Hvac School - For Techs, By Techs

Alex Meaney returns to the podcast to explain why it REALLY gets hot upstairs and what we can do about it. He also talks a bit about his new business. Heat technically doesn’t rise; warm air is less dense than cooler air, so cooler air sinks as warmer air rises. In many cases, people blame stratification and the stack effect for warm upstairs areas, but there may actually be other issues at play, especially if the issue only seems to happen in the summer.  Many apparent convective problems are actually due to building science errors, especially poor insulation when walls are exposed to attic space. When air moves via convection, it brings the heat it contains with it, which can contribute to comfort problems. To help figure out what is going on, try to see what the floor temperature is; a cold floor usually indicates a building design mistake, particularly a joist bag problem.  Some of the solutions that may sound good aren’t actually that effective, including placing return ducts higher. In many cases, we ha

In this short podcast, Bryan busts the common electrical myth that single-phase 240v power is really two-phase power. When power goes into a structure that runs 240v appliances, we may understand that two 120v sine waves are 180 degrees out of phase with each other, but that isn’t 100% accurate. If we were to use an oscilloscope to watch the electrical sine waves, we would see two sine waves 180 degrees out of phase because the transformers are center-tapped. Center-tapping creates a neutral center point that becomes our reference. The transformer has two sides: a primary and a secondary. The number of wraps on each side is proportional to the other, and the number of wraps also dictates whether a transformer steps the voltage up or down. However, when you use the center tap as a reference, that also makes the voltage appear to be halved.  In many residential structures, a single phase of power goes into the transformer from the power company. If you were to use the center tap as your reference on each side o

Moe Hirsch joins the podcast to discuss the hydronics side of the industry, particularly focusing on Dan Holohan’s Pumping Away and exciting developments in the hydronics market, especially regarding electrification. Pumping Away is many people’s entry point to hydronics. It contains some good basic information about boilers, especially when it comes to learning about the pressures involved in pumping and how the components manipulate pressure throughout the system.  Boilers use many of the same fundamentals as compression-refrigeration HVAC systems; pressure drops are similar, as are phase changes in steam boilers. Boilers also employ pumps instead of compressors, but the processes are similar.  The pump or circulator makes a pressure differential within the boiler, which adds pressure to the circulator outlet and results in negative pressure on the suction side. However, problems like air bubbles and magnetite buildup can negatively impact performance. The electrification side of the boiler industry is exci

In this short podcast, Bryan busts the myth that hard starts reduce the start current on the run winding of a compressor. A single-phase motor’s main winding is the run winding; it has a lower resistance and a higher current than the auxiliary winding, also known as the start winding.  Hard start kits are often used on HVAC systems with single-phase compressors (which usually have PSC motors). These kits usually consist of a start capacitor and a potential relay, which takes the start capacitor out of the circuit. We don’t typically use hard starts on three-phase motors or ECMs. Single-phase compressors often have to start under a big load, especially in long-line applications (at the manufacturer’s recommendation) or if the compressor simply has a hard time starting. In cases where you have a voltage drop or low voltage, particularly due to long branch circuits, you may also use a hard start kit. However, they do NOT reduce the starting current or “save” compressors. Hard starts reduce the time-averaged star

Andy Holt joins the podcast to talk about what it means to be a 24-Hour Technician. We talk about what it means to be HVAC/R technicians AND deal with the human aspects of our lives at the same time. Service technicians differ from installers in that they do much of their work solitarily. They spend a lot of time by themselves. They’re also on their feet very often and may do emotionally exhausting work, but they can earn a respectable living and accumulate savings for the future. To make our work and the emotional burdens that come with it more manageable, we can try to control how we react—take out head trash. Most people—but especially technicians—experience anxiety, and worrying about things takes a major toll on us. We also may need to apologize to people who we simply can’t access. Andy goes over some of his best tips for dealing with those sources of worry. The goal is to eliminate negativity—clearing up negative aspects of your life and not being weighed down by individuals who negatively affect your

Jim Bergmann returns to the podcast to talk about furnace commissioning procedures and the development of measureQuick 2.0. MeasureQuick 2.0 has been a collaborative effort between Jim Bergmann and Joe Medosch, and it comes with an upgraded user interface that allows for faster operation and easier system data access and storage, and it works with more tool manufacturers’ tools. Gas furnaces need to be commissioned to reach their maximum potential (and lifespan). MeasureQuick 2.0 provides commissioning instructions and recommends starting with a visual inspection, including the flame rectification system (rod, circuit board, and grounding). Electricity is conducted during the flame rectification process—only in the microamp scale—so a dedicated circuit is crucial to keep it working as it should. When commissioning a high-efficiency furnace, we should make sure the condensate drain cannot become clogged. The filter should block the airstream completely and not allow for any bypass, which could make the seconda

Mike Klokus and Jeff Crable walk us through Kalos Services' light commercial PM process.  First, we verify that everyone is clear on the agreement. Then, we start the PM with a thorough visual inspection, taking copious notes about things that look concerning.  Once we’ve done a visual inspection, we clean the condensers. We try to use only water when possible, though safe cleaners may be necessary in some cases. When checking the electrical components, we make sure the wires are neat and have tight connections. We take our electrical readings and check the capacitor. Then, we check the system’s refrigerant temperatures and pressures. We measure the superheat, subcooling, and pressures throughout the system and record those. Once we move indoors, we check and replace the filter in accordance with the agreement. We do another visual inspection at the air handler, paying special attention to blower wheel cleanliness, panel insulation, and wire routing and connections. When cleaning the evaporator, we want to tr

In this short podcast, Bryan covers a common electrical myth about wire length and its relationship with the National Electrical Code. The NEC is concerned with safety—protecting buildings and people—but less so with making sure things work. Wire sizing is a common topic, and length is important because it can contribute to the voltage drop in a circuit. In many cases, we refer to the MCA (minimum circuit ampacity) to select an appropriate wire size.  If you run more current through an undersized conductor, it gets hotter and will experience a voltage drop—though not proportionally. It’s worth noting that nothing in the circuit is fixed; voltage, amperage, and resistance all follow Ohm’s law but are variable as different things start happening in a circuit. In many cases, the NEC generally doesn’t require us to size conductors to accommodate for voltage drop. Conductors have some degree of resistance, so longer wires will result in a greater voltage drop than you would see in a shorter wire. It makes sense fo

Trevor Matthews, the founder of Refrigeration Mentor, returns to the podcast to talk about why CO2 matters in commercial refrigeration and even HVAC applications. CO2 (R-744) has entered the residential HVAC sphere in some places around the world, though it hasn’t come to the North American markets yet. CO2 is one of the most eco-friendly refrigerants on the market, with a GWP of 1, and it’s very good at moving heat. However, CO2 has some challenges, including its low critical point and higher pressures.   CO2 comes with some safety concerns, and its systems have a complicated infrastructure. Since CO2 can exist as a liquid, vapor, or solid under operating conditions, you could end up with dry ice in the system. These issues require skilled, attentive technicians. As the industry moves to natural refrigerants like CO2 and hydrocarbons, we need to stop the race to the bottom. Technicians need to learn how to take their time and do the job right when they work on CO2 equipment so that they can be safe and save

This podcast is Bryan’s full-length electrical basics class for the Kalos technicians. He covers electrical theory and circuit basics. Volts, resistance, and amps all affect the behavior of electricity in circuits. These are also critical factors in electrical safety. Watts and kilowatts come from the multiplication of the volts and amps, though not every volt-amp does work; the power factor indicates how much work the volt-amps are actually doing. Some of the volt-amps are reactive (kVAR) and don’t do the real power of watts. Electrons move by interacting with other atoms. Substances can be conductors or insulators, and conductors have very few valence electrons, which move in and out of other atoms easily. Insulators have many valence electrons and are more stable. Insulators have high resistance, and conductors tend to have low resistance. Circuits consist of loads, switches, and power supplies. Loads actually do things and consist of light bulbs and motors. Switches pass power and don’t do work. Power sup

In this short podcast, Bryan debunks the myth that electricity only takes the path of least resistance. It is true that more current will typically take paths of lower resistance; it’s much easier for more electrons to flow through a path with lower resistance, which is consistent with Ohm’s law. Ohm’s law states that a circuit will have higher current with you have lower resistance so long as the voltage stays the same.  In most cases, the voltage stays relatively constant; transformers don’t often need to limit their currents, so there usually isn’t a voltage drop. When power supplies are regulated, the voltage is usually fixed, not the amperage. As a result, dropping the resistance in a circuit will increase the current.  Ohm’s law holds true for both resistive and inductive loads. Inductive loads, however, are a bit tricky because the resistance isn’t constant. As motors spin faster, they create back EMF or impedance, which is magnetic resistance. The resistance only shows up once a motor, solenoid, or an

Nikki Krueger from Santa Fe Dehumidifiers returns to the podcast to talk about dehumidification equipment and strategies in the shoulder seasons (spring and fall). The shoulder seasons (and the weeks leading up to them) are when many homeowners begin to notice moisture problems in their homes. HVAC units and dehumidifiers should have a king-queen relationship. The HVAC unit is the king and controls the bulk of temperature and humidity during the day, but the dehumidifier can take care of the humidity when the king needs help. To remove moisture optimally, an HVAC unit needs longer runtimes and a cold evaporator coil. However, there will still likely be gaps in performance, and that’s when the dehumidifier can step in.  Proper equipment sizing can help us achieve better runtimes; we want to avoid oversizing the HVAC equipment, but oversizing is a bit less critical when it comes to installing dehumidifiers. The actual install configuration is more important when it comes to dehumidifiers (i.e., whether it takes

In this short podcast episode, Bryan gives some quick tips for time management. You can save a lot of time by prioritizing what really matters and delegating tasks. One of the simplest but most effective ways to manage your time is to use a calendar. You can even apply the calendar to your personal life; you can get into a habit of scheduling important appointments, deadlines, and tasks. Google Calendar also allows other people to see and interact with your schedule, so it’s a great tool for scheduling performance reviews, interviews, and meetings. When you prioritize things, think about the negative and positive impacts of each thing. The ones with the highest positive and negative impacts should take priority over things with less significant positive or negative impacts. Many of the major business initiatives take place in the slow season, and many of our urgent client issues take priority during the busy seasons. Delegating is also a critical task. Just because you can do something, that doesn’t mean you

Eric Kaiser returns to the podcast to talk about how to become a better mentor. He explains the topic from the perspective of a mentor and a mentee. The goal of mentorship is to pass your knowledge on to someone else. When you give someone the knowledge to succeed in the HVAC/R trade, you move the trade forward and allow yourself to try new career opportunities when someone can replace you. Some of the most effective mentorship strategies establish the mentor as a guide rather than someone who spoon-feeds the mentee. Mentorship is about supporting discovery, which also builds the relationship between the mentor and mentee. Mentors can also learn from their mentees when they allow their mentees to discover the answers to their questions. Mentors can also benefit their mentees by talking about health, especially mental health. Those who have been in the trade a long time may know how to draw boundaries between their work and their personal lives; mentees can benefit from open discussions about those things, and

Eric Kaiser joins the HVAC School podcast to talk about HVAC measurement types and the benefits of taking each one. He also talks about point measurements and data trends. Point measurements include static pressure, voltage readings, and readings provided by gauges. We only take those measurements once. However, when you track those on several occasions over time, you can build data trends. Single-point measurements give us information about what is happening at the moment, but they don’t give us a long-term view of the system's health. Absolute and differential measurements also have different purposes entirely. Absolute measurements require us to compare a reading to a specific, unchanging reference point, but differentials compare one measurement to another. When we turn point measurements into trend measurements, we can see some degree of causation. Changes in data trends indicate that a problem occurred at a certain point in time and could be due to changes that coincided with the deviation from the norm

Genry Garcia joins the podcast to give an intro to ASHRAE Standard 62.2. He and Bryan also share a nice rant about accountability in HVAC design. Standard 62.2 is the ventilation standard for low-rise residential buildings, which dilutes airborne contaminants like VOCs and CO2. Before coming up with a ventilation strategy, we need to assess the leakage rate of the building, such as via a blower door test. However, we also need to consider how bringing in outdoor air might negatively affect efficiency and comfort if we don’t do it right.  Exhaust ventilation removes air from the structure and relies on infiltration to bring air back in. Instead, we can use controlled intake air, which is brought in from the outdoors instead of unconditioned spaces in the home.  Ventilating dehumidification is a strategy we can use to comply with 62.2; we can bring in filtered outdoor air and dehumidify it before injecting it into the supply ductwork. When we introduce ventilation in a Florida installation, bringing it in throu

RACT manual co-author Eugene Silberstein joins the podcast to talk about the titular topic of his book, Pressure Enthalpy Without Tears.  Pressure Enthalpy Without Tears is a book that introduces engineering concepts to HVAC technicians in a way they can understand and apply in the field. Enthalpy is a fancy way of saying “heat,” and we use it to refer to the total heat content (BTUs). The pressure-enthalpy chart shows the relationship between the refrigerant pressure and enthalpy in a system; it’s like a P-T chart that shows the relationship between heat content instead of temperature.  Each refrigerant has its own pressure-enthalpy chart, but the points and lines on the chart usually form a right trapezoid. Dirty air filters and other less-than-ideal conditions can distort the trapezoid or shift it on the chart. Each side of the trapezoid represents the refrigerant inside a major component of the HVAC system: evaporator, compressor, condenser, and metering device. The pressure-enthalpy diagram allows you to

In this short podcast, Bryan talks about THOR, total heat of rejection. He explains what it is and why we should care about it when working on HVAC/R systems. THOR is another aspect of pressure-enthalpy calculations, along with net refrigeration effect (NRE) and total heat of compression. When we talk about system capacity, we’re often referring to heat absorbed in the evaporator coil (NRE).  Heating is on the opposite side of the coin; when we bring heat into a home, we care more about how much heat is rejected than absorbed. That’s where THOR comes in. More heat is rejected at the condenser than absorbed in the evaporator. The total heat content increases due to additional heat being absorbed in the suction line. Compressors also have motors that aren’t 100% efficient, so a bit of inefficiency also adds a small amount of heat to the refrigerant (in a system operating normally). All of that heat adds up to the total heat of rejection (THOR).   Even though a higher total heat of rejection is desirable when we

Matteo Giovanetti from Micro-Air joins the HVAC School podcast to talk about the differences between a hard start and an EasyStart. Micro-Air’s “EasyStart” provides a soft start rather than a hard start. A hard start abruptly ramps up the voltage and current to the motor start; a soft start is a much gentler start that results from a gradual voltage and current increase on the start AND run windings.  The EasyStart marks a paradigm shift in how we think about “saving” compressors. It attempts to avoid drawing unnecessary inrush current, which is very common with hard starts. Hard starts may even lead to premature failure if the potential relay fails and can’t take the start capacitor out of the circuit.  EasyStart has a different wiring configuration compared to hard start kits. A hard start kit consists of a start capacitor wired in series with a potential relay, which increases the torque on the compressor and removes the start capacitor from the circuit. The EasyStart has four wires; the black and white wi

In this short podcast, Bryan explains what the heat of compression is and why we should care about it as HVAC/R professionals. More heat is rejected in the condenser than absorbed in the evaporator coil, and that’s because the compressor adds heat. That added heat is called “heat of compression.” That heat does NOT contribute to the net refrigeration effect (NRE), as it doesn’t contribute to cooling. When we compress something, we increase the system entropy during that process. Entropy is the waste and disorder associated with work. There is some inefficiency, which we see in the form of additional heat. So, the HVAC system needs to reject that additional heat of compression, and we can plot and track reversible changes by following lines of constant entropy. As the temperature increases, the molecules begin moving more quickly. However, the refrigerant doesn’t absorb many more BTUs in the compressor (in a properly operating system). The temperature spikes, but the compressor doesn’t typically add a signific