Author: Bryan Orr

Bryan Orr is a lifelong learner, proud technician and advocate for the HVAC/R Trade

When you walk up to a piece of equipment you want to follow a process to ensure that you accomplish five things.

#1 – You diagnose the fault correctly

#2 – If possible you find the “why” of the failure

#3 – Find any other problems or potential problems with the system that can cause inefficiency, low capacity, failure, safety or indoor air quality issues

#4 – Communicate clearly with the customer and and office about these issues via paperwork and / or verbal communication

#5 – Execute and repair the issues in an efficient and workmanlike manner

In order to accomplish this I recommend looking at the equipment with a wide, narrow, wide mindset

First, speak with the customer, read the call history, understand any concerns the customer may have and any past failures. Look at the equipment, look for any obvious signs of issues like oil stains, corrosion, rubbing wires, bloated capacitors etc…

Then go narrow and FIND THE CURRENT PROBLEM. The difference between a “Sales Tech” and a real service tech is the ability to quickly and accurately diagnose the problem at hand as well as find the likely causes of the failure.

Finally, once you find THE problem, go wide again and look for any other problems BEFORE communicating with the customer. Look at coils, contactors, capacitors, filters, belts, wire connections and potential rub outs, check coils and accumulator for oil stains etc…

When looking wide take the mindest that..

– The system was likely installed poorly / incorrectly to begin with

– Every other repair made to the unit was done improperly

This will put you in the mindset to double-check everything.

Now you are ready to talk to the customer and make repairs with confidence.

— Bryan

I’m a big dummy when it comes to my own air conditioning maintenance. I talk about the importance of changing air filters to customers and techs but I never stay up on replacing my own.

Yesterday I walked into my mechanical room and my 2-ton air handler sounded like a vacuum cleaner about to implode.

My filter was nasty… nasty to the point that I wasn’t willing to leave the filter in. So I pulled it out and think to myself “I’ll just grab a filter from the office tomorrow”. well… I forgot and I live 35 minutes from my office.

So today I grab a filter from my nearby hardware store, a common brand and pull it out of the plastic wrap to install it. Sure it was a MERV 11, but that was the only option other than the cheap, spun fiberglass “bug catcher”.

I know what you’re thinking, I should have known better

I’ve got to give it to this filter manufacturer for actually printing the static pressure drop on the filter (shown above).

My system is setup for 350 CFM per ton so it’s required running at right around 700 CFM which means on my system this filter is going to add 0.26″wc of extra static to the return side of the blower.

With most systems being rated at 0.5″wc TESP (total external static Pressure) this makes up more than half of that, before any ductwork, grilles, registers, balancing dampers or coils in the case of furnace systems.

On a PSC blower motor this extra static from this filter would result in lower airflow, poor system performance and poor air distribution.

With an ECM motor this extra static can result in higher blower motor power consumption and condensate drainage issues/difficulty maintaining trap.

While some systems may be able to deal with the extra static at a cost, many will have issues ESPECIALLY on older systems that have PSC motors and furnaces with coils.

This is why larger filter cabinets with lower pressure drop filters often make sense or oversized filter back return grilles.

When choosing a filter remember that airflow (Pressure Drop) is just as important to consider as filtration (MERV rating) and just because a filter fits doesn’t mean it’s the best filter for the system

— Bryan

 

Every contractor is different, I get that.

We don’t all need to do everything the same way or include the same services with repairs but there are some “best practices” that can save you a lot of heartache before, during and after you make a big repair.

Catch it During Diagnosis

Let’s say you find a failed, shorted compressor on a 7-year-old system that still has manufacturer parts coverage. If you simply quote the compressor and leave you may be missing a lot of other maintenance-related issues that can affect operation once the compressor is replaced. A shortlist of items to check would be –

  • Look at the accumulator for signs of corrosion
  • Acid test to see if a burnout protocol should be employed
  • Check the air filter
  • Inspect the condenser coil cleanliness
  •  Look at the underside of the evaporator coil
  • Perform a static pressure test on the system to check for duct issues
  • Check the crankcase heater (if it has one)
  • Inspect the contactor
  • Check condenser fan and blower motor amps
  • Test all capacitors
  • Visually inspect wires and cap tubes
  • Check high voltage electrical connections

And this is just for cooling side issues. If the system is a fuel-burning appliance you would inspect every part of the furnace operation as well.

  • Venting
  • Condensate drainage
  • Burners
  • Flame proving
  • Safeties

And much more…

Testing all of these things is commonplace AFTER a repair, but it makes so much more sense to do it beforehand so that you can either charge appropriately for any of these items that need to be addressed or let the customer know you are including them to differentiate you from the competition.

Things to Do Along With Major Repairs 

There are a few things you need to do as a matter of course during major air conditioning or refrigeration repairs that just make good sense to prevent callbacks. You can include them in the price or not or not but either way, it will save you more than it costs to do it.

  • Clean the drain line and condensate pan (seriously…. do this)
  • Wash the condenser coil
  • Clean the blower wheel (if it is dirty)
  • Change the air filter
  • Test all modes of operation

Do these things along with all of the standards tests you perform to make sure that you have no issues and that whatever caused the fault in the system has been rectified and you will save a lot of problems. When the customer spends a lot of money getting a system fixed, they don’t want to turn around and have it fail for an “unrelated” reason.

While this list is clearly tailored to the residential and light commercial air conditioning market, every piece of equipment has its common maintenance items. So what do you do every time when you make a major repair?

— Bryan

 

When the quiz or the teacher asks what “latent” heat is there is generally some reference to it being hidden heat, which is what the word latent means. We then learn that it is heat energy transferred that results in a change of state rather than a change in temperature.

Later on, we hear a lot talk about how much more heat it takes to change the state of water than it does to change its temperature with a graph something like this.

So we learn pretty quick that a lot more energy gets moved when we are changing matter from one state to another and in HVACR we are going from vapor to liquid and back to vapor again in the refrigerant circuit.

In the condensing coil, we see latent heat rejected as the refrigerant changes from full vapor to full liquid at the condensing temperature.

In the evaporator coil, we see latent heat absorbed as refrigerant changes from mixed vapor / liquid flash gas to full vapor at the boiling temperature.

But there is another kind of latent heat we deal with in air conditioning that can leave people confused when we talk fast and loose about latent heat and the evaporator. This latent heat is the hidden heat it takes to change water vapor in the air passing over the evaporator to liquid water on the coil surface.

Which is Which? 

Inside the evaporator, there is latent heat of vaporization as heat conducts into the coil and boils the refrigerant. That internal temperature is fixed so long as the pressure remains the same across the coil and the refrigerant is a single component or azeotropic (no glide). There are refrigerant blends that do change increase in temperature through the coil through “glide” but set that aside for another article.

On the outside of the coil there is latent heat transfer out of the water vapor causing it to condense on the coil fins so long as the coil is below the dewpoint temperature of the air. This is why we call the ability an air conditioner has to remove moisture at certain conditions its latent capacity.

These two latent heat transfers impact one another indirectly but all the heat that the air moving over the coil imparts on the evaporator is done via conduction through the tubing (or microchannel) walls of the evaporator.

Let’s break that down a bit.

Convection is heat transferred through a moving fluid. So heat moving THROUGH the refrigerant is moving via convection. Heat moving THROUGH the air over the coil is also transferred via convection.

But there is no direct fluid connection between the refrigerant in the tubing and the air moving over the coil is there? (Unless you have a big coil leak).

The heat that moves out of the air and into the refrigerant has to move through the solid walls of the coil and the only kind of heat that can make it through a solid with any significance is conduction.

This means that the only way that the latent heat inside the refrigerant and the latent heat in the air connect is via SENSIBLE temperature difference across the metal walls.

When the air moving over the evaporator has more moisture in it and therefore a higher RH and dewpoint the surface temperature of the coil is increased so long as the coil temperature is below the air dewpoint.

When the surface temperature of the coil is held “higher” by more latent heat of condensation on the coil more heat enters the refrigerant inside the evaporator resulting in a higher evaporator pressure and higher boiling temperature inside the coil (especially in a TXV/EEV system).

This may sound like magic but the quantity of heat that can enter the evaporator is as simple as the temperature difference between the inside of the coil where the refrigerant is and the outside of the coil where the air is. Because we have the potential for latent heat transfer on each side this temperature difference has a lot of contributing factors that can make the math a bit confusing.

Just remember… There are two kinds of latent heat at play

Refrigerant boiling inside the evaporator

Water condensing on the outside of the evaporator

Heat interacting between the two moving from higher temperature to lower temperature via conduction.

Simple!

— Bryan

 

 

When we say that there is “flash gas” at a particular point in the system it can either be a bad thing or a good thing depending on where it is occurring.

Flash gas is just another term for boiling.

It is perfectly normal (and required) that refrigerant “flashes” or begins boiling directly after the metering device and as it moves through the evaporator coil. In order for the evaporator to transfer heat from the air into the refrigerant in large quantities, we leverage the “latent heat transfer of vaporization”. In other words, we transfer heat into the boiling refrigerant, or “flash gas”.

In a boiling pot of water, we create flash gas by increasing the temperature of the water until it hits the boiling temperature. At atmospheric pressure that occurs at 212°F which is the boiling or flashing point, we are most familiar with.

Inside of a refrigeration circuit we get flash gas when the pressure on the liquid refrigerant drops below the temperature/pressure saturation point or if the temperature of the refrigerant increases above the same point. In other words, either a drop-in pressure, an increase in temperature or both can result in flashing or boiling.

This “flashing” can occur in the liquid line when the liquid line is long or too small and also in cases with line kinks and clogged filter/driers. All of these instances result in a pressure drop and a drop in the saturation temperature.

This flashing can be prevented by keeping line lengths and tight bends to a minimum, insulating the liquid line where it runs through very hot spaces and keeping the refrigerant dry and clean with one properly sized filter/drier.

It can also be prevented in most cases by maintaining the proper levels of subcooling. A typical system that has 10°+ of subcooling will not experience flashing in the liquid line under normal conditions. Setting the proper level of subcooling acts as headroom against pressure drop in the liquid line due to long line lengths.

When you walk up to a liquid line near the evaporator and you hear that hissing/surging noise or when you look in a sight glass and see bubbles you are seeing refrigerant that is at saturation, meaning it is a mix of vapor and liquid. This doesn’t necessarily mean it is “flash gas”in the truest sense, it could very well be that the refrigerant was never fully condensed to liquid in the condenser in the first place. This can be due to low refrigerant charge and in these cases, the subcool will be at 0° Even when taken at the condenser.

The true liquid line “flash gas” issues are cases where you have measurable subcooling at the condenser coil outlet but still see, hear or measure boiling/flashing refrigerant in the liquid line before the metering device or see it in a sight glass.

— Bryan

This tech tip was a COMMENT on a facebook question about how ductless systems achieve some of their high-efficiency numbers at the expense of dehumidification.

This was the question –

Bryan Orr mentioned that multi-stage mini splits often do very little latent cooling (dehumidification) because on low speed the manufacturers all “let the evaporator float, which makes it much warmer”. Can someone explain that? What does it mean to let the evaporator “float”? What’s the alternative?

I was pointing out that colder evaporator coils and longer run times equal better dehumidification. Ductless systems often ramp down the compressor (lower RPM) as the indoor temperature approaches set point resulting in a warmer evaporator and poor dehumidification. My solution to this is a dehumidification mode in ductless systems that keeps a colder evaporator at the expense of lower efficiency when it is needed.

All of this is a trade-off between a colder evaporator being better for dehumidification and a warmer evaporator / lower compression ratio being better for efficiency.

One of my friends is a tech named Joel Becker who happens to be an insanely smart and detailed guy. He tackled the question with so much detail that I asked if I could make it a tech tip. He agreed and here is his comment… which I find to be spot on. Enjoy.


Evaporator coils do two things to refrigerant: First, all the refrigerant boils to a vapor, then it gets superheated (heated above boiling).

Evaporator coils also do two things to what we call “air”, which is actually a gas-vapor mixture that includes water vapor. The coil removes sensible heat from the air (lowers the temperature), and also changes the phase of water vapor from the air to liquid. To state this in simple terms, it cools and dehumidifies. As the temperature of the coil drops, the difference between the surface temperature of the evaporator coil and the dew point of the air through the coil increases, and more water vapor from the air condenses on the coil. This “latent” heat removal takes away from the “sensible” capacity of the system to cool air. In A/C system expanded performance specifications, the “sensible ratio” shows how much heat will be used for each of these separate functions under various conditions of outdoor air temperature, indoor air temperature, indoor air humidity, and evaporator airflow rates.

Refrigerant enters the coil at a rate controlled by a metering device, and its pressure is controlled so that its boiling point is below the temperature of the air. If we reduce the refrigerant flow into the coil by closing the metering device but keep everything else the same, then the compressor suction will pull the pressure of the coil down lower. This results in a lower boiling point for the refrigerant entering the coil, and a lower surface temperature of the “active” portion of the coil. However, the coil is now “oversized,” so we’re not using much of it to boil refrigerant; the majority of the coil is now being used to superheat the vapor refrigerant after it has completely boiled off. At this point, if dehumidification is the priority, we can slow airflow down enough to reduce superheat and keep a greater portion of the coil colder. Again, the goal is to have a large surface area that is significantly lower than the dew point of the air (without dropping below 0° C/32° F). This all results in a big difference in pressure between the discharge and suction gas at the compressor (compression ratio.)

Since the priorities of regulators and consumers seem to be exclusively revolving around high efficiency, manufacturers respond by creating products that have a super high SEER/EER. Low compression ratios are mainly how these high ratings are achieved. Equipment is designed with large coils outside to transfer more heat and boil more refrigerant with the refrigerant condensing at a lower pressure and temperature, and larger coils indoors where refrigerant is boiled off starting from a higher pressure and temperature. Especially in “VRF” systems including residential mini-splits, where all the fans are variable, the refrigerant metering to the indoor coil is variable, and the compressor speed is variable, the SEER rating gets sky-high because of how they behave with a call for cooling under low load conditions. The outdoor coil pressure (compressor discharge pressure) is maintained just high enough for a small volume of refrigerant to condense, and the evaporator coil pressure (compressor suction pressure) is maintained so that refrigerant boils off at a temperature just lower than the air entering the coil. This rise in evaporator (suction) pressure is what Bryan is referring to as “floating.” This all works great in Arizona, but if you still need some dehumidification, you’re kinda out of luck. No part of the evaporator coil surface area is at a temperature far enough below the dew point of the entering air to condense any water vapor from the air; the system is operating very efficiently at a sensible ratio of 1.

There are a few different ways to fix this. The most economical, I would think, would be to set the equipment up with a “dry mode” that keeps the compressor speed/compression ratio up, the coil/suction pressure/refrigerant saturation temperature aka boiling point, and indoor fan speed low, but turn the fan up as needed to maintain temperature set point. The regular “cool mode” could stay the same as it is now, so their sky-high SEER rating wouldn’t be affected. This is not how the typical “dry mode” works on most mini-split systems. Daikin has a system with a subcooling coil inside that provides reheat, and it can maintain a narrow temperature and humidity range, but that’s expensive and I think usually unnecessary.

The other issue that comes into play often at least in my experience in the residential market is that 9000 btus/hr or 3/4 ton is still the smallest 1:1 system available, which in the 90s was the right size for a fairly small room. Under current codes, it is the right size for typically a very large area. We often install a 9K system in a room where the load is 2500-5000 btus/hr, so these are always going to run way below full speed and usually do absolutely no dehumidification. Again, fancy and expensive dehumidification features like the subcooling coil in the Daikin probably wouldn’t be necessary in some applications if we could just get a system that was sized closer to the load.

— Joel Becker

 

This article is a year old and I’m recycling it because it’s on my mind today. I had a fun conversation with Richard Trethewey on the podcast that has me thinking along these lines today. The link is HERE if the player isn’t showing up.


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?

 

First, let’s get straight that BRAZING is when you use a filler rod that isn’t the exact same material as the base metal but that melts ABOVE 840°F. Soldering is the same but at temperatures below 840°F.

With HVAC rods melting at around 1200°F it confuses me why we usually call it “silver solder” but we will often also call it brazing rod. The best term to call it a “brazing alloy” and I try to remember it but I often find myself calling it silver solder.

The most common rods used for typical HVAC brazing are 0%, 5% and 15% with several other levels mixed in there.

The percentage is the percentage of silver content in the rod. The only real reason to use lower silver levels is the cost and the difference can have many techs and owners wondering what the difference is.

So the big question is –

Is more silver worth the price?  

First, let’s establish that we are talking about copper to copper applications here because that is the most common use for these rods. In copper to copper none of these phos/silver/copper rods need flux or even benefit from it. The phosphorus allows the rod to self-flux on copper and flux when overused can get in the system and cause more harm than good. Flux is required when joining brass to copper using 15%, just make sure not to use too much flux, a thin layer on the male side of the tubing only is all you need.

The silver increases the “ductility” of the filler and allows it to flow at a slightly lower temperature. This results in a better flow of solder into the joint and a lower odds of cracking with thermal expansion and contraction or with vibration. The increased silver also allows the solder to remain strong when filling slightly larger gaps due to ill-fitting copper.

Have you ever seen a leak in a discharge line fitting that you SWEAR wasn’t leaking when the compressor was installed? This can be attributed to poor brazing practices (failing to pull solder into the joint) and often you will find that 0% or 5% rod was used.

The reason we went to all 15% rod is due to the costs of callbacks and refrigerant. With labor prices and refrigerant prices increasing and technician brazing skills on the decline, we want to give techs the best possible chance of making a connection that will stand up to temperature changes and vibration, especially when we are doing an install or making an expensive repair.

If you are going to use the less expensive rod make sure it won’t be in a location with a lot of vibration, that you get the fit between the tubing and the fitting REALLY tight and that more heat is used to “draw” the solder into the joint.

The biggest mistake new techs make is just “capping” the edge rather than pulling the solder into the joint for a solid bond.

— Bryan

PS – We are big fans of Solderweld products including the round 15% Sil-Sol rods. You can find out more at productsbypros.com

When you ask many people nowadays how to check the charge on a heat pump during low outdoor temps they will say that you need to “weigh in and weigh out” the charge. While this may be an effective method it isn’t always practical.

Now… If you are making a refrigerant circuit repair, weighing out and weighing in makes perfect sense, especially since microchannel condensers and scroll compressors make pumping down less viable anyway. But there are many cases where you just need to check the charge to make sure the system is working properly and in these cases, weighing in and out would be plain silly.

I originally wrote this guideline back in 2003 and truthfully, not much has changed since then in regards to checking a heat mode charge on a heat pump.

Step #1 – If there is any frost on the outside unit get it completely defrosted first.

Step #2 – Check all the obvious things first, filter, coils, blower wheel etc… If the unit isn’t clean it will be really hard to check.

When charging in heat mode Read manufacturer specifications first. Lennox gives specific instructions for charging their units in below 65˚ outdoor ambient conditions. It involves blocking off the condenser coil with cardboard (or even better using a charging jacket) while continuing to run the system in cool mode. Lennox gives specific instruction for how high to raise the head pressure, and what level of subcooling you should expect.

Remember that in heat mode on a heat pump the evaporator is outside, and the condenser is inside. This is important because in cool mode a dirty air filter caused low airflow on the evaporator. This would typically cause a low suction pressure, and a low superheat. In heat mode, a dirty air filter causes low airflow across the condenser. This can cause Extremely high head pressure. In heat mode, a dirty outdoor coil can cause a low suction pressure.

As an example, Trane includes a pressure curve chart with many heat pump condensing units. Be sure to use the scale all the way to the right that says heat mode. Indoor and outdoor dry bulb temperatures are necessary to use the Trane pressure curve. Carrier supplies many heat pump condensing units with a pressure guideline chart. Carrier only wants the heat mode pressure chart used as a guideline, not as a charging tool. Always reference manufacturer guidelines before setting any charge.

100˚ Over Ambient Rule of Thumb

Even though manufacturer specifications should be followed, there are some basic guidelines that will aid in charging and diagnosis in a pinch. The most widely quoted rule of thumb is the 100˚ – 110˚ over ambient discharge rule. This guideline states that a properly charged unit will have a discharge line temperature of 100˚ – 110˚ above the outdoor temperature. If the discharge line is too hot add refrigerant (If the charge is the issue and not another problem). If the discharge line is too cool remove refrigerant (again only if the charge is diagnosed as the issue).

Keep in mind that this rule only works if you are close to being in the correct zone. For example, an extremely overcharged system with an outdoor TXV can actually show a high discharge temperature. It’s just a rule of thumb and you shouldn’t reply too heavily on it.

First off, the photo above was taken in 2003 so give me some slack on my gauges. Nowadays I would be using my Testo 550’s.

To give a simple example using the 100˚ – 110˚ over ambient rule. If it were 60˚ outside you could say by the 100˚ – 110˚over ambient rule, the charge is about correct. If it were 30˚ outside the 100˚ – 110˚ over ambient rule would show undercharge (or other conditions that can cause high discharge line temp see this article) . If for example the discharge temperature were 210˚ with a 150 P.S.I. head pressure and a 10 P.S.I. suction with a 50˚ outdoor temperature; this would show an extreme undercharge. Subcool and superheat can still be checked in heat mode, the problem is since there are rarely any set guidelines it is difficult to tell when the charge is set correctly by simply checking subcool or superheat alone. Generally, you will see normal superheat (8-14) on a system with  heat mode TXV and the subcooling will generally be a bit higher than usual, especially when measured outside.

Suction Pressure / EVAP DTD Rule of Thumb 

Another common old school rule of thumb is suction pressure should be close to the outdoor temperature in a R22 system. However, this rule of thumb (obviously) does not work on an R-410A system. A more applicable guideline is 20˚-25˚ suction saturation below outdoor ambient. This means if it is 50˚ outside the suction saturation temperature should be between 25˚and 30˚ (on most systems).

Head Pressure / CTOA Rule of Thumb

Because the evaporator coil is substantially smaller than the condenser you will usually see higher head pressure (condensing temperature) in relationship to the condensing air, in this case, the indoor air. This can vary a lot depending on the age / SEER of the unit, the size of the coil and how the indoor airflow is setup but generally will be 30˚ – 40˚ condensing temperature over the indoor dry bulb.

Checking Without Gauges 

Here are some quick tests you can do on a heat pump to confirm it is operating close to specs without using gauges when the coil is frost-free and the outdoor temps are 65˚ – 15˚.

  • Check the discharge (vapor) line, it should be 100˚ – 110˚ over the outdoor ambient temperature
  • Suction line Temp should be 5˚ – 15˚ cooler than the outdoor temperature
  • Liquid Line should be 3˚ – 15˚ warmer than the indoor temperature
  •  Delta T indoors will vary greatly depending on the outdoor temperature.

If anything looks off, go ahead and connect gauges to verify further…. and like I said several times already, follow manufacturers guidelines.

The best way is to verify total system capacity (with heat strips off) using dual in duct thermometers and manufacturer specs but I understand how challenging it can be to ACCURATELY verify system airflow so it likely won’t always be your first move. We are a big fan of MeasureQuick around our business so I would suggest checking it out for this.

— Bryan

I’m far from a country boy but I did grow up in a rural area with animals, playing in the woods and cleaning out chicken coups. Like many of you, we would play most of the day outside without our parents knowing or worrying about where we were.

Was that an “unsafe” way to grow up?

I guess it wasn’t always perfectly safe but it did result in a lot of unintentional learning as we navigated the world around us and gained experiences and feedback via trial and error.

It’s undeniable that one of the quickest and most reliable ways to learn is to try and fail until we get it right.

It’s how you learned to ride a bike, rollerskate and probably how you learned to swim.

Like David Sandler said –

You can’t teach a kid to ride a bike in a seminar

We know it’s true but so often we attempt to teach topics through talking and reading and writing and watching rather than allowing people to learn through good old trial and error.

The problem with the “trial and error” method of learning professionally is the “error” part of the equation and the potential cost of those mistakes.

Learning From Mistakes Without Disaster

I have a friend who works as a nuclear analyst for power plants. He learned much of what he knows in the Navy while working on a nuclear submarine. On a nuke sub you can’t afford to “learn from your mistakes”, a mistake that could kill everyone and possibly bring an end to civilization isn’t a mistake you can risk. In these mission-critical environments, the military doesn’t resort to teaching the book over and over without practice. Instead, they do drills and work through redundant checklists with hands-on practice over and over and over.

It isn’t that they remove practice and trial and error… far from it. Instead, they allow the trial and error to occur in an environment where the mistakes are controlled in a way that can NEVER result in a mistake in real life.

In other words…

They don’t practice until they get it right. They practice until they can’t get it wrong.

Previous generations understood the importance of drills and practice where more modern education has focused on cognitive understanding as the foundation.

Understand it first and then you can do it. It’s as if understanding all about a bike, the chain and how it made, the gears, the brake mechanism etc… must be learned first before a kid should get on the darn thing and learn to ride it.

Often it’s nerds like me that try to force-feed new people a bunch of technical mumbo jumbo because it interests me rather than helping them get on the bike so they can learn how to turn and peddle.

Applying Trial and Error Into HVACR

We can all agree our trade faces an honest to goodness shortage of skilled workers that is only getting worse. We can sit in our ivory palaces and pine away about how to give everyone a perfect education with every detail listed out and taught in a nice clean classroom but it won’t work and it’s too little too late.

In order to get people trained fast we need to allow them to put their hands on tools and equipment in realistic situations and practice, practice, practice until they can’t get it wrong. We need to shorten the list of things we expect workers to know in their brains before we start to allow them to experience it.

After talking to world-class, innovative instructors like Ty Brannaman with NTI I am learning that narrowing down the curriculum and giving more tool time earlier in the training is leading to much better outcomes.

This doesn’t mean that we aren’t teaching safety and compliance but that we are teaching it as a part of drills and practice rather than separate from it.

It means practicing on equipment over and over with modern tools and techniques. It means charging, recovering and evacuating over and over until they can do it in their sleep. It means wiring and diagnosing electrical issues that will actually be seen in the field on the sort of equipment they are likely to see.

It means practice and trial and error before being so heavy-handed with books and theory.

What are your thoughts?

— Bryan

 

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