HVAC School - For Techs, By Techs

In today’s podcast, Nikki and Bryan discuss dehumidification. They cover the relationship between cooling and dehumidification, humidity control, and dehumidifier installation practices. If the A/C unit is the king, the dehumidifier is the queen. The A/C unit controls cooling and humidity, but it can only do so much. A dehumidifier helps the A/C manage comfort under more demanding conditions. Many factors contribute to comfort, including sensible heat ratio (SHR), relative humidity (RH), and ventilation. Dehumidification reaches all of those factors. Humidity control requires a holistic approach. Band-aid fixes DO NOT work. Dehumidifiers should work with the A/C system and building design to keep RH in the 50-55% range. Proper installation is vital. For example, tying into the HVAC supply is a recommended practice. Returns are the opposite; dedicated returns are preferred. Other factors to consider are proper sizing, Manual J, and customer expectations. Join Nikki and Bryan as they cover: Relative humidity targets Sensible heat ratio (SHR) Latent removal capacity Ventilation Building design and tightness Manual J Challenges with ductless systems Ducting into the supply with dedicated returns Installation practices Dehumidifier sales and customer service And much more… To learn more about Santa Fe Ultra series, go to www.santa-fe-products.com. You can scroll through the products to find the Ultra series free-standing ventilating dehumidifiers.   If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In today’s podcast, Trevor and Bryan discuss how to troubleshoot thermostatic expansion valves (TXVs/TEVs). They also dive into the various types, applications, and components of TXVs. TXVs are metering devices that control evaporator superheat to protect compressors from harm. Controlling heat also regulates pressure, which improves efficiency and prevents issues like floodback and overheating. TXVs contain several components that manage the forces that open and close the valve. These components include powerheads, diaphragms, springs, and more. The components all contribute to a delicate balance that can be broken when they fail or are installed improperly. TXV failures lead to high or low superheat and eventually compressor failure.  When you diagnose a TXV, you may encounter hunting, broken powerheads, filthy screens, and improperly sized valves. Once you verify the cause of the issue, you’ll likely have to adjust the TXV, replace a component, or replace the whole TXV. That can be a tricky decision that will largely depend on the type of failure, the type of TXV (conventional vs. balanced port), and the TXV’s application (residential HVAC, refrigeration, etc.). Join Bryan and Trevor as they cover: Opening and closing forces Internal and external equalization Non-bleed/hard shutoff TXVs and design limitations Conventional valves vs. balanced port valves Brazing in TXVs Strapping the TXV bulb to the suction line TXVs in refrigeration vs. HVAC Liquid quality, sight glasses, and subcooling TXV sizing Suction pressure/superheat hunting High and low superheat causes Adjusting vs. replacing valves And much more...   Check out Emerson’s HVACR training HERE. Then, navigate to “Contractor Tool Box Talks with Emerson.” 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 discusses push-pull recovery, how it works, and what we need to know about it. Push-pull recovery is a somewhat counterintuitive method of recovering liquid rapidly. We simply do that by pulling refrigerant out of the system and pushing it into the tank. However, when we pack refrigerant into a tank, the tank pressure and temperature increase. So, it can be more difficult to get refrigerant into the tank as the job goes on. When we recover liquid refrigerant on large systems (20+ pounds of charge), you connect a line from the liquid line or receiver and attach it to one side of the tank. Then, you pull from the system the other side of the tank should lead into the recovery machine. Attaching to the recovery machine helps depressurize the tank. When pulling out of the tank, you'll want to make sure the refrigerant is a vapor. The recovery machine should be pulling only vapor refrigerant out of the tank. While you're depressurizing your tank, you will be pressurizing your system to push the liquid refrigerant out of the system and into the recovery tank. (Short hoses with a large diameter are usually best for quick recovery.)   If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this short podcast episode, Bryan goes over one of his most valuable tips for pulling a vacuum on a small system. It can be very difficult to pull a vacuum on a small system, especially when you're dealing with a low-temperature application like a freezer. When you pull a vacuum, you're creating a low-pressure area that affects molecule behavior. So, you're creating a situation where the molecules push their way out of the system and into your vacuum pump. The low temperature and small tubing, especially capillary tubes, make this process exceptionally difficult. A very good vacuum pump can still have a hard time achieving a deep vacuum. To make this process a little easier, Bryan likes to add heat. When you add a heat blanket around components with oil, you negate the low-temperature obstacle and make it easier to separate refrigerant from oil. You may also use a heat gun on areas where using a heat blanket is impractical. If the area is cold or has refrigerant and oil together, then you'll benefit from applying heat. Don't go crazy and use open flames, but a heat blanket or heat gun will usually be safe.   If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.

In this podcast episode, Bryan and Eric Mele explain how HVACR technicians can END callbacks with a few best practices. Rushing through calls will often lead to callbacks. One of the most common mistakes techs make is failing to check the condensate drain before walking away from a job. To end callbacks, technicians would be wise to check the entire system and note any possible problem areas; in commercial HVAC and refrigeration, pay attention to variation across evaporators, condensers, and drainage systems. Customer service is a huge component of residential HVAC; you can prevent callbacks by listening to the customer's concerns, addressing their comfort issues (even if it lies beyond the obvious problem), checking your "five pillars," and thoroughly explaining what you've done. Even if a problem seems to drag out, take all the steps necessary to alleviate your customers' fears. Electrical problems also cause callbacks, especially dual-run capacitors. So, it's a good idea to check for wiring rubouts and make sure the wires look clean and organized. If you can offer an electrical solution to the customer at a cost, do it, even if they might decline it; that way, the callback is on them, not you. Overall, being thorough, communicating with the customer, and offering solutions is the key. If possible, it's best to explain everything at once and have one money conversation. If you can't get a full diagnosis until the customer approves a repair, be transparent about that. Eric and Bryan also discuss: Multi-equipment setups in commercial settings Dealing with difficult customers Managing customers' expectations HVAC in new homes Determining if a unit has been set up correctly Smart thermostats Cleaning drains and equipment Preventing flooded starts OEM vs. aftermarket parts Commonly replaced parts (reversing valves, TXVs, etc.) Establishing a process that works   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 podcast episode, Bryan and Eric Mele discuss the diagnosis and prevention of compressor overheating in HVAC and refrigeration. The main causes of compressor overheating are inadequate cooling back to the compressor, low charge, restrictions, and sometimes even poor suction line insulation. We want to keep the suction temperature low while maintaining appropriate superheat. If the suction line temperature is too high, the compressor can't cool down well enough. Dirty condenser coils, low voltage, weak capacitors, or an inadequate condenser fan can also lead to compressor overheating. Electrical problems, including too little capacitance, will make a compressor go out on thermal overload. When you have refrigerant problems, the thermal mass will just keep growing; it takes a long time to heat the compressor up, and it will take a long time to cool it down. In a thermal overload, a bimetallic disk in the compressor will open and break all three legs of power. When a compressor goes out on thermal overload, it will make an open circuit, and you will read infinite ohms. Knowing that the compressor has gone out on thermal overload is just the beginning of compressor overheating diagnosis. So, to begin diagnosis, you'll want to make sure there's refrigerant in the system. Inspect the unit visually and note anything that seems odd. Then, you'd check your capacitor for electrical problems. You can also feel the compressor to get an idea of the extent of the overheating (try not to burn yourself). You'll also want to monitor the amp draw, condensing temperature, suction pressure, and superheat. Eric and Bryan also discuss: Axial fans Condenser fan intermittent failures Resetting the compressor Cooling down the compressor Setting up your meter Being out on high pressure Wrapping wire to increase ammeter resolution High return gas temperature   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 and Eric Mele talk about re-tapping transformers for single-phase equipment in 208v applications. Most single-phase equipment can work for 230v or 208v, meaning that they can operate with low voltage. However, we typically see 208v in commercial buildings. The sine waves of 208v equipment are 120 degrees out of phase, not 180 degrees (as in split-phase applications). We get lower voltage from leg to leg (208v, though the voltage can be a little higher or lower). Power companies generally put out slightly higher voltage to reduce line losses. Most systems can work on multiple voltages, but they come with a transformer that's set to the 230v or 240v setting. However, under those settings, you can experience issues in 208v applications. If you put equipment tapped to 230v or 240v in a commercial setting, you may have issues, especially if you're farther away from the air handler. You may not get full 208v and may see contactors that don't pull in intermittently, and you may get intermittent cooling calls. Intermittent problems become worse when you have long thermostat wiring. In those cases, re-tapping the transformer is your only option. When the original voltage is incorrect, you'll need to re-tap the primary (high-voltage power going in). If you fail to tap the primary correctly, the voltage going out of the secondary won't be correct. When it's time to test the equipment, you'll always want to be sure to test the equipment under load. Make sure you cap extra wires and cap them independently of each other; those wires do have voltage, and we need to be cognizant of that.   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. Check out our handy calculators HERE.

In this podcast episode, Ben Reed from TZOA, a disruptive air technology brand, joins us to discuss the indoor air quality map and compass. We spend a majority of our lives indoors, so TZOA tries to improve IAQ in homes to keep us healthier. HVAC manages airborne chemicals, so indoor air quality ties right into our industry; HVAC technicians will become more valuable when they become well-versed in IAQ technologies. In residential HVAC, we are already used to listening to customer complaints and observing the home. Technicians (and even IAQ products) can "map" out the customer concerns and home features to develop a comfort and home-health solution. TZOA is working on putting together that "map and compass" model to optimize home health and comfort by noting problem areas and pointing us to the tools to solve the problem. HAVEN uses a central air monitor (CAM), which is an in-duct, whole-home IAQ monitor that measures particulates, temperature, and humidity. The monitor pairs with software to fulfill the "map and compass" model and assist with diagnosis. The air monitor and software help dispel uncertainty around IAQ products while providing accurate readings that point to solutions. It's also worth noting that HAVEN's tools can only be purchased and installed by HVAC professionals. So, they're helping bridge the communication gap between technicians and customers. TZOA is also attempting to build trust and confidence in IAQ products through education, collaboration with industry experts, and allowing HVAC technicians to use and experiment with their products. Ben and Bryan also discuss: HAVEN and TZOA's beginnings IAQ uncertainty and reputation Multiple chemical sensitivity Ventilation and dilution The future of TZOA products TZOA's personal use program Working with reputable companies and people Integrating IAQ into maintenance plans   Learn more about TZOA and HAVEN at haveniaq.com. If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this podcast episode, Bryan and Trevor Matthews of Emerson Canada discuss the Copeland 2-stage ZPS scroll compressors. Please join us by following along in bulletins AE4-1428 and AE4-1365. The ZP91KCE to ZP143KC Copeland compressors don't have internal pressure reliefs (IPRs). Those higher-pressure compressors make very loud noises when they go off, and it'll blow hot discharge gas on the internal overload to shut down the compressor. Some scroll compressors have temperature operating disks (TODs), which are bimetal disks that open upon a temperature increase and reroute the gas. Other compressors have advanced scroll temperature protection (ASTP), which is a snap-back disk near the floating seal. You don't just want to shut the suction service valve to pump the scroll down. Instead, common service procedures include checking voltage to the compressor, the internal motor, the blower/fan operation, the suction pressure, and the compressor wiring. If you install crankcase heaters for oil management, be sure to install them correctly to avoid overheating the compressor. You'll also want to verify that crankcase heater voltage and ensure that it is properly grounded. Two-stage modulating Copeland scrolls work with a 24v DC solenoid in the scroll set. That solenoid energizes and de-energizes, which either fully or partially loads the compressor. Load matching is ideal for efficiency and comfort, meaning that the two-stage Copeland scrolls perform well in those areas. Unsurprisingly, the fully-loaded option draws more current than the partially-loaded option. These two-stage compressors don't have IPRs, so you will need a high-pressure control set to 650 PSI. Trevor and Bryan also discuss: TOD vs. ASTP Operating envelopes Hipot testing Single-phase compressors Using Copeland compressors in pool heaters Oil and refrigerant dilution Wiring up CoreSense Reversing valve sizing issues   Visit climate.emerson.com for more resources. 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 podcast episode, Bryan, Trevor Matthews, and Jim Dick of Emerson talk about the screw compressor and how it works. This time, they focus on the Vilter single-screw compressors. Vilter is an industrial compressor division of Emerson (compare to Copeland). Vilter also makes reciprocating compressors, but the screw compressor is its claim to fame; you may want to consider using a screw compressor when you want greater capacity and control than a reciprocating compressor. Screw compressors also work well for applications with constant loads; they do, however, have microprocessors that can monitor system performance to maximize efficiency. Vilter uses a compressor with a single screw, whereas most compressors have twin screws. Twin screws have a motor that continuously turns the rotor, which causes the screws to mesh together; the compression happens as gas fits between the screws, and the gas volume decreases as the space between the screws closes. In a single-screw compressor, the gas compresses on the outside of the screw. In any case, we must seal the gas in the flutes, and oil helps us with that. Liquid should not get into either type of screw compressor, as liquid is not compressible and will damage the compressor. When you service a screw, the oil temperature and discharge pressure will likely be the most important values to watch out for. During maintenance inspections, you'll also want to pay special attention to the bearings, the four pressure transducers, and oil filtration system. Jim, Trevor, and Bryan also discuss: Microprocessors Star rotors Oil uses, management, and components Motor RPM Multiple compressors and added capacity Calibrating pressure transducers Zeroing vs. calibrating Suction screens Jim's interesting findings Injecting oil Value engineering and consistency   If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Check out our handy calculators HERE.