HVAC School - For Techs, By Techs

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.

Many contractors make a huge pricing mistake: confusing markup with margin. The distinction between those two things can be the difference between being profitable and losing it all. If you want to mark up something that costs $10 by 50%, you multiply it by 1.5 to get $15. So, did we make a 50% gross margin? No; we only made $5 on a $10 transaction; if we take 10/15, we get o.66. So, we really only made a 33% gross margin. When we factor overhead in, 33% is normally nowhere near enough. Not everything in the business will make money, and those costs become overhead costs. Businesses need to buy vehicles, pay for utilities, and save for emergencies, so you need a net profit from your sales to get enough money to pay or save money for those things. A good business makes 10+% net profit. If you don't do the math properly, you probably won't make that amount of money. If you use a 40% markup in cases where you have 30% overhead, you won't make enough money. If we have $70,000 in revenue and multiply it by 1.3, you won't get $100,000. Instead, you take the cost of goods sold and divide the number you're charging for by the cost of goods sold. 70,000/0.7 will get you $100,000, which accounts for what you need to earn to break even with 30% overhead. So, for a 10% profit, you'd divide 70,000 by 0.6 (30% overhead and 10% profit). So, using markup to set prices is a huge pricing mistake. The margins are where you really need to look. ("Margin" also sounds a bit better than "markup.")   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, Ron Saunders from Fresh-Aire UV comes on and answers questions about UVC. He clears up misconceptions and pulls no punches. Fresh-Aire UV (Triatomic Environmental) used to manufacture and sell ozone solutions, but the business evolved to sell UV and carbon-based IAQ solutions. UV lights exist on a spectrum of varying wavelengths. Some UV lights at the higher end of the spectrum produce ozone, but UVC light does not. UVC's frequency (~250 nanometers) is outside the range of light that produces ozone (shorter than 185 nanometers). Like any other IAQ product, UVC lights have advantages and disadvantages. To kill microorganisms, you need a mix of time, intensity, and proximity to the light. Since UVC effectiveness is so multifactorial, studies can be a bit misleading and can make the products look more effective than they really are by letting time and proximity make up for some slack in intensity. Visual light also doesn't necessarily reflect the light's intensity; you must be diligent about replacing them according to manufacturers' specs. UVC lights can kill all microbes, including viruses like COVID-19. However, light intensity and air velocity are both factors that determine how effectively UVC lights can kill viruses. Viruses don't propagate on coils like mold, though, so you don't have to worry about viral "growth" on coils in the same way you'd deal with fungi or bacteria. Ron and Bryan also discuss: Benefits and drawbacks of ozone solutions and oxidizers Time vs. intensity "Airstream kill rate" Viruses vs. fungi and bacteria How to answer customer questions about COVID-19 UV lights and component damage Handheld UV applications Hydroxyl radicals vs. ozone Scarce independent testing in PCO technologies UV light and skin/eye disorders Best COVID-19 product Using UV lights in ducts Measuring and detecting chemicals Stray light and VOCs   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 free-flowing conversation, the Trethewey family talks about growing up with This Old House, what the show is like behind the scenes, what Rich misses about the past, what the future holds for the trade, and some nerdy specifics between Bryan and Ross. The show business is a collaborative effort between the producers and talent (even though they're real people, not actors), and the Trethewey boys find the end result almost cathartic. This Old House was never scripted; there were beats and predictions about the content, but the content is all authentic. As the trade moves forward, Richard worries about weakening connections and producing leaks in the race to improve technology. He's glad that we work with far fewer deadly chemicals and materials nowadays, though. Many technicians are artisans at heart, and the future is bright because of techs who make ethical choices and do good, aesthetically pleasing work. (However, we can expect controls and ventilation to become increasingly important in coming years.) Bryan and Ross also brainstorm some innovative solutions for residential applications by looking at commercial equipment. Bryan enjoys thinking about using R-290 chillers and buffer tanks for residential applications. Ross anticipates a future focus on CO2 as a residential refrigerant; he thinks the future "magic box" solution is a CO2 split system for heating and cooling. Richard, Ross, Evan, and Bryan also discuss: Exposure to media Propane refrigerant Heat pumps vs. natural gas Hydronics Staying organized Pit corrosion on copper pipes What it means to be an "expert" at something and how it feels Core traits of successful skilled tradespeople Passive makeup air solutions New control strategies Getting new people into the trades   Thanks to Richard, Ross & Evan for making this happen. Check out the This Old House podcast “ClearStory” on your favorite podcast player. You can also learn more about the Trethewey boys' work at TE2 Engineering and RST Thermal. 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. TE2 Engineering    RST Thermal

Two of the great air and infiltration expert minds of our time, Gary Nelson and Steve Rogers from TEC (The Energy Conservatory), come on the podcast to talk about blower doors. They also discuss blower door testing and how it compares to real-life infiltration. A blower door has a fan to measure the air flowing through it, and you generally install it in a doorframe. Blower doors hook up to manometers to measure the pressure differential between the inside of a building and the outside. Generally, you need to adjust the fan speed to bring the pressure differential down 50 Pascals. Then, you measure the airflow through the blower. That is how you determine how leaky a building is; all the leakage comes out through the blower door due to the pressure differential. We use blower door data and mathematical models to estimate the natural infiltration rate. ACH50 is a means of expressing the leakage (air changes per hour at 50 Pascals). You take the CFM50 and multiply that by 60 to get the cubic feet per hour. Then, you divide that product by the cubic feet of the building to get your ACH50. You can apply a similar process to the surface area of a building instead of volume (though that's more common in commercial buildings). During natural infiltration, the leaks can move inside or outside the envelope, so it's difficult to use the blower door test to measure infiltration accurately. Wind and extreme temperatures also affect natural infiltration, and testing can't account for those. Gary, Steve, and Bryan also discuss: Testing pressure variations Analogies for measuring infiltration at 50 Pascals PSIG vs. PSIA Stack effect CO2 and infiltration Predicting infiltration rates with models Infiltration in cold climates How infiltration affects the latent load Duct leakage and building pressure Transfer grilles Balancing with precision manometers   Check out The Energy Conservatory at energyconservatory.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 explains how to keep your humanity and make moral decisions when selling IAQ products. As the COVID-19 pandemic has started to grab hold of the world, we've seen an uptick in IAQ interest. When you have greater consumer interest, there are opportunities to hoodwink customers. While some IAQ products are indeed not very effective against viruses, there are some good products that you can sell to customers to benefit their health. Pretty much every product has an appropriate application, but sales and marketing can lead to inappropriate, ineffective usage. Some techs sell IAQ products for inappropriate applications just to make a buck, but many others simply don't know any better. For example, UV and PCO technologies can work very well for certain applications, but they are not the fix-all that some people market them as. When selling IAQ products honestly, you'll want to understand the efficacy data in the exact application you're selling it for. If you don't have the data for the application, don't make claims about efficacy. When it comes to oxidizers, you must also be transparent about safety concerns. Sure, you can explain how particles combine, but you also have to explain safety issues with the particles' behavior. Independent testing is also important. Paid studies can be manipulated to make a product look favorable. Ask if the product does what it's supposed to do. Then, you have to ask if the product is safe. Cold plasma and oxidizing products are a bit less effective than other PCO technologies, but they are a bit safer. The goal is to educate yourselves and the customer so that you can both make the best decision for the customer's health.   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.

Nikki Krueger joins us to talk about how humidity impacts indoor health and some ways to make our indoor air quality better (for real). Indoor air quality is all about manipulating the air in our homes to reduce pollutants and keep our air quality high. From air dilution to running bath fans to air purifiers, there is a lot more we can do to make our homes healthier. We can't entirely isolate ourselves from viruses, bacteria, and fungi. However, there are many other things inside our homes that can suppress our immune systems, and we can address some of those things with IAQ. To incorporate humidity control into our plans, we must look at the dew point. Dew point will change across the country and throughout the seasons, so we must work with varying conditions to keep RH in the 30-60% range. You can run kitchen and bathroom exhaust fans to manage moisture and VOCs. However, we also have to make sure the air we draw in is high-quality and won't upset people's allergies. So, ventilating dehumidifiers are an attractive option to replace exhausted air with high-quality fresh air. Temperature is mostly about comfort instead of health, but filtration, ventilation, and humidity directly impact the healthiness of our indoor environments. When we can control those three things, we can create indoor environments that are truly healthy. Ultra-Aire dehumidifiers can tackle all three of those, but education and holistic thinking are the real solutions to healthier homes. Nikki and Bryan also discuss: Air dilution Long-term payoffs The tricky IAQ puzzle in multi-family buildings Building design and IAQ Talking to customers about ALL options The "dehumidifier graveyard" What makes Santa Fe Ultra-Aire unique   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.