In this informative HVAC podcast episode, Bryan and Bert dive deep into the complex world of locked and internal overload compressors, focusing specifically on single-phase residential units. The discussion begins with Bert explaining one of the most common challenges technicians face: diagnosing a locked compressor. He describes how compressors that are locked will typically run for only a second before overheating and stopping, creating a cycle that can be difficult to detect if technicians aren't carefully monitoring at the right moment. The hosts share personal experiences and practical diagnostic techniques, with Bert recounting how he once simulated a locked compressor by cutting the start winding wire and concealing it beneath other wires and zip ties. This demonstration highlights the importance of thorough inspection, including checking terminal connections. Bryan shares a story from his early career when he mistakenly condemned a compressor with damaged terminals, not knowing about terminal repair kits - a candid moment that illustrates how even experienced technicians continue to learn throughout their careers. A significant portion of the podcast is dedicated to explaining the electrical fundamentals of compressor operation, including an enlightening discussion about start windings, run windings, and common connections. Bryan passionately clarifies misconceptions about current flow through these different windings, explaining that the start winding actually has consistently lower amperage due to its connection through a capacitor. The hosts also detail the critical differences between a compressor that's overheating versus one that's truly locked, emphasizing that the physical temperature of the compressor often provides the key diagnostic clue. Key Topics Covered: · How to identify a locked compressor versus one that's out on internal overload · The importance of checking terminal connections and wire continuity · Why compressors that are truly locked don't have time to physically overheat · Common causes of compressor overheating: condenser fan failure, refrigerant issues, airflow problems · The proper diagnostic method for catching a locked compressor "in the act" · The mechanics of start windings versus run windings and their amperage differences · When and how to use hard start kits appropriately (and why they shouldn't be used universally) · How to communicate with customers when diagnosing compressor issues · The role of crankcase heaters in preventing flooded starts · Terminal repair techniques and when they're appropriate Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool. Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android
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32:08
When 0V Isn't Safe - Short #242
In this short podcast episode, Bryan covers some unique electrical cases: when 0v isn't safe. When you measure voltage, you're finding out the electrical potential between two points. Just because there is 0v between one point and another doesn't mean there will be 0v between those points and other points. Non-contact voltage detectors are good tools that measure the flux from the wiring, but they have their limitations. A common mistake is measuring voltage across a switch. When you measure 0v across the switch, that could mean there is 0 potential to ground, neutral, or the other leg, but it could also represent a closed switch where power is actively being passed. You need to measure voltage across a load or with neutral as the other point. You will also measure 0v when one of the legs of 240v power (with a two-pole breaker) stops making contact. You'll measure 0v between the legs, but that's because one of the legs is open. There may still be a complete path on the other leg; therefore, you will want to check for voltage between each leg and ground, not leg to leg. This condition is particularly common in pool heaters. In some cases, the meter isn't working and will read 0 when it's set to another unit setting, isn't on (if an analog), or the leads aren't fully plugged in. Check to make sure your meter is on the correct setting, is in proper working order, and has a good connection to the leads. Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool. Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android
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7:46
Compressor Ohm Mistakes w/ Bert
In this episode, Bryan and Bert dive into the often misunderstood world of compressor testing, focusing on common mistakes technicians make when using ohmmeters, compressor testers, and megohm meters. The conversation highlights how diagnostic errors can lead to unnecessarily condemned compressors and wasted time and resources. The hosts begin by discussing fundamental concepts like the difference between "open" and "short" conditions, emphasizing that a path doesn't necessarily indicate a short circuit—it simply means there's a low-resistance path. They explore how many technicians get confused when testing terminals, mistakenly thinking that normal winding-to-winding measurements indicate a problem. Through practical examples from their field experience, they illustrate why understanding normal readings is crucial before taking any measurement. A significant portion of the discussion centers on proper testing techniques for scroll compressors, which often show different measurements to ground compared to other compressor types due to their design, with windings submerged in refrigerant and oil. Bryan and Bert explain why standard motor testers can lead to false diagnoses when they indicate "bad" at threshold levels like 20 megohms—a reading that would be normal for many functional scroll compressors. They recommend proper megohm meters calibrated to appropriate voltage levels for accurate testing. Key Topics Covered: The difference between "open" circuits and "shorts" and how to properly interpret ohm readings Common mistakes when testing compressor terminals, especially misinterpreting normal winding-to-winding measurements How to properly check for shorts to ground and the importance of clean connections Why scroll compressors naturally show different resistance-to-ground readings due to their design with submerged windings Problems with inexpensive compressor testers that give false "bad" readings on functional equipment The "redneck test" for isolating a compressor to determine if it's truly the source of breaker trips The importance of understanding meter auto-ranging and correctly interpreting readings in ohms, kilohms, and megohms Why a reading below 0.5 megohms to ground is the general threshold for concern with scroll compressors Differences between megohm meters, high pot testers, and standard multimeters The misconception that winding-to-winding shorts are common without corresponding shorts to ground Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool. Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android
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35:15
Motor Ambient Rating - Short #241
In this short podcast episode, Bryan talks about what the ambient rating means on a motor. These ratings can be found on both condensing fan motors and blower motors. They have Cs in their rating, which represents the maximum ambient temperature the motor can handle in degrees Celsius (like 40C or 60C). Heat and overvoltage kill motors, and motors with higher ratings can withstand higher temperatures and last longer in hot conditions. Be careful not to confuse this rating with the insulation class (which is classed by letters and corresponds to temperature limits). You could have a condition where you exceed the insulation's rating but not the ambient rating. Air over operations (especially in the case of TEAO motors - totally enclosed air over motors) also play a role. The airflow helps cool the motor, and airflow restrictions like dirt and soil can create conditions that cause the motor to exceed its rating. Motor bearings also matter. Ball bearings tend to last longer and withstand higher temperatures than sleeve bearings, but they are noisier. Many motors use sleeve bearings, and replacing a sleeve bearing motor with a motor that uses ball bearings may negatively affect the homeowner's comfort due to the noise, so that's a conversation you'll want to have with the customer and set realistic expectations. Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool. Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android
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5:07
Superheat Talk w/ JD Kelly
In this episode of the HVAC School podcast, host Bryan discusses superheat with guest JD, who recently co-authored an article on the topic with Ty Branaman. The conversation explores the often misunderstood concept of superheat, its importance in HVAC diagnostics, and common misconceptions technicians have when measuring and interpreting it. Bryan begins by sharing how superheat was initially taught to technicians in the late 1990s and early 2000s, primarily as a method for charging fixed metering device systems. He explains how this limited view led to problems, as technicians would often add or remove refrigerant based solely on superheat readings without considering other system factors or giving the system time to stabilize. JD points out how the industry shifted when TXVs (Thermostatic Expansion Valves) became standard, with many technicians abandoning superheat measurements altogether in favor of subcooling measurements, missing crucial diagnostic information in the process. The discussion then evolves into a more sophisticated understanding of superheat as an indicator of evaporator coil "fullness." Bryan explains that lower superheat indicates a fuller evaporator coil, while higher superheat suggests a starved coil. They discuss the importance of measuring superheat in the correct location, noting that TXVs control superheat at the evaporator outlet, not at the condensing unit where technicians often measure. This misunderstanding leads to many incorrect diagnoses of "bad TXVs" when the real issues might be related to airflow, heat pickup in line sets, or other factors. Both experts emphasize the value of measuring superheat both inside at the evaporator outlet and outside at the condensing unit to get a complete picture of system operation. Key Topics Covered: Definition of superheat and its importance in HVAC diagnostics How superheat indicates evaporator coil "fullness" (flooded vs. starved conditions) The distinction between charging by superheat and using superheat as a diagnostic tool Common misconceptions about superheat measurement on TXV systems Why measuring superheat location matters (evaporator outlet vs. condensing unit) How to properly diagnose TXV issues using superheat measurements The relationship between airflow problems and superheat readings Normal superheat ranges for residential systems (7-14 degrees at evaporator outlet) How superheat affects both system capacity and compressor safety "Exercising" TXVs as a troubleshooting technique How line set conditions and installation factors can impact superheat readings System behavior during "hot pull down" conditions when starting with high indoor temperatures JD and Ty's superheat tech tip and worksheet: https://hvacrschool.com/solving-superheat/ Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool. Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android
Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.
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