Month: January 2019

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

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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?  

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