HVAC School - For Techs, By Techs

In this live episode, we talk about heat pumps, why Bryan likes them, why other people don’t, charging and diagnosing them, and defrost. Even though heat pumps work best in warmer climates, they can theoretically work as long as the temperature is above absolute zero (-460 degrees F). Viewers across the USA install heat pumps in their markets, even in places with cold winters like Wisconsin. Ideally, the discharge line should be around 100 degrees above the outdoor temperature in heat mode. Although this rule of thumb appears to work in many different climates, it is only really applicable on single-stage equipment. When charging heat pumps from scratch, check the manufacturer data in heat mode. Airflow for comfort or efficiency is something else to account for when you're commissioning a heat pump; the CFM should be higher if you want the system to be efficient, but the building will be more comfortable if you have a lower CFM per ton. Airflow is especially important to control in heat mode, as small changes can noticeably affect head pressure. When it comes to defrost, heat pumps typically use a time and temperature strategy. Defrost cycles usually run at a certain temperature for a fixed time period. Heat pump defrost boards usually look a lot more complicated than they really are; when you come across them, stay calm and remember that they're just like any other board. We also discuss: Absolute zero Climate zones “Vapor line” Discharge superheat vs. over ambient W calls Supplementary heat and dehumidification Confirming airflow on a heat pump in heat mode Controlling mean radiant temperature (MRT) vs. blowing hot air Using in-duct psychrometers and manufacturer charts to assess system performance How reversing valves may fail or get stuck Thermal imaging applications Copeland compressors and mobile app Testing defrost boards Carrier vs. Trane & Rheem defrost strategies Demand defrost Suction pressure and compression ratio under frost buildup   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 crossover episode (rantcast), Bryan talks with Gary from HVAC Know It All. They vent about some of the phrases that techs throw around that are often false. Technicians often throw around the phrase, "[X] will void your warranty." However, the truth is that manufacturers can't really void a warranty. Some modifications may go beyond the scope of the warranty, but you don't simply make modifications that "void" the warranty. Techs may say that something voids the warranty to shut down the conversation or to create a selling point (preventive maintenance). In many (but not all) cases, the manufacturer won't even check the installation in the case of a parts warranty; all they want is the returned part, and they will often honor the warranty. Since many manufacturers want to keep their customers, voiding warranties left and right would be a bad business decision; the customer base would opt to work with new manufacturers. However, if there is evidence that the customer, installer, or technician damaged the product, then the manufacturer has a reason to void the warranty. In several cases, the proof must be substantial, and the proof often isn't substantial when using natural additives like Nylog properly. Keep in mind that using additives comes with a calculated risk; you must rely on research and your own judgment to make the best decision for the customer. In this rantcast, Gary and Bryan also discuss: R-22 is not illegal Heat exchanger warranties Lightning and other "acts of God" The Nylog question Why use thread sealants on well-made flares Relationships with manufacturers and suppliers Warranties and original homeowners Putting the customer's needs above the manufacturer's Who really is a hack? How everyone in the distribution chain can take responsibility Complaining respectfully online   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 discusses the differences between air, nitrogen, and oxygen. He also explains why we should only use nitrogen for purging, flowing, and pressurization. You DON'T want to pressurize line sets with air because air contains water vapor and oxygen. Water acts as an oxidizer, and moisture can turn POE oil acidic via hydrolysis. You cannot dry out POE oil, and the acid can lead to compressor burnout. Nitrogen is non-reactive (unlike oxygen) and does not contain water vapor (unlike air). It also does a good job of chasing water vapor out of the lines. Because nitrogen won't react with anything we put in the line sets, it is an ideal medium for purging, flowing, and pressurization. Nitrogen DOES, however, change pressure with temperature; it obeys the gas laws, and you can see it in action when the pressure changes at different parts of the day (with varying temperatures). Oxidation can occur when oxygen reacts with copper to create a black scale called cupric (copper) oxide. It is similar to rust on iron; it is an undesirable form of corrosion. When the black scale comes off, it can get into screens on filter-driers and clog the system. You purge nitrogen to chase all of the air out before brazing. When you've finished purging, you use a flow regulator to reduce the nitrogen pressure (2-5 SCFH) to flow it during brazing. When we pull the vacuum, we only want nitrogen to be in the system; exposure to air should be very short, and any air in the system should be temporary. So, again, it's not a good idea to use air to pressurize the lines.   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 episode, we talk about diagnosing inverter-driven systems. We also discuss some of the issues and solutions for over-voltage. Inverter-driven systems, also called variable frequency drive equipment, provide comfort control across multiple zones in a building. Some systems may have multiple branch boxes that control various units throughout a building. These systems require a lot of patience; the diagnostic process can last a long time because you must test all of the terminals. Since these systems are very electrical-component-heavy, you may also encounter issues presented by lightning, power outages, or continuous high voltage. Installation errors are also common and can cause performance issues, such as incorrectly torqued-down terminals, nicked wires, and improper wire types. When these systems are on, line voltage runs into a bridge rectifier. So, the equipment takes alternating current (AC) and turns it into a form of direct current (DC). Capacitors smooth out the sine waves before running that current into the inverter, which switches the power into three separate phases, but the power doesn't look like typical three-phase AC power. Many power companies are familiar with single-phase AC equipment, so inverter-driven systems present a challenge. These challenges become clear in equipment near the initial power distribution source; inverter-driven equipment near the beginning of the power line is prone to excessive voltage and failure. We also discuss: Power surges and electrical damage ICM493 Loose connections Grounding Shielded conductor usage Pulse-width modulation (PWM) 230v-rated equipment Multi-stage equipment and airflow Bernoulli's principle Carrier Infinity equipment and locking out stages Ductwork and diffuser sizing Controlling radiant heat loads with multi-stage equipment Ventilation vs. dehumidification vs. heating and cooling R-22 retrofit refrigerants Metal oxide varistors (MOVs)   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.

Jim Bergmann is back on the podcast. This time, he talks about common faults with high-efficiency 90+ condensing gas furnaces and their installation. Like A/C units, 90+ furnaces often suffer from clogged drain lines. Other common problems stem from issues with inputs, temperature rise across the appliance, trapping, and venting. On high-efficiency gas furnaces, procedures like clocking the gas meter are much more important than on an 80% gas furnace; you must clock the gas meter to get the proper inputs. To get the furnaces to condense properly, you need to make sure you control excess air and get the temperature rise in the correct range. During the adjustment process, combustion analysis remains important as ever on 90+ gas furnaces. CO poisoning is always a deadly possibility on any sort of gas appliance work, and too many things can go wrong. You must use a combustion analyzer every step of the way. In high-efficiency gas furnaces, you essentially condense water out of the fuel-air mixture. (Think about water dripping out of your car's exhaust pipe in the winter.) Many furnaces counterflow, meaning that the flue gas gets pulled down instead of wandering upward. We need cold return air to meet with cool flue gases for optimal condensate production. Two-stage 90+ furnaces also use two-speed induced draft fans, which normally require an exhaust accelerator. Issues pop up in retrofit systems when we don't update the venting system to prevent the recirculation of flue gases. Two-stage furnaces tend to be very efficient, but they may not be as comfortable as single-stage furnaces. Jim and Bryan also discuss: Chemical causes of premature failure Orifices, fuel pressure, and impingement Heat exchangers Order of operations for checking condensate drainage CO poisoning Byproducts of combustion Energy savings of 90+ furnaces over 80% furnaces Interlocked systems Filtration   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.

Bryan explains the core differences between followers and leaders. There is nothing wrong with being a follower, but if you are ready to move into leadership roles, here are his tips. Leaders primarily leverage the work of other people. Conversely, followers have limits to their abilities and their earning potential; the leaders are the ones who set those limits. Good leaders create opportunities for others. Followers who attempt to be leaders are more likely to wait rather than move, complain rather than change, and assume rather than ask. Leaders actively seek out opportunities and tend to act rather than wait and assume that opportunities will come their way. Followers also accept but complain about the status quo, whereas leaders work to change their circumstances. Communication is a major area of difference between followers and leaders. Leaders ask questions, communicate, and propose ideas or solutions; followers typically hesitate to initiate communication and expect others to give them answers and opportunities. Followers also tend to think in terms of what they would do, not what they can actually do; they don't realize their abilities to make a difference and would prefer that the changes happen from the outside. On the other side, leaders seize opportunities to initiate change and create opportunities for other people (even if those are opportunities to fail safely). Moreover, the mark of a good leader is the number of followers who agree with their vision; leaders are also willing to make sacrifices for their followers and manage their resources well. True leaders also know how to listen to others, think broadly, and be kind but truthful; they don't take pride in being "brutally honest" or "knowing it 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.

Some great live guests join the podcast to discuss the advantages, disadvantages, and challenges of ductless and VRF equipment. We started off working on ductless equipment with Mitsubishi, especially installing them in lanais. Sunrooms have large amounts of radiant heat coming in, and the heat load often warrants getting an A/C system just for the sunroom/lanai. We even began oversizing them a bit (which was a lesson learned). We also learned that mini-split ductless systems tend to have filthy blower wheels because moisture tends to build up on them. However, bib kits make cleaning the blower wheel in place an easy process. High-wall ductless systems also work in houses, not just sunrooms. However, they may have issues dehumidifying effectively. To remove more latent heat, you have to ramp down your blower and ramp up your compressor to get your coil colder. Overall, Bryan is not a large fan of using multi-zone ductless units in residential applications UNLESS they are replacing window units. VRF systems are typically used in commercial applications. The systems typically use cassette-type units or low-static fan coils, unlike high-wall ductless units. Although VRF and high-wall ductless units tend to have different sets of advantages and disadvantages, both of them struggle a bit with humidity and may need supplemental dehumidification. Overall, while VRF and ductless systems are desirable because they can control sensible capacity, those modulation capabilities can also lead to serious problems in wet climates. We also discuss: Condensate pumps Blower wheel set screw issues Ductless and VRF filtration Sensible heat ratio (SHR) VRF serviceability Dehumidification vs. efficiency Regional VRF manufacturing practices EER vs. SEER Daikin dry mode What should HVAC systems really control? Engineering commercial buildings VRF refrigerant loss ICM493 controls   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.

Jamie is back on the podcast. This time, he talks about the merits and pitfalls of floating head pressure and why you might care. There is a relationship between floating head and floating suction, though the latter is easier to understand. You can stage fans to come on at certain temperatures, but you'll always be running fans above a certain temperature. When temperatures are below that temperature, you can save energy by not running the fans. However, you still have to worry about feeding the evaporator coil sufficiently. Floating head pressure refers to dropping the pressure differential across the metering device while letting it feed the evaporator coil properly. Allowing the head pressure and temperature to float is beneficial in applications that use large amounts of electricity and have low profit margins, such as grocery refrigeration. This practice is also great for energy savings in mild climates that stay below 80 degrees for most of the year. To use floating head, you first have to look at your metering device capacity. The metering device must have enough capacity to feed the evaporator coil and compressor adequately for the load conditions. Then, you must look at your other components' capacity balance, namely your evaporator and compressor. Sometimes, you also have to use floating suction to combat dehumidification issues that may result when you use floating head pressure. Jamie and Bryan also discuss: Energy efficiency benefits of floating the head pressure Compression ratio Fan staging and variable-speed fans Metering device sizing for load demands Electronic expansion valves (EEVs) vs. TXVs Evaporator and compressor sizing in relation to each other Evaporator pressure controls Oversized condensing units Temporary fixes to save product vs. permanent fixes Ease of locating and purchasing replacement parts   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 talks about circuit breaker facts. He also explains why they trip, what they do, and some different types and considerations. Circuit breakers break the circuit during an overcurrent situation. These do NOT handle all overloads, such as locked rotor amps (LRA); these handle significant overloads, such as shorts (when current takes undesigned paths). In air conditioning, we can size our fuses and circuit breakers a bit larger than usual, which prevents tripping from small spikes instead of truly dangerous or prolonged overload conditions. There are thermal and inductive circuit breakers. A thermal circuit breaker uses heat to determine when to trip; these are common breakers but are prone to nuisance trips from poor connections or on days with high ambient temperature. Inductive trip breakers are magnetic and trip at a certain point of inductance; these are not easily affected by ambient temperature but can be expensive. A breaker's temperature can tell you a bit about its condition. Hotter breakers may be closer to tripping. However, arc fault breakers, a type of thermal breaker, can also run hot but work fine, which may confuse technicians. You can use thermal imaging cameras or infrared thermometers to compare breaker temperature. Dielectric grease is a good tool but requires plenty of attention. You need to have the right connectors before you even reach for the grease. The dielectric grease protects the connectors from corrosion (from the outside), and it should NOT go directly on the connectors. Some people also use anti-seize grease; no matter which grease you use, you must be careful and avoid adding resistance. Bryan also discusses: Proper torque settings Measuring voltage drop across the device Using breakers as switches Double-lugging Arc fault vs. GFCI   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 episode from the archives, Dan Holohan joins us on the podcast and talks about his vast experience in the lost art of steam learned from long-dead men. Steam heating is a "lost art" nowadays; it has become increasingly uncommon and has been disappearing since the Vietnam War. Many people who understood steam heating either retired or died after the Vietnam War. Many elements of steam heating are difficult to understand or surprising. (For example, steam pressure has a surprising relationship with velocity: low-pressure steam moves through piping much more quickly than high-pressure steam.) So, Dan Holohan is on a mission to revive that knowledge and teach the newer generations about the lost art. There are many older steam heating systems still operating today, especially in the older large buildings in New York. Dan learned a lot about steam heating when working on these old systems and optimizing them. Most of the time, he optimized those systems by removing unnecessary accessories, not adding components like steam traps. Many old boilers used coal as a heat source. Nowadays, many old boilers have been fitted with conversion oil burners with thermostats, but they are still piped for coal. Some systems now have multiple risers or massive vents on the main riser to prevent the thermostats from getting too hot too early and satisfying the thermostat too early. We call that master venting, reducing pressure and allowing steam to move very quickly and efficiently. Dan also discusses: The 2-PSI standard Transportation metaphors for BTUs in steam Harmful renovations for old boilers Replacement vs. restoration mindsets Gaps in steam boiler education Monopolizing the market if you HAVE the education Boiler piping and venting Two-pipe vs one-pipe steam   Find out more about Dan and hydronic heating at HeatingHelp.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.