HVAC School - For Techs, By Techs

In this podcast episode, Jim Bergmann continues talking about standard air, air density, and mass vs. volume as well as some other methods of "directly" measuring airflow. It gets pretty deep.

Airflow hoods and vane anemometers can give you direct airflow measurements.

You use static pressure probes, not pitot tubes, to measure TESP. When measuring static pressure, you put the negative probe in the return and the positive probe in the supply. Then, you measure the TESP (away from wiring and airflow). However, air pressure fluctuates as that air moves in the duct. Velocity pressure occurs when air moves and creates turbulence. The blower moves air, which has weight. As such, density, volume, and mass are all important as well. As air density changes, the CFM remains constant at a variable mass flow rate.

When it comes to using any tool for measuring airflow, static pressure, etc., all tools are an investment of money and time; you must spend some time learning how to use those tools. You will discover those tools' limitations and must learn how to work with or around those limitations.

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Bill Spohn Jr. is a college intern working towards his business degree, but he took a week to see what it is like to work as an HVAC tech. He shares his impressions on this podcast. Bill is the son of Bill Spohn and has been a college intern working with TruTech Tools. However, he has just gotten his first real dose of the HVAC contractor experience in the full swing of summer.

Bill started off by riding with a Kalos residential tech, Tyler, who had seven calls that day, mostly for PMs; they worked from 8:15 to 9:00 PM. Bill was impressed with the professionalism of Tyler and how well he communicated with customers. The second day, Bill got to do an install, which was a physically taxing task (partially due to the Florida heat). He put in a new drain pipe, new copper tubing, a new air handler, and some new pieces of ductwork. Bill also spent a day with Jeff, where he did a lot of preventive maintenance.

As with many people, Bill learned a lot about the importance of refrigerant and proper charge. He also found SEER ratings and other efficiency measures fascinating.

Bill went into his experience with the idea to identify "pain points" for techs and suggest improvements to current tools and technology. Now that Bill knows what's important to techs in the industry, he can bring ideas to TruTech Tools to make the techs' lives easier and address the "pain points" that many contractors have to deal with.

Bill and Bryan also discuss:

• Tyler's past
• Working on trailers or mobile homes
• Organization (or lack thereof) in vans and tool bags
• Combined analog and digital gauges
• Inventory tracking systems
• Possible Testo 115i temperature clamp improvements

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this two-part podcast series, Jim Bergmann talks about measuring airflow in HVAC systems. He covers a wide range of airflow measurement instrumentation and readings.

In this first episode, Jim covers ECM motor considerations, delivered capacity, laminar flow, and more.

In the HVAC industry, many techs confuse static pressure for airflow. Although you need static pressure to have airflow, it is NOT airflow and can fluctuate rather wildly depending on the duct conditions.

Static pressure is an indirect airflow measurement. Airflow is actually a measurement of velocity (such as with pitot tubes) that you then convert to a volume measurement (CFM).

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In this podcast episode, Bryan talks about brazing basics and tips. He goes over safety, regulator settings, torch positioning, flowing nitrogen, heat control, and more.

Whenever you're going to be working with equipment that creates fire, you will want to make sure you know all of the safety procedures and have appropriate PPE. Make sure your gear is in really good condition; make sure your hoses and regulator have not been damaged. Be sure to have a fire extinguisher handy as well. When preparing copper lines, you'll want to keep things out of them. Make sure oxygen, dust, burrs, and flux can't get into the tubing.

Flowing nitrogen is a best practice, but it's also a staple among the brazing basics. Nitrogen displaces refrigerant, water, and oxygen that might be in the copper lines. Regulators can help you purge with nitrogen at somewhat higher SCFH (20-50) and then flow it at a very low SCFH (2-5). You should hear just a whisper of nitrogen when flowing it.

When you set up your torches, it's important that you look at the torch manufacturer's specifications. The tips have different designs for different functions, and it would be wise to read up on their purposes. When setting the oxygen and acetylene pressures, try to keep the numbers the same. Light acetylene first and THEN add the oxygen, and then you'll want to turn off the oxygen first and then acetylene. You'll want a neutral or slightly carburizing flame but not an oxidizing flame.

Bryan also covers:

• Protecting the workspace
• Unsweating
• Reaming copper
• Reducers, fittings, and swaging tools
• Nitrogen flow regulator types
• Wrenches for opening tanks
• Brazing vs. soldering
• Brazing/soldering rods
• Getting the copper hot enough
• Preventing carbon buildup
• Leak testing joints

Bryan talks to Ralph Wolf from T&N Services on YouTube and the Working Joe's podcast. We talk about blue-collar life, how the trade has changed for us, and what experience gives a tech that can't be read in a book. Ralph started off doing sheet metal work in the Navy before going into HVAC. He started as a sheet metal installer and learned most of what he knows about HVAC on the job.

Taking accurate superheat and subcooling readings have become much more important over the years. We can't get away with "beer-can cold" rules of thumb anymore, especially as MicroChannel and TXVs have evolved and become more prevalent. Efficiency is becoming more important as well, especially due to government mandates.

Blue-collar jobs have a ton of best practices for each trade. However, those who have been in the trade a long time typically know the appropriate times and places for those practices. (For example, you don't need to check static pressure on EVERY system, but it's a great idea when you're commissioning a system or working on a system with airflow issues.) As you gain experience, you'll know when to use best practices and when you can bypass them for the sake of time. So, you'll come across two types of senior techs in the trade: those who are plain lazy and those who simply know the exact times and places for best practices.

Even though the blue-collar lifestyle very much becomes a part of who we are, we each have a different relationship with the trade.

Ralph and Bryan also discuss:

• The practicality of best practices
• Corrosion
• System longevity
• Airflow problems
• Understanding individual pieces of equipment
• Carbon buildup
• Leak sealants
• Ralph's YouTube journey
• Differences between old-school tradesmen and millennials
• Calling out dishonesty and poor quality

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

This episode is a rebroadcast of a very useful episode from the Corbett Lunsford's Building Performance Podcast at https://buildingperformancepodcast.com/. Corbett talks to building moisture control expert Lew Herriman about moisture, ventilation, and what happens when you're drying "stuff."

When we think about humidity control, we have to ask if we're drying air or drying "stuff." Dehumidification is about drying the air, but many people think about it when they actually want to dry "stuff" like fabrics and other absorptive surfaces often found in residential applications. However, drying out "stuff" does affect how we would dry out the air.

Commercial buildings often don't have a lot of absorptive materials, as many have tile floors. Residences tend to have carpet and upholstery, making them challenging cases in building performance. The HVAC system controls moisture, whether they have a humidifier, dehumidifier, or neither. HVAC systems create pressure differences, which contribute to dry air infiltration. Homes heated solely by radiant heat would not be as good at drying the air, but good ventilation could supplement radiant heat.

When we have humidity control problems that affect comfort or moisture on absorptive surfaces, we might start thinking about controlling absolute humidity. Absolute humidity refers to the actual moisture content in the air, not the moisture relative to the temperature. However, most homes don't have the ventilation systems that would help dilute the humidity, including HRVs.

Then, when drying "stuff," you have to put heat in to get the moisture out.

Corbett and Lew also discuss:

• Absolute vs. relative humidity
• Dry-bulb temperature changes and dew point
• Duct leakage
• HVAC and building performance strategies for mixed climates
• Energy-recovery ventilators (ERVs) vs. heat-recovery ventilators (HRVs)
• Exhaust at the source
• Dehumidifiers
• Dehumidifying incoming fresh air
• Hypothetical makeup air systems for residential applications
• Comfort metrics

Learn more about Corbett's work at buildingperformanceworkshop.com.

Restaurant HVAC and refrigeration tech Nick Messick comes on the podcast to talk about restaurant equipment, especially the "hot side." The "hot side" refers to equipment that heats the food; it includes often deep fryers but has a lot of variation. The "hot side" also includes specialty equipment for frying noodles and performing other unique functions.

In Nick's opinion, the worst service call has to do with fryer pumps due to all of the grease. The grease gets all over tools and your hands, and it can be quite difficult to work on equipment with fryer grease. Other things he dislikes working on are machines that are on their last legs, as many owners are reluctant to replace equipment.

Many fryers go through a melt cycle that turns the heat on and off to avoid burning the oil. The flames heat the bottom of the vat using a heat exchanger like a furnace; then, the gas vents into the flue and out the hood. These systems generally use spark igniters and may use either direct-spark or intermittent-spark ignition with a pilot. Nick's favorite call is when fryers make loud popping noises, as it's easy to diagnose and fix; the cause is typically either the ice cube relay or a bad igniter.

In grease-heavy restaurant environments, we clean equipment by using cleaners meant for electrical equipment. You want to avoid leaving residue on the equipment and ruining the control boards. The restaurant staff should be cleaning out the fryers themselves, but you may encounter some dirty equipment (and workspaces).

Nick and Bryan also discuss:

• Dishwashers
• Replacing equipment
• Flame rectification
• Circuit boards
• Electric fryers
• Drawing the line when it comes to sanitation in HVAC service

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

P.S. - Don't pull the fire alarm

Phil Zito of Building Automation Monthly comes on the podcast to discuss building automation and what HVAC techs should know about it.

Automation essentially refers to control systems; we started off with pneumatic control systems, and then we went to analog and electromechanical control systems over time. Building automation refers to the process of automating controls on a larger scale, such as for an entire building. As long as you can read electrical and mechanical diagrams, you can work on automation systems; you don't need to know about IT or robotics.

Large buildings like malls may require HVAC automation. In other structures like university buildings, you may also end up automating lights and other electrical functions. Automation makes other systems talk to each other, and it does that by controlling on/off schedules and set points. These building automation systems consist of sensors, switches, conductors, and decision-making logic (such as simple desktop servers).

Regardless of the automation system, the sequence of operation will always go in the following order: server, supervisory device, field controller, and input/output. A communication bus transmits messages between field controllers; it works like floating controls or pulse-width modulation. You don't need to know the binary communication of the computer; you just need to know how to measure voltage with your multimeter to work on a communication bus.

An HVAC tech may also be interested in knowing that building automation has an air side and a water side. These systems may also interface with package RTUs and VAV systems.

Phil and Bryan also discuss:

• How Phil got into building automation
• Servers
• User and web interface
• Resistance vs. analog values
• Barriers to getting into BAS careers
• Installation vs. service
• Taking initiative and being resourceful
• How BAS and HVAC workers can make each other's lives easier

Visit Phil's website 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 Mike Layton of Shore Distributors explain how HVAC contractors and distributors can build a great partnership. Shore Distributors is a wholesaler in Maryland that carries Carrier, Bryant, and Payne.

The job of a territory manager is to help HVAC contractors, so they're there to help contractors. The territory manager's job is to help set contractors and dealers up for success, so they don't feel burdened by questions because it's their job to answer them. Territory managers know that the goal of business is to make money, so they understand the importance of moving boxes and making sales. That said, contractors who move boxes tend to make the rules and have access to privileges.

Warranty returns are a bit of a touchy subject; distributors tend to give contractors the benefit of the doubt and are generally willing to replace the part as long as you supply the correct information. However, Mike believes that the 10-year parts warranty has been detrimental to business.

End-user satisfaction is a goal we can all strive for. HVAC contractors can be more thorough when completing their jobs and setting up equipment; when installers take their time and explain proper use to the owner, they increase customer satisfaction. When HVAC contractors succeed, distributors succeed and can keep providing service to top contractors.

Overall, a healthy contractor-distributor relationship has mutual trust built on dependability. Distributors need to be dependable and available to help the contractors they serve.

Mike and Bryan also discuss:

• A day in the life of a distribution role
• Ego vs. results
• Contractors that abuse warranties
• Vetting techs and holding them accountable
• Controls
• What installers can do better
• Inverter products
• Understanding each other

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

In this episode, Bryan talks with Jamie Kitchen from Danfoss about why and how thermostatic expansion valves (TXVs) fail and how they function in the first place.

As fixed orifices become a dying breed with the development of higher-efficiency systems, TXVs take over the mantle as the primary method of expansion. Expansion valves meter the flow of refrigerant by aiming for a certain suction line superheat value. Unlike a fixed orifice, which has an opening of a constant diameter, an expansion valve adjusts the opening size to the evaporator based on suction superheat readings.

TXVs have a sensing bulb, diaphragm, spring, and cap tubes. Various pressures act on these components: bulb pressure, spring pressure, and evaporator pressure. The sensing bulb picks up the suction superheat adjusts its pressure on the diaphragm based on the superheat it detects. Spring pressure and evaporator pressure act against the bulb pressure. The combination of all three pressures (bulb vs. spring + evaporator) dictates the opening of the TXV orifice into the evaporator. The bulb pressure is an opening force, and the spring and evaporator pressures are closing forces.

You can cause TXV failure by adjusting it or brazing it in improperly. When too much heat is applied to the TXV, the components inside can warp. Some TXV failures also occur due to contamination. Flowing nitrogen while brazing flushes carbon and oxygen contaminants out and reduces your risk of TXV failure later on.

Bryan and Jamie also talk about:

• TXV anatomy (powerhead, spring, etc.)
• Internal vs. external equalization
• Pressure drop across the distributor
• Subcooling and its relationship with the TXV
• Solenoid and ball valve (upstream) malfunctions
• Filter-dryer placement
• TXV assessment during commissioning
• Locating restrictions
• Residential system airflow

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.