HVAC School - For Techs, By Techs

Jim Devlin from Weil-McLain joins us to talk about high-efficiency and cast-iron boilers. He also explains how to use them together in a "hybrid" configuration to serve your customers. Cast-iron boilers are standard-efficiency boilers. These boilers are "standard-efficiency" because they have higher return water temperatures; you typically measure about 330 degrees in the flue. Conversely, high-efficiency boilers have much lower return water temperatures, only around 180-190 degrees in the flue. The goal of a high-efficiency boiler is to get more BTUs out of the fuel, so your flue gases will be cooler. However, the standard boiler can be better for thermal transfer and gives us more leeway for our flue temperatures. Hybrid boiler plants aim to eliminate inefficiencies by using cast-iron and high-efficiency boilers together. These hybrid configurations usually exist in older constructions, but you also see them in new constructions with dual-fuel burner systems or where high-efficiency boilers won't have a good value on their own. You will often see a greater ROI on systems that use cast-iron and high-efficiency boilers together than on systems with multiple high-efficiency boilers. Hybrid configurations usually set up dissimilar boilers in series with a primary-secondary loop. The controls usually use sensors and 1-10v DC output signals, so these controls can modulate the burners. Many people make mistakes when piping these boilers; they don't understand the parallel positioning of the tees. When installers make these mistakes, the boilers lose efficiency. Jim recommends drawing out the piping to avoid making those errors. Jim and Bryan also discuss: Sulfuric acid and condensate Boiler metals Dual-fuel burner systems Boiler controls Hybrid vs. Combi-boilers Comparing utility reports and checking ROI Energy savings on cast-iron boilers Heat exchangers Future geothermal and solar hybrid systems   Visit weil-mclain.com to learn more. 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.

Do you need different gauges for each refrigerant? In today's short podcast, we discuss the answer to this common HVAC question. When we first started using R-410A, many people warned us that we'd have to use a separate set of gauges when working on R-410A systems. That's because R-410A systems use POE oils, not mineral oil, and they are not compatible. While it is true that R-22 and R-410A systems use different oils, there is no need to worry about using separate gauges for each type of system. Actually, some manufacturers recommend using a little bit of POE oil in mineral oil systems. What you cannot do, however, is mix the refrigerants themselves. Many of the gauge hoses have quick disconnects, which cause some confusion regarding the de minimis rule. (The de minimis rule permits tiny refrigerant losses from regular servicing, and de minimis DOES protect us.) However, we aim to keep our hoses clear anyway. We do that by bleeding liquid refrigerant back into the suction line after servicing. So, the real concern doesn't lie in which refrigerant we use with our gauges. The real issue is about taking steps to avoid contamination of the entire system and stay in compliance with EPA standards. Mixing POE and mineral oil does not negatively affect a refrigeration system; however, moisture does pose a threat to POE oil. Again, the core issue deals with best practices: flushing and purging hoses, minimizing the risk of hydrostatic pressure, avoiding venting, and avoiding mixing refrigerants. Of course, you don't have to worry about any of these problems and practices if you check the charge without gauges. Using probes is an easy way to get good measurements without worrying about contamination   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 two-part interview, Moe Hirsch goes deep and wide on buffer tanks and strategies for "parking" BTUs in hydronic systems. Systems with a high domestic hot water load can also benefit from a buffer tank. You can pipe the domestic hot water tank as its own zone and step down the rest of the structure. However, there will be some standby losses for a tradeoff greater capacity. You also cannot use the buffer tank as an air eliminator or separator; they work only for BTU parking. Contrary to popular belief, buffer tanks do NOT prevent flue gas condensation. If the buffer tank reaches 120-130 degrees, then it may prevent flue gas condensation via the flywheel effect. Flue gas condensation on boiler systems has to do with excess air, combustion, and run cycle length. Moe and Bryan also discuss: Water storage temperature Using a biomass boiler as a backup Stratification: tall tanks vs. wide tanks Cycle times and mathematical formulas Outdoor reset targets Boiler startup conditions Manual reset high limit

In this two-part interview, Moe Hirsch goes deep and wide on buffer tanks and strategies for "parking" BTUs in hydronic systems. When we use boilers, we want to use a heat sink to "park" BTUs in a buffer tank so that we can temporarily store extra heat and avoid short cycling through load matching. However, few boilers have an actual buffer tank; many systems have a means of creating a buffer, though. Buffer tanks are good for parking BTUs in systems with zones and microzones that require varied heating needs. The amount of BTUs you store depends on the temperature difference between the beginning and end of the tank and the water quantity. Moe and Bryan also discuss: Pressure tanks Variable frequency drives Getting extra BTUs Snowmelt systems and Combi-boilers Two-pipe and four-pipe configurations Creating and positioning buffer tanks Hydraulic and air separation Reverse indirect water heaters Parking BTUs in concrete Dirt and magnetic separation

In today's short podcast episode, Bryan covers the basics of refrigerant oil in HVAC/R systems. He also discusses what technicians can do to maintain oil systems. Oil lubricates the moving parts of the compressor. So, oil moves with the refrigerant and lubricates the parts as the refrigerant moves through the compressor. Unfortunately, oil can migrate to other parts of the circuit when it's not supposed to. Flooding occurs when liquid refrigerant enters the compressor crankcase, and slugging occurs when liquid gets into the compressor head. When either of those happens, they can eject oil from the system. When a system has insufficient oil, the compressor's moving parts can heat up and wear out quickly. We can use an array of preventative strategies to keep oil in the system and reduce the risk of compressor damage. We want to keep our discharge lines below 225 degrees to prevent oil (or lubricant) breakdown. To prevent the compressor from overheating, we want to look at mass flow rates and compression ratios. We should also make cleanliness a priority, as dirty components can increase the compression ratio. Oil has evolved with refrigerants. We largely used mineral oil with HCFCs like R-22, but we have begun using POE oil with HFC refrigerants like R-410a. Newer HFCs are generally NOT miscible with mineral oil, but we must be careful with POE and PVE refrigerants because they are hygroscopic. These oils break down via hydrolysis when they react with moisture, and they become acidic. So, we need to keep POE and PVE systems dry to prevent damage. Bryan also covers: Hard shut off TXVs Pump down cycles Oil return Viscosity Oil velocity and pipe design Miscibility AB oil   Check out our oil article 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 today's podcast, Kevan Mayer from NAVAC comes talks about recovery and ways to make it work better and more safely for you. Recovering refrigerant is better for the environment and safer for us. When designing recovery equipment, NAVAC's goal is to limit the gases we put into the atmosphere and leave the planet in better shape than we gound it. Recovery also ensures that refrigerants for phased-out refrigerants remain available. Tanks require vacuums of at least 1000 microns, if not deeper. We also need to remember what the previous tank contents were to make sure that we only fill the tank with those refrigerants and oils. You absolutely DO NOT want to mix refrigerants. Tanks should always be up-to-date and must be certified every 5 years. When recovering refrigerant, one of the best practices is to use a filter-drier to filter out moisture and contaminants. Reducing moisture and contamination will increase the life of your recovery machine. However, a filter-drier will not restore refrigerant back to the highest purity standards. The speed of your recovery will depend on your vacuum, recovery machine, hose sizing, and core removal. You can also raise pressure by turning the fan on. The goal to produce speedy recoveries is to reduce tank pressure and increase system pressure. When it comes to filling the tanks, we must pay attention to the tare weight and water capacity. However, we must understand that the water capacity is NOT the same as refrigerant capacity. We need to do a little bit of math to fill our tanks safely. Kevan and Bryan also discuss: Evacuation vs. recovery Reclaim company tank-handling protocols Refrigerant mixing costs/consequences Using recovered refrigerant legally Compression ratio Hose sizing and manifolds Push-pull method The 80% rule NRDD recovery machine   Learn more about NAVAC tools at navacglobal.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.

In this short podcast episode, Bryan covers the difference between volt-amps (VA) and watts when we take electrical measurements. We usually use VA to rate transformers, but we use watts for other electrical ratings. Even though you can multiply volts by amps to get wattage, the difference between VA and watts has to do with the power factor. Power factor is the ratio of apparent to active power. VA is the apparent power, and watts is active power. The difference between volt-amps and watts is called KVAR (kilovolt-amps reactive). The reactive volt-amps are not effective; you can compare them to the foam on a beer (if the entire beer is the VA, the watts are the actual beer). When we look at motors, we want to know how much actual work that motor is doing. That's why motor ratings are in watts or horsepower; the utility company is also probably going to charge you in watts. However, we want to measure transformers in VA because we are more concerned about the exchange of current, not necessarily the work to be performed. (Smaller transformers use VA ratings, while larger transformers have KVA ratings.) Our goal is to have a power factor of 1, as that indicates a minimal amount of ineffective reactive power. In those cases, our motors and other electrical components will be working efficiently. There is also less unnecessary heat when our systems have a power factor of 1. When our systems get out of whack, we may have to do power factor correction.   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, I talk with tech, contractor, and consultant Genry Garcia. He tells us about his experiences with independent consulting and helping other contractors in South Florida. A chunk of Genry's work deals with independent consulting, which primarily focuses on helping other HVAC businesses and contractors instead of customers. South Florida has unique climate considerations, and Genry focuses on improving workmanship in a way that works well with the climate. Diagnosis remains important in Genry's work, as he needs to find and solve issues with HVAC companies in his work. Genry and Bryan both believe that the future of the industry lies in a non-judgmental approach towards technicians and customers; Genry's consulting approach aligns with that vision for a better HVAC industry. In South Florida, oversizing equipment is a severe issue. The hot and humid climate of South Florida leads to technicians oversizing the equipment to deal with the heat, but the runtime is too short to help with latent heat removal. So, Genry tries to get the full picture of an install by contacting everyone associated with the installation to gather information. He also focuses his education and training on correct equipment sizing and air balancing to help technicians in his climate zone. Equipment sizing has to do with heat load and air balance. So, some of Genry's work also involves measuring pressures and balancing the supply and return air to maximize comfort. We also have to be aware of balancing heat and moisture when we adjust the structure or system. Genry and Bryan also discuss: Tech support "Competing" for customers Repetitive HVAC training and education Data logging Building occupancy and its effect on load Helping consumers understand sizing issues Load matching Zonal pressure matching   Check out Genry's website HERE or contact him via his email address: garcia@cdi-hvac.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.

In this short podcast episode, we talk about condensate drains. We get into the basics of cleaning, pitch, drain pans, and more. Cleaning drains sounds like an easy task, but it can be a bit time-consuming and difficult to get right. Instead of just "blowing out the drain," you must check the entire drain and be aware of buildup in traps and other hard deposits that form inside the piping. Sometimes, you may need to use cleaners to dissolve the sludge and grime. Cleaning is about understanding the drain anatomy and checking it thoroughly to identify and attack the source of the buildup. You also need to clean the drain pan. Drain pitch is also important for proper drain operation. The horizontal runouts need a slight downward pitch to move the pipe contents. We recommend using 1/4" per foot of fall on horizontal runouts. Insulation is also important on horizontal runouts in areas like attics and other unconditioned spaces. Secondary drain pans should have about 3 inches of overlap in all directions, especially over the supply. Improper drain pan setup can cause messes later, and we don't want condensate dripping all over the place. Make sure you install your units in the proper configuration. Be willing to tweak the design to make sure the drain pan is sturdy and collects condensate well. As you would ensure that your unit is level, you need to make sure the secondary drain pan is level and supported properly. You also need to think about float switches. If you have multiple float switches, you need to wire these in series. These components also require thorough testing; each one should be able to break the circuit. We also discuss: Strapping the drains Venting Double-trapping   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.

Bert and Bryan discuss the commonly repeated phrase, "refer to manufacturer's specs," in HVAC work. They discuss when referring to the manufacturer's specs works and when it feels like a crutch. Sometimes, you need to read the manufacturer's specs so that you can use the correct kits and components if specific parts or tools are necessary. Without knowing the specific product numbers given in the specs, you wouldn't be able to do the job properly. The manufacturer's literature can also explain equipment performance under certain conditions. In very specific applications, including VRF/VRV systems, you will want to be aware of specific procedures. Manufacturer specs also provide vital information for installations; while manufacturer literature can help with troubleshooting, the manual isn't always always as trustworthy for servicing equipment. However, manufacturer specifications can also be outdated or incorrect. For example, many manufacturers refer to outdated evacuation methods in their literature; they use information based on poor vacuum pumps. Many manufacturers also recommend doing triple evacuation, but a deep evacuation can usually suffice without needing to do a triple evacuation. Manufacturers also aren't aware of products like Nylog that don't contaminate the system, so manufacturers advise NEVER to use thread sealants. Overall, you must understand your equipment and use the manufacturer's specs to help you understand the equipment. If you use them as a step-by-step guide for servicing, then you may be using those manuals as a crutch. Some techs also use the specs to justify certain charges and services, which Bryan finds quite annoying. Bert and Bryan also discuss: Technician profitability Advanced functions in the Ecobee thermostat manual Flare leaks Nitrogen usage Understanding applications and misapplications Customers, equipment failures, and spending money Charging the customer "according to manufacturer specifications"   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.