Cover image of HVAC School - For Techs, By Techs

HVAC School - For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

Popular episodes

All episodes

The best episodes ranked using user listens.

Podcast cover

Furnace Sequence Of Operation

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.


10 Jan 2019

Rank #1

Podcast cover

The Basic Refrigeration Circuit

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.

1hr 15mins

5 Oct 2016

Rank #2

Similar Podcasts

Podcast cover

How to Charge an AC

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.


22 Aug 2019

Rank #3

Podcast cover

Short #34 - Heat Pumps

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.


18 Dec 2018

Rank #4

Most Popular Podcasts

Podcast cover

Commercial Refrigeration for A/C Techs w/ Dick Wirz

Dick Wirz, author of Commercial Refrigeration for Air Conditioning Technicians, talks about making the switch from A/C to refrigeration. Dick Wirz is an advocate for using rules of thumb, which is a controversial position. However, rules of thumb are an excellent way for A/C techs to dip their toes into the refrigeration world. Rules of thumb are less likely to overwhelm technicians than the exact technicalities of certain readings and measurements. Some prime examples of using rules of thumb in air conditioning are condenser split, evaporator split/TD, subcooling, and superheat. Those all have relatively neat "rules of thumb" that don't vary too much. (30-degree condenser split, 35-degree evaporator TD, 10-degree subcooling, and 10-degree superheat.) On medium-temperature refrigerators, a common rule of thumb is a 10-degree TD for a 35-degree box with an evaporator running at 25 degrees (35 - 10 = 25). On low-temperature applications, the box temperature is -10 degrees. You still have the 10-degree TD, so the design conditions for the evaporator would be -20 degrees (-10 - 10 = -20). The pressures will vary across refrigerants, but the temperatures WILL REMAIN the same as the rule of thumb. Ice is an alarming sight for residential technicians. However, commercial refrigeration technicians will occasionally see frost or ice under perfectly normal circumstances. Frost merely indicates that the temperature of a pipe is below freezing. Ice alone does NOT indicate floodback. In commercial refrigeration, the fans run all of the time to defrost the system (even during the off cycle). However, in freezers (low-temperature refrigerators), hot gas or electric defrost is required. Dick also talks about: Subcooling vs superheat in diagnosis R-410a pressure confusion Reach-in and walk-in refrigerators Medium and low-temperature refrigerators Defrost controls Common issues in commercial refrigeration If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

1hr 11mins

28 Aug 2017

Rank #5

Podcast cover

Leak Detection w/ John Pastorello

John Pastorello from Refrigeration Technologies is back on the podcast to talk about leak detection procedures from start to finish. Big Blu was what started the Refrigeration Technologies empire. John developed Big Blu to create a bubble leak detector with a higher sensitivity to leaks than any other bubble test solution on the market. Big Blu differs from other leak detection solutions because it detects gas leakage down to 0.65 ounces per year, putting it on the same level as some of the best electronic leak detectors. One of the most common misconceptions in our industry is that systems don't leak at all. That is simply not true; all systems leak to some extent. When we check for leaks, we want to check for unacceptable leak rates; detectors will normally reveal when a leak occurs at an unacceptable rate. Most of the leaks we check for are standing leaks, which we pinpoint when the system is off. We also have pressure-dependent leaks, temperature-dependent leaks, and vibration-dependent leaks. Those leaks vary with system operation, and you may even hear the leaks when the system is under a certain set of conditions. Overall, you want to use your senses to look for oil spots, listen for hisses, and feel for oil residue before using an electronic leak detector. If you get a hit, pull out the Big Blu. When using soap bubbles, also be sure to use a mirror and light source to look all the way around a joint. John and Bryan also discuss: Pressure distribution in the compressor Leak rate and molecule size Leaky valves and mechanical issues Cumulative micro-leaks Losing refrigerant from hooking up gauges repeatedly Leak detector sensitivity and calibration Efficiency during leak detection Oil spotting Evolution of leak detectors Checking for leaks on furnaces Testing leak detectors Learn more about Refrigeration Technologies HERE. You can also find their FREE Leak Detection Manual HERE. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE


2 May 2019

Rank #6

Podcast cover

Heat Pumps, Reversing Valves and Defrost

In this episode of HVAC School, Bryan covers the basics of heat pumps. Heat pumps are common technologies in Florida. They reverse the sequence of the typical refrigerant circuit: the indoor coil can become the condenser, and the outdoor coil can become the evaporator. Heat pumps can achieve that transition via a reversing valve, which changes the directions of the suction and discharge lines. They also have two metering devices. Reversing valves contain a solenoid (typically 24v) that rediverts the suction and discharge lines via shifting the slider with a pressure differential. Pilot tubes shift gas from one side of the slider to the other, which shifts it and triggers heat mode or cooling mode. Reversing valves are typically energized in cool mode (except for Ruud/Rheem reversing valves; they energize in heat mode). Defrosting is rarely necessary for us in Florida, but it can be a scary occurrence when we do need it. The outdoor coil can freeze over entirely when it gets cold enough due to Florida's high humidity. Hot gas goes through the coils during defrosting, and it may make alarming noises. Many Floridian heat pumps also use auxiliary heat strips to provide heat while the system defrosts. Many defrosts rely on set times and sensors to determine when to initiate and terminate defrost. (That is true of heat pumps AND most refrigeration systems.) Thermistors are common sensing technologies used in defrost. Join Bryan on this informative monologue about: Reversing valves Aux heat W and W2 Heat Pumps Defrost Checking refrigerant charge in heat mode Heat mode expansion valves Common heat pump considerations For a more detailed written explanation of heat pump reversing valves with pictures, check out this article. As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE.


5 Dec 2016

Rank #7

Podcast cover

Condensing Temperature, Condenser Split and Subcool

In this podcast, Bryan talks about condensing temperature, condenser split, and subcooling. All three of the values are proportional. If one changes, all three of them will change. Saturation is also a critical concept that relates to all three of those, so we also cover those relationships. As you remember, a condenser rejects heat and turns vapor refrigerant back into a liquid. Condensing temperature is the saturation temperature at which the refrigerant changes from vapor to liquid; it can change depending on ambient temperature. While in the condenser, the refrigerant will be at saturation and be a liquid-vapor mix throughout most of the coil. Subcooling indicates how low a liquid is below liquid-vapor saturation. For example, if you had a condensing temperature of 110°F and took a liquid line measurement of 98°F, you would have 12°F of subcooling (110 - 98 = 12). Although some high-SEER HVAC systems may get their liquid line temperatures pretty close to the ambient temperature, you cannot have a liquid line temperature below the ambient temperature. Otherwise, you probably have a restriction in the line. Many technicians set a charge based on subcooling. Condenser split is a bit trickier to define. You DON'T compare the temperatures of air going into the condenser and air going out. Instead, it is the difference between the condensing temperature and the outdoor temperature. The outdoor temperature MUST be lower than the condensing temperature. Otherwise, heat rejection cannot take place. In general, most manufacturers tend to engineer their HVAC systems to maintain a 15-30°F condensing split. Heat mode has its own set of challenges. For example, subcooling can be difficult to predict in heat mode. However, between 20-30°F of subcooling in heat mode is normal. As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE.


22 Feb 2017

Rank #8

Podcast cover

Pulling a Vacuum 2.0 w/ Jim Bergmann

In today's podcast, Jim Bergmann joins us to talk about evacuation. He discusses pulling a vacuum, conductance speed, microns, core removal, decay rate, and all that other nerdy vacuum stuff. Jim has helped develop some new BluVac hoses with AccuTools, and he's here to explain why we need those. He also explains why we need to be more educated on evacuation. While we have many good hoses today, we still have a way to go when it comes to moisture removal. Jim Bergmann has seen the need for more durable hoses that perform better when there's moisture and acids in the system. Pulling a vacuum that makes the system dry is crucial for that equipment's longevity. You cannot over-vacuum a system, so the deeper vacuum you can make, the better your evacuation will be. Evacuation often takes place on new pieces of equipment, and some people worry that deep vacuums will compromise the oil quality of those new systems. That is actually not a real issue to worry about during evacuation, and it's a piece of misinformation that makes people misunderstand the importance of evacuation. Not enough people understand how evacuation works, and that is how misinformation and distrust around evacuation spread throughout the HVAC industry. Evacuation best practices come down to the materials you use. We'd like to use a dedicated evacuation rig with the highest possible conductance speed. So, to achieve that, you'll want as few fittings/connections as possible and wide, short, high-quality hoses that are impermeable and leak-free. Remember to remove all Schrader cores and use your micron gauge away from the pump. Pull the vacuum down as deep as you can get it and do a decay test. Bryan and Jim also discuss: Degassing and dehydration Best evacuation technologies of yesterday and today Evacuation education gap TruBlu hoses Pressure, density, and air "thickness" Moisture adhesion Behavior of water Hose ratings POE oil and moisture 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.


16 Aug 2018

Rank #9

Podcast cover

The Basic Refrigeration Circuit, Pressure & Enthalpy w/ Carter Stanfield

Carter Stanfield, a co-author of Fundamentals of HVACR, talks about the entire refrigeration circuit. He also explains how to read and plot a pressure-enthalpy diagram. The refrigeration circuit has four main components: evaporator, compressor, condenser, and metering device. When teaching, Carter likes to explain that boiling is a cooling process and condensation is a heating process. He describes saturation as the breaking point at which liquid refrigerant can no longer hold more heat (in the evaporator). The superheated vapor from the suction line then enters the compressor; the compressor adds even more superheat. So, the discharge line has very superheated vapor. In the condenser, saturation occurs when the vapor cools to the point that it can no longer hold more moisture; the temperature stays the same until the refrigerant becomes entirely liquid. Subcooled liquid travels to the metering device via the liquid line. The metering device reduces the pressure of the refrigerant and feeds the evaporator. However, some flash gas occurs and helps drop the temperature of the remaining liquid. A pressure-enthalpy diagram illustrates the refrigerant's changes in and out of the saturated state as it moves through the refrigeration circuit. The chart looks like a curved dome, and saturated states are inside the dome. Pressure is on the y-axis, and enthalpy is on the x-axis. Pressure is a logarithmic arrangement; a linear arrangement would be impossible to plot. The bottom of the chart shows low pressures, and the top shows high ones. Enthalpy is the heat content of the refrigerant. We express it in BTUs/lb. When you plot one of these diagrams, you can start with four lines and readings: high and low-side pressure, suction line temperature into the compressor, and liquid line temperature into the metering device. You will end up drawing a parallelogram shape on the chart.If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.


4 Sep 2017

Rank #10

Podcast cover

Basic Refrigerant Circuit Revisited (Part 1)

Part 1 -Bert (Kalos tech) and Keiran (Kalos apprentice) join Bryan in the studio to talk through the basic refrigerant circuit and how it functions. They talk compressor, condenser, metering device, and evaporator as well as the four lines and the states of the refrigerant as it travels They talk about the compressor, condenser, metering device, and evaporator as well as the four lines and the states of the refrigerant as it travels. We have already covered all of the basic components in earlier podcasts, which you can check out HERE; we focus more on accessories, refrigerant movement through the circuit, and scientific concepts in this episode. We also discuss: Pumps vs. compressors Refrigerant and air-cooled compressors Flooding a compressor with liquid refrigerant Crankcase heaters Temperature vs. heat vs. BTUs VRF vs. ductless


5 Jun 2018

Rank #11

Podcast cover

Friction Rate and Duct Design w/ Dr. Bailes

This episode is very exciting to me because we get to have Dr. Allison Bailes on the show. Today, he shares his knowledge about friction rate and duct design. Allison got his start teaching college-level physics before getting into the building design industry. If you have a forced-air system that blows heated or cooled air through a duct system, that blower creates a pressure difference. Some of the pressure is used up on the filter, registers, and dampers, so you will see pressure drops. Anything left over is the available static pressure, which pushes air through the ducts. When you do a duct design, you must account for pressure drops and your blower's static pressure rating. When designing a duct system, you want to minimize friction as much as possible. Counterintuitively, you want a high friction rate. Friction rate refers to the availability of static pressure compared to friction provided by the effective length, not the total amount of friction. Fittings significantly impact your total effective length. By extension, fittings can have a major impact on friction. In flex duct designs, the turns add additional resistance. Oversizing often happens due to poor load calculation. While you increase capacity with an oversized system, there are plenty of drawbacks. The capacity will rarely match the load, you may spend too much on the equipment, have ineffective dehumidification, and you will deal with short cycles, which lead to comfort problems. Allison and Bryan also discuss: Home energy ratings Equivalent length and total effective length Flex duct design Seasonal runtime Surface area challenges Unconditioned spaces Filtration To find out more about everything Dr. Bailes has to say about building performance and duct design, visit his site at: https://www.energyvanguard.com/blog 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.


21 Nov 2018

Rank #12

Podcast cover

Using Volts and Ohms in Diagnosis

In today's podcast, Bryan talks about voltage (volts) and resistance (ohms), specifically using a voltmeter and an ohmmeter for diagnosis. We also discuss voltage drop. In many cases, Ohm's law is impractical for field usage because of the additional resistance from inductive reactance. We also don't typically measure impedance and only care about resistance on the windings. However, Ohm's law is still a valuable concept because it teaches technicians the relationship between voltage, amperage, and resistance (ohms). Ohm's law states that volts equal amps multiplied by ohms (E = I x R). Therefore, if the volts stay constant, ohms will increase as amps decrease and vice versa. We distinguish lines from loads in circuits; we say that loads are the parts that "do" something due to resistance in a circuit. There are two kinds of loads: inductive and resistive. Inductive loads generate expanding/collapsing magnetic fields, which can also cause rotational force or activate a solenoid. Resistive loads generate light and heat, so heat and resistance are related. Of course, the diagnostic tools we use (multimeters, voltmeters, ammeters, ohmmeters, etc.) also have their limitations. A voltmeter merely determines a difference in charges between two points. When using a voltmeter on a low-voltage circuit, try to plant one of your leads on the common side and take readings throughout the circuit with your hot lead. Ground is also NOT a reliable reference point for diagnosis. The point of measurements is to prove what we suspect to be true; we must understand what our data mean for system operation and what our tools' diagnostic limitations are. For example, when we ohm out contactors, we check to see if they're open. Bryan also discusses: Fixed wattage or resistance Reading between wires Meter lead placement Amperage (dynamic current/electrons) Undiagnosed shorted circuits Contact points Voltage drop and resistance Infinite ohms Wire length If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

1hr 13mins

5 Dec 2017

Rank #13

Podcast cover

Prevent Compressor Murder Part 1 w/ Emerson

In today's podcast, we talk with Trevor Matthews with Emerson. He tells us about the causes and prevention of air conditioning and refrigeration compressor failure. Most compressors don't die a natural death... they're murdered. Of course, that's to say that installation and maintenance play a major role in the compressor's operation and lifespan. Electrical and mechanical failures are the two broad causes of compressor failure. When it comes to electrical failures, Trevor often sees single-phase compressors fail early when their electrical components don't receive proper inspections and care. For example, contactors may go too long without inspection or replacement. Three-phase compressors are also prone to phasing issues and may run backward. Common mechanical failures deal with oil in the system. Oil lubricates the bearings inside the compressor. Unfortunately, that oil can mix with liquid refrigerant, become diluted, or experience acid contamination. Some oil-related failures include floodback, flooded starts, slugging, overheating, oil loss, and contamination. Compressors cannot compress liquids, so many of them fail when the refrigerant condenses to a liquid inside the compressor. Many failures occur because technicians don't think they have enough time to troubleshoot or inspect the whole system. Trevor recommends setting up a checklist with all of the tests you need to perform. Trevor also discusses: Service replacement compressors vs. OEM compressors Megohmmeter usage Causes of floodback/flooded starts Compressor superheat Suction accumulators Bearing wear Temperature control and pump cycles for controlling flooded starts Verifying System Operation Sheet from Emerson  http://hvacrschool.com/CompFailures 


17 Apr 2018

Rank #14

Podcast cover

Air Flow - Latent, Sensible, WB, DB, RH and Static

In this episode, Bryan talks a bit about the air side of the system. Understanding airflow is all about seeing the relationship between readings. We cover latent and sensible heat, relative humidity, wet and dry-bulb temperatures, and static pressure. Latent and sensible heat refer to heat that we can feel (sensible) or heat that contributes to a phase change and cannot be felt (latent). Both latent and sensible heat have a major impact on equipment sizing, especially in coastal regions and other areas where humidity is naturally high. When we attempt to control sensible and especially latent heat, we have to look at the airflow over the evaporator coil. When you run the blower more slowly, you pull more moisture (latent heat) at the expense of efficiency and capacity. Therefore, for peak capacity, efficiency, and sensible heat removal, you will want to max out the blower speed. Delta T (or air temperature split) is another important reading. Delta T is the temperature differential from the return to the supply. When you measure delta T with a dry-bulb thermometer, you will only get a sensible heat measurement. You need a wet-bulb temperature reading to account for humidity and latent heat changes. Relative humidity (RH) is the ratio of moisture in the air compared to the maximum at that temperature. Therefore, wet and dry-bulb temperatures are the same at 100% relative humidity. Static pressure is an indicator of airflow, but it isn't airflow. Static pressure is essentially resistance pressure that exerts itself on all surfaces. It is not the force of air flowing through the duct (that's velocity pressure). Also, consider adding a differential manometer to your toolbox. They make measuring TESP a breeze. As always, if you have an iPhone, subscribe HERE, and if you have an Android phone, subscribe HERE.


16 Feb 2017

Rank #15

Podcast cover

Why A/C Units Freeze w/ Eric Shidell

In this episode, Bryan speaks with Eric Shidell about some of the basics of system freezing, what causes it, and what to do about it. Freezing is a normal part of some equipment, such as low-temperature freezers and outdoor units on heat pumps. On straight-cooling systems, freezing is NOT normal and indicates poor operation. Ice formation starts on the evaporator coil and may spread to the compressor via the suction line. The best way to remove ice and defrost the system is to pull the disconnect on the outdoor unit but let the indoor fan keep running. Or, you could turn the unit off but leave the fan on. The goal is to defrost slowly and steadily. Defrosting too quickly could potentially cause damage. Horizontal air handlers in the attic can flood the home if ice forms and melts off too quickly. In an upflow furnace, defrosted ice could damage the electrical components. You will typically find low suction pressure on frozen systems. Many technicians who merely attach gauges and don't thoroughly inspect the unit for freezing will mistake the low pressure as a result of a low refrigerant charge. However, low pressures are a SYMPTOM, not the cause of freezing. Freezing is generally caused by poor airflow over the evaporator coil. As frost appears on the evaporator coil, airflow will be further impeded. On top of that, the suction pressure drops even more. From there, all of these factors feed each other and cause the frost to snowball out of control (almost literally). Sometimes, coils may freeze due to low refrigerant, but the amount of ice will typically be minimal compared to freezing that occurs due to an airflow issue. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.


2 Jun 2017

Rank #16

Podcast cover

ECM Motors A-Z w/ Eric Kaiser

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.


29 Aug 2019

Rank #17

Podcast cover

Measuring Air Flow - Static / Capacity & ECM Motors Part 1 w/ Jim Bergmann

In this two-part podcast series, Jim Bergmann talks about measuring airflow in HVAC systems. He covers a wide range of airflow measurement instrumentation and readings. In this first episode, Jim covers ECM motor considerations, delivered capacity, laminar flow, and more. In the HVAC industry, many techs confuse static pressure for airflow. Although you need static pressure to have airflow, it is NOT airflow and can fluctuate rather wildly depending on the duct conditions. Static pressure is an indirect airflow measurement. Airflow is actually a measurement of velocity (such as with pitot tubes) that you then convert to a volume measurement (CFM). If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

1hr 5mins

19 Jul 2017

Rank #18

Podcast cover

Short 19 - Superheat, Evaporator vs. Compressor

In today's podcast, we cover why both compressor and evaporator superheat matter. We also address some common confusion related to each. Evaporator and compressor superheat are two different readings that give you different indicators about the system's health. When you look at evaporator superheat, you see how far you feed boiling refrigerant into the evaporator coil. You don't want to overfeed your evaporator coil and risk flooding your compressor. However, you also don't want to starve your unit and reduce suction pressure. You'll want to stay between 5 and 14 degrees (F) of superheat at the evaporator outlet on typical A/C systems. On TXV systems, we can control superheat at the evaporator outlet. Evaporator superheat is the reading that helps you optimize your capacity. Increasing it will decrease your evaporator capacity, as the evaporator coil won't be fed as much refrigerant. The lowest possible value is your best bet for maximizing efficiency and capacity. Compressor superheat can be measured before the compressor. When you know that value, you can predict how hot your compressor will be when it runs. The temperature can increase from the evaporator outlet to the compressor inlet. Poor insulation in close proximity to the liquid line can be a cause; heat can transfer from the warm liquid line to the cool suction line. Our goal is to minimize heat gain in the suction line, so we want to insulate our suction lines and keep them as short as possible. However, you don't want the compressor superheat to be so low that you end up flooding the compressor. In most cases, you should check both values to evaluate the heat gains or losses in your suction line.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.


21 Aug 2018

Rank #19

Podcast cover

Beacon 2 Refrigeration Talk Through

In this service manual talk-through episode, Eric Mele helps us discuss the Heatcraft Beacon 2 refrigeration system. We talk about what it can do and what it entails. The Heatcraft Beacon 2 is a refrigeration system with more electronic controls than electromechanical. However, it is quite user-friendly, and it allows you to see what the system is doing at almost all times. The monitor doesn't allow you to adjust anything in the system, but it lets you see valve position, superheat, time until defrost, and more as the system is operating. The Beacon 2 has a suction pressure transducer that maintains superheat. You can dial in the superheat on the control, and the system should control it almost exactly as long as all the components are working properly. You can also manipulate the wiring to run multiple evaporators off of one condenser. (There are master and slave evaporators, and you must differentiate them when configuring the controls.) When it comes to parameters, you have to set your defrost type to air or electric. In general, you use electric defrost for freezers. You must also set your refrigerant type accordingly. Then, you set your box temperature. Medium-temperature applications tend to be around 35 degrees, and many low-temperature applications tend to be around -10 degrees. You also have control over defrost settings and temperature units (Fahrenheit or Celsius). You can also find frequent parameters on the evaporator panel for more information. Most errors will be sensor errors. Many sensor issues are easy to test because of the user-friendly monitors. You can compare your reference sensor to the data to check the accuracy of what's being reported to the board. Eric and Bryan also discuss: Forcing pump-down and defrost Schematics and wiring practices/applications Headmaster valves Setting pressure controls Defrost frequency and failsafe 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.


24 Jan 2019

Rank #20