Category: Tech Tips

Photo by Ulises Palacios

Refrigerant circuit restrictions can be common things like a plugged filter drier or a restricted metering device. They can also be more difficult to diagnose and exotic issues like a kinked liquid line, blocked evaporator feeder tube or a compressor connected improperly with a discharge line full of solder (I’ve seen it).

To start with let’s talk about the symptoms.

When an undesigned restriction occurs, refrigerant will “back up” against the restriction resulting in more refrigerant being present before the restriction and less afterwards than designed. Think of it like a refrigerant traffic jam with the refrigerant “road” being congested before the restriction and free and clear afterwards. This restriction will result in a pressure drop across the restriction with higher pressure being on the inlet side and lower pressure on the outlet side of the “traffic jam”.

First we must be aware that a restriction exists in the first place. In the case of the most common liquid line restrictions on HVAC equipment (with no receiver) we will see low suction pressure, high superheat and normal to high subcooling. In cases like this we know it is not simply “low on charge” because of the subcooling reading, and we also know it isn’t just a an evaporator airflow issue because of the high superheat. This leaves us in the realm of restriction.  Like anything else, some common sense, a look at the system history and a visual inspection can find many restrictions without any fancy diagnosis, but sometimes you have to put on your thinking cap, grab a pipe or a cigar, and go to work.

In a perfect world we could just connect a gauge anywhere in the system and we could find the pressure drop, in the real world we only have two or maybe three points on connection and they are not sufficient for us to pinpoint a restriction. Luckily we have temperature drop as a proxy for pressure drop, whenever the pressure drops there will also be a temperature drop. The trouble is, by the time the temperature drops enough for us to reliably measure it with a thermometer it is usually pretty bad, making minor restrictions hard to find.  It can also be challenging when the metering device itself is a suspect (and it often is), because the metering device is a DESIGNED RESTRICTION. This means that a pressure drop is it’s very purpose, but is it restricting too much?

So to actually FIND a restriction you are left with a few tools in your arsenal.

Common Sense

Get acquainted with the history of the system. How old is it? What has been done on it recently? Has the refrigerant circuit been open to atmosphere?  If you recently had a burnout compressor then it is very likely that suction and liquid line driers could be restricted. If the system has been running just fine for 7 years it is more likely that that TXV element tube rubbed out and now the TXV is slammed down. If the distributor just a leak repaired on it, it is very possible that they accidentally filled one of the feeder tubes with solder when they made the repair. A little common sense can save a lot of random hypothesis. Any experienced technician will agree with the problem solving principle called Occam’s Razor that states

“With all things being equal, simpler explanations are generally better than more complex ones”

This certainly hold true when looking for restrictions.

Temperature Drop 

Grab your most accurate line temperature clamp and start making measurements across possible restrictions like line filter driers and the liquid line itself. If you find any confirmable temperature drop across a line drier than you can knows it’s restricted, just make sure to double check. Across a typical liquid line you will generally only see a few degrees of temperature drop but it does depend on the ambient temperature, condensing temperature and the line length.

Freeze Test

Sometime the exact point of temperature change can be tough to locate. In these cases when the metering device, distributor, feeder tubes, inlet screen or evaporator are all suspects you can do the freeze test. Disconnect the blower and watch the frost patterns. On a properly functioning system the ice will start right at the outlet of the metering device and extend forward though the feeder tubes and work its way fairly evenly through the coil on the coil piping route. Look for inconsistencies in the pattern and you can often find a restriction.

If for example, you see that the frost is starting BEFORE the metering device instead of after, you can bet the restriction is an inlet screen. This test is finicky and requires a trained eye to track the tubing patterns, otherwise you might think a coil is restricted when it’s just the way it’s piped. Also be aware that the designed pressure drop of metering devices that also contain a distributer and feeder tubes is cumulative across all of those restriction points. This means that in some cases you may get more frost after the distributer than you do between the metering device and the distributer, this is to be expected.

Photo by Ulises Palacios

Thermal Imaging The holy grail of finding restrictions is the thermal imaging camera. You are able to see restrictions in real time and pinpoint the exact location where the temperature change begins. Thermal imaging can even be used to find illusive restrictions like discharge line restrictions caused by poor brazing practices, condenser feeding issues, evaporator restriction Photo by Ulises Palacios

So the process for finding restrictions is –

  1. Prove you have one by looking carefully at your readings
  2. Use some common sense and perform a visual inspection
  3. Take lots of temperature measurements until you find it
  4. Whip out the fancy pants thermal imaging camera and spot that sucker in no time flat and be the hero with throngs of adoring fans

Keep in mind it get’s even trickier to diagnose when you are working on a system with a receiver, because the receiver can usually hold a lot of excess refrigerant, often making a liquid line restriction appear more like a low charge in the readings. Also, minor suction line restrictions like a kinked suction line can be very difficult to find because the temperature drop will usually be unmeasurably low.

This is why taking all the system readings in conjunction with some common sense and knowledge of the systems history are your best allies. And when in doubt… get a thermal imager from TruTech tools .

I told you it wasn’t easy

— Bryan

Here is a great article addressing restrictions in refrigeration systems – Diagnosing A Restricted Liquid Line Can Be Tricky

Think of it like this…

It’s a cold, wet, windy day

You can take an umbrella to protect you from the water alone… but that won’t deal with the cold (temperature) or the wind (air convection)

You can add in a light windbreaker and that will help keep the wind (convection) off as well. But if you also wear a thick sweater… that will help insulate you from the temperature difference (conduction).

In a building, we need to keep outside air out of the home unless it is properly conditioned, we need to keep moisture out and we need to insulate it from temperature differential outside.

You may ask why you care as an HVAC/R contractor? That’s simple, you customer looks to you as the expert in all things comfort and health-related in their homes and building because you work on the system that keeps them comfortable and moves the air around. Many times we try to fix building problems with equipment which can be a recipe for disaster.

Here are some basics to help you diagnose and solve building issues.

Air Barrier / Sealing 

Air barriers are materials and sealant that don’t allow air to enter or leave the building due to simple air pressure differential. We want to use door sweeps and weather stripping, use sealed can lights, seal holes in the tops of stud walls, keep chimney dampers closed when not in use and seal duct boots where they penetrate into the conditioned space.

Some people may say that you don’t want a building to be “too tight” otherwise you won’t have the proper amount of outdoor exchange. This is true, but you also don’t the outdoor air entering from musty attics and crawlspaces and across dirty floors. It is a much better strategy to bring in an appropriate amount of outdoor air from a clean and designed location and temper it through filtration, ERV / HRV or a dehumidifier as appropriate for the climate. This does require testing and planning but it is the best way to make a home “airtight”.

This air leakiness of a home is impacted by

#1 – How leaky is the home
#2 – How great are the pressure differences inside to out

Some pressure differences are natural due to stack effects, wind etc… Others are caused by duct leakage, imbalanced return/supply into a space within a building and due to ventilation both overall and localized such kitchen hoods and bath fans.

The leakage rate can be tested using a blower door and a precision manometer can be used to figure out the pressure differential impacting the space and areas within the space.

Vapor Barriers

Water vapor can move through many surfaces through a process called permeation. This is when vapor molecules, in this case, water vapor, can move through a porous material in the direction of high relative humidity to low relative humidity.

In Florida we have many block homes that have no exterior vapor barrier at all other than paint. Over time moisture in the vapor state can work its way through block, plywood or whatever else is used to sheath the walls and roof unless an appropriate vapor barrier is installed.

The issue is that you also need to consider condensation. If water vapor makes contact with a surface below dew point it can condense into liquid water which can then result in nasty biological growth. This is why a properly installed vapor barrier is located in a place that allows for drainage on the warm side that will be prone to condensate.

If you fail to have vapor barrier there is less likelihood of moisture issues within the wall structure but more likelihood of moisture issues inside due to moisture diffusing into the space through the walls.


Insulation generally isn’t an air barrier or a vapor barrier and air and vapor can move through it freely and easily. There are some exceptions such as closed cell foam which is all three and open cell foam which is an air barrier and insulation (but not a vapor barrier).

Insulation is there to prevent heat from traveling through surfaces from hot to cold. Insulation is rated in R-value, with the higher the R-value the greater the resistance to the movement of heat. This is an important part of keeping heat in and/or out of a space in walls, attics, crawl spaces etc… but isn’t a replacement for thinking about air and vapor barriers.

A few more factors … 

Radiant heat  is the transfer of energy through “radiation” which does not require the direct transfer of heat from one molecule to another. Radiant heat can jump distances through the air or even through a near vacuum (like the Sun) and we see it in the way a room can heat up through sun shining through a window, or on an unshaded side of the home when the sun beats down on it.

We see this often in offices where a worker likes to sit in front of an unshaded window (radiant) while sitting in front of a warm computer screen (radiant) and then still feel warm even though the room is 72 degrees.

Liquid Water intrusion can happen into a home from roof leaks, leaking appliances and plumbing, improper flashing, capillary action from the ground up through the walls etc… These are all building issues that can impact health and comfort inside the home that left unresolved can cause major issues.

Interior Moisture Loads occur every time we cook and boil water, when we take showers and baths, when we do dishes and even when we exhale. The more people are in a space doing these things the more moisture there will be. I have 9 kids, we cook three meals a day at home and do the laundry all day long… my house is quite tight (3.5 ACH) but it still has MASSIVE internal moisture load that could lead to issues if don’t have lots of dehumidification.

Speaking of that… I just Installed a Clean Comfort dehumidifier in my home.

So remember…

High Temp Goes to Low Temp

High Humidity Goes to Low Humidity 

High Pressure Goes to Low Pressure

— Bryan

So I hear you’re just finishing trade school? Well done.

You chose to take an excellent path and now your journey is just beginning.

How this will go is really up to you and that’s a good thing! You aren’t going to be forced in one direction or another, you get to choose.

Let’s talk about what choices you will make and what you need to know to end up where you want to go (unintentional rhyme there).

Choosing an Industry Segment

Many of you may end up working in a particular segment because you were recruited into it, or you know someone, or it was the first place that offers you a job. There is nothing wrong with that, but I would first consider all of your options.

Stationary vs. Field 

There are some jobs where you work as a stationary mechanic or tech on a single, or group of facilities, generally as a direct employee of the facility. In other jobs, you will work for an independent contractor on many different locations and for various customers.

Stationary jobs tend to be well suited for people who enjoy routine, a slower pace and less variability. Often the benefits (Vacation, health, retirement) in stationary jobs can be very good though the competitiveness of the pay may vary.

Field jobs have more risk and variability and are generally best suited for people who are always looking for a challenge and prefer not to have a set routine day in and day out.

Install vs. Service – Install or projects work tends to be more physically taxing but generally has a more fixed work schedule. Good install and project mechanics need to have a combination of productivity and efficiency as well as a strong mechanical sense and attention to aesthetic detail (how things look). Install mechanics must be able to read plans and specs but usually don’t need to learn as much from reading as service.

Service has a lot more scheduling variability and often work long hours in peak seasons. Service requires strong problem-solving skills, communication and an ability to think well under pressure. The best service techs can learn from many different sources including reading.

Residential vs. Commercial – In residential you will generally be able to stay busy in or near your own hometown.  You must be able to talk with people and handle tense situations and be willing to quote repairs and have money conversations with customers. In general, residential requires less travel and isn’t as technically difficult as commercial but can be more socially stressful.

Commercial work does not generally require nearly as much customer interaction but will often require more climbing, lifting, and travel. On the projects side, commercial work will often require periodic night work.

Specialty Segments 

HVAC/R has many specialty segments like chillers, controls (EMS, BAS), VRF, Market refrigeration, ammonia and many more. Specialty segments may be more challenging to get into right out of school but often have excellent long term opportunity for pay and advancement. One of the best ways to learn if an industry segment may be right for you is to strike up a conversation with a tech or owner in that segment on one of the forums or social media groups like HVAC school.

Initial Pay vs. Ultimate Opportunity

You will be tempted to choose a job based on which one pays you the most right out of school. For some of you, the need to make as much as you can right away is critical and I understand that.

But that isn’t how I would make the decision.

I would suggest looking into segments and companies where the pay after 5 years is the best rather than only considering what they pay out of school. The best way to find this info is to talk to people who have actually done it rather than trusting what a company says about themselves.

I know you may think you already HAVE an education, but your education is really only starting. Find a company that will continue to invest in training you rather than one that throws you to the wolves right out of school.

Don’t get the wrong idea…

There isn’t a job or career path out there that will work out exactly like you planned. The planning isn’t so you will check every box, it’s so you will get started out in the best direction. There will be many course corrections in your journey and you will learn a lot about yourself as you go.

Character is Key

Before we cover what you do to get where you want to go we need to discuss who you ARE.

You are a combination of your genetics inherited from your parents, the things that have happened to you and the choices you’ve made along the way. When questions of character come up you will be tempted to blame your genes (I’m just not a good reader) or your circumstances (I don’t have time to study), I beg you DON’T DO IT.

Every human that has ever lived is born with advantages and challenges and everyone has the choice to allow these external forces to define their existence or to choose to own what they become.

Whether life happens to you (victim mentality) or whether you happen to life (ownership) depends on you

Character means making a set of choices based on rules that you set for yourself of proper conduct. Here are some great character rules.

  1. Keep your word, especially when doing so requires sacrifice
  2. Treat everyone with respect whether they deserve it or not
  3. Spend time with people that make you better
  4. Listen more than you speak
  5. Practice gratefulness daily
  6. Work hard even when you think it doesn’t matter
  7. Do the right thing even when nobody will ever know
  8. Replace negativity with solutions
  9. Don’t complain… ever
  10. Make decisions you will be proud of 20 years from now

Sorry for writing a little self-help novel here… but character really matters.

You need to decide what sort of person you are or your circumstances will decide for you.

What Not to Do

If you are under the age of 25 I want to state once again how glad I am that you chose this business and I really think you made a great choice.

But please, recognize that some of the things culture and social interaction with your peers have taught you will wreak havoc on your career in this trade.

So please, for your own sake don’t –

  • Keep looking at your phone (seriously, don’t look at it…)
  • Come into work looking all sleepy and disengaged
  • Show up late
  • Make snarky remarks to more experienced workers (or anything that could be misinterpreted that way)
  • Tell experienced guys how you “did it in school”
  • Stand Around (Find a broom, organize something somewhere or read something directly related to your job)
  • Fall asleep at work (even in the van)
  • Tell people about personal stuff you don’t want everyone to know

This applies to workers of all ages of course, but these traits tend to be really common in younger workers.

What to Do Instead

Getting ahead is actually pretty simple (but not easy). You need to

Learn continuously, communicate positively and do good work consistently

Here are my top recommendations for actions you can take right out of school

  1.  Put aside money from every check for tools. Buy your own tools even if the company provides them. This is about investing in yourself, not about the company you work for right now.
  2. Remember things the older techs tell you. Thank them later on for specifically what they taught you and how it helped.
  3. Read Manuals. If you work on something new read the manual beforehand if you can. At a minimum, do it later on at home if you didn’t have time during the day. I don’t care if you are a “hands-on” learner thats not an excuse not to read. This is why I suggest doing just before or after you worked on it. You can’t get really good if you never read so start making it a habit.
  4. Show up to Work Early. On time is late, set your clocks 10 minutes forward if you need to.
  5. Share Facts from Others. If you find that someone more experienced is doing something incorrectly, share something you read in a manual or article and ask their thoughts on it rather than “confronting” them.
  6. Use Your Resources. Do some research and study before asking a question. There is still a time to ask, but it’s once you’ve already put in some work.

The Rule of Bob 

“If Bob has a problem with everyone, Bob is the problem”

I get contacted all the time by people fresh out of school who express that everyone in the trade is out to get them. They ALL do it wrong, they are ALL jerks, EVERYONE abuses and mistreats them.

There are really only two options when someone has these sorts of complaints

  1. They work for the worst company ever
  2. They don’t know how to overcome challenges

Sure, there are a lot of grouchy, sad, negative people in our trade. That’s true in EVERY job, tradespeople just tend to express it with a few more expletives than some other more “refined” professions. You’ve really got to learn to deal with negative people while finding ways to spend more time with positive and helpful people. Sometimes that means finding a different company and sometimes it means using it as an opportunity to build some resilience within yourself.

Some companies and bosses are bad… You won’t change them. If you work at a place that doesn’t match your character don’t complain, find a better fit.

Remember, this is all about you choosing a path that will take you where YOU want to go. Everything else is just circumstances and you will decide whether they make you better or bitter.

In the words of Forest Gump…

“That’s all I’ve got to say about that”

— Bryan



This is a business article I wrote several years ago. No hard hitting tech tips but I still hope you find it beneficial.

“What would you do if you had a time machine.” It’s a question that came up at least 17 times in your first week of 6th grade, answered with the typical “Kill Hitler” and “See dinosaurs” answers. It can be more than a juvenile question if you apply it to your business.

So. Time machine. What would you do?

The rules are that you only get to go back 10 years and in this time machine you can only go back and give yourself business advice. No stock picking or lottery numbers you cheater! that would destroy the space-time continuum!

I wouldn’t go back and instill new skills. Skills can only be developed over time and no amount of information can make you better at something when you don’t have the hours at the grindstone.  I wouldn’t even try to prevent myself from making mistakes, as they are the catalysts for growth in the business.


So here are the things I would encourage myself to do differently if I could go back 10 years.  


Stop working in isolation

When I first started in business I kept my head down and worked. It made sense to me; there was so much to do and very few people to help me. What I didn’t understand at the time was that insulating myself caused me to become unproductive over time and helped to maintain the false reality that I was the only person willing and able to get the work done.

Over the past years, a wealth of experienced, trustworthy advisors have helped me develop and challenge my thinking in ways that I wouldn’t have imagined in my early days. Resources like business courses, mentorships and mastermind groups have allowed me to see how other people have solved my very same problems.

Don’t get me wrong, I understand that “Doing the work” is critical, but it’s easy to get stuck there when you’re a one-person band. Make sure you are building in support right from the get-go.


Open up to possibilities

The idea of specialization was strong in me when I first started. I wanted to be clear on what I/we did and DID NOT do so that I wouldn’t lose focus. It’s interesting because in general this trait is a good thing, but the way I practiced it was shutting down opportunities before they even had a chance to take root.

“Don’t respond with negativity.” Your eyes may have just glazed over,  but that was me. My response was always “My concern is…” or “That can’t work because…” Choose responses like “That sounds very interesting” and “Tell me more about that”. By allowing the conversation to proceed without adding in negative comments I have found that we get great opportunities without over-committing.  


Stop Being Defensive

I used to be DEFENSIVE about my business. I took every comment and criticism to heart. I still struggle with this, but it helps to know that most people react based on what’s going on inside of them. People are generally not aware of their own “why” let alone yours, and in most cases, they won’t even listen if you tell them. Let them criticize. Respond with an “I can see where you’re coming from,” and let it go.

If I am less concerned about “What I did wrong” and instead I focus on the relationship with the other person: how I can be present with them, serve them, and learn from them. Show you care about a person more than defending yourself, and there is a much better chance that a negative experience turns positive.

At the end of the day, if something doesn’t work out, I know two things: brushing over an offense is almost never as bad as my defensive self would want me to believe it will be, and not correcting the other person will at minimum work out better than if I had let my defensive self “HANDLE” the situation.

If you could go back in time, what would you do differently in your career?  

I have a confession to make. I’m a bit of a snob.

It’s embarrassing to admit because I never wanted to be a snob. I’ve consistently railed against snobbery whenever I bumped up against it.

But now I am one.

My snobbishness has been YEARS in the making.

I remember being on call when I was 20 years old and hearing my emergency pager going off at 1 am. At that time we had a toddler who wasn’t the best sleeper and we were living in a one-room “house”. I rolled out of bed and walked outside to call the customer, speaking out loud beforehand to try and get the sleep out of my voice before I dialed.

Me: “Hello, may I speak with Mr. Pedergast?”
Customer: “Yes, Who is this!”
Me: “This is the A/C technician with (redacted), I received a call that you have an emergency?”
Customer: “Yeah, you guys were JUST out here and now my A/C isn’t working and I need you out here right away!”
Me: “Ok, I will be out within a few hours, please have any recent invoices available so I can take a look before I start working”
Customer: “What! TWO HOURS! You won’t be here until 3 am? I need to WORK in the morning”
Me: “I will be there as soon as I can sir, It would be two hours at most”
Customer: “OK, just get here as soon as you can… (click)”

Needless to say, Mr. Pendergast actually had 3 systems in his home but the one that wasn’t working was his master bedroom so it was an absolute emergency, heaven forbid he use the spare room or **gasp** SLEEP ON THE SOFA.

It also turns out we hadn’t worked on THAT system recently, we had worked on another one but that didn’t prevent him from pitching a fit when I wrote down a diagnosis fee on the invoice.

So I have a question directed at the mindset that drives people like this customer to devalue the trades and the people who work in them. What can you ACTUALLY DO Mr. Pendergast? What real value to YOU add to society? Who needs YOU at 2 am? What does YOUR work day look like? How many real-world problems do YOU solve?

I have these thoughts now that I didn’t necessarily have when I was 20, because at that time I may have had much the same view of my work and value that Mr. Pendergast had. Back then I wasn’t a snob that looked down on people like Mr. Pendergast, now I am, much to my own chagrin.

What does this have to do with the skills gap? 

This customer is an extreme version of a larger challenge that exists in the minds of people from CEOs to Tradespeople themselves. This is the belief that one type of work is “more important” than another and therefore doing one thing over another makes you (or others) more or less important.

As I’ve progressed in my career and interacted with more people from various “prestigious” professions I’ve noticed three things that relate to this topic.

  1. Many of them are excellent people that I enjoy immensely
  2. They have no idea what it takes to do what we do
  3. They aren’t any better, smarter or more important than tradespeople

You see, most of them don’t really think they are BETTER than you and I, they just don’t have clue what it means to BE you and I. They can imagine what it’s like to work in an attic or crawlspace, to drag a gas furnace through the dirt, up a hill with a hand truck or to work on call into the wee hours of the morning but they still have NO CLUE what it really takes.

And that’s OK! it isn’t their experience so they can’t be expected to understand. You cannot change how others see the world by complaining about their worldview. We can change it by taking steps to value the trade ourselves and start thinking about all work, education and recruiting a bit differently.

Manifesto for Filling the Skills Gap 

#1 – The Trades Don’t Always Need to be a Full Contact Sport

I hear it all the time, some version of “I don’t want to be turning a wrench when I’m 60, my body can’t handle it!”.

That would be like asking a running back to carry the ball in the NFL or a pitcher still throwing it 96 MPH when they’re 60. There are aspects of our trade that are very physically demanding, there are segments that are minimally demanding and then there are roles that will allow you to sit in front of a screen and talk on a phone most of the time.

I wrote that last one because I knew 99% of you who have worked in the field got hives just THINKING about sitting in front of a computer all day. Many of us work with our hands because we ENJOY working with our hands, getting some fresh air, turning a wrench now and then and ultimately solving problems in the real world.

Which of us as little kids dreamed of a future where we would sit behind a desk answering emails and attending meetings all day?

We all have a desire to DO COOL THINGS not just talk about cool things and certainly not to sit on our butts staring at a screen all day.

The real problem isn’t turning a wrench, the issue is that we are afraid that the trade will use up our bodies and then leave us hanging when we can no longer throw the ball 96 MPH.

Here’s the truth, nobody who continues to invest in their mind and personal growth will be left hanging by this trade moving forward. There is just too much to do and too few people to do it. Getting left behind will happen due to lack of development and preparation not because of something intrinsic to the trade.

We have never needed the minds of those who have been around the business for 30+ years more than we do today. There just needs to be a shift in thinking from working our whole careers with the exact same focus to shifting from mostly physical to mostly mental work as we mature, I call this shifting from blue-collar to new-collar. This shift from physical to mostly mental takes time and intentionality but it’s critical to the future of the trade.

If we begin to phase more experienced people into training and supervision earlier it will keep more people in the trade and help improve the next crop, but there is a catch… The grouchy, inflexible, ego-driven, foul-mouthed tech won’t fit into these roles and will be left behind because they cannot be trusted to supervise and train.

Here is the litmus test for whether you are ready to begin making the transition. If you have been in the trade for 15+ years go ahead and think about a new technology that’s come out in the last 5 years that you are really comfortable with. Now think about your three favorite books, audio-books or podcasts on personal development or leadership. If you are drawing a blank then that is where you start.

We must have intentional programs and processes to transition more experienced workers to roles that utilize their field knowledge while coaching them on educational and leadership skills and traits. We need to leverage technology and resources to train and develop skills into existing tradespeople before looking forward to the next generation.

#2 – The Education System is Broken 

There are many incredible educators, schools and resources. Learning isn’t broken, the education SYSTEM is broken, especially for the trades.

“I have never let my schooling interfere with my education” ~ Mark Twain

Humans learn through concept association (how this works reminds me of how that works) and practice. Yet the education system tries to teach using disassociated facts and memorization.

Imagine the US education system trying to teach a baby how to speak. They would develop a 4-year program where the baby would be taught Latin and Greek word roots, the history and science of words and then given speaking tests to see what they remembered.

How do babies actually learn to speak? They learn by hearing language used constantly and once they learn some words they make inferences on the meanings and pronunciations of other words which they then practice in context. Once the baby starts speaking then other adults and children begin to provide them with feedback on ways to improve their vocabulary and pronunciation.

Learning  is natural and organic and it has three necessary components

  1. Desire to Learn
  2. Observation & Practice in Context
  3. Feedback & Instruction in Context

The education system can only provide #3 and it can only be expected to do it well when the first two elements are in place. Many of us grew up watching adults do things around the house like installing an outlet, changing a tire or soaking a mower carburetor. Once we started in a trade school or in the field we already had a “language” of tactile skills we could draw from when we saw things in our trade of choice. If we had a good instructor or worked with a good journeyman they would draw on the language and mechanical concepts we already understood to relate concepts in HVAC/R. This is why many of us learned electrical theory as related to the flow of water in pipes, we had already seen water flow so this would help us understand the movement of electricity.

Many young people entering the workplace today don’t speak the same mechanical language we spoke as kids because their experiences are more likely to be of screens and computer keyboards than fire, gasoline, and plumbing.

With this being what it is we need to give new students and apprentices more experiences with the basics of mechanical assembly and tools before we can expect them to understand mechanical concepts taught in a lecture.

This is not only true of the trades, this is also why many young people don’t have basic skills like balancing a bank account, doing laundry or dealing with disappointment. You don’t learn these skills in a class, you learn them by doing them and dealing with them and often the culture emphasizes skills that are far less necessary for life than these. To bring it to a point, we think you need to learn theory and facts and then gain practice when really you must have a constant cycle between facts and application for it to make any sense. Often this means seeing something done and doing it before you can learn why you did it or why it matters.

We must develop programs that allow for a continuous loop of observation, practice, instruction, and feedback that focuses on the application of a skill more than the information. Effective education develops the tactile “language” of learning rather than just hammering away at the information. We cannot wait for government programs to do this for us. Contractors, OEMs, wholesalers, educators, influencers and reps need to work together to make this a reality.

#3 – Change Starts Between Our Ears

Back to me being a snob.

I don’t know what Mr. Pendergast did for a living, maybe he was a scientist working on a cure for cancer or an astronaut or a recently deposed dictator (which I imagine to be most likely). I can tell you that I’m glad that I work in a job where what I do makes a difference in peoples lives. I’m glad for an honest days work, doing pretty awesome stuff with some pretty neat tools, working alongside some really smart people. I’m glad I don’t devalue the hard work of others and their sacrifice like Mr. Pendergast did with me.

I spoke on a panel the other day where the question came up about recruiting the next generation and why young people don’t flock to the trades. I asked for a show of hands from the audience of how many of them encourage their kids to enter the trades. Only a few hands went up out of hundreds of people.

Maybe the reason we have a problem getting young people into the trades is because parents encourage kids to go into a career where they don’t need to put in a hard physical days work.

Why is that?

Do we think there is something wrong with having dirty hands and lifting heavy things every once and a while? I don’t think that’s it based on how many people pay GOOD MONEY to attend CrossFit classes and mud runs.

I think much of society has bought into a lie that working in blue collar jobs is somehow a “lesser” option. You are OK with your kids working an apprenticeship and attending a trade school if “college isn’t for them” or if they “Just aren’t academic” but not as a first option.

Those of you pushing your kids towards college, how would you feel if I said “Yeah I understand, some kids just aren’t suited to work for a living”. It’s insulting and ridiculous to assume that a kid needs to choose a trade if “college just isn’t for them”. Maybe they should choose a trade because it’s an interesting, rewarding and tactile career path where you get to solve real problems every day.

Ultimately I want my kids to do whatever they do with excellence and I want them to enjoy the path they choose whether that is as an HVAC tech or a physicist, although I’m pretty biased to HVAC myself.

We need to ask ourselves if we are ashamed of being in a blue-collar industry and if that impacts how we talk about our work to young people. If we are excited about this trade then don’t be afraid to be outspoken about it. 

Let’s get the skills gap filled by creating better paths for experienced people, improving education and being really excited about the opportunities in our trade for the next generation.

Oh and that toddler who my pager almost woke up… he just started as an apprentice in the trade. Don’t worry, he can always go to college as a plan B if he can’t cut it 😉

— The HVAC Snob – Bryan Orr

And no… his real name wasn’t Mr. Pendergast. That name is taken from a grouchy guy in one of my favorite movies as a kid. Do you know which one?


Jesse Grandbois is one of the techs who reads the tech tips and he wrote a few tips that he wanted to share on some gas furnace control basics. This tip is about the basic terminal designations on typical 24v gas valve. Thanks Jesse!

Have you ever noticed the TH / TR terminal on a gas valve?. When I was in school, I’ll admit I didn’t know what it was. I’ve worked with people that are experienced and still think you need to use it. 
Nobody ever explained to me what it was. Being a newbie at the time it never clicked when I looked at the wiring diagrams. All my teachers would give the same response, “it’s a common.” 
That’s where the confusion set in. It’s a common. We throw this word around like it’s going out of style it seems in the HVAC industry. Everything is a “common” and technically a common is just a “common” point of connection but it really doesn’t clear up it’s intended purpose, or what part of the circuit it is intended for.
Following the diagram below while reading the rest of the article should clear things up.
Lets look at what each of these terminals mean:
TH – The 24v hot leg from the thermostat on a call for heat (R+W closing) to the gas valve (TH terminal) to open the solenoid to allow gas to flow. This is assuming the transformer is good and the high limit is closed.
TR – The 24v common/return side of the transformer.
TH/TR – This is not internally wired to the gas valve. Not using this makes no difference to the circuit. You could run your 24v hot from the transformer directly to your NC high limit in the above example and be just fine. This is nothing more than a convenience terminal. Joining these wires with a marette (Wire nut or terminal multiplier) does the same thing as this terminal.
Hope this helps clear up any confusion.
— Jesse

This article is written by up and coming young tech and new contributor Kaleb Saleeby. Thanks Kaleb!

Recently, I came across a work order description in my dispatch that made me scratch my head.

“Clean Salamander broiler”

I had to ask the omniscient Google for answers. Turns out, it has nothing to do with vividly-colored, “fireproof” amphibious creatures! The name does, however, pay homage to 17th-century lore that salamanders could withstand the heat of a fire, and were even believed to come from fire itself.


None of this information aided me in understanding how to clean this particular type of open-air broiler, so I did more research on how the appliance was constructed, and how it operates. From my findings, the overhead broiler is a very simple design. The basic components of a gas salamander broiler are as follows:

  • Gas valve

  • Gas manifold

  • Fuel orifice

  • Distributor

  • Igniter

  • Burner

  • Food racks


The gas valve on the appliance I worked on was quite literally just a knob the client manually turned on or off. When open, the gas valve allows a set fuel pressure through the manifold to be fed out a single orifice, which then gets fed through the burner. The gas is spread through the burner via a distributor to feed the ceramic plates at the end of the burner. The igniter would be the next in this sequence of operations; however, the appliance I worked on did not have a functioning igniter, and the client refused replacement, resulting in manual lighting. The ceramic plates of the burner are littered with tiny holes that allow the flame to burn uniformly across the burner with little to no major fluctuation.


None of my research gave me any answers on how to clean this equipment. I reached out to Refrigeration Technologies’ Chief Executive Officer and Founder, John Pastorello for advice on what chemicals, if any, he recommended for this job. According to John, Viper HD cleaner is safe and appropriate for the cleaning of this type of broiler. Viper HD is a slightly alkaline (basically neutral on the PH scale) cleaner that will not damage the fragile ceramic burner, as long as it gets rinsed. John states,


“You will need Viper HD and a scrub brush. As long as you rinse you will not have a problem with the heating elements. On stainless [steel], you can use HD with a soft scrub. Rinse then use a stainless steel cleaner to finish. The [stainless steel cleaner] will have a mineral oil that leaves a finger proof coating and brings out the luster. This is a labor [intensive] job because of the heavily carbonaceous soil.”


The cleaning of the appliance was fairly simple, albeit frustrating. The grease and grime were the hardest part. Once everything was clean and dry, I reassembled the appliance and relit the burner. After a few minutes of allowing the flame to stabilize, the appliance was operating well and to the satisfaction of the client.


In retrospect, I probably would avoid forcing water into the burner section. The burner assembly I worked on was riveted together, and did not allow access to the inside. I have since learned that there is insulation on the inside of the burner assembly, and wetting the insulation can potentially cause issues with the equipment, even if it has been dried off. I would recommend anyone else who encounters a job like this to use a Viper HD saturated towel and wipe the ceramic burner to clean it, and then rinse with a water-damp towel. I would also recommend focusing on the distributor inside the burner, as it may be heavily caked with carbon buildup. All other steps would remain the same. I also learned that there are overhead broiler models that have a burner design that does allow you to change the ceramic plates and insulation, if necessary, to make the cleaning process easier.


I hope this helps other guys, like me, who may get sent to do hot side service. It certainly is interesting!

– Kaleb


Dissimilar metals, like Aluminum, Copper, Brass, and Steel are some of the main metals one may experience in their trade and few are comfortable working with. They don’t trust their brazed joint, or they are afraid of melting away material. To put some of the nerves of those in the field at ease let’s understand our metals with a specific focus on thermal effects on structures of metals.


To review the extreme, we theoretically come upon a copper and aluminum joint. The plan is to braze the two together with my copper being my male and the swaged aluminum as my female. I find an applicable alloy and bam!!! Would you look at that nice joint, I quickly cool the joint off by applying a wet rag to it, then tug on both ends which separates the two Alloys completely.


What the Flux!!! Only thing I can think of that I did not do was clean my joining metals.


Our issue here goes much deeper than a proper cleaning.


Thermal Expansion Coefficient of:Thermal Expansion (Microinch per °F)



Each material has a different response to the heat, which is characterized by its thermal expansion coefficient. The thermal expansion coefficient represents the amount that the material expands per each degree increase.  It is important to know that whatever the solid expands when heated it also contracts when cooled, but not necessarily at the same rate of expansion.


Each time you are cycling through expansion and contraction you are altering the structure of the metal as well as reducing its ductility or ability to flex without becoming brittle.


What should we consider when working with two different (Dissimilar) metals?

  • Melting temp of brazing alloy and brazing metal
  • Metal thickness
  • Brazing Metal Ductility
  • Heating and cooling rate of joint
  • The heating rate of the torch being used
  • Galvanic Corrosion between the two dissimilar metals
  • Oxidation of the metals heated

Referencing Copper to Aluminum, the vastly different thermal expansion rates of two metals make this joint very difficult to make.  When joining the two, we would use a brazing alloy that has a fluid melting temperature below our brazing metal as we want our brazing alloy to be pulled and filled into our joint through capillary action. The alloy must also be ductile enough to maintain the bond throughout the expected temperature range of the joint while in service.

Without the proper clearance between the aluminum and the copper, there is no guarantee that the brazing alloy will properly fill the joint and create a trustworthy bond and when working with dissimilar metals you will generally want to allow the work to cool naturally rather than cooling instantaneously with water.

— Sal Hamidi w/

If you ever sat close to a bonfire on a really cold night, you may have noticed that your face starts to get really warm. The minute you put your hands up and shield your face from the light of the flame your face cools off almost immediately.

This happens because the flame is heating your face through THERMAL RADIATION not by heating the air in between.

Many have taught that radiant heating (thermal radiation) happens when one body of matter is exposed to a light source such as the sun or a fire. While this is partly true, the VISIBLE light spectrum is only a small part of the story.

Take a look at this photo above taken using a Testo thermal imaging camera. This image could have been taken in complete darkness and yet it displays the thermal radiation.

This is because EVERYTHING that is above absolute zero puts off thermal radiation in the form of electromagnetic radiation, because everything in our world is above absolute zero (-460°F) everything emits radiant heat.

In the case of the human body, we are putting off radiant heat to everything around us as well as picking up radiant heat from all of those same objects. The net thermal (heat) effect on our body is based on whether the average surface temperatures we are exposed to are higher or lower than our body temperature.

Thermal radiation can be “reflected” in the same way as visible light. This is why these weird “space blankets” can keep a person warm by simply reflecting back their own thermal radiation.

The real world effect of thermal radiation on heat load and human comfort are huge.

You can have a room with an air temperature at a comfortable 72° that can still feel hot or cold to an occupant based on the temperature of the surfaces around them. In fact, studies have shown that the wall surface temperature has the same effect on comfort as room air temperature.

A 1°F change in wall surface temperature is nearly equal to a 1°F change in air temperature as it relates to overall thermal gains/losses to the human body.

This shows that why radiant cooling and heating and products like radiant barriers make such a big difference.

It also makes a difference in cases of thermostat and sensor placement. It isn’t just a matter of keeping the thermostat or sensor out of the sun, you must also consider what objects the sensor is “exposed” to through line of site thermal radiation.

— Bryan

This article is written by tech and business owner Genry Garcia from South Florida. I met Genry at a Solderweld demonstration and he later offered to write this excellent article. Thanks Genry!

Though dehumidifiers have increased in popularity thanks in part to the implementing of new building codes, at the same time they have become a kind of red-haired stepchild…the runt of the litter if you will. We all know is there but nobody gives it too much attention. I have seen a few that a couple of years later still have the original filter in and likely haven’t worked right in a while. For the purpose of this article, I am only gonna refer to ducted, vapor compression refrigeration ‘whole house dehumidifiers’ like the ones in the picture above.


What is a dehumidifier?

A vapor compression refrigeration dehumidifier works exactly like any other refrigeration system in the sense that has a compressor, a condenser coil, a method of refrigerant metering and an evaporator. The main difference is that the condenser coil is placed immediately downstream from the evaporator and as such the air that has been cooled and dehumidified through the evaporator it’s then reheated before being discharged. Most dehumidifiers are rated at 80 ºF. and 60% RH entering air conditions and their capacity is expressed in PPD (pints per day of condensate removal). Most of these units have all their components arranged inside one single cabinet but, there is at least one manufacturer that offers a split system option where they claim there is no sensible heat load added to the space.

I personally like this hot gas reheat strategy. It removes water vapor from the air in the space we’re trying to condition while adding sensible heat back as to not overcool it. The discharge air can be 20 to 30 degrees higher than the return. This is by design, a sound tactic since the warmer and drier discharge air has a larger specific volume which results in a lower percentage of RH when this air mixes with the rooms. However, special consideration should be given to where and how this warm and dry air is going to be introduced into the controlled space as not create unwanted warm spots.


Why a dehumidifier?

The two main reasons in my experience are to pre-condition ventilation air that is needed and/or required by building codes in humid climates and my favorite, which is to control the inherent water vapor that can accumulate in attics, when the line of the building envelope is moved to the roofline by insulating it with spray foam. What? Inherent? Why is there humidity accumulating in the attic if is not ventilated? Great questions, Dr. Joe Lstiburek explains it in this article. There is also the occasional retrofit job where a dehumidifier gets added (hopefully the discharge air does not get connected to the return side of the system) in an effort to alleviate high humidity issues in a space. A dehumidifier’s application and its connection/integration method it’s a controversial enough subject, here is great new research on what is the best way to connect a dehumidifier  by the Florida Solar Energy Center. Special care should be taken when ducting these, whatever the configuration might be. They don’t move a lot of air to begin with and any scenario that results in mild to high static pressures will seriously tax their capacity.



So, let’s say you get a call where you eventually arrived at the suspicion that the dehumidifier might not be doing what is supposed to. This type of call is usually tied to a consumer complaint for lack of comfort in areas where “it used to feel fine but it hasn’t in the last few weeks” or the most common one in my experience; sudden occurrences of condensation on supply vents and on ductwork surfaces.

First things first, you want to make sure that there is a demand for the dehumidifier to be operating and that both, the fan motor and the compressor are working. If they are not, those issues are normally simple to address by following the wiring diagram. Once we’ve established that all the components are operational and its capacity performance it’s what’s left to check then like almost all things HVAC, the manufacturer’s specs rule. In this article, we are going to be following this one from Honeywell.

There are 3 methods to check the performance of a dehumidifier in the field:

  1. We can measure the volume of condensate that is generated over a pre-determined period of time.
  2. We can measure the inlet and outlet air temperature and humidity.
  3. We can measure its power consumption.

Condensate Volume

One pint is 16 ounces of volume and one pound is 16 ounces of weight and like the saying goes “A pint’s a pound, the world around” so for the purpose of this test we’re going to use them interchangeably. Let’s say that we are working on a DR65 (65PPD nominal capacity) from the specification data document referenced above. As plotted in the chart below, if our entering air condition is 80 ºF and 60% RH then that would mean that the unit should be removing about 68 pounds of condensate per day.

The nominal capacity of 65 pounds of condensate in 24 hours equals to approximately 2.71 pounds per hour, so if we wanted to check this unit’s performance using this method, we would cut the drain line and collect the condensate in a measuring cup. It should produce about 14 ounces in 20 minutes.

Easy right? Not so fast, here is my issue with this method. This would work fine if we knew for a fact that the unit has been working enough time to have produced enough condensate to wet the whole evaporator coil, to have enough collected at the drain pan so it flows out the line and to top it all off, from this manufacturer at least, the drain connection port is under negative pressure so it will need a P trap, which would also have to have enough water in it for it to flow out into our measuring cup.

This is not a bad way to check a dehumidifier’s performance but it has a few variables, it can be deceiving and it certainly takes more than 20 minutes. How much more? Who knows, depends on how much water its already inside the unit and the drain line upstream of where you are collecting the condensate.

Measuring the Inlet and Outlet Air Conditions

Using the same scenario from the first method, we are gonna try it a different way now. At our known entering air conditions of 80 ºF and 60% RH the first step is to remove the duct connections if any (more on that in a minute). After the unit has been running for a few minutes we then take our leaving air conditions which I would expect them to be at 100 to 110 ºF dry bulb and 15 to 20% RH. If instead, our entering conditions were at 75 ºF and 50 %RH, then our leaving air conditions would be closer to 90 ºF and around 22 to 24% RH. On the opposite extreme, if our entering conditions were 100 ºF and 35% RH (as the case may be in a “ventilated” attic) one can expect our leaving conditions to be closer to 130 ºF and 12 to 14% RH.

Disclaimer: These readings are based solely on my personal experience. As a matter of fact, I have in many occasions reached out to technical support reps of at least two different brands and asked them point blank why is it that the math doesn’t add up when I use the latent heat formula (QL = 0.68 x cfm x ΔW) and the response has always been something along the lines of “It doesn’t work that way” or a plain “I don’t know”.

I have consistently logged this numbers on properly functioning dehumidifiers for the very reason of being able to cross-reference them when working on one which performance is questionable.

About removing the duct connections: As you can see below, a dehumidifiers’ airflow does not fare well at even mild static pressures. For this reason, to perform this test it is best to disconnect the ductwork if it’s a ducted application. Consequently, an additional valid test is to, once we have recorded our measurements without ductwork, we can then re-connect it and perform the same tests for the purpose of comparing readings. This can and will reveal that perhaps the unit is not the problem but the duct configuration is.


Caveat: These units tend to have the compressor located right upstream of the discharge air collar, maybe on purpose. For this reason, when measuring the leaving air conditions, the mean radiant temperature of the compressor can affect our reading when taken too close to the discharge air connection, despite the lower emissivity of its black painted shell…in other words move the probe out 6 to 10 inches so you don’t pick up radiant from the compressor body.


Power Consumption

This is probably the simplest and easiest one of the three methods as long as we have access to the manufacturer’s literature. Let’s look at the chart below.

At the established entering air conditions of 80 ºF and 60% RH, the dehumidifier should be consuming around 600 Watts. 597 to be more exact.

We can obtain the Watts reading in one of two ways…or both but one is easier I promise:

  1. Using a multimeter capable of Bluetooth connectivity, we can open the dehumidifier, place the clamp over one of the line voltage wires, close it back up and record the amperage reading in a phone or tablet while is running. We will then multiply this current value by the line voltage to get the power consumption. Depending on which meter you are using, a direct Watt readout might be possible but getting the leads to safely stay on the points where the incoming line voltage can be measured will be tricky.
  2. Get yourself a Kill A Watt and get a faster and safer Watt reading which we can then cross-reference in our chart to confirm the dehumidifier’s performance.


In conclusion, all 3 methods have their merits and disadvantages. As it is the case with many of the issues that we solve in our industry taking the time to analyze and look at all the aspects of a problem and/or consumer complaint will offer a broader view of what the possible solutions can be. Focusing on any single reading or test method and offering a diagnostic based on that alone will invariably lead to mistakes that could’ve been avoided. There is no replacement for good ole’ common sense and thorough research.

— Genry Garcia

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