HVAC School - For Techs, By Techs

In this podcast episode, Bryan goes over best practices for diagnosing and replacing an A/C or refrigeration compressor. When testing for a shorted compressor, make sure the compressor is isolated from all of its circuitry. You would see low ohms to ground in a shorted compressor. Do NOT measure from winding to winding or terminal to terminal to diagnose a short. You may also come across an open winding failure. In the case of an open compressor, the power is going to the compressor, but it's not doing anything. Locked compressors also go out on internal overload and draw high amps. Try your best to unlock the compressor but be realistic about the state of compressor health. Poor compression also indicates a failure. You would typically see low head pressure and high suction pressure with low system capacity. When replacing the compressor, you'll want to start off by knowing the type of failure that was diagnosed. Reconfirm the diagnosis. Then, do your acid test and make sure you have a matching capacitor and enough refrigerant to do the job. Know your connection types, compressor model, and warranty status. Fully recover the old refrigerant charge and remove all existing driers in the system. Braze in the new compressor and pressurize the lines with nitrogen. Bubble-test all new joints and check them thoroughly. Then, pull your vacuum before adding charge by weighing a factory charge into the liquid line. When you power on the unit, monitor the performance and inspect the unit closely. Bryan also discusses: Clarification on flowing nitrogen Learning theory vs. application Pulling terminals off Proper megohmmeter use "Redneck" test (running the system without the compressor) Acid and oil testing Hard start kits and oil migration Accumulators and acid protocols Suction line driers Mufflers Vacuum pump oil If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode of HVAC School, Bryan covers the "5 pillars of refrigerant circuit diagnosis" and why they matter. They are: Superheat Subcool Suction pressure Head pressure Air temp split (delta T) These 5 readings give you a holistic idea of the A/C system. Instead of getting hooked on checking only superheat and subcool all the time and dismissing potential diagnoses, you can use these five readings to get an idea of the health of several parts of the system. Making it a priority to take these five readings also promotes open-mindedness, which is perhaps one of the most vital qualities of a diagnostician. The five pillars will give you the clues to diagnose overcharge or undercharge, a wide variety of restrictions, kinked suction lines, expansion valves failing open, improperly seated pistons, condenser fan issues, and so many more conditions. Also, regularly check and calibrate your tools. These 5 readings won't be helpful if you aren't constantly making sure your tools are accurate. As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this episode of HVAC School, Bryan talks to his sons about basic electrical theory. Electrical theory normally requires trigonometry, calculus, and all of those fun maths. However, the basics are so easy that a 12 and 14-year old can figure it out. Electrical theory follows many of the same principles as thermodynamics—however, electrical theory concerns charges rather than heat. Conductors and insulators behave similarly with electrical charges as they do with heat. Ohm's and Watt's laws establish what volts, amps, power, and resistance, and they explain the relationships between those units. However, magnetism can add a bit of confusion to those equations. We drive motors with inductive loads, making Ohm's law seem invalid, but the magnetism resists itself, which goes unnoticed on ohmmeters. That is untrue of DC motors, and Ohm's and Watt's laws will appear to check out under most circumstances. An electrical component can fall into three main functional categories: power source, switch, or load. If something doesn't fall into one of those categories, it merely adds resistance. The power source could be a transformer, which provides homes with power from the power company (and goes from a higher voltage to a lower one that our appliances can use). A switch opens/closes or rewires an electrical path, and a load is what does the work. That's the short of it, but it's still pretty easy. Join Bryan and his sons as they talk about: Differential charges Electromotive force Ohm's law Volts, Ohms, Amps, and Watts Electrical paths Conductors and insulators Resistive and inductive loads And much more... As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

This episode of HVAC School is a Kalos meeting where Bryan talks to his team about an incident where a leak was erroneously detected on the evaporator coil. The system was three months old, and one of our junior techs diagnosed a leak on the evaporator coil. (What?? That never happens!) So, the customer was quoted for a new evaporator coil. One week later, the charge was low again. The junior technician quoted the customer for more refrigerant charge and leak detection. The customer freaked out. Unfortunately, there were so many things we could have done to prevent the hassle and frustration for the customer. All was fine in the end, but we could have gathered more data to perform a more thorough diagnosis, sent out senior technicians to verify the issue, and kept the bigger picture of the service call in mind from the start. During this meeting, Bryan stresses the importance of: Reconfirming parts before installing them Performing a complete diagnosis Using a micron gauge Becoming a valuable technician And much more... As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE.

In this episode of HVAC School, we discuss the entire basic refrigerant/compression refrigeration circuit. We are in the business of moving heat. Heat refers to motion in the molecules. Temperature is the average velocity of those molecules. Heat needs a temperature differential to move. So, HVAC systems absorb heat when the refrigerant is colder than the ambient temperature. They reject heat when the refrigerant is hotter than the ambient temperature. Remember the components and their functions in the following order: Compressor: increases the vapor refrigerant's temperature and pressure. Discharge line: carries hot, high-pressure, superheated vapor to the condenser. Condenser: changes the vapor to a liquid. Liquid line: moves the subcooled (high-pressure) liquid to the metering device. Metering device: drops the liquid's pressure (creates some flash gas). Expansion line: leads the low-pressure liquid/vapor mixture to the evaporator. Evaporator: changes the liquid/vapor mix to a vapor. Suction line: moves superheated vapor to the compressor. Note: Heat pumps can shake things up a bit; the suction line becomes the discharge line (and vice versa), and the condenser becomes the evaporator (and vice versa). However, heat pumps have two metering devices and a bi-flow liquid line drier, so the liquid line stays the same. So, watch out for heat pump systems with that tricky little reversing valve. We also elaborate on some fancy accessories. These include accumulators, discharge line mufflers, receivers, and more. And we discuss much more... As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE.

In this episode of HVAC School, I talk with my brother Nathan... and he whines a lot about cool tools I like. As you might have guessed, Nathan is in the camp of people who believe that proper training promotes good practices; fancy tools won't make an outstanding tech. Even though I respectfully disagree with him on some things, he has a point. Tools will only be useful if a tech knows how to use them. They should make your life easier, but they shouldn't have much bearing on performance. He doesn't like wasting money or time on tools that probably won't help him. So, he doesn't like solder rings or thermal imaging cameras. On the other hand, I'm in the "tool nerd" camp. I love new technology and think tools can make us do much better work if we learn how to use them properly. On the job and in my spare time, I enjoy reading up on the latest technology and trying out the newest tools. Missing out on the newest "wow!" tools is a fear of mine. Spending money on a tool that will help me do better, more efficient work is ALWAYS worth it. I think solder rings and thermal imaging cameras are cool and can be put to good use. We talk about how efficiency, organization, training, job performance, and customer trust relate to tools. We can find some common ground in some areas, even if we have fundamentally different attitudes toward tools. Oh, and we talk about digital gauges and the jumping spider that lives in Nathan's van. —Bryan As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this episode of HVAC School, Bryan talks to some apprentices about basic thermodynamics. That is the fancy scientific way of saying that we're moving heat. The way we think of "hot" and "cold" is relative to our comfort. However, the scientific concepts of "hot" and "cold" are very different from our relative understandings of those qualities. For instance, there is only ONE value of "cold" in the universe: absolute zero (0 kelvins, -460°F). Any temperature above that contains heat. Heat and temperature are NOT synonymous. Instead, heat refers to molecular motion, and temperature is an average measurement of molecular motion. Therefore, not all heat results in a temperature change. For example, adding heat to an ice cube at 32°F (0°C) changes the ice cube from a solid to liquid water. The heat added is called latent heat. Heat cannot move unless there is a differential in temperature, and it always moves from an object with more heat to one with less heat. Everything in nature tends towards equilibrium, and heat is no exception. In those cases, heat transfer will theoretically occur until both objects are at the same temperature. There are three main methods of moving heat: conduction, convection, and radiation. Conduction moves heat when a warmer object touches a cooler one. Convection occurs when heat moves through a fluid. Radiation occurs when heat moves on electromagnetic waves, such as when the sun's heat passes through a window. Join us as we cover: Heat & temperature and the difference Boiling and superheat Fahrenheit, Celsius, and Kelvin scales Absolute zero Molecular motion Hot and cold British Thermal Units (BTUs) Tons of air conditioning (and BTU/ton) Energy conversions Pressure and its effect on temperature Conduction, convection, radiation How heat transfer works in HVAC/R systems If you want to learn more about heat transfer, check out this article. As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE.

In this episode of HVAC School, Bryan talks to Leslie about the deceptive TXV. Thermostatic expansion valves, also known as TXVs or TEVs, are metering devices that maintain superheat. They contain an external equalizer. External equalizers give the pressure reading that you would normally take with a suction gauge at the end of the evaporator coil. They supply the closing force to the TXV. TXVs also contain a sensing bulb. The sensing bulb picks up the superheat on the suction line. When a vapor is superheated, its temperature exceeds its saturation temperature. The superheat value indicates how much the vapor temperature exceeds its saturation temperature. The bulb uses that superheat reading to adjust the TXV's opening force. System diagnosis can be tricky with TXVs, and you must set the charge by subcool on TXV systems. (Still check the superheat and follow manufacturer instructions, though.) However, TXV issues are pretty straightforward. Many of their issues deal with an undercharged sensing bulb. In those cases, you will notice issues with the opening force that acts on the valve. When replacing a valve, you typically make a new port for the external equalizer. However, getting solder in the tube can block off the closing force of the equalizer. Restrictions are also common issues for TXVs, and improper superheat is an indicator of a TXV restriction. When we think about the way TXVs manage superheat, "TXV" seems like a misnomer. We might be better off calling them "constant superheat valves" (CSVs). In addition, Bryan and Leslie discuss: Why Bryan doesn't like the name TXV Bulb, external equalizer, and spring forces Superheat and subcool Evaporator load How a TXV is supposed to work and how they fail As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE. Thanks to Daniel Anderson for making this his first episode suggestion.