HVAC School - For Techs, By Techs

Latest Episodes:

A Steam Heat Primer by Dan Holohan Oct 07, 2017

Show notes

Dan Holohan is the father of modern steam heat training. This episode is a narration of his in-depth steam article "A Steam Heating Primer" from HeatingHelp.com.

Read that article HERE.

Check out more about Dan's work at heatinghelp.com.

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

The Lost Art of Steam Heating w/ Dan Holohan Oct 03, 2017

Show notes

In today's podcast, Bryan talks with legendary Hydronics author and trainer Dan Holohan about the history of steam heating and some practical applications of old ideas. Recently, Dan has been working on more novels, having published two of them over the past few months.

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.

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

Bonus - The Spark Ranger Sep 30, 2017

Show notes

This special podcast episode focuses on the tragic life and times of Spark Ranger Roy Sullivan.

Roy Sullivan was a park ranger who was born in Virginia in 1912. He grew up in the 1920s when the mining industry was in full swing and had scrapped up the beautiful mountain landscape. In 1935, Shenandoah National Park was founded, and Roy decided to become a park ranger. He wanted to help restore the land and protect it from human destruction, such as the mining industry.

One of Roy's duties was to scope out the forest on the new fire lookout tower. That new tower had yet to have a lightning rod installed. One day, a lightning storm approached while Roy kept watch, and lightning struck the tower. Roy survived the strike, though he was badly burned in the incident.

In July of 1969, Roy encountered lightning once again. That time, Roy was driving a car. Although many people believe that the tires are insulators, most people are protected from lightning by the Faraday Cage effect; the current travels through the metal around you until it reaches the ground. Roy, unfortunately, forgot to close his window and had a lightning charge from a nearby tree strike him through the window.

Roy got struck with lightning yet again while doing yardwork a little while later after a transformer was struck by lightning. He was allegedly struck by lightning several times after that, including on a fishing trip where he ALSO had to outrun a bear after getting struck by lightning. However, even though Roy had the scars, these lightning strikes are unconfirmed.

Sadly, Roy died by a[n allegedly] self-inflicted gunshot wound. However, the legacy of the Spark Ranger continues through his ongoing world record for "Most Times Struck By Lightning."

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

Electronic Expansion Valves (EEV) w/ Jamie Kitchen Sep 27, 2017

Show notes

In today's podcast, Bryan and Jamie talk about the electronic expansion valve (EEV). Bryan and Jamie describe how EEVs work and the reason they exist. In the process, the hosts also review a wide range of metering devices. We made this podcast to address the rising demand for EEVs in the aftermarket element of the HVAC business.

Like the TXV, the EEV is a metering device. Metering devices create a pressure drop as refrigerant moves from the liquid line to the evaporator. Traditional refrigerators typically use capillary tube metering devices because they require a constant temperature and operate in a fixed temperature environment. However, TXVs are a bit more variable but open linearly and are dictated by a minimum stable superheat value. EEVs are also variable, but they can influence the superheat more directly; the superheat always exceeds the minimum stable superheat. Therefore, EEVs can increase efficiency by reducing the evaporator temperature and compression ratio by increasing saturation temperature.

Even though EEVs dominate the grocery refrigeration market because of their head pressure control, we can use them in residential HVAC too. The EEV controls superheat more precisely than a TXV, and their algorithms can maximize efficiency and fill the evaporator coil with the most refrigerant possible.

There are two types of EEVs: the pulse-width EEV and the stepper motor EEV. The stepper motor has "steps" to modulate the degree to which it opens or closes. The pulse-width EEV either opens or closes, much like a solenoid valve.

Bryan and Jamie also discuss:

Hot pull down
Ideal compression ratios and efficiency
Minimum stable superheat
Compressor cooling accessories
Downsides of oversizing TXVs
Evaporator superheat vs. suction superheat
Technological advancements for EEVs, especially for Danfoss EEVs
Less obvious advantages of EEVs over TXVs

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

(Bonus) HVAC/R Industry State of the Union Sep 22, 2017

Show notes

In today's podcast episode, trade school student Chris Caldwell interviews Bryan about trends in the HVAC industry, his business, and the future. Chris works in the HVAC business as a service tech and attends trade school in Alabama.

New trends include spending more money on testing instrumentation. Nowadays, there is a greater reliance on test instrumentation to produce accurate measurements. Diagnostics have certainly improved over time. On top of that, Bryan sees the industry's potential to improve other practices like evacuations.

Customers have paid more attention to indoor air quality recently, and that trend is likely to continue. There is a new emphasis on comfort over energy efficiency, especially in humid climates like Florida and Alabama. As such, HVAC techs can expect an intersection between the HVAC industry and the building science industry. Customers also enjoy having integrated controls, such as thermostats that connect to wi-fi.

However, some service companies and manufacturers have focused too much on shiny new technology. Bryan owes this phenomenon to the "sales-first" business model. He would prefer to see techs and manufacturers focus on basic serviceability. As such, Bryan would like to see an emphasis on creating thorough solutions to problems instead of seeking quick fixes.

In the future, Bryan hopes to see further development of tools like measureQuick. He would love to see better data collection practices. He would also like to see more unified communication protocols between appliances.

Bryan and Chris also discuss:

Solar solutions
Human comfort and IAQ
Communication between techs in the digital age
New ASHRAE outdoor air standards
"Sales-first" business models and the skills gap
How to make the HVAC industry appeal to the new generation
How to find fulfillment and validation in HVAC work

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

Filter Drier Basics w/ Chris Reeves Sep 19, 2017

Show notes

In today's podcast, Chris Reeves joins Bryan to discuss filter driers, including suction driers, liquid driers, core driers, different media, and basic applications. Filter driers are simple components, but they have plenty of room for misunderstanding within our trade. We refer to Parker-Sporlan Bulletin 40-10 throughout the podcast, and you can read that bulletin HERE.

Above all, filter driers act as filters that prevent debris from reaching the expansion valves and destroying them. As such, the best place to install a liquid filter line drier is as close to the expansion valve as possible. These filter driers also catch and hold water from the system; they minimize moisture to keep HVAC systems functioning properly. Filter driers also catch and remove acids from the refrigerant circuit. A filter drier and its desiccants CANNOT remove non-condensable gases.

However, filter driers should NOT be the primary method of removing moisture. Proper evacuations with deep vacuums should be the main method, as filter-driers are limited in their moisture removal capacity. You also don't want to use a filter drier that has been exposed to atmosphere any longer than a few minutes; the drier has had time to collect moisture and will be less effective. Each time you open up a system, removing the filter drier is the best practice.

We use biflow filter driers on heat pumps. The refrigerant can flow in both directions; a check valve directs the flow, so the flow always goes through the core and filter pad the same way, regardless of operation mode.

Suction line filter driers are for older HVAC systems with issues. You'll want to install them close to the compressor for maximum protection and watch the pressure drop across the drier.

We also discuss:

Temperature control
Overheating driers and exposing them to heat
HH-style filter driers (with activated carbon)
System sizing as a consideration
Burnout and contamination

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

Nitrogen Pressures do Change with Temperature - the Basic Gas Laws Sep 16, 2017

Show notes

In today's podcast, Bryan covers the four basic gas laws and how they apply to you as an HVAC technician in the field, not just in theory. Remember, when dealing with pressure, you must convert the units to PSIA, not just PSIG. To do that, you merely add 14.7 to your gauge pressure.

In every equation, the "1" indicates an original value, and the "2" indicates a new value.

The simplest of the gas laws was discovered first, Boyle's law. The law states that there is an inverse relationship between absolute pressure and volume. When a gas's pressure increases (such as via compression), you decrease its volume. Inversely, when you decrease a gas's pressure, that gas will expand, and its volume will increase. Mathematically, the law looks like this:

P1 x V1 = P2 x V2

Charles's law focuses on volume and temperature. This gas law states that volume and temperature rise or fall together so long as the pressure stays the same. You can mathematically describe the law with the following equation:

V1 / T1 = V2 / T2

The general law of a perfect gas combines Boyle's and Charles's laws. You can mathematically describe the law like this:

(P1 x V1) / T1 = (P2 x V2) / T2

As HVAC technicians, we should care about the gas laws because our pressures and volumes will change as temperature changes throughout the day, such as when doing a standing pressure test with nitrogen. Nitrogen is a relatively non-reactive gas, so it will follow the gas laws and won't condense to a liquid or react with other chemicals.

Dalton's law is the final law, and it states that the combined pressure of all gases in a closed space is equal to the sum of the individual gas pressures.

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

Bonus - Tips from a VRF Tech w/ Alex Figueroa Sep 15, 2017

Show notes

Alex Figueroa is a VRF and refrigeration tech in Puerto Rico, and he talks to Bryan about his work and specialized experiences. Since Mitsubishi is a forerunner in the ductless industry, many of the units that Alex has worked on are Mitsubishi units.

Alex works on lots of ductless mini-splits and VRFs in central air in commercial buildings. He typically works on VRF units that have ceiling cassettes or fan coils. Some VRF units also have branch boxes with electronic expansion valves (EEVs), and those components help distribute refrigerant flow. These systems have expansion lines, which some technicians may confuse for liquid lines.

As with other large commercial HVAC units, oil is also a concern in VRF systems. Smaller-tonnage systems have large accumulators, but larger systems may also have large separators. Some of these systems are large and may contain 200-300 pounds of refrigerant. Unlike many other HVAC units, these systems have an electronic interface that indicates superheat, subcooling, and other criteria that can help with charging and troubleshooting. (Techs can, however, hook up gauges at the condenser, but the practice is not often necessary.)

When you open up a VRF system for the first time, you will see lots of solenoids and other components that resemble refrigeration parts. Therefore, Alex felt that his experience as a refrigeration technician benefited him as he began working on VRFs. Like heavy refrigeration (especially grocery refrigeration), VRF systems may have several compressors and refrigerant circuits in a single system. Digital scrolls are common compressor types for these systems.

The greatest maintenance issues with VRFs deal with are dirty evaporator coils and filters. In Alex's experience, the electric controls are the most commonly failed component.

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

Ductless and VRF Diagnosis w/ John Chavez EP2 Sep 12, 2017

Show notes

What do you need to know to walk up and fix a VRF or ductless system? John Chavez, longtime VRF/ductless pro, covers his approach to ductless and VRF diagnosis in Part 2 of this podcast. (Listen to Part 1 HERE.)

If you believe that there is a component failure, you'll want to check the voltage going into the unit. You'll want to pay special attention to the board and see where power is going in and out. In other words, pay attention to your inputs and outputs on the board and pay attention to the documentation in the manual. Make sure you have a quality voltmeter on hand.

Another potential electrical issue occurs when the board blows out entirely. When that happens, you'll have to watch the input voltage and be mindful of the utility quality and local geography. Utility companies WILL NOT admit if they are part of the problem, so it is good for a technician to ask about the property and utilities to study the history of the unit and the location.

Watch your discharge air temperatures and make sure they perform correctly under AHRI conditions (the standard is 95 degrees outdoors, 86 degrees indoors); should have 40-50 degrees coming out of the discharge of the ductless unit. Pipes may even get as cold as 37 degrees before discharge protection kicks in.

To sum everything up about VRF diagnosis, you'll want to do whatever you can to find the root cause; don't be a parts-changer. To consider all possibilities, you must take your time to understand the unit.

We also discuss:

Lightning strikes and power surges
Determining delivered capacity
Critical charge
Electrical/controls terminology
Building science, thermal envelopes, and VRF performance
Sensible and latent heat loads
Inverter-driven compressors

Resources

Computer Room Application Formula

Ductless Steps

Friedrich Service Form

Seven Common Install Answers

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

Matter, Mass, Weight, and Volume Sep 11, 2017

Show notes

This episode covers some basics of matter that relate to HVAC/R. These basics include mass, weight, and volume. There will also be some talk of specific gravity and specific volume.

Matter and energy are the building blocks of the HVAC industry; we move matter around and transfer energy. Matter refers to anything that exists and takes up space, including all solids, liquids, and gases. We use three means of measuring matter: volume, mass, and weight. Volume refers to how much space an object occupies. Even though we use mass and weight interchangeably, they mean two different things. Mass refers to the amount of matter an object has, and weight is the force exerted on an object by gravity.

Density is a mass-to-volume relationship. Density comes into play when items float or sink in water, and it is a component of specific gravity. Specific gravity does not have an absolute unit of measure; it merely compares an object's density to water. For example, propane has a specific gravity of 1.5 in comparison to air and would sink. Conversely, natural gas has a specific gravity of 0.6-0.7, meaning that it would float in air.

Specific volume is NOT relative; we use a set unit for it, typically cubic feet per pound. The cubic feet of air per pound changes with temperature, humidity, and barometric pressure. So, "standard air" isn't a fixed value. All gases can be compressed and can be affected by temperature much more easily than the other states of matter. Specific volume is important because it helps us determine the amount of refrigerant we can safely put into a recovery tank; you must know the difference between the specific volume of water and the refrigerant you are using.

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