Hvac School - For Techs, By Techs

In this short episode, Bryan discusses the unique features of hot deck, cold deck systems. These systems have separate heating and cooling components (if not entire systems). Older systems may have completely separate duct systems: one for heating and one for cooling. These ducts would go to each space, and you'd essentially have twice the ductwork you'd expect nowadays. Some systems also have a separate hot deck and cold deck in a single appliance (a bit like gas furnaces with case coils). We also use the term "hot deck, cold deck" to refer to systems with secondary fluid in a single appliance that produces heating and cooling. Heat recovery or heat-pump chillers use secondary fluids to carry heat around (these fluids don't expand and change state like refrigerant). A traditional chiller is often used in combination with a boiler system, and both can be shut on or off; this configuration can be tricky in shoulder seasons, and a hot deck, cold deck system could be beneficial instead.  Buffer tanks also allow

In this episode of HVAC School, hosts Bryan Orr and Bert discuss practical tips for preventing callbacks and failed inspections in residential HVAC installs and maintenance. Bryan and Bert stress the importance of getting the basics right, like properly cleaning condensate drains, ensuring proper drain pitch, and sealing ducts completely before relying on tapes and mastic to cover gaps. They emphasize verifying full system operation at the end of a job, from checking that drains flow freely to testing float switches and pressure testing for leaks. Bryan and Bert also cover wire and breaker sizing for equipment changes, securing disconnects, proper thermostat wall seals, inspecting joints with bubbles to find microscopic leaks, and more thorough evacuations and leak checks. Throughout the casual, conversational show, the hosts inject colorful commentary on doing quality work with a little sarcasm, including praising the merits of duct board and flex ducts. The tone is partly tongue-in-cheek but drives home the

In this short episode, Bryan talks about the situations when permits are not needed to install HVAC/R (or HVAC/R-related) components. A few codes are universal in residential HVAC, including the International Residential Code (IRC) and the International Mechanical Code (IMC). The local municipality, also known as the authority having jurisdiction (AHJ), chooses which codes to adopt.  You do not need a permit to install plug-in, cord-connected appliances. However, you need UL-listed plugs. You can also replace plugs without needing a permit, but the ratings need to be correct. Anything less than 25v that doesn't put out more than 50 watts of energy also doesn't require a permit. Thermostats and many IAQ accessories, including UV lights, fall into this category. Portable heating and ventilation appliances, including space heaters and portable cooling units or dehumidifiers, also don't require permits. Evaporative or "swamp" coolers also don't need a permit for installation. Self-contained units with 10 pounds o

In this podcast, Bryan Orr and Bert discuss various aspects of pool heaters, focusing on issues that make them different from typical HVAC systems. They cover the basics of pool heaters - the main types (heat pumps and gas heaters) and how they operate similarly or differently from things HVAC techs work on regularly. The bulk of the 45-minute podcast looks at common service and troubleshooting situations with pool heaters, which are usually installed by pool contractors initially and not HVAC contractors. Bryan and Bert talk through typical causes of common error codes and problems like units frequently going out on high pressure. They cover water flow issues and the role of pressure versus flow switches, the sizing and limitations of heat pumps, low ambient operation challenges, freeze protection, and proper refrigerant charging. There is also a good amount of discussion on gas pool heaters - frequent component failures due to heat and corrosion issues, piping considerations due to their large BTU capacity,

In this short episode, Bryan explains the fundamentals of capacitance, focusing on the unit of measure: farads, including micro and pico. Farads are named after scientist Michael Faraday and measure capacitance; one farad represents the capacitance of a capacitor in which one coulomb of charge causes a potential difference of one volt across the plates. Farads measure the storage of electrical energy and indicate the capacitor's ability to create a phase shift. Since farads are large units, our capacitors are rated in microfarads (1/1,000,000 farads). Bigger capacitors have higher microfarad ratings and store more charge. Capacitors create a phase shift and limit current on the start or auxiliary winding. (You'll read less current across the start winding than the run winding or common when a run capacitor is in the circuit.) The start winding helps get a single-phase motor up and running (but it isn't present on all motors). Three-phase power has three windings, and it has three sine waves 120 degrees out of

Bryan Orr hosted a live podcast discussion all about 90% efficient furnaces with HVAC professionals Ty Branaman, Adam Mufich, and Matthew Bruner. They covered the basics of how 90% furnaces work compared to traditional 80% furnaces, troubleshooting tips, and best practices for installation and service. A key difference with 90% furnaces is the addition of a secondary heat exchanger that extracts more heat from the exhaust gases before they go out the flue. This allows the furnace to achieve at least 90% efficiency. The condensing of water vapor in the exhaust also releases latent heat. However, the acidic condensate must be properly drained, and pipes must be corrosion-resistant. Proper airflow is also critical. The experts emphasized starting any service job by carefully looking over the furnace and venting. Check for any signs of problems like leaks, debris buildup, or animals/pests blocking vents. Verify gas supply and use combustion analysis to optimize performance. When troubleshooting, methodically trac

In this short podcast, Bryan breaks down the differences between analog and digital sine waves. Analog readings deal with an unlimited number of values; they are very precise and can have any number of decimals. As a result, the alternating current (AC) analog sine readings have very smooth curves when we read them on an oscilloscope (in the US, we see 60 peak-and-valley cycles per second because the frequency is 60 hertz).  Variable frequency drives (VFDs) and ECMs work with digital outputs instead. The alternating current (AC) input is flattened out and then replicated as a direct current (DC) digital output that mimics an analog sine wave using technologies like pulse-width modulation (PWM). Digital outputs appear as a series of steps on an oscilloscope, but PWM doesn't output different "steps" of voltage. PWM just changes the length and frequency according to the duty cycle (percentage of the time energized or unenergized). Digital scrolls turn on and off very often, and the time they spend "on" is the du

Bryan Orr interviews Tyler Nelson, an HVAC expert with over 20 years of experience as a contractor. They have an in-depth discussion about combustion analysis and why it is becoming increasingly important for HVAC technicians to utilize this process. The conversation provides an overview of combustion analysis benefits and why HVAC pros should incorporate it into their standard operating procedures. Tyler offers insightful perspectives from his decades of contracting experience, including his knowledge of how field conditions vary and factory settings may not translate perfectly. Carbon monoxide poses several dangers to customers and HVAC technicians. Tyler talks about CO poisoning risks and how analyzers can help detect issues. He also covers AHRI Guideline X for cracked heat exchanger testing and emphasizes the need to use combustion analyzers, not just visual inspection, to reliably detect cracks. Tyler also demonstrates the use of the Sauermann combustion analyzer and mobile app. He highlights key feature

In this short podcast, Bryan talks about checking the charge of a heat pump in heat mode. This skill will become more critical as ambient temperatures get cooler. The most reliable way to check and set the charge regardless of operating mode and season is to weigh the charge. This method is most practical during installation and commissioning, and proper commissioning can prevent issues with charge levels later. Weighing the charge is recommended for big repairs, like major component replacements. But in many cases, we don't need to check the charge by hooking up gauges; we can check for proper operation by taking a few line temperature readings. Before carrying out any tests or taking readings, make sure the heat pump is defrosted and that you've carried out a full visual inspection. You can carry out a full delivered capacity test in either cooling or heating mode (without the electric heat strips energized) to determine how many BTUs the system is moving. Some simpler tests will require you to compare the

Nikki Krueger and Genry Garcia return to the podcast to talk about a recent IAQ & dehumidification case study on a vintage home in Miami. The home was very clean but had a musty odor and VOC concerns. You can read the case study in the “Literature” section at https://www.santa-fe-products.com/about-us/media-resources/ or https://hvacrschool.com/case-study.  Blower door tests and ZPD revealed that the home was leaky, and the crawlspace was also not properly encapsulated. The options were to tighten the building and/or mitigate the problem by improving the HVAC system. The homeowners chose to improve the HVAC, which Genry did by installing a ventilating dehumidifier (Santa Fe Ultra98H), reducing system tonnage (3.5 to 2 tons), and putting in new ductwork. One of Genry’s key tips to address intermittent moisture issues is to pay attention to fluctuating pressures, not just under the blower door test conditions. Ongoing monitoring is crucial in these studies to measure the home under several different typical

Skilled trades entrepreneur Tommy Mello joins the podcast to talk about creating a business where everyone wins: business owners, employees, vendors, AND customers. Tommy's main motivations in business are relationship-building and helping employees make a good living. Those motivations contribute to the development of company culture; even though cultures build themselves naturally, developing the right leaders will help build a positive company culture that values all employees equally. Tommy trains leaders to develop their strengths, shows them that they are valued, and gives them the resources they need to succeed. When companies grow, communication tools and project management technologies need to be standardized to help organize the company, including using checklists and SOPs. Departments also need to keep their focus on the company's main goal, not just the success of their division. The goal is to make sure that people are aware of their responsibilities early on and on board with the company's visio

Refrigeration Mentor Trevor Matthews returns to the podcast to share some of his tips for supermarket rack service. The supermarket refrigeration world is ripe with high-paying opportunities and uses similar skills that HVAC technicians use daily. Switching from HVAC to refrigeration will require a little bit more attention to some new components, especially controls and control systems. Technically-minded people tend to do well in the refrigeration field regardless of where they come from. When you're sent to a job site, you'll need to investigate the store and the case (where the refrigeration happens) before checking the controller and looking at the alarms and trends. As with HVAC, you'll want to start by looking for the obvious, like frozen drains. (Even though these systems are designed to freeze, we still need proper airflow and don't want standing water in the drains to freeze.) We don't want to go in there with our tools and start adjusting valves immediately. Attention to detail is critical in refri

In this short episode, Bryan covers traps, vents, and drains. He explains some common misconceptions and best practices for fabricating drains, especially in residential and light commercial structures in Florida. Cleanouts and vents are commonly confused with each other, and people often cap vents and leave cleanouts open. However, cleanouts (which must be capped) will always be before the trap, and vents come after the trap. When you have an indoor air handler, furnace, or fan coil, vents must be higher than the drain pan to allow the float switch to trip when the drain backs up. (Rooftop units have shorter vents.) Vents should stay open. We use static pressure to determine the trap depth, and the trap outlet must be shorter than the inlet. The best practice for drain pitch is to have 1/4" of fall for every foot of horizontal run, and we must avoid making double traps where air can get trapped between them. Vents prevent air bubbles from forming in drains with multiple traps. Double traps often form when dr

HAVEN IAQ founder and CEO Kevin Hart returns to the podcast to discuss cracking the home health comfort code, diving into IAQ’s illusory ideals. Even though the industry has been generating well-thought solutions to common problems, it’s difficult to put those solutions into practice on a large scale. As a result, it’s common to rely on selling “bolt-on” IAQ products, which don’t actually solve systemic IAQ problems. HAVEN’s recent work has also shown that only a few HVAC technicians are proactively offering IAQ solutions to homeowners; the vast majority wait for the owner to ask about a solution instead.  Some IAQ issues stem from duct and building envelope leakage, meaning technicians could offer to perform diagnostic tests (like blower door testing) and address the solution holistically with building envelope and duct sealing. However, not all customers are willing to pay for these, which is one of the biggest challenges of comfort consultations. The question about the real long-term, widespread effectiven

In this short podcast episode, Bryan goes over a few tubing insulation tips. Tubing insulation is also commonly known as Aeroflex, Armaflex, and Thermaflex—all brand names for black copper line set insulation. We typically have to insulate just the suction line in typical residential split HVAC systems, but you'll typically have to insulate both lines in ductless/VRV/VRF or refrigeration applications. The insulation should be on the tubing before brazing, gluing the ends together (only using a specialty tubing insulation adhesive, NOT duct tape!). Since these adhesives are types of contact cement, you will need to apply a thin coating on each side of the joint and wait for a few minutes before pushing the ends together. Some forms of tubing insulation are split and have an adhesive flap instead. Then, you'll want to hold the insulation back with a clamp about 8-10" away from the area where you're brazing to protect it from heat damage. When you finish brazing, you'll want to put the insulation back and make s

Jim Fultz returns to the podcast to talk about the new HSI module from White-Rodgers, the 50E47U-843. You can learn more about this new universal HSI module at https://hvacrschool.com/hsimodule.  Hot surface ignition modules control the burner for gas appliances that use hot surface ignition, not just furnaces. Since the HSI module doesn't need to work with a blower fan, it can be used in water heaters, pool heaters, and many more appliances that don't primarily move air (except for combustion). It also controls the inducer blower and monitors the pressure switch. All White-Rodgers universal ignition modules work with the WR Connect app, which allows users to set up controls with a smartphone via NFC technology. The controls do not need to be powered on, and users do not need to be online during use. Users can also use the app to auto-configure their new White-Rodgers controls based on the old control settings. Technicians aren't required to use the app and can configure controls manually if desired. Universa

In this short podcast episode, Bryan talks about locked compressors and hard starts. He explains what actually happens when a compressor locks and covers when and how to use hard starts appropriately.  Locked compressors are compressors that trip on overload during startup; they're considered "locked" because the rotor doesn't turn inside the stator and generates heat instead. The overload opens, but the compressor shell typically does not heat up very much when the overload opens.  When you have a locked compressor, you need to start investigating the root cause with a thorough visual inspection. Then, check the run capacitor. A hard start kit helps you get the equipment working, but we should make sure we've addressed underlying electrical issues or installation conditions before installing a hard start kit. If the unit is old, then we may use a hard start as a temporary solution until the customer can purchase a new unit. In any case, it's best to use a factory hard start if the system requires it, but it'

Licensed mechanical engineer Tony Amadio joins the podcast to talk about residential exhaust codes and best practices. He also put together a presentation about the topic, which you can view at https://hvacrschool.com/exhaust.  When choosing duct materials for residential exhaust, you will want to stick to sheet metal and mind the gauge; flex ductwork can easily be damaged and will rack up a high total equivalent length in a way that sheet metal will not. Exhaust air should always discharge outdoors, not into an attic or crawl space, and that air needs to be replaced by air entering the conditioned space; makeup air is the air we draw in to replace the exhausted air, and we need appropriate undercuts to make sure we're getting the right amount of makeup air. Domestic cooking exhaust may also come in a few different varieties, each of which has different code requirements (with downdrafts needing much more CFM per ASHRAE). Range hood shape is also important for capturing as many particles as possible, but make

Phil Barr and Nathan Orr join the podcast to talk about wiring refrigerated cases in commercial spaces, including convenience stores and supermarkets. Cases may be medium-temp (or high-temp, in some cases) or low-temp. Medium-temp cases can typically defrost on their own during the off cycle, and low-temp cases may have electric or hot-gas defrost to help get ice off the coil at set intervals. Each system has an evaporator (and fans), compressor, condenser, and metering device (often a TXV or EEV), and low-temp refrigeration may have anti-sweat heaters, EPRs, and other components to manage. Challenges arise when electricians don't understand the fundamentals of commercial refrigeration, especially as the electrical circuitry relates to the refrigeration circuit components. Time crunches also apply a lot of pressure to electricians and refrigeration technicians. Testing circuits, such as fans and lighting, or using circuit tracers are good ways to get an idea of how an existing system is wired. Labeling wires

This podcast is a class taught by Bryan: Things to Keep Out of the System. He covers some installation best practices along the way to keep contaminants and non-condensable gases out of the system. We want to keep air, water, dirt, copper shavings, solvents, and nitrogen out of an operating system. All we want in an operating system is the appropriate oil and refrigerant for the system. Unfortunately, the POE and PVE oil we mostly use in residential systems nowadays are very hygroscopic; they attract water, and POE mixes with water to form acid, another thing we want to keep out of the system. We can pull most of the moisture out of the system by pulling a deep vacuum and following the best practices for a fast and deep evacuation. However, we can also reduce the probability of moisture getting into the system in the first place by NOT working on copper while it's raining outside, sealing the copper tubing adequately when routing it underground or in a chase (a common installation practice in Florida), and in