HVAC School - For Techs, By Techs

Phil Barr and Nathan Orr join the podcast to talk about wiring refrigerated cases in commercial spaces, including convenience stores and supermarkets. Cases may be medium-temp (or high-temp, in some cases) or low-temp. Medium-temp cases can typically defrost on their own during the off cycle, and low-temp cases may have electric or hot-gas defrost to help get ice off the coil at set intervals. Each system has an evaporator (and fans), compressor, condenser, and metering device (often a TXV or EEV), and low-temp refrigeration may have anti-sweat heaters, EPRs, and other components to manage. Challenges arise when electricians don't understand the fundamentals of commercial refrigeration, especially as the electrical circuitry relates to the refrigeration circuit components. Time crunches also apply a lot of pressure to electricians and refrigeration technicians. Testing circuits, such as fans and lighting, or using circuit tracers are good ways to get an idea of how an existing system is wired. Labeling wires and breakers and keeping those labels or information in places where others can read them can help you and other electricians in the future. One of the most common issues happens when technicians or electricians refuse to test out their results to catch their mistakes before callbacks happen. Even seemingly small electrical issues, such as improper lighting, can cause costly losses if product spoils and cannot be sold. Phil, Nathan, and Bryan also cover: Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

This podcast is a class taught by Bryan: Things to Keep Out of the System. He covers some installation best practices along the way to keep contaminants and non-condensable gases out of the system. We want to keep air, water, dirt, copper shavings, solvents, and nitrogen out of an operating system. All we want in an operating system is the appropriate oil and refrigerant for the system. Unfortunately, the POE and PVE oil we mostly use in residential systems nowadays are very hygroscopic; they attract water, and POE mixes with water to form acid, another thing we want to keep out of the system. We can pull most of the moisture out of the system by pulling a deep vacuum and following the best practices for a fast and deep evacuation. However, we can also reduce the probability of moisture getting into the system in the first place by NOT working on copper while it's raining outside, sealing the copper tubing adequately when routing it underground or in a chase (a common installation practice in Florida), and insulating it properly. Dirt can easily get into the system when we're modifying piping, especially when adding fittings or reaming, but we can use nitrogen or line set cleaners to flush it out. Purging the lines and flowing nitrogen while brazing also help keep air and water vapor out of the copper lines. When deburring, try to avoid letting the burr or copper shavings from falling into the tubing. Bryan also covers: Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this short podcast, Bryan talks about air changes per hour, also known as ACH, and what it means in HVAC design and indoor air quality (IAQ) discussions. ACH tells us how frequently the entire volume of air in a room or structure is replaced; we are referring to the cubic feet of air leaving a space and then being replaced within that same space. If we have a balanced number of cubic feet per minute (CFM) of air supplied to and returned from the room in one hour, we would multiply that CFM by 60 to get the ACH, as there are 60 minutes in one hour. ACH should not be used to calculate heat loss and heat gain, even though BTUs are moved with air. ACH is a practical guideline for HVAC design. Ventilation needs will vary based on the purpose of a room and the number of occupants in it, and ACH tends to be a more important factor for determining how we can meet ventilation needs in commercial and industrial structures than in residential structures, in which we mostly rely on Manual J calculations of sensible and latent BTU gains and losses. However, we should not confuse ACH with outdoor air ventilation requirements as described in ASHRAE Standards 62.1 and 62.2. ACH also comes into play when it comes to infiltration and the tightness of an entire structure. When used in the context of blower door testing, the ACH will tell us if a building meets tightness standards. There is also a term called ACH50, which refers to air changes per hour at the standard pressure for blower door testing: -50 Pascals. ACH50 does not reflect ACH under natural conditions (ACH natural). If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

Roman Baugh joins the podcast to talk about oil return and the refrigerant charge in VRV systems. VRV systems—also known as variable refrigerant volume (or variable refrigerant flow/VRF) systems—have one outdoor unit, one or multiple compressors, and multiple indoor units. The outdoor unit modulates to meet the indoor units’ fluctuating demands. They are versatile and flexible systems. Like parallel racks, VRV systems have long lines and a lot of piping, so oil return and refrigerant charge are especially critical. VRVs have specific control protocols, as they need refrigerant volume and velocity to move oil and keep it lubricating the compressor for its entire lifespan; oil return mode, the refrigerant charge, and the piping protocols are supposed to support that function. When it comes to piping protocols, line sizing is critical. Whenever there is a need to relocate the outdoor unit and change the piping configuration, the charge needs to be adjusted, and the piping may even need to be upsized to prevent restrictions from happening. Daikin has VRV WebXpress (and SplitXpress) software for equipment selection; the goal is to help installers out with the line length and charging whenever it needs to be changed. When trying to get the oil return and line sizing right, you ultimately need to look at the manufacturer’s literature and resources. It also helps service technicians if the installer makes the charge and line information readily available to anyone who works on their VRV install in the future. Roman and Bryan also discuss: Where and how oil can settle in VRVs Consequences of improper charge in VRVs Liquid lines in VRVs Violating piping rules and safety protocols Vertical separation in liquid line sizing Suction line sizing POE and PVE oil miscibility Daikin’s resources Check out daikincity.com to find Daikin’s literature and software programs. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this short podcast, Bryan talks about oxidation and all the buzz behind “magical air-cleaning oxides” and other similar IAQ products. Oxidation is the loss of electrons, and reduction is the gain of electrons; oxygen commonly loses electrons. Rusting is a common example of oxidation; it happens when iron and oxygen interact in air or water. Metals that are more likely to react with oxygen (or corrode) are “less noble” than more noble metals. Less-noble metals, known as anodes, are sometimes used sacrificially to prevent the oxidation of nobler base metals, known as cathodes. While iron oxidation results in corrosion, some IAQ products use the process to bind oxygen molecules to unwanted substances. The IAQ products that use oxidation use the natural tendency of oxygen to lose electrons when bonding with other molecules. Ozone is a common agent of these IAQ products because an ozone molecule is very unstable and has three oxygen atoms, meaning it combines with other molecules via oxidation; it stabilizes other unstable molecules. Ozone, however, also reacts similarly with cells in our respiratory system and can cause irritation. In our industry’s efforts to reduce the negative effects of COVID-19 viruses, oxidation has generated a good deal of interest. Nowadays, some IAQ products use smaller amounts of ozone or use activated carbon to catch ozone before it enters the conditioned space. Many manufacturers that use oxidation as a strategy use other ion-based oxidizers, just not ozone. Some of these oxidizers can break pollutants into aldehydes and other chemicals that may harm our bodies. If you want to learn more, you can read Oxidizers and What It Has to Do With COVID-19. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this short podcast, Bryan talks about filtration and IAQ, especially as they relate to virus control. He also answers the age-old question: “Can filters capture viruses?” While it may seem like particle size matters when it comes to filter efficacy, filters are not nets that strain air particles and prevent pollutants from passing through. When we talk about particles, we tend to focus on ones that are 0.3 microns in diameter, which tend to be medium-sized particles. Viruses tend to be among the smallest particles that we aim to control when it comes to IAQ. Filter media are crisscrossed fibers that catch particles in different ways. Inertial impaction is one means of stopping particles from passing through; the initial impact stops the particles from passing through. Interception happens when particles graze filter fibers and get stuck. Electrostatic attraction relies on energy to attract and catch particles. Diffusion happens when smaller particles move more erratically due to Brownian motion and get caught in the filter media. Viruses are among those smaller particles. Smaller particles’ erratic motion makes them more likely to collide with the filter media, so they aren’t necessarily harder to catch. Higher MERV ratings are associated with higher capture efficiencies. HEPA filters surpass the MERV scale and have also been proven to filter viruses out of the air, but we rarely use true HEPA filtration in residential HVAC because they are too restrictive for total system airflow. We can use bypass HEPA filtration to filter the air without creating a massive restriction at the unit. Large filter-back returns with 2” filters can help catch more particles with a greater surface area without tanking the static pressure. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

Joey Henderson returns to the podcast to talk about heat pumps and inverters. The reversing valve, defrost cycles, and auxiliary heat can cause confusion for people who have primarily worked with furnaces or straight-cool A/C systems. Heat pumps use defrost cycles and bring on the auxiliary heat when the coil is ice-bound, which can present a challenge; we need to maintain cold coils without going into defrost all the time. Even though heat pumps were significantly less effective in years past, we will still see reduced performance in very cold conditions with the newer inverter-driven systems. Proper design, installation, and commissioning will also help occupants get the best performance out of their heat pumps. Inverters offer plenty of advantages for the cooling aspect of heat pumps, too, especially when it comes to achieving longer runtimes for dehumidification. They can also float their coil temperature, much like how refrigeration systems can use floating suction or head pressure. Condensate assemblies absolutely must be run properly to prevent backed-up drains and other related problems. Liquid line sizing and proper commissioning are also especially crucial for ductless inverter-driven systems. Joey and Bryan also discuss: Check out Joey's training, social media, and contact information at https://joejoehvac.com/. You can also check out Greg Migliaccio's book about mini-splits at https://www.acservicetech.com/mini-split-book. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

Joey Henderson joins the podcast to talk about airflow and how we can get air where it needs to go. Duct design is one of the subjects that fuel Joey's passion for HVAC. In many cases, people focus too heavily on the equipment when diagnosing airflow problems; sometimes, the equipment simply can't perform as it should due to a poorly designed duct system. In residential HVAC, many duct systems aren't adequately planned out, and the airflow can't overcome restrictions like filters. We also need to keep in mind that flex ducts need to be as straight and tight as possible, and it's usually best if we slightly upsize them (compared to sheet metal). Even though balancing dampers aim to solve airflow problems, they often lead to other issues when installed and used incorrectly. In many cases, proper duct design would solve problems without the need for balancing dampers. Bypass dampers are also commonly misapplied. Some technicians also aren't properly trained to position their static pressure probes appropriately to measure total external static pressure, which leads to faulty readings and misinformed diagnoses. We can start by looking at things that can improve system performance at the equipment, like filtration; we can think of the equipment as the heart and the duct system as arteries (with static pressure as blood pressure), and the equipment also has the biggest pressure drop. Joey and Bryan also discuss: Check out Joey's training, social media, and contact information at https://joejoehvac.com/. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

This podcast episode contains some of the questions and topics from the Business Round Table at the 4th Annual HVACR Training Symposium. Panelists include Tersh Blissett, Luke Peterson, and Andy Holt. One of the most critical parts of HVAC business ownership is knowing when to grow your business (i.e., hiring more techs and incorporating standalone maintenance and install departments). Ultimately, we need to think about how many service calls we're assigning to each technician per day and how many customers we have to turn down due to a busy schedule. Getting family members involved in the business can also have a range of positive and negative effects on a business. Delegating is another important skill that can help you run an HVAC business smoothly and focus on ownership and management over your day-to-day tasks. You need to understand your business's core processes but can delegate tasks that take time away from developing your business. When it comes to economic issues like inflation, we need to be looking at our own costs and competitors' costs to set our prices and pay our employees appropriately for the economic climate. We can use indicators like the consumer price index to assist with pricing and setting pay rates. Tersh, Luke, Andy, and Bryan also discuss: Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this short podcast, Bryan goes over some information about cap tubes (capillary tubes) and flow facts. Cap tubes are metering devices; they're long tubes with small diameters, and their flow rates are dictated by the tubing diameter size and tube length. Pistons and TXVs are some of the most common metering devices in residential HVAC, and flow restriction doesn't just happen at the metering device; distributors also contribute to the pressure drop and act like small capillary tubes in addition to the metering device. Older units, simple refrigerators, and window units are more likely to have capillary tubes as metering devices, as cap tubes are an easy and versatile use of small-gauge tubing. The diameter is the primary factor that influences the flow rate, and length is usually secondary. However, longer tubes cause the fluids to encounter more resistance (in the form of friction) as they flow from one end of the tube to the other; the longer the tube, the lower the flow rate. Longer tubes also cause the fluid velocity to decrease more than a short tube. When you have long runs of small-diameter tubing, you can replace a few sections with larger-diameter tubing to improve the flow rate. Sometimes, the ends of cap tubes are in hard-to-reach places, so replacing middle sections with larger-diameter tubing will still help decrease the static pressure and friction in the tubing. Oil traps and risers may be smaller than other areas of tubing, and they have a larger pressure drop and more friction associated with them. (However, the smaller tubing also increases the fluid velocity.) The same principle applies to 1/4" vs. larger-diameter vacuum hoses. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

Jim Fultz and Jim Hagl from Copeland join the podcast to talk about filter driers and system cleanup. Filter driers come in many types and sizes; they typically go on the liquid line (bi-flow filter driers are used on heat pumps), but suction line filter driers also exist. Copeland’s liquid line filter drier models include the EK (premium), BSL (smaller diameter), BOK (with HH desiccant to assist with burnout cleanup), and CU (copper spun). Bi-flow filter driers in Copeland’s lineup include the BFK and BSB categories. These liquid line filter driers protect the metering device and should typically be installed as close to the metering device as possible (with some exceptions for heat pump startups in heating mode). These filter driers typically need to be replaced anytime the system is opened for service, the pressure drop across the drier exceeds 3 PSI, or the system is wet. Suction line filter driers in Copeland’s lineup include the ASD, SFD, and CSFD models, all of which come in different shapes and sizes for varying applications. The ASK suction line filter drier has activated carbon to assist with burnout cleanup. When used to assist with contamination cleanup, suction line filter driers must be taken out of the system within a few days. Jim F., Jim H., and Bryan also discuss: Check out Copeland’s filter driers at https://hvacrschool.com/copeland-driers. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this short episode, Bryan goes over the fourth chapter of his new book, Unconformed. The chapter is called "So... What Do You Do?" Parents always want to be proud of their children, but it seems as though children are more proud of children who attend college than take up apprenticeships. However, these feelings largely seep in due to peer expectations; we want our children to measure up to our friends' standards or success, not necessarily our own. Parents are also less likely to encourage their children to get into the trades and value the time and expertise of tradespeople. All jobs, even less prestigious jobs, matter and have a purpose. Society tends to devalue tradespeople and manual laborers, but those jobs do a great service to society. Nevertheless, the competitive drive between parents and our fear of failure makes us fall into these mindsets where we devalue manual labor. The media and family members also trap us in these expectations. Society runs on the ability of people to solve problems and innovate, which means that blue-collar work is necessary for society to function. Not to mention, popular media and DIY culture have also brought attention to the artistry of the skilled trades. These positive changes are important to the perception of blue-collar work, and we can accept (and encourage) a child's choice to find purpose in the skilled trades, not just blindly seek happiness. Bryan also covers: You can purchase Unconformed on Amazon's website HERE. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

This podcast is based on a Kalos meeting about pipefitting best practices, particularly in commercial refrigeration applications. It begins with a few words about quality workmanship by the Kalos founder and CEO, Robert Orr. Pipefitting consists of repairs and joining metals; when joining metals, we need to liquify the alloy and draw it into the joint via capillary action. When pipefitting, oxygen can present some problems by coating the inside of the pipe with oxides that can contaminate the system. We can reduce the likelihood of oxide formation by flowing nitrogen while brazing; purging nitrogen displaces the oxygen in the lines before brazing, and flowing keeps oxygen out during the brazing process. Tip selection will be based on the piping diameter; tips that are too small won't adequately heat the pipe, and tips that are too large will consume too much fuel. You'll also need to leak-check your torch tanks and ensure that you have the appropriate ratio of oxygen to acetylene by aiming for a neutral flame rather than a carburizing or oxidizing flame. After brazing, we need to perform a nitrogen pressure test to ensure that the system is leak-free. Then, once the pressure test is passed, we should evacuate the system to keep the system clean, dry, and tight. Bryan, Matthew, Roman, and Nathan also cover: Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this short episode, Bryan talks about filter driers and their important role in HVAC/R system protection, especially in accordance with Copeland's (formerly Emerson's) AE24-1105 R5. We can really start keeping our systems contaminant-free by handling tubing properly, purging and flowing nitrogen, and keeping copper shavings out of the tubing when deburring or reaming. Suction and liquid filter driers protect the system during operation and are designed for specific purposes. We typically don't install suction filter driers in residential systems unless we're fixing a system with compressor burnout or acid contamination; in those cases, we also want to make sure we replace accumulators and clean out the line set as well as we possibly can. Commercial refrigeration tends to have more rigorous contamination prevention protocols, including testing oil for acid and installing suction filter driers in everyday operation, due to the use of multiple compressors in a single system. However, suction driers are recommended in ALL applications per AE24-1105. In many cases, we don't install them in systems because they can create a significant pressure drop in the suction line and damage the compressor, but suction filter driers can provide a net positive effect if we monitor them. We should install suction filter driers as close to the compressor(s) as possible, and we should cut them out when we need to remove them, not unsweat them. Bryan also covers: For more information about filter drier selection by model number, visit https://hvacrschool.com/copeland-driers. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

This podcast episode is one of Alex Meaney's HVACR Training Symposium presentations: HVAC Design Backwards, Forwards, and In Between. Load calculation factors in all three means of heat transfer: conduction, convection, and radiation. It doesn't directly tell you the tonnage; it just tells you how many BTUs (sensible and latent) are entering or leaving a structure. When designing systems after doing load calculations, we need to be mindful of industry standards and their pitfalls, as well as the climate conditions and the difficulty of obtaining manufacturer data. Equipment selection by tonnage is only part of the picture when it comes to HVAC design; we also need to factor in airflow and duct design, especially duct sizing. However, many rules of thumb and poorly explained terms are counterproductive to a thorough understanding of HVAC design. In some cases, the best way to design a system may seem "backward," especially when starting with blower selection instead of ductwork. Duct design is particularly difficult, especially when software identifies several problems with designs that seemed to look good on paper. However, the software points out areas where you can adjust the duct size and manage restrictions to allow the fan to do its job without being derated by friction. Alex also covers: Check out Alex Meaney's consultation business at https://www.meanhvac.com/. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

This podcast is the Santa Fe Panel from the 4th Annual HVACR Training Symposium. The panel focused on dehumidification, was moderated by Nikki Krueger, and featured Andy Ask and Ken Gehring. "Matchmaking" a residence to the climate requires us to design and install equipment that keeps occupants healthy and comfortable. HVAC contractors need to focus on the dew points, especially as they remain high at night and in the shoulder seasons. Humidity loads tend to hold steady (even peak dew points), while sensible loads increase and drop, making it difficult to control latent heat loads the same way we control sensible loads. The equipment will typically be less efficient if you focus on long runtimes to remove latent heat under partial load conditions and maintain 50% humidity. Dehumidifier efficiency is determined on a pint per kilowatt basis, but a constantly running dehumidifier will do its job a lot more efficiently than one that starts and stops regularly. The dehumidifier adds heat to the house and should only come on when the HVAC system is having trouble maintaining the desired humidity load; the dehumidifier has a reheat effect, but the HVAC system will need to deal with the increased heat load. When you add a whole-house dehumidifier, adding a fresh air ventilation component is highly recommended. Nikki, Ken, and Andy also cover: Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this short podcast, Bryan talks about where to place the micron gauge during evacuation and how to think about micron gauge positioning. Evacuation (deep vacuum) doesn't remove solid contaminants, and vaporizing liquid water is a time-consuming process; its main purpose is to remove water vapor, air, and nitrogen gases from the HVAC/R system. When you pull down below 500 microns and hold that pressure, we can make sure we have a clean, dry, and tight (leak-free) system. As we started using R-410A and POE oil, water in the system became a much bigger issue than it was with mineral oil (it was never to have water in the system, but it breaks down POE oil). Before we start pulling a vacuum on the system, we need to attach our micron gauge to the pump while it's isolated to make sure the pump is working. A modern vacuum pump should pull down below 100 microns in 30-60 seconds; if your pump can't pull down to 100 microns in under a minute when isolated, then you'll want to change the oil (possibly multiple times). Be sure to change the oil regularly and store it properly. When you pull a vacuum on a system, you'll want to attach your micron gauge as far away from the pump as possible to get an accurate indicator of your vacuum. Use core remover tools to isolate the system and make sure the far side of the system is brought below 500 microns during evacuation. The time it takes to pull down a system and the time you'll hold the vacuum will depend on your application (residential vs. commercial). Check out Review of Vacuum for Service Engineers (revised by Jim Bergmann and Bryan Orr, 2020) at https://www.trutechtools.com/accutools-review-of-vacuum-for-service-engineers.html. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

Brett Wetzel joins the podcast to talk about his journey from resi tech to industry-leading refrigeration trainer. Brett is best known for his educational content, but he is also the manager of technical troubleshooting and training at CoolSys. The skills gap is widening, and CoolSys was inspired to create a solution to that problem. Brett's goal is to offer training that provides education and a sense of community all at once. Since he likes to keep his training simple and establish a solid foundation for his students, one of Brett's favorite training practices includes going over a system's P&ID diagram with his students before even looking at it. He focuses on classroom engagement and keeping trainees interested. Brett does regional training sessions and has written technical documentation to help technicians. As he has shifted from a field role to a full-time educator role, he has noticed that he has had more time at home. CoolSys focuses on commercial and industrial refrigeration, including system components, racks, and controls. The transition from residential HVAC to commercial HVAC and refrigeration requires an inquisitive mind and a drive to keep learning. Independent learners tend to do particularly well. There is an additional step that people will have to take when they move from fieldwork to education; communication skills and an ability to keep students engaged are crucial. Brett and Bryan also cover: Check out CoolSys at https://coolsys.com/ to learn about the company and some job opportunities. You can also email Brett at bwetzel@coolsys.com or listen to the Advanced Refrigeration Podcast (YouTube channel: https://www.youtube.com/@advancedrefrigerationpodca9389). Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this short podcast episode, Bryan gets into some oil talk, covering some common refrigerant oil terms and types. Esterification is the process by which organic acid and alcohol come together to form polyolester (POE) oil and water. Hydrolysis refers to the decomposition of a substance when it comes into contact with water; when POE mixes with water, it will break down into esters, organic acids, and alcohol. Once POE oil undergoes hydrolysis, the process can't be reversed to get the same original oil. POE oil is also hygroscopic; hygroscopicity refers to the ability of the oil to absorb moisture. Miscibility refers to the ability of an oil to mix with refrigerant and be carried with it. In the context of refrigerant oil, "polar" refers to a molecular structure with an uneven distribution of electrons; oils with polar structures attract water molecules. Solubility refers to how well one compound can dissolve into another. Mineral oil is a product of the distillation of crude oil and was common in systems that used CFC and HCFC refrigerants. Mineral oil isn't as miscible with new refrigerants that lack a chlorine molecule. Alkylbenzene (AB) is a synthetic oil used in some commercial refrigeration systems that is compatible with mineral oil. Polyolester (POE) oil is one of the most common synthetic oils we use in systems that use HFC refrigerants; its main downside is its high hygroscopicity and tendency to undergo hydrolysis. Polyalkylene glycol (PAG) oil is common in automotive A/C systems (R-134A) and is more hygroscopic than POE oil but does not undergo hydrolysis. Polyvinyl ether (PVE) oil is used as an alternative to POE oil; it is more hygroscopic but does not undergo hydrolysis. Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this short podcast episode, Bryan talks about using a megohmmeter on a scroll compressor (or "megging" a scroll). Scroll compressors are among the most common compressor types nowadays, and they come with their unique needs and best practices. You can't pump them down into vacuums (in many cases, you can't do that anyway due to internal protections), run them in a vacuum, or run a high-voltage megohmmeter or hipot test. Scroll compressors differ from reciprocating compressors. A scroll compressor's motor is located at the bottom of the compressor, meaning it is immersed in refrigerant and oil when the system is operating AND when it is off; when the compressor is off and cold, there is a chance that there will be liquid refrigerant at the bottom. Compared to reciprocating compressors, scrolls tend to have a more compact and balanced design, and there could be a higher risk of internal arcing due to the tighter electrical tolerances associated with the design. Many inexpensive megohmmeters will say that any measurement below 10-20 megohms indicates a short, but some scrolls will have acceptable readings as low as 0.5 megohms to ground; these readings will typically show up on the smaller kilohm scale. You must only use a megohmmeter to ground, not from winding to winding. Moisture contamination, metallic debris, and lubrication issues can also cause a lower ohm reading than acceptable, so it's best to have historic data and track readings over time to make a diagnosis. Many modern multimeters can help you determine if a compressor is shorted to ground; you don't necessarily need a megohmmeter. You may also read the following tech tip to learn more: https://hvacrschool.com/scroll-compressor-pump-down-megohm-test-fusite-plugs/ Learn more about the HVACR Training Symposium or buy a virtual ticket today at https://hvacrschool.com/symposium. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.