preferred. Other factors to consider are proper sizing, Manual J, and customer expectations.   Join Nikki and Bryan as they cover:   Relative hu

In today’s podcast, Trevor and Bryan discuss how to troubleshoot thermostatic expansion valves (TXVs/TEVs). They also dive into the various types, applications, and components of TXVs.   TXVs are metering devices that control evaporator superheat to protect compressors from harm. Controlling heat also regulates pressure, which improves efficiency and prevents issues like floodback and overheating. TXVs contain several components that manage the forces that open and close the valve. These components include powerheads, diaphragms, springs, and more. The components all contribute to a delicate balance that can be broken when they fail or are installed improperly. TXV failures lead to high or low superheat and eventually compressor failure.    When you diagnose a TXV, you may encounter hunting, broken powerheads, filthy screens, and improperly sized valves. Once you verify the cause of the issue, you’ll likely have to adjust the TXV, replace a component, or replace the whole TXV. That can be a tricky decision th