HVAC School - For Techs, By Techs

David Richardson with NCI, author of Duct Dynasty, joins us on the podcast to talk about mixed air temperature and more topics of interest. When you bring outside air into the home, you introduce positive pressure into the home. That way, you can offset air lost via mechanical ventilation or through cracks, improving air quality. We often assume that the building will "breathe," but tighter constructions make it difficult for the home to bring in enough fresh air to offset harmful chemicals and VOCs. We need to measure two different kinds of airflow: fan airflow and outside air. When we have these numbers, we must figure out how much air is coming through the outside air intake. The fan airflow represents 100% of the air content after mixing has taken place. You can perform a duct traverse to get the airflow measurement; when you plot the fan airflow, subtract the two to know how much return air you're getting BEFORE mixing with the outside air. Once you have your airflow measurements, you must break those into percentages. You must determine the percentage that matches up with the temperature you want to use for the mixed air. Subtract the outside air from the fan airflow to get the CFM from your baseline. You could get 95% of your airflow from the return and 5% from the outside. Once you know the outside air temperature and the percentage of outside air, you will know how much the outdoor temperature will affect the return air and space temperatures. David and Bryan also discuss: How David got into writing Blown-in cellulose insulation Designed and undesigned leakage Duct traverse tools and procedure Dry-bulb vs. wet-bulb measurement applications SEER vs. AFUE Duct leakage   Learn more about NCI at nationalcomfortinstitute.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, Bryan briefly explains why we use a voltmeter to measure “voltage drop” across loads and switches. He also covers some of the differences between passing and consuming power. Many of us are naturals at using voltmeters already. Voltmeters have two leads, and those exist to measure the difference or potential between them. Voltage is a reference to what is going on between the leads; whenever resistance exists, we have a voltage drop. Resistance can sometimes be designed or undesigned. When we think about power passing and consuming, we should note that "consuming" refers to turning energy from a usable form to an unusable one. Stored energy becomes potential energy when it needs to do work. Power consuming results in work; a coil in a contactor or a filament in a lightbulb is a load (the load has resistance). On the other hand, power-passing components do not have resistance, and the charges merely move. We must keep the intended resistance in mind whenever we measure the voltage of energized components; resistance will impact the voltage drop. If you have a high-limit furnace safety, you will want to measure the voltage drop across the limit. There should NOT be a voltage drop across it because it is a power-passing component; there should be no resistance. Of course, you must determine if there is an energy potential present in the first place. Conversely, you SHOULD see a voltage drop when measuring the potential across a heater or fan motor. Overall, wires and switches are power passing components that should not have voltage drops across them. Heaters, compressors, and fan motors are all loads that "consume" power.   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.

Ty Branaman from NTI comes on the podcast to share his passion for teaching. He also discusses his approach to impactful HVAC/R instruction. It can be difficult for instructors to create an appropriate balance between teaching theory and practical knowledge. Students and trainees need to have technical skills in the field, but they also need a solid foundation. Impactful HVAC/R instruction requires a balance of the nerdy stuff and physical skills; good instructors put the theoretical parts simply and give students the opportunity to apply theory to hands-on skills. Engagement is another important part of HVAC/R education. If students are sitting down for 15 minutes, that's too long; the students need to be moving and active with the learning material to stay engaged and help the topics stick. Ty emphasizes the importance of spending time in the lab instead of staying in the classroom the entire time. Unfortunately, many trade schools nowadays don't prepare students for fieldwork because there is not enough emphasis on working with equipment in education programs. The best teachers are those who love teaching AND working in the field, and trade schools need more people who are passionate about BOTH. Passionate technicians need to get involved in education by offering to be a substitute or guest speaker or by joining an education advisory board. Ty and Bryan also discuss: Teaching the refrigeration cycle What the current generation values and needs in education Dealing with distractions in the classroom Using mobile apps to supplement learning Teaching newbies effectively Creating an HVAC/R instruction program on a budget Old equipment Getting involved in education How to guide young people in their careers "Thinking outside the box"   Check out Ty's YouTube Channel 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, we take a quick look at Bryan’s take on practical safety improvements. He also discusses the safety year in review at Kalos. Kalos had a great year in terms of safety. As the managers look back on the year, they attribute their success to having a practical approach to safety. To make practical safety improvements, we must be safety-conscious without obsessing over the risks of our job. Our jobs always have an element of danger, and our goal should be to minimize those and abide by OSHA standards. As an industry, we can do a better job of wearing our eye protection on almost every job. Ear protection is also an area we tend to neglect, especially in motor rooms and industrial environments. Ladders also provide a clear source of danger; we need to make sure our ladders are secure (tied off, set on level ground, etc.) and place some responsibility on our customers to give us a safe work environment. Electrical safety is also critical. Especially on commercial jobs, we should use proper lockout-tagout procedures when we can't monitor the power source while we work on equipment. We must also verify that no power is present after we shut off the disconnects. We also experience some fire safety threats, especially while brazing. Eye protection and gloves are critical if you want to keep yourself safe while brazing. (Gloves are also important when cutting sheet metal.) You should also know where fire extinguishers are anytime there is a fire risk on the job. Perhaps our most dangerous work environment is the road. We must avoid texting while driving, drunk driving, and other unsafe practices. We must also drive defensively to avoid accidents with other commuters who partake in unsafe driving practices.   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.

Tim Fregeau from Goodway joins us to talk about descaling large equipment. He also discusses best practices and why they matter to you. Scale refers to mineral deposits that build up in any water source. Water can be brackish, rusty, muddy, or otherwise high in mineral content, and those minerals begin to accumulate on heat-transfer surfaces on large equipment. Scale can cause metallic components to weaken and leak, and it can block microchannel coils. The large equipment can't reject the heat efficiently or function as it should when it has scale buildup, so that's where descaling comes in. When it comes to chillers, you can either brush or chemically clean the tubes to remove scale. There will be times when you physically cannot brush the tubes, so you must rely on chemicals to descale the equipment. When you use chemicals, you pump the chemical solution into a low point of the condenser and make it come out of a high point. Factors that influence success are the chemical makeup, flow rate, and pump size. Boilers are quite similar to chillers, but the higher water temperatures come into play. Various chemical agents have different functions. Acids dissolve calcium, and inhibitors protect the base metals. Wetting agents reduce the surface tension and allow the chemicals to spread out. Penetrating agents allow the chemicals to get deeper into the mineral deposit to dissolve calcium and free up the rest of the deposit. Tim and Bryan also discuss: Plate heat exchangers Separating open loops from chillers Goodway clean-in-place systems Chemical selection and dilution Circulation time Why track oil levels and approach temperatures? Compression ratio and system efficiency Common cleaning challenges and mistakes to avoid Water pH Calcium spot tests Goodway products Legionella   Check out Goodway's site 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 a bit about brazing temperature. He also covers how to heat your copper to the proper temperature. You can use torches with oxyacetylene or air-acetylene tips. Joining two metals with an alloy above 840 degrees classifies as brazing; anything that uses an alloy to join two metals below 840 degrees is technically soldering. When you join two similar metals by melting the base material (not using an alloy), that's welding. Another temperature of interest is 500 degrees; oxygen rapidly bonds to copper at temperatures above 500 degrees, so we will want to flow nitrogen while brazing to prevent cupric oxide (black scale) from forming on the copper. (We always recommend flowing nitrogen even if you are soldering below 500 degrees.) When brazing with a 15% silver alloy (with a phosphorus fluxing agent), you will want to reach a temperature of 1100-1200 degrees. Solidus is when the rod gets a putty-like consistency. However, we want liquidus, which is when the alloy can flow freely into the joint. The color of the copper will be either dark or medium cherry. To be clear, you DO want to see redness when brazing; the color shouldn't be very bright red or orange, but a dark or medium red is ideal. The brazing indicators hold true for copper-to-steel and copper-to-grass brazing as well. Aluminum brazing should stay below 1200 degrees; aluminum also doesn't have the same color indicators as copper, steel, and brass. Steel is complicated because it has a lower melting temperature, but it has much lower thermal conductivity than steel, so it will take longer to heat up and may heat unevenly. You also CANNOT use an alloy with a phosphorus fluxing agent when brazing steel or brass; you need a silver alloy with a separate flux.   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 live episode, we talk about heat pumps, why Bryan likes them, why other people don’t, charging and diagnosing them, and defrost. Even though heat pumps work best in warmer climates, they can theoretically work as long as the temperature is above absolute zero (-460 degrees F). Viewers across the USA install heat pumps in their markets, even in places with cold winters like Wisconsin. Ideally, the discharge line should be around 100 degrees above the outdoor temperature in heat mode. Although this rule of thumb appears to work in many different climates, it is only really applicable on single-stage equipment. When charging heat pumps from scratch, check the manufacturer data in heat mode. Airflow for comfort or efficiency is something else to account for when you're commissioning a heat pump; the CFM should be higher if you want the system to be efficient, but the building will be more comfortable if you have a lower CFM per ton. Airflow is especially important to control in heat mode, as small changes can noticeably affect head pressure. When it comes to defrost, heat pumps typically use a time and temperature strategy. Defrost cycles usually run at a certain temperature for a fixed time period. Heat pump defrost boards usually look a lot more complicated than they really are; when you come across them, stay calm and remember that they're just like any other board. We also discuss: Absolute zero Climate zones “Vapor line” Discharge superheat vs. over ambient W calls Supplementary heat and dehumidification Confirming airflow on a heat pump in heat mode Controlling mean radiant temperature (MRT) vs. blowing hot air Using in-duct psychrometers and manufacturer charts to assess system performance How reversing valves may fail or get stuck Thermal imaging applications Copeland compressors and mobile app Testing defrost boards Carrier vs. Trane & Rheem defrost strategies Demand defrost Suction pressure and compression ratio under frost buildup   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 crossover episode (rantcast), Bryan talks with Gary from HVAC Know It All. They vent about some of the phrases that techs throw around that are often false. Technicians often throw around the phrase, "[X] will void your warranty." However, the truth is that manufacturers can't really void a warranty. Some modifications may go beyond the scope of the warranty, but you don't simply make modifications that "void" the warranty. Techs may say that something voids the warranty to shut down the conversation or to create a selling point (preventive maintenance). In many (but not all) cases, the manufacturer won't even check the installation in the case of a parts warranty; all they want is the returned part, and they will often honor the warranty. Since many manufacturers want to keep their customers, voiding warranties left and right would be a bad business decision; the customer base would opt to work with new manufacturers. However, if there is evidence that the customer, installer, or technician damaged the product, then the manufacturer has a reason to void the warranty. In several cases, the proof must be substantial, and the proof often isn't substantial when using natural additives like Nylog properly. Keep in mind that using additives comes with a calculated risk; you must rely on research and your own judgment to make the best decision for the customer. In this rantcast, Gary and Bryan also discuss: R-22 is not illegal Heat exchanger warranties Lightning and other "acts of God" The Nylog question Why use thread sealants on well-made flares Relationships with manufacturers and suppliers Warranties and original homeowners Putting the customer's needs above the manufacturer's Who really is a hack? How everyone in the distribution chain can take responsibility Complaining respectfully online   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 discusses the differences between air, nitrogen, and oxygen. He also explains why we should only use nitrogen for purging, flowing, and pressurization. You DON'T want to pressurize line sets with air because air contains water vapor and oxygen. Water acts as an oxidizer, and moisture can turn POE oil acidic via hydrolysis. You cannot dry out POE oil, and the acid can lead to compressor burnout. Nitrogen is non-reactive (unlike oxygen) and does not contain water vapor (unlike air). It also does a good job of chasing water vapor out of the lines. Because nitrogen won't react with anything we put in the line sets, it is an ideal medium for purging, flowing, and pressurization. Nitrogen DOES, however, change pressure with temperature; it obeys the gas laws, and you can see it in action when the pressure changes at different parts of the day (with varying temperatures). Oxidation can occur when oxygen reacts with copper to create a black scale called cupric (copper) oxide. It is similar to rust on iron; it is an undesirable form of corrosion. When the black scale comes off, it can get into screens on filter-driers and clog the system. You purge nitrogen to chase all of the air out before brazing. When you've finished purging, you use a flow regulator to reduce the nitrogen pressure (2-5 SCFH) to flow it during brazing. When we pull the vacuum, we only want nitrogen to be in the system; exposure to air should be very short, and any air in the system should be temporary. So, again, it's not a good idea to use air to pressurize the 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.

In this LIVE episode, we talk about diagnosing inverter-driven systems. We also discuss some of the issues and solutions for over-voltage. Inverter-driven systems, also called variable frequency drive equipment, provide comfort control across multiple zones in a building. Some systems may have multiple branch boxes that control various units throughout a building. These systems require a lot of patience; the diagnostic process can last a long time because you must test all of the terminals. Since these systems are very electrical-component-heavy, you may also encounter issues presented by lightning, power outages, or continuous high voltage. Installation errors are also common and can cause performance issues, such as incorrectly torqued-down terminals, nicked wires, and improper wire types. When these systems are on, line voltage runs into a bridge rectifier. So, the equipment takes alternating current (AC) and turns it into a form of direct current (DC). Capacitors smooth out the sine waves before running that current into the inverter, which switches the power into three separate phases, but the power doesn't look like typical three-phase AC power. Many power companies are familiar with single-phase AC equipment, so inverter-driven systems present a challenge. These challenges become clear in equipment near the initial power distribution source; inverter-driven equipment near the beginning of the power line is prone to excessive voltage and failure. We also discuss: Power surges and electrical damage ICM493 Loose connections Grounding Shielded conductor usage Pulse-width modulation (PWM) 230v-rated equipment Multi-stage equipment and airflow Bernoulli's principle Carrier Infinity equipment and locking out stages Ductwork and diffuser sizing Controlling radiant heat loads with multi-stage equipment Ventilation vs. dehumidification vs. heating and cooling R-22 retrofit refrigerants Metal oxide varistors (MOVs)   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.