HVAC School - For Techs, By Techs

In this podcast episode, Eric Mele joins Bryan for some weird transformer talk. They discuss corner-tapped transformers and some thought experiments. We hadn't been able to get our heads around corner-grounded transformers until recently. "Grounding" doesn't necessarily change the phase or lead that you ground. If you take the secondary of a 24-volt transformer and measure from your two colors, you'll measure 24v. However, if you connect a lead to ground, you'll still read 24v. (Don't ground both, or you'll get a short.) Ground is just a path back to the power source. Electrons don't suddenly "leak" from something connected to ground. Grounded and neutral conductors can potentially be dangerous. There can still be potential even though your leads wouldn't pick it up. In residential HVAC, we're used to seeing neutral and ground connected at the main distribution panel. However, it's not always okay to connect ground and neutral or use ground as a current-carrying conductor. If you've got split-phase power going into a regular home, you've got 120 volts 180 degrees out of phase with each other. If we don't have a center-tap neutral, it would function similarly to a 24v transformer. In that case, it's not necessarily unsafe to read 0v on neutral. We get tripped up because we think in terms of using a meter, not in terms of actual potential voltage. In a delta configuration, you will have a high leg connecting to neutral (B phase is usually high; A and C phases are usually normal). You can't really center-tap a delta, so you have to tap the center of one phase. Eric and Bryan also discuss: Working out of a truck vs. a van Shunting high-voltage spikes to ground Center-tapped transformers and "wild legs" Ground is NOT necessarily the earth Hot legs on the primary AND secondary Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast episode, Bryan compares internal and externally equalized valves. He also covers how forces act upon the TXV. Equalization does not happen on the off cycle. When we talk about equalization, we are merely talking about a force that balances against the bulb force. A TXV sets the superheat within an operating range at the evaporator outlet; the sensing bulb on the TXV detects temperature and pressure at the evaporator outlet. So, those readings apply an opening force to the bulb. (Think of this process as being quite similar to you measuring the superheat and suction pressure.) The equalizing force is a closing force. When the closing force is applied to the TXV, it balances against the opening force provided by the sensing bulb. So, we have two ways of providing the closing force: within the valve at the evaporator inlet (internal) or externally. In an internally equalized TXV, the closing force that equalizes the bulb's opening pressure is taken at the evaporator inlet. The measurement is internal to the valve at the evaporator inlet. However, in externally equalized valves, the closing force comes from the evaporator outlet, which is beyond the valve. Externally equalized valves work best on systems with significant pressure drops within the evaporator coil or on systems with distributors. If we were to use internally equalized TXVs in those cases, it would be like measuring superheat at the wrong location. If you don't have a significant pressure drop, then you can use an internally equalized valve. These systems will usually be small (less than one ton) and won't have distributors. Most of the time, we will see externally equalized TXVs; these will ideally take readings within six inches of the bulb. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, Bryan talks with Bill Spohn about his most recent project, SpohnHome. SpohnHome explores Bill's journey in custom home performance. Projects are complicated because so many trades work together to accomplish a building. However, custom homes are particularly challenging, especially in Bill Spohn's case. His home is a "personalized performance home," so he's prioritizing energy efficiency, indoor air quality, and comfort as well as aesthetics. The home's design and purpose resemble that of a passive building. Although much of the construction went smoothly, there was a misunderstanding about the sewer conditions; unbeknownst to the township, a nearby property had a private sewer installed, so Bill could no longer tie the plumbing into the existing sewer system. That development put a monkey wrench in the plans, and Bill's team had to come up with new ideas for a septic system (and had to follow a bunch of rules). Even though a project may seem to have a perfect plan, setbacks can still occur due to miscommunication or unfortunate events (such as the death of someone integral to the project, as Bill experienced). Bill also used an air-source heat pump with zones for his HVAC system. He had to experiment with his home's ventilation to strike the ideal hybrid solution, as IAQ and efficiency were very important to him on this project. Custom constructions also have plenty of room for the team to do some unconventional things, including making 3D models of the home that gives accurate volume measurements. Bryan and Bill also discuss: Customer follow-up Modular building Plumbing conditions Divining and drilling wells Fresh air and filtration solutions Air sealing and blower door testing Dealing with snow Humidity considerations TruTech Tools news You can find out the details of Bill's home construction at spohnhome.com. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast episode, Bryan talks about some tips you can use when working with a multi-position service valve. A service valve will have a line connection, which connects the valve to your line set. You also have a gauge port that you can connect to, a valve stem, and a packing gland nut (directly beneath the valve stem). If your stem is completely back-seated, then your gauge port is completely closed from both the line and system connection. If you crack the stem off the back seat, then the gauge, line, and system can all communicate. Completely front-seating the valve will generally close off the line connection, but it may also close off to the system connection on some valves. Mid-seating puts the valve stem right in the center for maximum flow. If you're working with a service valve in a grocery refrigeration application or old A/C system, you may be tempted to use any old wrench on the valve and can damage the valve. So, whenever you work with one of these valves, make sure you use a refrigeration service wrench only. Also, be sure to exercise caution. The packing gland nut helps keep everything together and prevents leaks. However, you need to loosen it by a quarter to full turn before opening the valve. If you don't loosen the packing gland nut, you will have a hard time adjusting the valve, and you may even damage it. Whenever you do any brazing on or near a service valve, be sure to protect it from the heat (such as with Refrigeration Technologies WetRag). You'll also want to mid-seat the valve before you start flowing nitrogen. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, Bryan and Trevor Matthews from Emerson talk through scroll compressors in commercial refrigeration equipment. Scroll compressors are not a monolith; although they all function similarly, they have different fine details and manufacturing protocols by application. Low-temp, medium-temp, high-temp, and A/C scroll compressors each have unique designs, operating conditions, and service considerations. Copeland has a medium-temp scroll compressor line (ZB and ZS) for medium and high-temp applications. They also have a low-temp line (ZF). Within those lines, there are also small displacement and large displacement compressors, advanced scroll temperature protection devices, and other unique features. Since scroll compressors are prone to thermal overload, some Copeland compressors have advanced scroll temperature protection devices. These devices help redirect the discharge gas to the suction gas, which gets the compressor to trip out on thermal overload more quickly. In cases when you're tempted to condemn the compressor, shut it off and let it cool down before you jump to conclusions. The compression ratio is the main difference between A/C and refrigeration scroll compressors. A/C scrolls can handle a compression ratio of 11:1. Conversely, refrigeration scrolls can handle 26:1 compression ratios. Copeland scroll compressors also have electronic controls. When setting up these controls, you need to keep the scroll compressor type and special features in mind, including temperature protection devices. In other words, you can't set up a low-temp compressor the same as a medium-temp and so on. Bryan and Trevor also discuss: Differences across Copeland scroll compressors Low-temp vs. medium-temp vs. high-temp refrigeration Copeland compressor nomenclature Compressor pump down Proper vacuum CoreSense diagnostics Vapor injection and compressor capacity PTC (positive temperature coefficient) thermistors Using AE bulletins as tools Crankcase heaters and other accessories Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode, Bryan and Bert talk about soft skills. They also discuss why soft skills are important in highly technical trades. Bert's class defined "soft skills" as communication skills; these can be verbal but may also include body language and how we respond to emotional situations. Bert thinks these skills are some of the most important skills you can develop in the HVAC industry and in life overall. You will only be able to make the most of your talents and career if you work on your communication and people skills. You can start improving your soft skills when you learn to see yourself accurately. Are you introverted or extroverted? Have a Type A or Type B personality? Once you can see your strengths and weaknesses, you can learn where you need to be more engaged with the customer or give them some space. You can analyze your relationships to see where your strengths and weaknesses are (or if you're the problem in your interactions with others). Listening skills are also crucial for interactions with customers. Being a good listener, keeping your emotions in check, and proposing solutions will give your customers a better experience. Having the discipline to be a good listener will also help your work and personal relationships. If you need some tips or have some questions about your general vibe, ask people who want to tell you the truth about their "experience" with you (and listen to them). Body language is also critical. Do your best to show that you're attentive, helpful, and friendly. Bert and Bryan also discuss: Residential vs. commercial interpersonal skills Skills vs. natural abilities Metacognition Customer experience Discipline Working well with your bosses or other employees Eye contact Complaining (just don't do it) Dos and don'ts of showing empathy Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, Bryan and Jim Bergmann talk about gas furnace diagnosis and inspection. They cover the ins and outs of furnace assessment. A gas furnace diagnosis requires a few important measurements, but a solid visual inspection is perhaps even more vital. You'll want to look at the venting and condensate disposal systems. You'll want to make sure the flue gas can escape properly and that the terminations are correct and safe; if you're not looking at the manual and checking the venting, you can put your customers at risk of serious CO poisoning and even death. On the condensate disposal system side, you risk trapping flue gases in the trap. Condensate can also build up into the secondary heat exchanger, which leads to a rise in CO. We also need to look out for issues on the electrical side. Reverse polarity and poor grounds are often the greatest culprits for electrical failures. Broken connections are also common problems as with other HVAC systems. Dust and dirt can also get behind the circuit board, which can cause flame rectification problems. Fixing an electronic circuit board can intimidate some techs, but soldering a circuit board is quite a bit like soldering a coil. When it comes to measurements, your pressures are going to be some of the most important readings you can take. It's also a wise idea to have your own combustion analyzer and make sure to take care of it over time. Bryan and Jim also discuss: New MeasureQuick developments Measurements to use in MeasureQuick CAZ testing CO sources 90+ furnace condensate drains Air filtration and MERV ratings AHRI CO testing steps Conduction through the flame rectification circuit Incoming gas pressure Incorporating MeasureQuick into diagnosis Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast episode, Bryan talks about the differences between pitot tubes and static pressure probes. He also explains how each one works. People often mix up static pressure probes and pitot tubes. A pitot tube is a tube within a tube, and a static pressure probe is just a tube with holes in the side but not at the end. When we measure static pressure, we're measuring the pressure against the duct. (Think of it as balloon pressure rather than air velocity.) We use static pressure probes to look for a differential between a probe and atmospheric pressure or between two probes. As the air travels around a static pressure probe pointing in the correct direction, its velocity force will not act on the probe. We do NOT want to measure velocity with a static pressure probe. Pitot tubes, however, come in twos. One tube comes off the side (attach a hose to this one), and one comes off the bottom. You can use the side port of the pitot tube to measure static pressure. You also have an end port to measure total pressure, which is static pressure plus velocity pressure. When using a pitot tube, you can get the velocity pressure by subtracting the static pressure from the total pressure. You point the pitot tube into the airstream to get that measurement. However, pitot tubes will only give you accurate data if you have an accurate manometer and have ideal velocity conditions. Proper positioning and duct traverse techniques are also integral to getting accurate data. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, Bryan and Nathan discuss balancing evaporators in a multi-coil circuit. They specifically focus on using the TXV to do so. When we say "balancing evaporators" in a multi-coil circuit, we're referring to the temperature of the air leaving the system; we are worried about the air keeping the product cool in grocery refrigeration. If everything works correctly, the evaporators on a rack can have different temperatures due to different refrigerant flow rates. That's when we can turn out attention to the expansion valves, which meter the refrigerant into the evaporator and manage the refrigerant flow. Balancing evaporators with the TXV is a controversial practice; many people insist that you should balance evaporators with the equivalent line set length only. However, it's not usually possible to repipe the entire circuit, so using the TXV is much more practical. You essentially run higher superheat on the colder cases by using the TXV to create a restriction. When you adjust the TXV, you'll want to do so in quarter-turn increments on the highest and lowest cases and wait for the temperatures to stabilize (about 30 minutes) before making further adjustments. Tuning on rack refrigerators is another related concept. We don't see mechanical EPRs very often anymore, so we can rely on the system to make programmatic adjustments. Once the temperature and operation are stable, you can set your superheat. Typically, balancing evaporators will be more important on systems with electronic EPRs than mechanical EPRs. Bryan and Nathan also discuss: Pressure drop associated with fittings Where to take superheat Flood back risks Modern TXVs and EEVs Defrost controller considerations Discharge air differences Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast episode, Bryan discusses the difference between mass flow and volume flow when referring to HVAC equipment processes. When you are confused as to whether you're dealing with mass or volume flow, think about the units. For example, cubic feet per minute (CFM) is a measure of volume because we're talking about cubic units. We care about the volume when we think about air mixing and velocity, but volume isn't much of an indicator of the actual cooling power. The mass or weight of the air matters more when we think about cooling a space. There is a lot of variation in how much air weighs, which will impact the performance of HVAC equipment under given conditions. Standard air has a weight of 0.075 pounds per cubic foot, but that can vary depending on humidity, temperature, and pressure conditions. When you think about volume flow rate, think about moving boxes of matter. As a blower operates, it moves a series of air "boxes," which is a useful way to look at air velocity. Compressors have a fixed volume in their compression chambers, unlike blower wheels. (Blower wheels move different volumes of air based on motor staging and other conditions.) However, mass flow is NOT fixed. In a compressor, we can fill those boxes with more weight (higher mass flow). On occasion, too much mass will move at once; a hot pull down is a common scenario where we have too much mass flow. In those cases, we can use crankcase pressure regulators. A system's compression ratio also has a major effect on mass flow rate; the "boxes" might be too light to keep the compressor cool enough to operate efficiently. In the worst-case scenario, the compressor may overheat. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode, Bryan and Sam discuss freezing evaporator coils. They explain why frozen coils happen and how to address them. When the coil's surface temperature drops below freezing (32 degrees), the moisture in the air that condenses on the coil can freeze to the coil. In those situations, your suction saturation will probably be in the mid to high twenties. Generally, freezing evaporators will occur when you have less load on the evaporator. When there is less heat, the evaporator temperature will drop accordingly. The return air temperature is usually around 35 degrees, though that number can fluctuate on older equipment or on systems with dirty coils. Freeze-ups usually happen due to poor airflow or low refrigerant charge, though low refrigerant is usually less severe than airflow or compound airflow-charge problems. Conditions that cause low mass flow can lead to freeze-ups. When you approach a frozen coil, the first thing you want to do is defrost the coil completely. Then, you will want to check airflow (filter, blower wheel, and coil cleanliness) and then refrigerant restrictions and charge. You'll especially want to make sure you check the liquid line for temperature drops and ensure its temperature is warmer than the outdoor ambient temperature. In addition, static pressure is a valuable reading for determining airflow. Drain lines can also freeze, though it's a rare occurrence. When that happens, you do NOT want to blow out the blockage with nitrogen! You will break the drain line before any ice comes out. Sam and Bryan also discuss: Driving the temperature down Low charge as a cause of freezing Considerations for various system types Using a scale for charging Heat pumps in heat mode ECM motor failures Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Mike Klokus and Corey Cruz from Kalos come on the podcast to talk about drain cleaning. They discuss their tips and some best practices. Approximately 50% of the calls in the light commercial division have to do with drains, and drain cleaning is a common PM procedure. The procedure starts off when you pull the panel off the air handler and look in the drain pan. Muck can accumulate in the pan and in the back and side channels. Pay attention to the unit orientation and the drain pitch before you even start cleaning. If you need to get underneath the channels, you can use bottle brushes. Dedicated drains are associated with only one unit. However, communal drains have multiple units running into a single drain line and have a special set of considerations. You don't want to pour something caustic into the common drain and have it overflow on the lower levels. It's also best to know where the drain leads; you don't want chemicals to wash out into a garden. Water can also create a slippery surface and cause someone to fall. Generally, the top 3 drain cleaning methods use a shop vacuum, compressed air, or plain water; each one has its place, but they also have drawbacks. While water is ideal for cleaning, it's not always available and practical. Shop vacs are good, but the suction is limited. Compressed air is better at unclogging than cleaning, and it can cause you to blow away piping if there's a loose pipe fitting. Mike, Corey, and Bryan also discuss: Condensate safeties Using shop vacs and extensions Weight in the drain pan Cleaning with chemicals Copper vs. aluminum for bacterial zoogloea Priming the drain line Condensate assembly cleanings in residential HVAC Capping vents (don't do it) Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast episode, Bryan talks about the differences between single-phase and two-phase refrigeration. This particular episode is about the fundamentals of physics, chemistry, and science in general. When we talk about phases, we're referring to the changes in the states of matter. We typically think of the states of matter as solid, liquid, and gas. In refrigeration systems, the refrigerant usually changes from a liquid to a vapor in the evaporator and then from a vapor to a liquid in the condenser; that is an example of two-phase refrigeration. We get two-phase refrigeration anytime we're changing the state of matter in order to accomplish refrigeration. When you change the state of matter, you transfer a lot more heat than with a single-phase system. You get more heat in and out between phases due to latent. Between a solid and a liquid, the energy that goes towards the phase change is the latent heat of fusion. Between a liquid and a gas, the energy that goes into the phase change is the latent heat of vaporization. It takes a lot more heat to condense or boil water than it does to change its temperature by one degree, so we take advantage of that capacity to absorb heat into the boiling refrigerant. There are also forms of single-phase refrigeration, including John Gorrie's open-refrigeration machine. Gorrie's machine was just compressing and decompressing air; it was not changing the state of the air. In single-phase refrigeration, we can't make use of the extra energy from changing states. In those cases, condensers would be gas coolers. However, when you think about it, the process of refrigerating the space is a form of single-phase refrigeration; we don't change the phase of the air. So, we merely use two-phase refrigeration to drive single-phase refrigeration. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode, Bryan talks with Peter Capuciati and Bryan Johnson from Bluon. They discuss how refrigerant regulations keep changing and how technicians can make sense of it. We've begun phasing out R-22; the refrigerant can no longer be imported or manufactured in the United States. We can still recover and reclaim R-22, but the recovered refrigerant on the market can't meet the usual demand. R-22 went through a phaseout because of its ODP; R-410A has 0 ODP and was the main replacement. However, refrigerant regulations are still changing, as R-410A will soon be ready for a phase-down due to its high GWP. There are two main replacement options for R-410A: R-454B and R-32 (A2L refrigerants). There is also R-466A, but it cuts out even earlier than R-410A on high-pressure and has worse heat transfer capabilities. Right now, R-32 is perhaps the best refrigerant (beside ammonia, which is toxic), and it's even an ingredient in the R-410A blend. However, HVAC technicians and customers alike are apprehensive about the flammability. Although these regulations can be confusing and frustrating, the Bluon team recommends holding off from making capital decisions. While regulations are changing, it may not be a good idea to make a definitive equipment swap without knowing the final rulings. As a technician, it's good to benchmark the equipment. If you need to convert equipment, make sure to tune it to the specific refrigerant that's going in. Peter and the Bryans also discuss: Ozone-depleting potential (ODP) vs. global warming potential (GWP) Equipment efficiency and its effect on GWP R-32 and flammability risk aversion AR5 vs. AR4 Refrigerant blends as replacements Converting various equipment designs Benchmarking Bluon support and training Check out more information about Bluon HERE. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast episode, Bryan talks about the differences between single-phase and two-phase refrigeration. This particular episode is about the fundamentals of physics, chemistry, and science in general. When we talk about phases, we're referring to the changes in the states of matter. We typically think of the states of matter as solid, liquid, and gas. In refrigeration systems, the refrigerant usually changes from a liquid to a vapor in the evaporator and then from a vapor to a liquid in the condenser; that is an example of two-phase refrigeration. We get two-phase refrigeration anytime we're changing the state of matter in order to accomplish refrigeration. When you change the state of matter, you transfer a lot more heat than with a single-phase system. You get more heat in and out between phases due to latent. Between a solid and a liquid, the energy that goes towards the phase change is the latent heat of fusion. Between a liquid and a gas, the energy that goes into the phase change is the latent heat of vaporization. It takes a lot more heat to condense or boil water than it does to change its temperature by one degree, so we take advantage of that capacity to absorb heat into the boiling refrigerant. There are also forms of single-phase refrigeration, including John Gorrie's open-refrigeration machine. Gorrie's machine was just compressing and decompressing air; it was not changing the state of the air. In single-phase refrigeration, we can't make use of the extra energy from changing states. In those cases, condensers would be gas coolers. However, when you think about it, the process of refrigerating the space is a form of single-phase refrigeration; we don't change the phase of the air. So, we merely use two-phase refrigeration to drive single-phase refrigeration. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Don Gillis joins us again to talk more about common types of CO2 systems and how they differ

In this episode, we are joined by three people who know a lot about heat pumps and cold weather. We also cover everything from the way technologies have changed, some of the pitfalls to keep away from, and why heat pumps work even in really cold climates nowadays. Chad Gillespie: Chad is a senior manager, part of Mitsubishi Electric's Performance Construction Team. He currently leads a national team of business development managers tasked with growing the new construction market for high-performance heat pumps. He has also worked in the construction industry for 26 years and has been with Mitsubishi Electric for 9. Dana Fischer: Dana is a residential area manager at Mitsubishi Electric. He supports and promotes the installation of high-performance, ductless heat pumps in homes across Maine and New Hampshire. Prior to his work at Mitsubishi Electric, he was a program manager for the Efficiency Maine Trust. Scott Libby: Scott is the owner of Royal River Heat Pumps. He has over 35 years of experience and training in the residential HVAC industry. His team sells Mitsubishi Electric exclusively; they are one of the largest heat-pump-only contractors in the country. Heat pumps are becoming more effective and comfortable, so they are now more appealing for cold climates. Although we previously relied on gas and oil in colder climates, we have seen people using heat pumps with success in New England and even Norway. We partially have R-410A and high-speed compressors to thank for those technological advancements to heat pumps. Chad, Dana, Scott, and Bryan also discuss: Offsetting fossil fuel usage Compressor advancements Heat pump performance during the polar vortex Leaky vs. tight buildings Load calculations and equipment selection Seasonal loads Single-zone vs. multi-zone heat pumps Design software Flaring tools Triple evacuation Responsible refrigerant handling Auxiliary heat Mitsubishi Kumo station Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Trevor Matthews is back and dropping more compressor knowledge on us. This time, he talks about demand cooling and liquid and vapor injection. In low-temperature applications, the discharge temperature would get very high and lead to oil breakdown and thermal overload, so demand cooling is a means of cooling the compressor. Demand cooling injects saturated refrigerant into the compressor body to cool it down. You're not jamming liquid into the compressor; the refrigerant flashes, which achieves a cooling effect. A demand cooling system consists of a module, temperature probe, liquid line solenoid valve, and injection valve. On the Discus compressors, the sensor will go in the port in the compressor head. When installing these, it is important to make sure high-quality goes to the valve. It's normal to have some frost at the outlet during operation; look for frost to make sure the demand cooling system is working properly. Scroll compressors use liquid and vapor injection almost exclusively nowadays. However, there is a difference between liquid and vapor injection for scroll compressors. A liquid injection system helps the compressor avoid high discharge temperatures (and high compression ratios). The vapor injection improves capacity and efficiency. When troubleshooting demand cooling or liquid/vapor injection systems, you need to keep a few things in mind. For example, you need to make sure you have the right amount of tees when you retrofit a compressor with a vapor injection system. You may also have to repipe the vapor line and add a DTC (discharge temperature control valves). Trevor and Bryan also discuss: What happens when we change refrigerants Return gas temperature and mass flow rate Compressor head cooling fans Motor operation and spinning indicators Visual inspection Vapor injection vs. mechanical subcooling KVE vs. K4E Part replacement DTC vs. EEV w/ CoreSense diagnostics Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Don Gillis with Emerson joins us on the podcast to teach us the basics of CO2 as a refrigerant. He explains how it works and its applications. Carbon dioxide is a colorless, odorless gas that is becoming an important refrigerant for commercial refrigeration (R-744). It is desirable because it has a low critical point and high triple point, so we can use subcritical (below the critical point) and transcritical (above the critical point) CO2. Carbon dioxide also has a very low global warming potential (1), is inexpensive, and is very efficient at transferring heat. Above the critical point, we see transcritical fluid, which is a high-pressure fluid. Below the critical point, you get lower pressures. We don't see CO2 in our everyday air conditioners because it doesn't have the typical pressure-temperature relationship above the critical point (over ~88-degree ambient conditions). It is also more common in regions with colder ambient conditions like Canada. We rarely encounter the triple point in other refrigerants, but it is crucial in CO2 refrigeration. The triple point is the temperature and pressure at which a substance can exist as a solid, liquid, and gas. The triple point of carbon dioxide is very high, so we can come across it in normal equipment operation. We don't want dry ice in the system, so we want to charge the CO2 system with our pressure well above the triple-point pressure. Don and Bryan also discuss: John Gorrie's original machine Recovery (or lack thereof) Sublimation of dry ice (solid to vapor CO2) Risk of asphyxiation in confined spaces Leak detection Saturation and operation pressures of CO2 compared to HFCs Liquid vs. gas tanks Piping and fittings CO2 grades and moisture content Sales and distribution Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Sam Myers of Retrotec joins Bryan and Kaleb on the podcast to discuss building performance. He also answers some of our listeners' questions. Checking airflow is important for building science as well as HVAC. However, "airflow" is vague and can refer to static pressure readings (which isn't actually "airflow" at all), air from whole-home ventilation systems, or CFM per ton. We can also look at total system airflow with flow hoods. Equipment settings also matter when it comes to measuring airflow as it relates to building performance. Leakiness (of the ducts or structure) is a common building performance issue. Blower door tests can determine the building pressurization and are a great tool for determining leakiness. However, we usually only do comprehensive "airflow," duct leakage, and building envelope tests during renovations or other large-scale projects; we don't typically check "airflow" and duct leakage when we do small repairs like capacitor replacement. When balancing airflow, we usually rely on room-by-room load calculations. However, Sam finds that finding a pressure differential between rooms can be a bit more reliable. The main drawback is that a pressure differential won't tell you if a room isn't getting enough air, but the opposite problem is far more common and can be addressed. The duct system's location also has a lot to do with a building's ventilation or sealing strategy. If the attic is in an unconditioned space in a humid climate, it may be best to seal the area to control the dew point. Sam, Bryan, and Kaleb also discuss: Airflow measurement instruments Total system airflow Balancing and isolating rooms with comfort issues Grilles, diffusers, and vents in zonal duct design Using your senses during balancing Ventilating vs. sealing the building envelope Infiltration and air mixing Split-level homes Blower doors Building performance in commercial HVAC Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

The great Ed Janowiak (Jon-Oh-Wok) joins us to talk about what correct airflow really looks like. He also explains how to design for it appropriately. The ACCA design series (Manuals J, S, and D) all go hand in hand to design HVAC systems properly for a given space. Correct airflow will depend on how a technician or designer uses the ACCA design series. When we say "correct airflow," we mean that the CFM per ton matches the sensible and latent load for a space while maximizing comfort for building occupants. In many cases, 400 CFM per ton is the rule-of-thumb baseline for many systems, but it's not a one-size-fits-all solution. The point of the ACCA manuals is to use math to determine solutions tailored to a specific space and avoid rules of thumb. Many technicians prefer higher airflow in the field because it leads to fewer technical problems. However, the occupied space can suffer from reduced latent removal when you have higher airflow. Variable-speed technology helps a bit to allow longer runtimes to help with dehumidification, but consumers may not be in the market to purchase those solutions. We can use airflow grids to determine the CFM on a running system. When those grids determine that the CFM per ton is below 300, that means the equipment is likely failing to match the required sensible BTUs. Airflow also affects pressurization, which you can measure with a manometer. Overall, you will want to track airflow trends and work to optimize the airflow. Ed and Bryan also discuss: Using software for calculations Friction rate Sensible heat ratio (SHR) Equipment selection and code compliance Relative humidity targets Intermittent ventilation Ancillary dehumidification Duct sweating Residential vs. commercial equipment design gap Blower door testing Testing delivered capacity and balancing Zonal pressure testing Extended performance data Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Have you ever heard a compressor that keeps changing in sound as it runs? Trevor with Emerson tells us more about what that is all about and how the digital compressor operates.

Joe and Eric join us, and we have a general conversation about small self-contained refrigeration units, including residential and commercial. Small refrigeration includes self-contained reach-ins and small walk-ins. These units typically use capillary tube metering devices. Some of the biggest failures that occur in small refrigeration systems happen because of dirty condensers and user error (leaving doors open, etc.). You'll also want to check that the fans are working, the compressor is running, the coil is free of ice, and that the airflow isn't blocked. Inspection is the key, and gauging up is typically a last resort. Refrigeration temperature measuring strategies can vary wildly by application. For example, open cases measure discharge air temperature. Systems with enclosed boxes (like walk-ins) typically sense return or box temperature. Small reach-in systems also typically have dial cold controls in a challenging location: buried at the end of the evaporator. There are straight and curly cold controls, but new equipment has made a shift towards electronic controls. On small refrigeration units, we don't usually see start capacitors or hard start kits; however, we do see PTC relays and thermal overloads. Domestic refrigerators also count as small refrigeration. They have independent controls that move air from the freezer to the refrigerator section of a normal household fridge; there is usually no cooling apparatus in the refrigerator. In systems with defrost timers, a bimetal defrost thermostat would open when the element detects no more ice on the coil, and defrost would terminate. Joe, Eric, and Bryan also discuss: Capillary tubes vs. other fixed-orifice metering devices Capillary tube restrictions and R-134A Leaky systems Vacuum Box temperature vs. coil temperature controllers Set point and customer expectations Safety controls Resistance in circuits Defrost fan delay and failsafe Hoarfrost Learn more about Refrigeration Technologies HERE. 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.

Kaleb, Joe, and Eric join us again to discuss some myths about single-pole contactors. We also cover some weird crankcase heater wiring configurations. When you have a single-pole contactor on a unit with no other resistance crankcase heater attached, the contactor energizes the compressor but is NOT a source of crankcase heat. That myth about single-pole contactors likely stems from a misunderstanding of Ohm's law and resistance heat. We care about crankcase heat because we want to prevent refrigerant from migrating into the compressor during the off cycle. A crankcase heater keeps the compressor shell warm and prevents vapor refrigerant from condensing in the compressor. Overall, crankcase heat helps prevent flooded starts and oil loss. Some crankcase heaters can be wrapped around the outside of the crankcase, and others can be inserted into the compressor. The crankcase heater and compressor winding can connect across an open contact to form a series circuit. (If you hook across L1 and T1 so that the other side has constant potential when the contact is open, a path can go to the crankcase heater.) The resistance in the compressor winding can contribute to the crankcase heat strategy, but Joe and Eric argue that the resistance is insignificant. Overall, we need to remember that resistive heat is resistive heat; in a resistive circuit, your wattage is your wattage, and you can convert that directly to BTUs. Kaleb, Joe, Eric, and Bryan also discuss: Two-pole and three-pole contactors Resistive heat Operating A/C and heat pumps in low-ambient conditions Ohming compressors Jumpering in place of a single-pole contactor Wire sizing Loud thumping when the unit shuts off Trickle current during the compressor off cycle Power factor, reactive power, and actual power Low-resistance circuits Capacitor purposes, wiring, and sizing Small charge and flood back prevention 3/8" lines Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Trevor Matthews with Emerson Canada comes on the podcast once again to talk about electronic expansion valves (also known as EEVs). He explains how they work, what they do, and how to diagnose them. Trevor compares electronic expansion valves to TXVs on steroids; they accomplish similar tasks, but EEVs have faster response times, better accuracy, and can improve system efficiency. The valve operates on a controller, which is the "brain" of the EEV that tells it to open or close. EEVs can come in the on-off variety (pulse-width modulation) and stepper valves, which rely on a motor to control the mass flow through the metering device. Pulse-width modulators are less accurate than stepper valves because they only have two operation settings. When installing EEVs or systems with EEVs, in many cases, the valve will point down. When brazing in stainless steel valves, you'll usually use a 30% (or higher) silver solder. It's also a good idea to wrap the valve and flow nitrogen while brazing. The bulbs of these valves MUST be insulated and strapped properly. The bulb and transducer need to be outside the refrigerated box in low-temperature conditions. When troubleshooting EEVs, the best thing to do is start off by reading the manual; you want to understand the valve and controller. Then, check the parameters and determine where the pressure transducer and temperature probe are located. Trevor and Bryan also discuss: Balance of forces and superheat control Solenoid valves How stepper motors control the mass flow Various refrigerants and EEVs Setting parameters on EEV controls Flux and flux-coated rods Evaporator feeding EXD-SH and EXD-U02 controllers Connections, cabling, and wire splices Expansion valve hunting Objectional current and electrical issues with controllers Battery backup vs. solenoids Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Trevor Matthews from Emerson Canada joins us on the HVAC School podcast again to talk about CoreSense by Emerson. Each CoreSense module has the potential to protect compressors. The technology can detect issues like overheating, short cycling, locked rotor, missing phase, low oil, and more. In short, the goal is to notify the technician or mechanic that something happened; sometimes, the control can also shut the compressor off and lock it out. Overall, it wants to communicate with the technician; different flashing codes indicate different sets of issues. If you have CoreSense software on a laptop, you can access compressor data while the system is running. The software is available for A/C and refrigeration applications, so you can use the technology in residential HVAC as well. Modern compressors can take a lot of abuse but last a long time. However, they can be expensive and are a total nightmare to install. Technologies like Emerson's can help technicians diagnose and fix compressors before we need to go through the financial and physical hassle of installing a new compressor. When you think about it, buying several CoreSense modules for a rack will probably cost less than a single compressor replacement. While the up-front costs may seem a bit high, Emerson packs the value into their new technology and allows customers and technicians to invest in guided troubleshooting and failure prevention. Trevor and Bryan also discuss: LED light flashing codes Tying CoreSense into Emerson controllers Scrolls vs. semi-hermetic compressors Compressor expenses Residential product line accessories Zero point Performance Alert vs. phase monitors Application Engineering bulletins (AE8-1367 [semi-hermetic] and AE8-1424 [scroll]) Outlier diagnostics Refrigeration Software (CoreSense Protection, Diagnostics & Performance Alert) – https://climate.emerson.com/OPI/documents/clc/CoreSense_PC_Communication_Software.exe Air Conditioning Software (CoreSense Communications) - https://climate.emerson.com/OPI/documents/clc/CoreSense_PC_Communication_Software_AC.exe HVACR Fault Finder App: (Android) - https://play.google.com/store/apps/details?id=Emerson.FaultFinder&hl=en_US (Apple) - https://apps.apple.com/ph/app/hvacr-fault-finder/id465325739 Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Alex Meaney from MiTek/Wrightsoft joins us again because he's an awesome trainer and knows a thing or two about how to more out of online education for the trades. During the COVID-19 pandemic, we've seen a dramatic shift from in-person to online education. The transition has been hard on students and educators alike, but there are still ways to make it work. Preparation is the key. Before you enter a class, make sure you look at the agenda and required or suggested reading. It's also a good idea to make sure you have the correct devices to access and participate in your online class; don't wait until right before the class to see if you have the right software or technology. We also recommend familiarizing yourself with the vocabulary before attending a class. One way to boost the effectiveness of online training is to make yourself responsible for another person's learning. When you tutor or teach others, you raise the stakes of your own education. It's also good to take a class with a buddy, as you can fill the gaps in each other's learning. The learning environment is also important; put away all your distractions, have a clean work area, and close the door to get the most out of your online class. On that same note, make sure you're comfortable; have a snack and a drink during your online training. If you need to keep your hands busy, find a quiet way to get your hands moving; we suggest writing notes down with a pencil. Alex and Bryan also discuss: Wrightsoft education changes Preparation tips for instructors Education as an investment Ineffectiveness of PowerPoint slides Accountability in education Forcing yourself to have the space to learn Time management Asking questions Watching recorded material Microphone and camera awareness Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Our good friend Trevor Matthews from Emerson Canada joins us to talk about compressors, mostly preventing compressor failure and troubleshooting issues. Whenever we're installing or servicing a compressor, we need to think about possible systemic issues right off the bat. The compressor is the heart of the system, but everything else in the system affects how the compressor runs. You'll want to know which type of compressor you're working with as well as the manufacturer. As always, you'll want to check the superheat, subcooling, amps, TD across the condenser, and (especially) discharge line temperature. The compression ratio is also a telling sign of the system and compressor's health. You take the compression ratio by dividing the absolute suction pressure into the absolute discharge pressure. However, we must also consider the compressor's application; by design, refrigeration compressors can deal with higher head pressures than A/C compressors. Anytime a compressor fails, you'll want to investigate why it failed. You can only see what happened inside a compressor if you cut it open and inspect it. During the inspection, look for signs of overheating and damaged components. Whether a burnout, flooded start, or thermal overload caused the failure, you will be able to see clues about the failure and can piece together the compressor's story. Once we finish troubleshooting and diagnosing a compressor, we can focus on preventing future compressor failure. We'll have a better idea of the operating conditions we need to avoid. Trevor and Bryan also discuss: Head pressure (discharge pressure vs. liquid line pressure) Compressor types Compressor overheating Return gas temperature Burnout Line driers The 80/20 rule Flooded starts Short cycling Non-bleed TXVs Recovery and evacuation Thermal limit Advanced temperature scroll protector (ATSP) Emerson Flow Chart - https://www.hvacrschool.com/wp-content/uploads/2020/08/2004ECT-126_NOTRUNNING.pdf Compressor Installation Guide - https://hvacrschool.com/wp-content/uploads/2018/01/Compressor-Installation.pdf Emerson System Cleanup Bulletin - https://climate.emerson.com/CPID/GRAPHICS/Types/AEB/ae1105.pdf Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast episode, Bryan discusses the importance of suction line temperature and what it can tell you about an HVAC system. There are two main places to take your suction temperature: at the evaporator outlet and right where the suction line goes into the condensing unit. When the former number is high, you could have a starved/underfed evaporator. When the latter number is high, you may have poor suction line insulation. If the refrigerant is too hot when it goes into the compressor, you can overheat the compressor over time. Under normal operating conditions, you will see about a 10-degree swing. At a 75-degree indoor temperature, the evaporator temperature will probably have around a 35-degree TD. So, you run around a 40-degree evaporator coil under 75-degree indoor conditions. (That is true of all refrigerants.) If the refrigerant picks up 10 degrees of superheat in the evaporator, you'll have about a 50-degree suction line at the evaporator coil outlet (+/- 5 degrees or so). Then, when you measure the suction line before the compressor, the temperature can increase about 3-5 degrees more. Overall, you'll want your temperature to be below 65 degrees at the compressor inlet. If you see a lower temperature, then you'll want to start looking at airflow. If you see a warmer suction line temperature, you'll want to make sure the suction line is insulated, that there are no restrictions, and that the system is not undercharged with refrigerant. We are fans of non-invasive testing; that way, you can measure the temperatures without hooking up gauges and getting the pressures. Measuring pressures is not always necessary, but we highly recommend checking the suction line temperature whenever possible to benchmark the system. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, Neil Comparetto from Comparetto Comfort Solutions joins Bryan and Kaleb to discuss some duct installation best practices he has learned. You might be able to take away some of his duct installation tips and apply them in the field. Neil used to focus a lot on making the ducts look good, but nowadays, he focuses a lot more on performance; the work of art is in the data, not the beauty of the building materials. The quality of the seal on the duct is more important than the duct's appearance. Neil focuses a lot on leakage, and he says it all starts by committing to low-leakage connections in your mindset. He does as much sealing as he can before hanging the ducts. Flex duct is one of Neil's favorite materials even despite its poor durability. Flex duct is quiet, well-insulated, pretty cheap, normally leak-free, and quick to install. Of course, you must install it in straight lines and pull it tight for best results, but its performance is pretty close to that of normal sheet metal. It can be difficult to separate the install from the design, so some design features are beyond the installer's control. However, if possible, it's best to keep the duct system as small as possible. Shorter ducts reduce the likelihood of leakage and the area available for thermal transfer, especially in unconditioned spaces. Neil, Kaleb, and Bryan also discuss: Design and preparation before installation Squeegee, tape, insulation, and mastic Brands that Neil likes Splicing flex duct Finding friction rate and balancing Downsizing equipment Building codes and inspections Balancing supply and return Return grille placement on homes with few large returns Getting feedback Equivalent lengths of straight vs. 90 boots Duct vs. register velocity Takeoffs Dos and Don'ts of duct installation Filters Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast episode, Bryan explains what happens to a compressor when it's overheating. He also covers possible causes and troubleshooting strategies. One of the Kalos techs came across an overheating compressor case that looked like a textbook TXV problem: the superheat was high at the condensing unit on the compressor side. However, the air handler superheat was appropriate, and the suction pressure was low. TXVs, however, respond to the superheat dropping and reduce the pressure even more. Overall, the mass flow rate and velocity drop, meaning that the refrigerant temperature can increase as it spends more time in the suction line. We were missing a few key measurements to diagnosing compressor overheating. In those cases, we want to know the return gas temperature, discharge line temperature 6 inches out from the compressor, and the compression ratio (absolute discharge pressure / absolute suction pressure). You'll generally want to see a compression ratio between 2.6 and 3 on residential HVAC equipment; the lower the compression ratio, the better the efficiency. A compression ratio higher than 3 can lead to compressor overheating. A return gas temperature consistently above 65 degrees can also make a compressor run hot. The discharge line temperature should not exceed 225 degrees. Then, you must determine if the charge is correct. (Are you starving the evaporator?) Check if you have restrictions and if your suction line is improperly insulated. Restrictions and heat transfer in the suction line can lead to compressor overheating. It's bad for a compressor to run hot, but they can go their entire lives without tripping on the thermal limit. Compressors that run hot can have lubrication issues and will have shorter lifespans. The best thing you can do is try to reduce the compression ratio. (Clean the condenser, keep head pressure low, keep good indoor airflow, etc.) Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, Kaleb, Joe, Eric, and Bryan answer some troubleshooting and commissioning questions from Facebook. Whether we're talking about troubleshooting, commissioning, or any other HVAC/R task, the best training is on-the-job training. Meetings, educational videos, and quizzes also help to a lesser extent, but bypassing training altogether is a mistake. Senior techs can also become better diagnosticians when they teach others. "The Diagnostic Game" is an especially useful tool to help teach newbies how to troubleshoot a system. However, training is something that is ultimately what you make of it. When you consider external training, you must consider the value of that training. (For example, NOVAR training would be useless for a residential tech but critical for a grocery refrigeration tech.) You also want to make sure your training makes you a valuable job candidate and that you stay motivated throughout training. When it comes to diagnosis, you can't truly diagnose the equipment until you know how it operates under normal conditions. Until you become familiar with normal equipment operation, you're essentially relying on trial-and-error. Getting the answer correct is only part of the equation; you also need to know why the answer is what it is when troubleshooting. Kaleb, Joe, Eric, and Bryan also discuss: Leaving subcooling just shy of the target value Balancing the charge during a hot pull down How much can we expect techs to do training on their own time? Just-in-time education The relationship between training and pay raises "Understand before you do" Replacing parts on a unit with a failed compressor Megohmmeters and multimeters The Kalos residential commissioning process Troubleshooting no-cool calls Inspecting customers' homes Communicating with customers Money-losers for residential companies Classroom training vs. field experience Fluid dynamics in ductwork Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, Ty Newell from Build Equinox comes on to discuss the CERV2 and how it embodies "advanced fresh air." The CERV2 is the second-generation version of the CERV. A basic ERV allows for discharge air leaving the home to pass the intake air. When the airstreams cross through a core, there is an exchange of sensible and latent energy. The ERV may promote dehumidification and cooling of the incoming air. The CERV is a form of ERV technology, but it addresses the issues that may arise from crossing the airstreams. For example, we don't always want to exchange energy, so sensors can examine the air content and determine when and when not to exchange energy. The CERV, an advanced fresh air solution, went into development in 2008, and the first unit was built in 2010. The CERV has sensors for carbon dioxide and VOCs; either one of those may dominate the air quality in the home. The CERV also uses a heat pump to exchange energy and help heat or dehumidify fresh air coming in. The CERV also has higher CFM than most ventilation solutions, meaning that it can flush out pollutants effectively. So, the CERV acts as a supplementary heating/cooling source for maximum comfort and indoor air quality. Build Equinox is a small company, and it has about 400 CERV/CERV2 units spread throughout North America. However, because the market is small, they can examine feedback very closely. Ty and Bryan also discuss: Potential downsides of bringing in outside air Dehumidification for CERV Recirculation mode CERV unit controls Using hydrocarbon refrigerants Concerns with microchannel coils Oil carry, miscibility, and foaming Superheat control Assessing indoor air quality Sensitivity to IAQ threats Latent-dominated, sealed residential constructions Testing and choosing sensor technology Check out more at buildequinox.com. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Our main man, Bill Spohn, joins us again to talk specifically about combustion. He also explains how to select and properly utilize a combustion analyzer. It's critical to do combustion analysis when you service equipment for the first time or just after installation. We need benchmarks, so that's when our combustion analyzers can come in handy. (Of course, you also want to use your senses to inspect the equipment.) Commissioning is another good time to bust out your combustion analyzer. Combustion analyzers should properly measure oxygen, temperature, and CO. Oxygen and temperature sensors tell you the combustion efficiency, and the CO sensor tells you about the carbon monoxide content. However, the CO sensor should also have a NOx filter to prevent nitric oxides from showing up as CO. The goal is to have no CO present in the living space, and sensors that pick up NOx can raise a false alarm. Some combustion analyzers also have pressure sensors, which can detect static pressure drops across heat exchangers or filters. You can use these for some building-performance tests, including zonal pressure diagnostics. You can also potentially measure ambient CO with your combustion analyzer. Once you have your combustion analyzer, you need to calibrate it and maintain it. Temperature sensors rarely need recalibration, but your CO sensor needs occasional recalibration after repeated exposure to gas. NOx filters can also expire and may need replacement. Overall, combustion analysis is a critical part of gas furnace inspection. However, it's best to use other inspection methods too, such as looking for heat exchanger leaks. Bill and Bryan also discuss: Flame displacement Condensation buildup Nitric oxides on CO sensors Dilution of CO and base signals CO alarms How CO sensors work How air enters the home Induced-draft systems under negative pressure in the flue Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast, Bryan shares some of his advice for people looking to get into the trades by starting an HVAC/R career. When you step into the HVAC/R trade, you must remember that you'll acquire a mix of skills and talents that all work together. You must reflect on yourself and see if you'll be a good fit for the trade. Do you enjoy working with your mind and your hands? Do you enjoy working to some degree? If you don't like pressure or dislike working with your mind or hands, then the HVAC/R trade isn't for you. When starting an HVAC/R career, you don't want to rely on a system or process to provide you with everything you need. Trade schools won't provide the full scope of field education, so you can't rely on them for everything. Instead, join social media groups where professionals discuss equipment and answer questions. Watching reliable YouTube channels helps a lot, too. Self-motivation is the key to success in this career. Don't go into an HVAC/R career if you aren't motivated to jump into new tasks or subjects. The best way you'll learn in the trade is by practicing with your own hands. Brazing and soldering are more advanced skills that your senior techs probably won't let you do on customers' equipment. However, you can read plenty of guides and practice on your own once you feel confident. You can also study for and take EPA tests on your own. There are several points of entry to the trade: apprenticeships, trade schools, and entry-level positions with companies. The one you choose will largely depend on the availability and quality of each in your area. You want to spend a lot of time working with your hands, no matter which path you choose. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Jaden Lane joins us to discuss some best practices when using an air flow hood. She also explains how the Dwyer Smart is innovating in the hood space. An air flow hood is an excellent tool, but we can't just assume that it'll work correctly in any system. Various vents and diffusers can cause different flow patterns to reach the hood, so you can get an incorrect reading if the flow hood is not aware of the flow pattern. Unless we give the hood background on what's going on in the duct, there's no way the hood will know the correction factor to give you the correct reading for the conditions in the duct. You can adjust smart flow hoods to compensate for inaccuracy factors. Hoods are like big canvas skirts that you place over a vent, and there's a flow grid at the bottom. As air moves through the hood, the grid takes airflow readings. There are pitot arrays that act as traverse points on a duct traverse; these arrays take multiple measurements and give you an average. These devices work better when the air is a bit turbulent. If you doubt your measurement, you can also try the hood in different 90-degree orientations (but keep it centered). Dwyer does a lot more than just make test instruments. They have a rigorous testing process for their products; their products can also work as permanent installations within buildings, not just tools for technicians. Jaden and Bryan also discuss: Dwyer products, including the Magnehelic Vent vs. grille vs. register vs. diffuser Computational fluid dynamic analysis and other test methods Calibration vs. zeroing Predictive balancing Choke and backpressure Vane and hot-wire anemometers Check out Dwyer at dwyer-inst.com. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Russ King joins us to discuss simplifying duct design for residential contractors. We focus on using 3D software for duct modeling. While computers are great tools for duct design, you must be careful with them. Computer technology doesn't correct your mistakes; it allows you to make mistakes more quickly. Russ made 3D software specifically for duct modeling, and its goal is to help technicians/contractors with duct designs and equipment sizing. The software is good for quick duct design, can determine flex duct design, and is ideal for broad usage in residential HVAC. Russ has noticed that existing energy modeling and load calculation software ask for extremely specific inputs, which can confuse technicians. He was frustrated with the process and wanted to make software that could help technicians solve the problems that mattered in a way that made sense. With the help of his son, Russ came up with Kwik Model (of Coded Energy). They developed software that allows users to design ducts and adjust parameters easily. The goal is for Coded Energy to be a simple, straightforward duct design software that addresses the hardest duct design issue: making the ducts fit. Coded Energy is written in Unity, which is used for video games and architecture/automotive design. The user essentially imports a floor plan, scales it, places boxes, and stretches the boxes to meet the design conditions. Once the user has built the house, the software can calculate the surface area automatically. Then, the user can use EnergyGauge for load calculations and equipment selection. The user can then draw ducts and have the software size the ducts for them. Russ and Bryan also discuss: Equipment selection for latent removal capacity Oversizing issues Designing ducts for building plans Comfort diagnostics 2D vs 3D modeling Getting feedback in the field post-design Visit kwikmodel.com to learn more. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Bill Spohn with TruTech Tools joins us to talk about why being "approximately correct" is better than being "exactly wrong" when it comes to test instruments. When you see a number, that doesn't necessarily mean that you're dealing with a number you're supposed to see. For example, nitric oxide can present as "false CO" to a carbon monoxide sensor. Test instruments that mistake nitric oxide as carbon monoxide will give a different reading than ones that don't pick up nitric oxide as CO, but that doesn't necessarily make either of them wrong. So, some instruments can give you false positives based on exactly what they measure. On the other hand, false negatives may have to do with poor sensitivity. A common case happens with leak detectors; on occasion, a leak detector won't be sensitive enough to pick up a leak. You can't just say that a set of numbers on an instrument absolves you of responsibility for errors; you must understand the instrument, what it measures, and its sensitivity to use it appropriately. Being rigid in terms of specifications is also a mistake when communicating with customers; customer satisfaction is the goal, and it's okay if their comfort needs deviate from the specifications a bit. Overall, accommodation and mental/financial investment in your tools are the keys; for the sake of the customer, we need to make acceptable compromises, and that's something you must factor into your measurements. Bill and Bryan also discuss: NOx filtration Bacharach PGM-IR Personal protective CO detectors and overloading Laboratory-grade instruments vs. normal test instruments Getting valid wet-bulb readings and using sling psychrometers Analog gauge variables and inaccuracy Lab testing and controlled conditions Ductwork in conditioned spaces Flow hoods Using our senses Olfactory fatigue Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Bernadette Shahin of Aeroqual joins Bryan and Kaleb as they all dig very deep into indoor air quality (IAQ) sensors and instruments. They also cover the certainty and uncertainty of measurements. Reference method instruments generally have to operate within a set of parameters, notably a temperature range. Gas laws make the gases act differently, so you want the temperatures and pressures to stay within a range that allows you to measure the air conditions effectively. While we can use reference methods for full-scale instruments, there are no reference methods for IAQ sensors. The only way to make something close to a reference method on IAQ sensors is to use the near reference method. We measure humidity and temperature, and we do an atmospheric chamber and calibration. You have to pair sensors within an instrument to have a product that properly senses conditions. Measuring indoor air quality is important because we spend 90% of our time breathing indoor air with very little fresh air. Air pollutants build up in indoor spaces, and you could spend time in environments with harmful VOCs, allergens, and bacteria. Most people don't have the means of using HEPA filters or fresh air mixing in their homes; so, we need to focus on other solutions to control indoor air quality. Those solutions include air purifiers, but they also include sensors that monitor the air quality. One such sensor is the photoionization detection (PID) VOC monitor. With sensors, we must also think about sensitivity; we want the sensor to measure what it's supposed to measure in the amounts it's supposed to measure. Bernadette, Bryan, and Kaleb also discuss: Barometric pressure instrument calibration Algorithmic adjustments Sick building syndrome Formaldehyde off-gassing, ozone, and CO Aeroqual's solutions for BTEX Automatic baseline correction R2 factor AQI Automating IAQ strategies Pricing Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Jordan Cummings is back to discuss some of the most important points in the proper installation of VRF and VRV systems. We especially cover piping best practices. When it comes to piping, the biggest concerns on VRF and VRV systems are making sure the piping can handle the refrigerant velocity and ensuring proper oil return. Most VRF systems use PVE oil, but you still want to be cognizant of oil type, as not all manufacturers use PVE. You must consider fittings, length, and elevation changes when you pipe a VRF or VRV system. In our suction line, we want minimal pressure drop because too much suction drop reduces the mass flow rate through the compressor. You also need to think about avoiding too much of a pressure drop on the dual pressure line when it sends refrigerant to the compressor. You want your piping to be below the connections on the outdoor unit. The piping should be pitched up towards the unit when the outdoor unit is elevated on a stand. Of course, you'll also want to be mindful of where you place the outdoor units; the units should avoid the elements and be mindful of any awnings above. VRF/VRV systems come together at a variety of joints, including REFNETs and wyes (multi-chassis kits). Indoor units use REFNETs, which are basically engineered, balanced wyes. Outdoor units use typical wyes. Positioning these joints also makes a huge difference when it comes to proper feeding. Jordan and Bryan also discuss: Pipe sizing with software Dual pressure line PVE vs. POE oil Miscibility and oil carry Air-cooled vs. water-cooled condensers Condensate drains and trapping Reduced pumping/flow on water-cooled condensers External static pressure Alarms Piping limitations Cross piping on the branch selector box Expansion valve staying shut Pipe expansion 550 PSI, 24-hour pressure test Testing as you go Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Bryan and Eric Mele have a relaxed conversation on time management on the job. They also explain how to manage time in life as a whole. Some people are naturally fast because they cut corners in the name of time management. Instead, something Eric has learned to do is optimize his processes. He gets his work done a lot more quickly because he knows how to get the most out of the trips to his truck. Eric is also familiar with the tasks to perform them confidently, and he knows which diagnostic tools he'll probably need. Overall, repetition leads to efficiency. There are also plenty of ways to streamline evacuation and recovery. For example, Eric recovered refrigerant by piercing the liquid line from the air handler. His setup consisted of two charging hoses, a line dryer, and a recovery machine; it was an economic way to save his tools and recover refrigerant in the rain. Eric has done a lot of installs with people of varying experience levels. If there's one thing he learned, it's that you can streamline the process by starting at the outdoor unit, getting the old unit out, and getting the new unit set. The entire time, only one person should be working on the one-person jobs while the other gets supplies and makes preparations as needed. When it's time to work on the new unit, one person can work outdoors while the other works indoors. Eric and Bryan also discuss: Diagnostic tools to keep close or go without Dealing with paperwork Scavenging and saving small parts Cleaning the drain pan Pulling a vacuum through difficult fittings Working with people of diverse experience levels Using tin snips Efficiency and payment Work-life balance Prioritizing parts of your life Working with cranes Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast episode, Bryan explains what suction line traps and inverted traps are. He also covers the purposes they serve. It's a bit hard to find literature on suction line traps, so it's always best to read the manual and follow the manufacturer's guidelines. We traditionally use P-traps on suction lines to hold oil and let it go up the walls of the refrigerant piping. You need enough velocity to lift oil (mineral or alkylbenzene) up the riser. We know that POE carries much easier with refrigerants than mineral oil; it is very miscible with common refrigerants. That's why it's especially important to get all of the mineral oil out of retrofit systems. In refrigeration, we have lower temperatures, pressures, and densities; that combination adversely impacts oil carry. Oil logging is a bigger concern even with POE oil. So, P-trapping with POE oil is a more common practice in refrigeration than it is in air conditioning. In air conditioning, we can make a case for the inverted trap: in an air handler that's higher than the condenser, we want the suction line to go above the air handler and then go down into the evaporator coil. When the system goes off, there is still refrigerant in the evaporator coil, so refrigerant will condense into a liquid. We don't want that liquid to rush down the suction line and into the compressor upon startup, so we use an inverted trap to prevent flooded starts from happening. However, we can use hard shutoff TXVs and other strategies to prevent liquid refrigerant migration. Unfortunately, inverted traps can also keep mineral oil stuck in the evaporator coil. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast episode, Bryan explains how you can prevent and overcome price objections in your HVAC business. You can prevent price objections by avoiding the "budget" reputation. If your company establishes itself as a "budget" or "cheap" company, you will attract coupon-clipper customers. Coupon-clippers can be difficult to work with because of how cost-conscious they are. Customers who aren't looking for a deal will be less likely to object to pricing. You also don't want to shy away from money conversations with friends or family members. Once you get your business model and clientele established, you need to overcome pricing objections in yourself. "Expensive" isn't the issue; value is. If you set a price, then you need to be confident in it; pricing is a business decision, not a moral imperative, and you won't please everybody. If you're not comfortable with the prices, your discomfort can show in your body language and turn the customer away. Another tip is never to talk down your own value or make your work seem like it should be cheap; don't be afraid to explain labor or warranty costs if the customer asks. You can also prevent price objections by avoiding dramatic language. Instead of saying, "This will be expensive," or, "I've got bad news," you can just give the facts and the quote. If the customer gets emotional, you can empathize with them and give them a positive outlook on the situation. It also helps if you can keep money conversations as comfortable, clear, and fact-based as possible. Make sure you get customer approval and allow your customer to decline new procedures every step of the way. Bundle in extra value if you can. Oh, and remember to be empathetic and do a good job. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast, Bryan explains why latent capacity is prone to disappearing. He also explains what actually happens when the latent capacity drops. When you measure enthalpy split across the coil, you'll learn that the equipment design makes it perform to AHRI design conditions. Those design conditions are 95-degree outdoor temperature and 80-degree indoor temperature at 50% indoor relative humidity. So, the A/C system must remove a lot of moisture. However, we don't usually run A/C units for 80-degree indoor temperatures; we usually aim for a 75-degree indoor temperature. When we have 80 degrees, the sensible AND latent heat loads are higher. Things get tricky when we encounter disappearing latent capacity, which is when you remove less moisture. If we have equipment with a sensible heat ratio (SHR) of 0.75 at design conditions, we'll likely have a higher SHR with our typical conditions. When the dew point is lower, water condenses on the evaporator coil at a lower temperature; water holds up the surface temperature of the evaporator coil and optimizes heat removal, suction pressure, and compression ratio. When heat transfers to the water on the coil, the sensible heat in the air decreases via a latent process. When we don't have moisture on the coil, all of the heat going from the air into the refrigerant is making it in via conduction through the metal coil walls. Unless the coil gets below the dew point, it won't remove any moisture; we can still remove sensible heat, but you don't have the advantage of the moisture "holding up" the surface temperature. In very dry climates, we increase the airflow because we don't want to remove moisture from the air, but we still want heat to be available to the evaporator coil. However, we have to be careful about the bypass factor. Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast, Jeremy Smith joins us to discuss demand cooling in low-temperature applications that use R-22 refrigerant. R-22 is NOT an ideal low-temperature refrigerant because it leads to high compression ratios. The discharge gas also gets really hot and can burn up the oil in the system. (The head of the compressor is even hotter than the discharge line, so if the temperature is high enough to cause oil breakdown in the discharge line, it's almost surely worse inside the compressor). However, R-22 is starting to go away in rack refrigeration. Demand cooling injects saturated refrigerant into the compressor to help mitigate the high discharge temperature and oil damage. It may seem like demand cooling intentionally slugs the compressor. However, the saturated refrigerant should boil off almost immediately, and it should not make it to the head of the compressor under typical conditions. On the diagnostic and repair side, demand cooling is usually pretty straightforward; if a sensor fails, then it's likely a thermistor issue. In the case of thermistor problems, you can diagnose those issues with the information given in the application engineering bulletin. Loose connections and valve restrictions can happen, but those are also pretty easy to diagnose and repair. Perhaps the most complicated issue occurs when rack systems have low liquid levels. The injector valves can't get a solid column of liquid, but many other components will work fine. Demand cooling solutions are usually brand-specific; each manufacturer has a slightly different setup. To learn more about the Copeland Discus compressors with demand cooling, check out the AE4-1287 bulletin. Jeremy and Bryan also discuss: Outdoor air and head pressure DTC valves Desuperheaters and hot gas bypass Tube-in-tube heat exchangers as "subcoolers" Seasonal changes in discharge temperature Why should we pay more attention to discharge line temperature? Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Bryan and Kaleb cover the basics of low-voltage electrical applications. They focus on the practical stuff, not just the theory that confuses techs. Many techs have a hard time with low-voltage electrical concepts and components because it's not easy to visualize what happens; we only see wiring diagrams, not metaphors that help us understand what's going on. The low-voltage control circuit starts with the transformer. The transformer has a primary side (where the high voltage comes in) and a secondary side (where the lower voltage comes out). The secondary is only connected to the primary via electromagnetism; it helps to think of the secondary as an independent electrical circuit. Color coding is a simple concept, but it has changed over the years and can confuse techs. You can only truly understand the wires by doing a complete visual inspection and tracing the wiring. (Though generally, blue will be common/C, and red will be hot/R.) We also typically use yellow for Y1, but Y is a confusing concept. Y ISN'T the compressor or cooling! Y pulls in the contactor coil; it is really the high-stage contactor. Y2 is a higher staging, and Y1 is a lower staging. On heat pumps, the white wire is usually for heating, and the orange wire is usually for the reversing valve. G is for the indoor fan and often has a green wire. Kaleb and Bryan also discuss: Tapping transformers W and O calls on heat pumps G calls DH on 24v controls Communicating controls Float switch configurations and issues Breaking Y or R with the float switch Wire routing: air handler and condenser Preventing conductor corrosion NASA or lineman splice Stranded shielded wire vs. solid wire Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this short podcast, Bryan talks about the impacts of compression and airflow changes. He also discusses some of the ramifications of those changes. In order for us to energize the second stage of a compressor, we need to energize both Y1 AND Y2. On stage 2, we're running that compressor at full speed (350-450 CFM per ton). The compressor will also perform at rated capacity. When you stage down to stage 1, your blower should ramp down, and the compressor should produce less capacity (move less refrigerant). When moving less refrigerant, the compressor should use less current but still be cooled properly. Naturally, the suction pressure goes up while the head pressure goes down when we ramp down the compressor. However, when you reduce the blower speed at the same time, your evaporator coil picks up less heat. In that case, the suction pressure would drop. You normally don't want the suction pressure to go up in the low stage from the high stage. The impacts of compression changes are multifaceted, and there are several moving parts to think about when it comes to capacity. When the compressor slows down, it moves less refrigerant over the same period of time; your compression ratio goes down if your airflow over the evaporator coil remains the same. However, if the airflow drops proportionally, then your suction pressure should stay close to the same. If the compressor pumps the same amount of refrigerant, the suction pressure will drop. If the compressor pumps less refrigerant proportionally to the airflow, then the suction pressure should remain the same theoretically, but it usually increases. An increase in suction pressure results in a lower compression ratio, which is good for efficiency. Bryan also discusses: Floating the evaporator temperature Broken valves on reciprocating compressors Improperly seated scrolls Improper tonnage ratings across components Oversized coils Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, we ONCE AGAIN talk about superheat and subcooling. This episode is a recap to help people who struggle with the concept. You get superheat when you have 100% vapor, and you have subcooling when you have 100% liquid; any liquid-vapor mixtures are in a saturated state. We usually measure superheat outside at the suction or vapor line. It's best to take the superheat reading as close to the port as possible. Anything in the saturated state is boiling; you can only get the mixture at the boiling point of a refrigerant. Anything above the boiling point is all vapor, and it's superheated. Very high superheat indicates that the refrigerant boiled off very early in the evaporator, meaning that the system could be low on charge. On fixed-orifice systems, you charge a system via superheat. Zero superheat indicates that you have liquid in the suction line. When you have liquid in the suction line, you can cause compressor slugging, which leads to failure. You will usually only measure subcooling at the liquid line, usually right at the outlet of the condenser. When you read a higher level of subcooling, that means the system has more liquid stacked in the condenser. Any refrigerant below the condensing temperature is subcooled. In many heavy commercial/refrigeration equipment, you will have a sight glass instead of taking subcooling readings. Excess subcooling indicates that too much refrigerant has stacked up in the condenser, so you will likely also see an undesirable rise in head pressure. Bryan and Kaleb also discuss: Superman and submarine analogies Problems with the pot of water boiling analogy What really is steam? Sensible vs. latent heat Metering devices Superheat and subcooling targets vs. measured superheat/subcooling Adjusting charge Condenser as a desuperheating component Evaporative effect on the condenser Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this psychrometric basics podcast, Bryan and Kaleb talk about the properties of air. They also discuss dry-bulb, wet-bulb, dew point, and relative humidity. Psychrometrics is the study of the relationship between air and its properties. The psychrometric chart can be a bit intimidating, but you can use it in a variety of ways. A technician should care about this chart because it helps with whole-home diagnosis. You can't see the whole picture of someone's comfort unless you know the properties of the air. The left side of the chart is centered on wet-bulb and enthalpy, and the right side is centered on the absolute moisture content; the chart provides a comprehensive comfort profile if you use it correctly. Dry-bulb temperature is the basic sensible temperature of the air and gives you a one-dimensional heat measurement. Wet-bulb temperature directly relates to the evaporative properties of water in the air; the wet-bulb temperature changes based on the moisture content even if the sensible heat stays the same. So, wet-bulb temperature gives us a better picture of the enthalpy, which is the total heat content (latent AND sensible). The wet-bulb temperature will usually be lower than the dry-bulb temperature, and the difference is called wet-bulb depression. The only time when wet-bulb and dry-bulb temperatures will be the same is at 100% relative humidity, also called the dew point. At the dew point, the air can no longer hold any more moisture, so any additional water vapor in the air has no choice but to condense. Bryan and Kaleb also discuss: Radiant gains and dry-bulb measurements "Cold air is dry air" Relative vs. absolute humidity What really is temperature? Sling psychrometers vs. digital probes Load calculations Supply air and relative humidity Insulation and humidity Learn more about Refrigeration Technologies HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.