HVAC School - For Techs, By Techs

Chris Stephens from HVACR Videos joins us to talk about his experiences with and perspective on R290 (propane) refrigerant in restaurant refrigeration. Chris sees R290 propane on a daily basis, and his perspective as a tech differs from that of an R290 equipment manufacturer. While the temperature sensitivity contributes to flammability, R290 is also under pressure in a system. Therefore, propane refrigerant systems require a lot of caution. R290 equipment must undergo thorough redesigning to be entirely spark-proof. Hydrocarbon refrigerants also require OEM components; aftermarket components change the design and can cause problems down the line, and technicians WILL be liable for any damages related to aftermarket components. When techs evacuate/recover R290, all evacuation and recovery tools must also be spark-proof; you also need to check to make sure that those tools are certified to work with propane refrigerant, even digital gauges. When using approved service gauges, also be sure to use short hoses. More so than ever, following the manufacturer's guidelines is an invaluable practice. Unlike R-22 and R-410A, you CAN vent R290. However, the location should be well-ventilated. Chris recommends that you take extreme caution when venting refrigerant, such as by using a leak detector to let you know when to stop. Most of all, we need to be aware of our surroundings when we work with highly flammable R290. When we use our senses and are aware of our surroundings, the refrigerant becomes much more predictable. Chris and Bryan also discuss: Buying and sourcing R290 Recommended R290 training resources Piercing valves Basic R290 behavior Flowing nitrogen Evaluating hydrocarbon systems and using a "common-sense" approach Leak detectors to avoid using for R290 systems   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, we discuss the common myth about cleaning flame rods/sensors/rectification devices. Flame sensors or rectification rods are NOT the same as thermocouples or thermopiles. Thermocouples and thermopiles use two dissimilar metals to create a temperature differential. So, we do not clean thermocouples and thermopiles because the heavy abrasives in cleaners can damage and reduce the effectiveness of those devices. However, you don't have to worry about that sort of damage on a flame sensing rod; we can indeed clean those. The flame rod sits in the flame (regardless of ignition type) and allows for a DC current to travel through the ions in the flame to ground. The flame creates a path for that current, which makes a closed circuit. Flame sensing rods are merely pieces of metal that allow current to flow when there is an active flame on a furnace. So, you want to keep your flame rods clean to allow for conduction. You may want to avoid using sandpaper or Emory-type materials to clean the rods because sediment can build up on the flame rod. When the flame ignites, the sandy substance on the rod can turn glassy and impede conduction. However, you can use an appropriate cleaner without damaging the rod. You can also replace the rod if you happen to have one on your truck, but you don't have to replace all dirty rods. Pool heater flame sensors can get exceptionally nasty due to the chemicals they encounter. If a piece of equipment has a flame rod that gets dirty a little too quickly, try to find the cause of the excess grime and take care of 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 podcast episode, Eric and I discuss his new home and his plans for installing central air the Eric-Mele way. Eric's home doesn't have an attic, crawlspace, or basement. So, designing and installing central A/C will be a challenge, especially since Eric doesn't like high-wall ductless systems. Eric considered using an air handler with exposed ductwork, but he doesn't want the noise issues associated with that design. He also considered using a package system, but it has the same noise concerns as the previous option. In the end, he decided to go with ceiling cassettes. Cassettes have a condensate pump, differentiating them from high-wall ductless systems and making them a bit more expensive. Eric has also collected his latent-sensible capacity data. Moisture removal is critical in his South Florida home, and equipment sizing is an important factor when installing central air. Sizing contributes to dehumidification because of its effect on runtime. However, smaller ductless/VRF units may not have sufficient heat even when they're properly sized. In the future, we expect companies to utilize heat sensors to improve the sensible heat ratio when moisture removal is needed. For filtration, Eric plans on seeing how the fan motors react to pleated filters. Upgrading the filters could help control sensible heat ratio and VOC contamination, but static pressure remains a concern. We also discuss: Ductless unit cleaning Filtration for air handlers with exposed ductwork Lagging vs. drilling Ceiling cassettes and condensate pumps Flex vs. duct board vs. metal ducts Oversizing VRF Two-pipe systems Activated carbon filtration Making flare fittings vs. brazing in factory-made flares   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 today's short live podcast, Bryan discusses the importance of context in education and the challenge presented by information. When we learn, we do ourselves a disservice by searching for information alone. Just-in-time education allows us to "search instead of research," and it works in a limited and inefficient way. Instead, we'd be much more effective if we knew how to learn efficiently. To learn efficiently, we need to bring context to the learning process. Instead of focusing on raw facts or abstract information, we need to know about the surrounding information. It's also beneficial to use similes and metaphors to grasp how something works. In other words, we need to connect new information to past experiences. Therefore, the learning process that most of us accept seems rather backward. Instead of feeding people answers immediately, we can supply them with experiences that can help them draw similarities between those experiences and demonstrations and the theoretical elements. The goal of context in education is to equip us to understand situations and solve problems repeatedly. As humans, we are likely to forget information that is fed to us directly and not connected to our experiences. Ideally, a learning process would begin with observation. We would show students how to do something or how something works. Then, we explain the theory behind why that thing works. Finally, the student or apprentice would be given the space to apply the principles themselves and work with their own hands. We also answer questions and respond to comments about: The value of schooling MeasureQuick compatibility Self-driven curiosity Companies working with educators   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, Jordan Cummings comes on the podcast to review application-based system selection considerations for VRF/VRV systems. A VRF/VRV system works a bit like a hydronics system, but it provides hot or cold air to various zones in a space, not water. The key to having a reliable and long-lasting VRF system is a good installation. Proper maintenance practices, including pulling deep vacuums for dehydration, will also improve the performance and life of a VRF system. When you choose a system to install, you have to determine if you want a heat pump or heat recovery system. Occupant type will play a major role in that equipment selection. Budget is also a variable, but it is typically less of a concern than occupant type and building purpose. Some VRF/VRV systems that have been primarily designed for cooling may need to provide heating in low-ambient conditions. In many cases, these will close fresh-air dampers and recirculate discharge gas. Some units may even have auxiliary heat or be backed up by other heating equipment. Defrost is also something you'll need to consider in low-ambient applications. Sizing is another important part of VRF/VRV selection and design. Consider nominal capacity but don't accept it as a hard and fast value. Keep your design conditions in mind; which temperatures and humidity percentages are you trying to maintain? What is the outdoor air temperature? Also, think about the piping total equivalent length and the estimated total distance between the outdoor unit and the farthest indoor unit. Jordan and Bryan also discuss: Buildings with cooling towers and boilers SEER vs. IER Aurora VRV equipment and technology Connection ratio Air handler unit and branch box selection Control boxes and accessory selection Discharge air control Condensate control Maintenance concerns for VRF/VRV systems Indoor unit turn-down   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 today's short podcast episode, we talk about specific gravity, also known as relative density. We explain why it matters to technicians. When we talk about specific gravity, we're actually talking about density. We're actually using that value to assess how a vapor or liquid's density compares to air or water, respectively. Regardless, we are working with the pressure conditions of 14.7 PSIA, or atmospheric pressure. In the case of liquids, we're relating them to water is at its densest, which is 39.2 degrees Fahrenheit. You may have noticed that ice cubes float in water. That's because water becomes less dense as it gets colder than 39.2 degrees and when it freezes. Ice is less dense and more buoyant than water. So, specific gravity requires a reference. Because it requires a reference, it is also a relative measurement, so "relative density" is another appropriate term for specific gravity. Regardless of units, we are still comparing one thing to a constant in the form of a ratio. (For example, a liquid with a specific gravity of 0.85 is equal to 85% of the density of water at 39.2 degrees Fahrenheit.) The relative density also explains why some liquids sink and others float when mixed together. Gases can also rise or sink based on how much lighter or heavier that gas is when compared to air. If the specific gravity of a vapor is less than one, it will rise to the ceiling. Natural gas is an example of that. If the specific gravity of a gas is greater than one, it will sink. LP is heavier than air and will sink. Therefore, LP is a bit more dangerous than natural gas because of how it takes up space due to its interaction with the air.   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, we speak with Embraco about R290 (Propane) refrigerant, hydrocarbons, and what you need to know about them. Embraco is primarily focused on compressors and is involved in the residential and light commercial market. The greater demand for natural refrigerants or hydrocarbons has made R290 popular. Hydrocarbons have hydrogen and carbon chains; although these refrigerants are very similar to grill propane, they are much drier and purer. R170 is another hydrocarbon for very low-temperature refrigeration. In some European countries, R290 and CO2 are becoming much more prevalent than synthetic solutions. China has invested a lot in hydrocarbon technology, and the United States has shown interest in using hydrocarbons for auto coolers and natural refrigerants for grocery refrigeration. R290 is flammable, but most techs' aversion to working on those systems likely stems from a fear of the unknown. These systems have several safety controls that prevent gas leakage from getting in contact with sparks. So, these systems rarely ever catch fire. Embraco also has a commitment to putting safety first when they design compressors. You can also vent R290 to the environment, which you can't do with many other refrigerants. Unlike other refrigerants, R290 has a very low global warming potential. R290 and CO2 are not perfect, but they will be the future as we move away from ozone-depleting substances and greenhouse gases. R290 is also making its way into the residential sector. You can find it in smaller applications, such as mini-fridges and even some other domestic refrigerators. We also discuss: Overloads and why systems aren't as flammable as they seem Terminal venting Embraco's design goals and philosophy Contamination and evacuation   Links: http://refrigerationclub.com/ http://naturalrefrigerants.info/ http://embraco.com/Default.aspx?tabid=40 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.

We talk about measuring tricky amperage on a blower and condensing fan motor. We also cover why you may be measuring inaccurately, resulting in a misdiagnosis. When measuring amperage on a PSC blower motor, you may have noticed that amperage on the common is higher when the panel is off. Conversely, on ECM or X13 motors, the amperage is generally lower with the panel off. When measuring amperage, we recommend using a Bluetooth ammeter to take readings without letting the panels interfere with your measurements. Anytime the amperage is low, the more difficulty the ammeter will have in measuring an accurate value. In cases where you're dealing with a very low amperage, you will need a higher-resolution ammeter for accurate measurements. One old-school way that you can increase your resolution is by using the 10-wrap method and putting that in series. Then, you take the amperage measurement and divide it by 10. We don't recommend doing the under-load test on a blower; a bench test is much safer. However, the compressor and condenser fan motor capacitance can be measured under load. Outdoor tests can be a bit challenging because there is a greater possibility for interference. Current drawn outside of the clamps can indeed affect the reading, and several other nearby conductors draw current inside condensing units. Sometimes, technicians replace perfectly fine run capacitors because the amperage seemed too high on an under-load test. To avoid interference, perform a bench test and check the actual microfarads. Tricky amperage interference also leads techs to condemn condenser fan motors when they really just picked up amperage outside the clamp. So, keep in mind that your meter could be running high or picking up interference. Any possible fail parts should undergo further testing to confirm that there's something wrong.   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 service manual talk-through episode, Eric Mele helps us discuss the Heatcraft Beacon 2 refrigeration system. We talk about what it can do and what it entails. The Heatcraft Beacon 2 is a refrigeration system with more electronic controls than electromechanical. However, it is quite user-friendly, and it allows you to see what the system is doing at almost all times. The monitor doesn't allow you to adjust anything in the system, but it lets you see valve position, superheat, time until defrost, and more as the system is operating. The Beacon 2 has a suction pressure transducer that maintains superheat. You can dial in the superheat on the control, and the system should control it almost exactly as long as all the components are working properly. You can also manipulate the wiring to run multiple evaporators off of one condenser. (There are master and slave evaporators, and you must differentiate them when configuring the controls.) When it comes to parameters, you have to set your defrost type to air or electric. In general, you use electric defrost for freezers. You must also set your refrigerant type accordingly. Then, you set your box temperature. Medium-temperature applications tend to be around 35 degrees, and many low-temperature applications tend to be around -10 degrees. You also have control over defrost settings and temperature units (Fahrenheit or Celsius). You can also find frequent parameters on the evaporator panel for more information. Most errors will be sensor errors. Many sensor issues are easy to test because of the user-friendly monitors. You can compare your reference sensor to the data to check the accuracy of what's being reported to the board. Eric and Bryan also discuss: Forcing pump-down and defrost Schematics and wiring practices/applications Headmaster valves Setting pressure controls Defrost frequency and failsafe   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.

This short podcast episode covers the why and the how of low ambient cooling and refrigeration. Low ambient cooling refers to operating A/C equipment during low outdoor ambient conditions. Typically, the cap of operation is around 55 or 60 degrees. However, some commercial facilities need cooling when the outdoor temperature is cold. For example, those facilities may have to cool electronics or large volumes of people. In buildings that don't have economizers, running the A/C in cold ambient conditions may be the only option. The same applies to restaurants, which always need to run freezers and coolers. When the outdoor ambient temperature drops, the condenser rejects more heat to the outdoors. Head pressure drops, and there may be an insufficient pressure drop across the metering device. We also can't run A/C evaporator coils below 32 degrees, as there is no defrost mechanism in straight-cool A/C systems. So, the strategy to get around those issues is to focus on raising the head pressure by modulating the condenser fan motor. A fan cycling control can turn the condenser fan on and off based on pressure. So, we try to maintain a fixed pressure in the condenser by allowing that control to shut off the fan when the pressure drops too much. However, fan cycling can be a bit jarring for the system. Motor master controls help modulate the motor by decreasing voltage to the motor. However, that fluctuating voltage isn't necessarily good for the motor. In those cases, you must have a ball-bearing motor. Unlike the motor master, a refrigeration headmaster is a valve that allows discharge gas to enter the drop leg. Variable frequency drives can work with a three-phase motor to vary the speed of the motor. When the speed can vary easily, you can manipulate the pressure.   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.