HVAC School - For Techs, By Techs

In this short podcast episode, Bryan talks about brazing and soldering. He also weighs in on patching and if it is an allowable repair. Brazing is when you use a dissimilar metal to join metals at a temperature above 842°F, and soldering occurs at temperatures below that. (Welding occurs when you use the same metal as a joining metal.) In our trade, we generally use soldering on copper plumbing and brazing on line sets. We also often call brazing alloys "solders," such as silver solder. When making a joint, you want to have a sufficient (but not oversized) gap between the male and female surfaces of the joint. That's because the joint needs a large surface area where the solder or alloy can flow in via capillary action. Temperature is critical, as it needs to be high enough to draw the alloy into the joint, but it can't be too high. Patching is a controversial practice, but you CAN do it. If you are going to patch a system, it's best to do it on the low side of the system at a low temperature and with minimal vibration to minimize the risk of damage. Unlike traditional brazing, patching is when you use an alloy to seal up a small crack or leak; you don't want to draw the alloy into the joint. If you decide to patch, one of the best alloys you can use is 15% silver solder. You also risk blocking the tube. If you can cut the leaking section out and patch it with a coupling, that's an even better practice. We DON'T recommend patching on the discharge line at all.   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.

n this live podcast episode, we have a fun conversation talking with Nathan Orr and Kevin Compass about grocery refrigeration. The most common types of calls are those where the machine is "not making temp." Usually, the cases can't maintain temperature due to frozen evaporator coils or backed-up drains. On low-temperature/freezer applications, we must rely on electrical or hot gas defrost to mitigate frozen coils. Hot gas defrost is a complicated but quintessential part of low-temperature grocery refrigeration because the coils easily freeze. The discharge gas has to go to the evaporator coil and merge back into the liquid line; that gas CANNOT make its way to the suction line without causing damage, so the liquid line pressure needs to remain lower than the discharge line pressure. Kevin sometimes recommends running the fans all the time in open cases because the fans aid in the defrosting process, especially when it comes to warming the drain pan. Another common issue that refrigeration techs encounter is starved coils. Clogged TXV screens often cause starved coils, but we don't usually replace the entire TXV in grocery refrigeration. Instead, we only replace the part that needs replacing (the screen). The same practice applies to other TXV components; we replace only the powerhead if the powerhead has an issue. Most grocery refrigeration systems use refrigerants that are quite different from residential HVAC refrigerants. Some of the most common refrigerants are propane and carbon dioxide. However, propane is flammable, and CO2 doesn't work very well in hot climates. Nathan, Kevin, and Bryan also discuss: Electric vs. hot gas defrost Walk-in boxes Bunker cases/coffin cases Hoarfrost Water heaters Defrost termination Offsets and thermistors Underground line sets Charging refrigeration systems for a wide range of ambient conditions Ammonia refrigerant   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.

Nathan Rothenberg and Ed Janowiak join Bryan to talk about the good, the bad, and the uncomfortable of ACCA Manual J, D, and S. Manual J load calculations exist to make the BTU inputs and outputs predictable. Then, Manual S comes in to assist with equipment selection to meet the load calculations and the customer's comfort needs. Manual D is a collection of mathematical formulas that exist to help you calculate your friction rate, which is important for comfort in terms of noise in the ducts (from excessive air velocity). Ed believes that the best way to learn Manual J is from the physical manual; several instructors will teach the calculations straight out of the book, not on computer software. The difficulty of learning Manual J is one of the manual's shortcomings. Also, while Manual D is often required by code, Manual J is not often required, meaning that technicians can get away with poor designs. A common argument against Manual J is that comfort needs also tend to vary with each customer; therefore, standardized calculations and targets may not help individual customers meet their preferences. The typical temperature and humidity targets are 75°F at 50% relative humidity. Under those conditions, the dew point is 55°F (meeting the 20°F delta T rule of thumb), meaning that the air should remain well above the dew point. When the air remains above the dew point, the risk of a moisture problem greatly decreases, even at the expense of comfort. Nathan, Ed, and Bryan also discuss: Bad square-footage rules of thumb ACCA Manual T (register placement) Temperature and humidity effects on comfort Oversizing equipment Single-stage vs. two-stage equipment Ductwork in unconditioned spaces   Check out the ACCA website at acca.org. 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 compares under load vs. bench capacitor testing to find out which testing method is better. When we test the system while the motor is running, we call that testing under load. Testing under load is fairly easy; you take the voltage across the capacitor (V), amperage off the capacitor's start winding (A), and then you use the following math problem: (A x 2652) / V (You can also punch those numbers into the calculator on the HVAC School app.) While you can test under load on an off system, the test will provide a more accurate picture of the operating capacitance if you perform the test while the system is running. On a bench test, you disconnect the leads, discharge the capacitor, and test it with a capacitor tester. The tester will charge and discharge the capacitor; then, it will measure the amount of current going into and leaving the capacitor. The voltage will be lower than on a test under load. If either of those tests yields vastly different results, then it's likely that one of your readings is incorrect; it's unlikely that the performance differs that much under load or on the bench. For example, some ammeters can read higher or lower than the true amperage value, which affects the total capacitance in the math equation. Capacitors merely have foil plating and oil to make them work. The attraction between those forces creates a charge. Normally, these shouldn't "overheat." The plate-to-plate surface area can break down over time, leading to poor capacitance. Capacitor testing gives us a picture of the capacitance, and the state of the compressor materials could provide an explanation for the test results.   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.

Eric Kaiser joins the podcast again, and this time, we are talking ECM motors. We discuss types, history, diagnosis, and failure prevention. An ECM motor has a permanent magnet rotor, which means that the magnetism never deactivates. The variable frequency-driven motor is typically an induction motor, and the rotor only becomes magnetized by the stator's field. Eric describes ECM motors as three-phase AC motors, but we can control the AC pulses, resulting in oddly shaped sine waves. Those motors essentially convert the AC power to DC power and then to controlled AC power with the help of a microprocessor that measures back EMF. ECM motors have been in the industry since the 1980s. General Electric designed them to put out a constant volume of air against a wide range of static pressures. As time has gone by, manufacturers have developed those motors to overcome a wider range of duct challenges. and to communicate with controls and display components. One of the most significant developments in ECM motor manufacturing was the constant torque motor, also known as the X13 motor. There are also constant speed and constant airflow ECM motors. When diagnosing ECM motors, you will want to be aware of the signals. The 24v signals work similarly on constant speed and constant torque motors but differently on constant airflow motors. Sometimes, only the module has an issue, which can be separated from the motor and individually replaced quite easily. Eric and Bryan also discuss: Modified or pulsed sine waves RPM as feedback PSC vs. ECM motor efficiency Temperature's effect on a motor's lifespan Achieving rated static pressure How moisture can impact motors Overvoltage events and motor failure Programmable speed taps Informational resources on ECM motors   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 lively discussion, representatives from Chemours and Bluon Energy join the podcast. They talk about retrofit refrigerants and what to look for in a good retrofit. The R22 phaseout has been on the agenda for a long time due to its ozone-depleting potential. However, R-410A is also due for a phase-down in the future due to its global warming potential. While neither refrigerant will be outright banned, we will have to consider alternative retrofit refrigerants in the future, especially if reclamation rates stay low. Almost all of the replacement options are refrigerant blends. When we deal with refrigerant blends, we have to think about temperature glide and oil return. Many of the R22 retrofit replacements are compatible with mineral oil, and that's because manufacturers add hydrocarbons, which are chemically similar to mineral oil. We try to avoid toxic (B) and flammable (2-3) refrigerants on the ASHRAE classification system, but the hydrocarbons add just a little bit of flammability to the blends (2L). Retrofit refrigerants also behave differently in the way that they transfer heat, as refrigerants with glide may be colder in the evaporator. They may run with exceptionally cold evaporator coils, which could be an issue in climates with a high latent load. At that rate, some airflow reduction may be necessary to prevent the coil from freezing. The Chemours and Bluon representatives, Eric Kaiser, and Bryan also discuss: Net refrigeration effect (NRE) Offsetting hydrocarbons Mineral oil return and velocity issues POE oil as a lubricant Latent heat of vaporization Retrofit refrigerants' heat transfer in the evaporator coil R22 pricing expectations post-phaseout Education and training for flammable refrigerants and blends Benchmarking equipment Manufacturing R22 replacements Off-grid refrigeration   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 discusses the importance of the trap and vent in condensate drains. He also describes some trapping and venting best practices. Anytime you have long runs of horizontal drains, you run the risk of having a double-trap. A double-trap creates a water seal, which traps air between the two traps and prevents a system from draining properly. To avoid the complications of double-traps, you can create a proper trap at the air handler. When making a P-trap, make sure the outlet is lower than the inlet; traps need some fall. Then, you would vent it. When creating a vent, make sure it has enough height to be higher than the pan. That way, it should take longer for the drain to overflow if it backs up. If the system has a float switch, that should be tripped before condensate can overflow from the vent. On RTUs, the cleanout is close to the unit, and the vent will go after that; RTU units can have shorter vents. Do NOT cap the vents. Some best practices to avoid double-traps include strapping the drain properly. PVC can be especially challenging because it tends to bow and bend over time. Location can also present challenges, as we run drains underground due to the building structures and geology in Florida, which can cause backups. However, in the end, the main goal is to create a drain line that prevents air from blocking up the drain and doesn't cause property damage when it backs up.   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 podcast episode, Bryan talks through real home IAQ solutions with Jim Bergmann and others. They also answer audience questions. Indoor air quality is a place where the HVAC and building science industries intersect, so it is an important topic for occupant health and comfort. Home IAQ is much more holistic than UV lighting or ionization solutions. For example, duct leakage is one of the fundamental challenges of indoor air quality in the vein of controlled ventilation. However, some more advanced IAQ devices include particulate counters, which focus on tracking pollutants in the air and understanding how those pollutants work with relative humidity. Some common pollutants include pollen, dust, VOCs, dander, carbon dioxide, and carbon monoxide. While most of those are bothersome and may cause comfort or minor health issues, carbon monoxide is potentially deadly. Homes that use gas appliances must have appropriate venting (and proper combustion) to keep CO out of the home. VOCs and carbon dioxide are two IAQ villains that require ventilation to dilute them. When lots of occupants are in a space, the carbon dioxide load can get very high, and furniture, paints, and other household objects can off-gas VOCs. Ventilation also helps us control energy usage in a home. Relative humidity is another important IAQ factor, especially when it comes to sealing ducts and controlling ventilation. Sweating is undesirable in the home, and we don't want to drive indoor temperatures below the outdoor dew point. Bryan and Jim also discuss: MeasureQuick duct leakage test Return vs. supply leaks Aeroseal CO poisoning and testing Building pressurization and balanced ventilation How to use mechanical ventilation properly CO2 sensors Determining practical and impractical IAQ practices Carrier Infinity controls Reheat electricity and dehumidification Ozone Oversized air filters Discussing IAQ product maintenance costs with customers   If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Craig of AC Service Tech on YouTube joins Bryan on the podcast to explain how to charge an A/C unit. He also discusses his excellent new book. Before you start charging a unit, you must know about superheat, subcooling, and other means of determining how much charge is already in the system. You must also know how the refrigeration cycle works so that you can tell if the system is operating properly. Other must-understand concepts are saturation and the pressure-temperature relationship. To start off, you'll want to pull the disconnect on the outdoor unit. Then, get information from the homeowner and check the airflow; check the filter and examine the ductwork before turning the equipment on and using an anemometer to check airflow. When you actually begin to charge the equipment, you want to screw on your hoses clockwise and read your pressures. After you read the pressures, push the disconnect back in. Monitor the low-side gauge and keep the saturated temperature in mind. Verify the metering device and refrigerant type. Your metering device will determine the charging method; you would use the total superheat method on fixed-orifice systems and the subcooling method on TXV systems. You use those values and compare them to the target values to determine if you are low on refrigerant or overcharged. Then, you add or remove the refrigerant accordingly to reach those targets. Craig and Bryan also discuss: Well-roundedness Sliding calculators Saturated temperature Service valves Superheat vs. total superheat Frozen evaporator coils Adding refrigerant at different points of the system Line set length Breaking the vacuum with refrigerant Refrigerant Charging and Service Procedures   Check out Craig'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 and nerdy science podcast, Bryan discusses how electromagnetism impacts every part of our lives. Electromagnetism refers to the movement of electrically charged particles. From transformers to the visible light that helps us see, the movement of electrons is a critical part of our lives. For example, light is an electromagnetic wave within the visible part of the spectrum. On the more complicated side, AC motors generate a rotating magnetic field, which generates electricity. Transformers can also step down or step up voltage via two electrical coils that transfer energy via magnetism; electricity moves on the other side. Electromagnetism deals in waves. The distance between these waves varies, and the space between each wave is called the frequency. Many radio stations nowadays rely on frequency for listeners to tune in, and you can fir several stations just between the values 88 and 108. With TV, you wouldn't even get a single channel in that range (88-108 is somewhere between channels 6 and 7 on the old VHF analog system). Frequency rates also dictate many properties of a wave. Radio waves and microwaves are on the low-frequency side of the electromagnetic spectrum, whereas ultraviolet and gamma rays are on the high-frequency side of the spectrum. Visible light is right in the middle, and frequency helps us determine which color we see. Waves move through a vacuum and can self-propagate, but old scientists believed that waves moved through a substance called the aether. Bryan also discusses: Hertz scale Electromagnetic vs. sound waves Electrons in chemistry and physics Atomic structure   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.