HVAC School - For Techs, By Techs

In today's podcast, I talk to John Oaks about his experience as a VRF tech in the field, including branch boxes and two-pipe vs. three-pipe technology. John primarily works on the troubleshooting and service side rather than the installation and programming side of the field. Variable refrigerant flow (VRF) systems, also called VRV systems when manufactured by Daikin, are commercial HVAC systems. VRF systems work best in commercial buildings with some degree of fragmentation, like offices and medical facilities. These systems are similar to multi-zone ductless systems, but they operate on a much larger scale. VRF systems have a branch box, which acts to direct traffic between the various zones of a building and parts of the system; the branch box allows the unit to heat and cool simultaneously. A 24v signal drives most of the controls. These controls are "daisy-chained," as VRF systems are very interconnected, and a defrost signal can have up to about 50 destinations to various components. The entire VRF installation process requires careful attention to detail, not just on the programming side. When it comes to common issues with VRF systems, the refrigerant charge is one of the most critical problem areas. These systems mask issues with the charge, so it is difficult to find out if a system is undercharged or overcharged. In addition, you can't weigh out the charge in the same way that you would in a residential system. John and Bryan also discuss: Metering device placement Industry improvements and upgrades Inverter boards Line set length and charge issues Flares, brazing, and ZoomLock Condensate removal and drainage strategies Diversity of zones and efficiency Two-pipe vs. three-pipe configurations Cooling mode, heating mode, and mixed conditions   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 is a voice-over audio presentation of the article of the same title on the HVACRschool.com website ("The Trade Skills Gap: A Manifesto). The manifesto discusses the value of technicians and the trades in modern society. It also covers the plague of snobbery that we are all too familiar with in the world. You can read "The Trade Skills Gap: A Manifesto" 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.

Jason Obrzut comes on the podcast and talks us through his furnace sequence of operation training: "Take It Slow, It's Gonna Blow!" There are 6 main steps in Jason's furnace sequence of operation training. The phrase, "Take It Slow, It's Gonna Blow!" should help you remember the sequence (Thermostat, Inducer motor, Safety switch, Igniter, Gas valve, Blower motor). The first component in the furnace sequence of operation is the thermostat, which initiates the call for heat. So, the thermostat has to send the signal to the circuit board. After the board receives that signal, it sends 120v out of the board to the inducer motor. Next, the inducer pulls the gas combustion air into the heat exchanger. That air will then be deposited into the exhaust. The inducer is what aids the venting action and is a critical part of a furnace. The safety switch is a general term for a negative pressure switch with a hose connected to the inducer housing or heat exchangers. Negative pressure from the inducer motor will close that switch. When that switch closes, 24v goes back into the board. Then, the board sends a signal to the igniter. Now, you will finally begin to see heat delays. Silicon carbide and silicon nitride are common igniter materials nowadays, but they are fragile. Once the igniter has worked long enough, the gas valve opens. We get 24v from the board to the gas valve, which brings on the gas flow and starts a timer. When the timer expires, the blower motor will come on. This component is the LAST one to come on. Jason and Bryan also discuss: Pressures on the flue Cracked heat exchangers Safeties not closing Hot-surface vs. intermittent-spark vs. direct-spark ignition Flame sensors and proving flame DIP switches   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 talk through stack effect. We explain what it is and what sorts of comfort issues it can cause in a home. Most of us understand that hot air rises even though heat itself doesn't rise. The stack effect is precisely a version of that piece of common knowledge; hotter air is less dense than cooler air, so it floats above the cooler air. In hotter air, the molecules move a lot faster than they do in cooler air, so they can start to separate from each other, which reduces the overall air density. For the most part, we don't work pressurize air in HVAC work (not refrigerant), but we do change the temperature. The temperature changes cause the difference in air densities to emerge. If we're dealing with a furnace system in a two-story house or a home with high ceilings, we see that stack effect in action. When that hotter air rises and cooler air sinks, the hotter air makes way for a vacuum that draws colder air into the building. While that hot air rises, the colder air comes in under doors and through low cracks. Although the air that's coming out of the appliance is warm, it can't do much to heat the space before rising. The reverse stack effect can also happen. When you have poorly sealed can lights or cracks in the ceiling, the colder, denser air will sink and create negative pressure near the highest point of the room. When we have that negative pressure, hot air can get pulled in from the attic or other undesirable locations. In Florida, we have to worry quite a bit about the reverse stack effect, whereas the stack effect is more of a concern for colder climates.   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.

Jim Bergmann gives us a year-end review of all that is happening at MeasureQuick and his predictions for the future of app-based diagnosis. He also covers what's been going on with Redfish, BluFlame, BluVac, Supco, Testo, and Fieldpiece. Diagnostic tools only work if the buyers understand how to use them. When apps can assist the tool buyers and users with diagnosis, the tool manufacturers can focus more on improving the technology; they can leave the software and education to mobile applications. Implementing gas appliance diagnostic education has been a challenge for Jim and other app developers. However, they are attempting to take app-based gas appliance diagnosis to the next level. The goal of diagnostic apps is to educate technicians about tools and readings and to make diagnoses more comprehensive. From the start, one of MeasureQuick's major focuses has been accessibility and ease of use. A diagnostic app that gives technicians a seamless way to take readings, store data, and learn about their measurements should be easy to use, so Jim has put a lot of work into making a user-friendly app. So, the next step for MeasureQuick in terms of accessibility will likely be to allow users to share data for remote viewing. MeasureQuick has incorporated education on the basic refrigerant circuit, electrical components, gas appliances, and vacuum within the app. Soon, Jim would like MeasureQuick to expand into the refrigeration and geothermal sides of the HVAC/R world; he'd also like to implement project notes. Jim and Bryan also discuss: Monetizing diagnostic apps Tying tools into diagnostic software Wireless range and BlueTooth considerations Working with programmers How much might I invest in an app-based diagnosis app? Third-party quality control Future-proofing Project or process-based functions Integration Electronic accessibility and 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.

What is the difference between accuracy, precision, and resolution? In today's short podcast, Jim Bergmann explains the differences and why they matter. People commonly confuse accuracy and precision. Accuracy refers to how close a measurement is to the correct value, but precision refers to the consistency of values. For example, you can get several infrared thermometers to measure the difference between circuit breakers, and the thermometer readings all come out close to the same value. They aren't necessarily accurate, but they are precise. In cases where we use a voltmeter to measure for the presence of voltage, we don't need a high degree of accuracy. However, when we want to measure exact voltage values, we want to make sure our tools are accurate. Sometimes, voltage that is too low can cause issues with the circuit boards. Resolution refers to the smallest possible amount of change you can detect. For example, one voltmeter may measure to the nearest whole volt, and another may measure to the nearest tenth of a volt. The resolution is higher on the latter voltmeter, as it detects a smaller change than the first voltmeter. Some tools measure with a high resolution, but the increased resolution may compromise the accuracy. For example, if a manometer reads into the Pascals range, it may only have a tolerance of +/- 5 Pascals, which leaves room for inaccuracy. However, again, accuracy is not always the most important value. Sometimes, resolution and precision are more important than accuracy. After all, in the words of Jim Bergmann, it's pretty difficult to measure feet with your car odometer. One common example where precision and resolution are more important than accuracy is when techs try to measure microns with analog gauges. The accuracy means nothing when the precision and resolution are poor.   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.

John guides us through all aspects of ventilation and system design. He gives us a review of point ventilation, ASHRAE 62.2, whole-home strategies, and much more. Nowadays, construction protocols instruct builders to make houses tighter than the builders of the past. The goal of building tighter homes is to give us more control over the temperature, quality, and energy impact of the outside air we bring into our homes. Common sources of ventilation are local exhaust systems, including bath fans and kitchens. However, in tighter constructions, there is a greater need for whole-home strategies to bring in outside air and dilute indoor-generated pollutants. Some of those pollutants include VOCs, odors, and moisture. We must think about how to introduce that outside air into the home and how that outdoor air will impact heat loads, moisture levels, and air quality inside the home. When we select equipment for airflow, we need to think about constant vs. intermittent flow. In humid climates, you also need to take extra steps to prevent moist outdoor air from leading to excess condensation in the home. Ventilation equipment either delivers outdoor air to each room or mixes that outdoor air with the return air. Try to ensure that the space temperature doesn't drop below the dew point, which can be a challenge in humid climates. Ventilating dehumidification is a promising solution for HVAC system replacements and new constructions in humid climates. In cold, tight homes, ventilating dehumidification can keep a home dry enough to keep occupants comfortable in the winter. John and Bryan also discuss: Why do people want energy efficiency? "Passive house" and airtightness standards Mixing air and filtration Carbon dioxide (CO2) ERVs vs. HRVs for balanced ventilation Fan cycler systems Duct installation quality Dedicated make-up air Fireplaces and gas appliances under negative pressure   Learn more about Think Little, John's company, at think-little.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.

Bill and Bryan discuss gas and combustion tools. These tools include manometers, combustible gas detectors, personal CO detectors, draft gauges, and combustion analyzers. Manometers measure gas pressure, and they require calibration but are usually quite accurate. Before using a manometer as a diagnostic tool effectively, you must understand your targets and resolution. Some digital manometers come with BlueTooth technology, so you can log, convert, and store your data on mobile devices. Gas leak detectors are relatively inexpensive tools. These should NOT be confused with combustion analyzers, which are different tools altogether. You usually cannot calibrate these tools. When using a gas leak detector, the leak detection process on gas pipes is similar to the electronic leak detection process on straight-cool A/C units. Draft gauges measure very fine pressure differentials in the combustion air zone. These may use flappers or vanes to give you data about the direction and amount of draft. Most importantly, you want to ensure that you have no backdraft. These tools take very fine measurements, so they have high resolution. Because of their high resolution, they require frequent calibration to stay accurate. Personal (or ambient) CO monitors are also important gas and combustion tools. Carbon monoxide (CO) is odorless and colorless, and it can be deadly. To avoid CO poisoning, use one of these monitors to remain aware of the CO content in your space. Combustion analysis has evolved a lot over the years. Today, we perform combustion analysis with a single tool. When combustion occurs, a chemical reaction occurs. Combustion analyzers determine what happens post-combustion by taking temperature and oxygen readings. However, they also account for the presence of CO, which indicates incomplete combustion. Bill and Bryan also discuss: Analog and Magnehelic manometers BPI-1200 Precision CO monitor upkeep/disposal Perfect combustion AHRI-1260 Nitric oxide filters Choosing tools   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 speed-talks through all the basics of heat pumps and how they function. Heat pumps are not physical pumps or components on an A/C system. A heat pump is an HVAC unit that is also capable of heating a home by reversing the refrigeration cycle. When that reversal happens, the traditional indoor "evaporator" coil acts as a condenser that rejects heat in the home. As such, the traditional outdoor "condenser" acts as an evaporator that absorbs heat from the outdoors so long as the refrigerant is colder than the outside. Due to how they function, heat pumps are more common in warmer climates. The heat pump's reversal happens on the reversing valve, which diverts refrigerant right before the compressor. A solenoid shifts the valve when you enter heat mode from cool mode (or vice versa), and that's how refrigerant gets diverted. These just slide back and forth, and they are pretty reliable; they don't typically malfunction. Before a reversing valve can work, the system must be ON; the valve cannot shift if the unit is OFF. Heat pumps typically have two metering devices, one by the indoor unit (cool mode) and one by the outdoor unit (heat mode). A check valve controls the flow of refrigerant to the correct metering device. Heat pump systems may also often have suction accumulators and crankcase heaters to help prevent oil loss and flooded starts in the compressor. The defrost controls for heat pumps typically have a timer and defrost sensors. We also discuss: Issues with heat mode TXVs Checking the charge on a heat pump Defrost sensor types and operation Auxiliary heat Economic balance point   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.

Jason from ESCO and Cengage comes on to talk about the varying landscape of EPA 608 regulations with what you need to know for now (circa 2018). The EPA has proposed to roll back some regulations regarding HFC refrigerants, including leak rate and leak repair mandates. There are also questions about the regulation of refrigerants that do NOT have ozone-depleting substances, not just HFCs. This choice reinterprets language within the guidelines put forth in 2016 and the Clean Air Act. However, this choice completely disregards global warming potential and limits regulations of refrigerants with global warming potential but no ozone-depleting potential. EPA 608 still prevents the venting of non-natural refrigerants, but the proposed changes aim to clarify the language in those regulations. EPA 608 Subpart F can potentially be rescinded entirely. That action could muddy the language as to what constitutes venting. HVAC businesses can also suffer, as technician certification may no longer be a requirement for purchasing refrigerants. (Not to mention, homeowners can ignorantly engage in harmful practices, like cross-contaminating refrigerants and venting. Substance abuse is also much more accessible if non-HVAC techs purchase refrigerant to huff it.) The USA is actually well behind other industrialized countries when it comes to refrigerant usage. We're one of the only industrialized countries that have yet to really move forward from HFCs. So, rolling back HFC regulations may be a step back for environmental initiatives, refrigerant innovation, and even the refrigerant reclamation job market in the USA. Jason and Bryan also discuss: EPA exam changes Individual state regulations and certifications Who benefits from these changes? Comparisons to other toxic chemicals Air quality, pollution, and resource exploitation Refrigerant recovery and mixing How will this change affect the job market? How will this change affect education and writing?   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.