Hvac School - For Techs, By Techs

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

Ed Janowiak joins the podcast to introduce us to ACCA Manual T. Compared to other manuals, Manual T is one of the least-considered ACCA manuals. However, it’s the manual that advises us on how not to blow high-velocity air on people and has maintained the same standards since the mid-1900s. Unlike Manuals J, S, and D, Manual T is not recognized in code compliance. Manual T deals with air distribution; it helps us find out the throw and spread, which informs our ductwork design in Manual D. We need to know the customer’s expectations and the air velocity we’ll need to manage at the registers before designing the ductwork. Register placement is also a critical element of Manual T. Throw and spreqd can vary wildly, and register selection and placement are going to have a significant effect on comfort as a result. Register placement on the ceiling may achieve the Coanda effect to assist with air distribution, and that can be especially useful in low-load or passive homes. Low-load homes are an interesting case, a

In this short podcast, Bryan explains what the net refrigeration effect (NRE) is and how it affects HVAC systems. The net refrigeration effect (NRE) is what happens in the evaporator coil. The evaporator is the heat absorber; as air passes over the coil, the cooler refrigerant within the evaporator absorbs that heat and boils. The NRE is the net energy change that occurs during that process. You can plot the NRE on a pressure-enthalpy chart. When air moves over the evaporator coil, there is a change in enthalpy or BTUs per pound in the refrigerant (usually called delta h). There should be more BTUs per pound in refrigerant exiting the coil than when it went in. We have to know how many pounds of refrigerant we’re circulating (mass flow rate) and how many BTUs are in those pounds. Many of those BTUs come from latent heat transfer, which happens when the refrigerant boils. When refrigerant undergoes a phase change, it remains at a constant temperature (sensible heat), but it continues absorbing heat. The heat a

Eric Kaiser returns to the podcast to talk about how we can use systems thinking to approach gas appliances and combustion in HVAC installation and service. Gas lines can be made of a few different materials, including black iron, copper, and CSST. These all have benefits, setbacks, and appropriate applications. For example, copper is common in propane (LP) systems but not natural gas. In coastal environments, galvanized pipe tends to be most common due to the increased likelihood of corrosion. Gas lines may also need sleeves to prevent them from interacting with moisture. The piping also needs to be routed in accordance with code; in many cases, joints need to be exposed so that a technician can check for leaks. Keeping joints inside walls is risky, especially when light switches cause sparks and could potentially ignite leaking natural gas. In any case, leak detection can be tricky unless you have a combustible gas leak detector and bubbles that work well for gas lines. Safety has to be the top priority whe

Some admins from the HVAC School Facebook group join the podcast to discuss the art of moderating a successful community. Bryan is joined by Eric Kaiser, Ty Branaman, Michael Housh, and Neil Comparetto. A community based on a skilled trade gives people an inviting space to share information and ask questions. It’s also a space that allows people to practice how they present information. Groups also connect people across geographical locations, and we can get regional perspectives that change the way we think about things. However, community standards are necessary to keep groups professional and on-topic. Swearing is a slippery slope that may lead to personal attacks, which make the community hostile and unhelpful. The main goal is to keep a respectful atmosphere, and moderators have to draw the line somewhere, but there’s a difference between cultivating a productive atmosphere and being dogmatic. People who interact in those communities need to do it for altruistic reasons, not to satisfy their egos. Giving

Eric Kaiser returns to the podcast to discuss high-voltage wiring, low-voltage wiring, and condensate assemblies as they relate to systems thinking. On the high-voltage side, the disconnect should be in a secure location, and it should be able to keep water out. The wires should be appropriately sized, have an appropriate level of tension, and should not be vulnerable to chafing or abrasion. Overall, best practices include using proper grommets and ensuring that you have a solid connection. Do not run high voltage wiring in parallel with low-voltage or control wiring. It’s also worth noting that double-lugging is a poor practice that is against code. On the low-voltage side, you also need to be careful of where you route your wires to avoid induction, contact with hot surfaces, or abrasion. The insulation ratings also need to be appropriate. We can think of the condensate assembly as its own system. Condensate drains have uphills and downhills, and they may have traps, vents, and cleanouts throughout. Cleanou

Eric Kaiser returns to the podcast to talk about how copper, piping, and line sets play into systems thinking. Nowadays, we have to think about POE and PVE oil, and we need to design line sets in a way that assists with oil carry while preventing liquid refrigerant migration. The height of the evaporator relative to the condenser is a major factor to consider during the design phase. Especially when chases are run underground, we need to watch for possible threats to the copper. Water softener discharge and excess pool water may damage the copper over time, and systems should be designed to keep line sets away from those. In many cases, Florida chases are sealed with mastic, which doesn’t prevent water from getting in (but does prevent rodents and insects from entering the home. Flowing nitrogen is one of the best practices you can do while brazing. Nitrogen displaces oxygen, which contributes to oxidation and produces scale. When cutting copper, you will also want to make sure that you don’t get copper shavi