It’s a documented (and unfortunate) fact that a significant percentage of HVAC refrigeration systems that have been serviced, or checked for seasonal operation on a regular basis, are overcharged. The underlying cause behind this problem is the misinterpretation of a suction side pressure reading that appears lower than normal, leading the technician to the conclusion that “adding a little gas” will bring the operation of the equipment to a higher level of performance. However, when refrigerant is added to a system without considering other factors that could affect the low-side pressure reading, the result is a negative effect on the performance and efficiency of the equipment. And, the factor at the top of the list regarding the proper operation of a refrigeration system is its relationship to the volume and velocity of air flow through the indoor coil.

Looking at this idea from a simple perspective, we’ll first consider the general approach of actual coil temperature and how it relates to what your gauges should show when you check a low side pressure. Generally, when considering the fundamental design of a tube and fin coil, it is common to find that the average temperature of the coil is about 5-degrees warmer than the refrigerant in the coil. What this comes down to is this: If a technician performed a simple temperature test of a comfort cooling system indoor coil at an approximate mid-way location with an accurate digital device, and the result was a 50-degree coil, the actual refrigerant temperature should then be 45-degrees. In Figure One, we’re showing the pressures that would result in both an R-410A and R-22 system with the 45-degree temperature we calculated.

Figure One

Figure One


From a theoretical point of view, this simple example explains the process of temperature affecting pressure. If the heat load in the building was found to be minimal once an accurate temperature was recorded, a lower suction pressure would be expected. And, a higher-than-normal heat load would result in a higher indoor coil (and subsequently, refrigerant) temperature, which, in the end would result in an increase in suction pressure. The point to keep in mind is that a properly charged refrigeration system in conjunction with correct air flow will allows the equipment to operate at the evaporating and condensing temperatures necessary for the efficient transfer of heat out of the building. The partial temperature-pressure chart in Figure Two explains this point further.


Figure Two

Figure Two


When we apply the 5-degree rule, and consider a 45-degree coil in a situation in which the air flow is correct, we arrive at the conclusion that a suction pressure of 118.1 could be expected for an R-410A system. And, considering R-22 equipment, the suction pressure could be as low as 68.6 PSIG.

What this comes down to is that, when accomplishing PM on a comfort cooling system, we can consider the temperature-pressure information above in conjunction with performing a simplified evaluation of air flow performance of the equipment. (See Figure Three).


Figure Three

Figure Three


With outdoor ambient temperature recorded, liquid line temperature measured, and superheat considered relative to manufacturer’s charging charts, four simple air flow temperature checks can provide valuable information about air flow through the duct system.

With a dry bulb temperature measurement accomplished first at the return air grille, and then finding a significant temperature difference with a second measurement at the point where the air enters the evaporator coil, the indication is return duct system leakage and/or insufficient insulation. A difference in wet bulb readings that ultimately shows a change in specific humidity indicates duct leakage that needs to be corrected. The same principles apply to differences in dry bulb and wet bulb temperature readings found between the leaving point of the evaporator coil and the supply register.

With these fundamental tests accomplished, and conditions corrected when necessary, the groundwork has been laid for further necessary testing to ensure the efficient operation of the equipment.

Learn From Yesterday…..Live For Today…..Look Forward To Tomorrow


When a technician finds that a three-phase motor has failed, replacing the motor is only the beginning of the repair. A critical thing to consider is whether or not the three phases of current applied to the motor are not in a stage of imbalance, which could be the underlying cause of the motor failure, and could shorten the life of the new motor. Consulting NEMA (National Electrical Manufacturers Association) Standard MG1-14.35 offers information on this subject. It reads:

Three phase induction motors are designed and manufactured such that all three phases of the winding are carefully balanced with respect to the number of turns, placement of the winding, and winding resistance. When line voltages applied to a poly-phase induction motor are not exactly the same, unbalanced currents will flow in the stator winding, the magnitude depending upon the amount of unbalance. A small amount of voltage unbalance may increase the current an excessive amount. The effect on the motor can be severe and the motor may overheat to the point of burnout.

From a technician’s perspective, this means that our responsibility is to make that that the voltages applied to each phase are evenly balanced as closely as possible, and the most effective way to determine the condition of the electrical supply is use a professional grade digital meter in order to obtain accurate measurements that will provide us with an average.

On the subject of the effects of imbalance, the NEMA standard also states:

The effect of unbalanced voltages on poly-phase induction motors is equivalent to the introduction of a “negative sequence voltage” having a rotation opposite to that occurring with balanced voltages. This negative sequence voltage produces in the air gap a flux rotating against the rotation of the rotor, tending to produce high currents. A small negative sequence voltage may produce in the winding currents considerably in excess of those present under balanced voltage conditions.

What this means to technicians is that when there is excessive current draw caused by a voltage imbalance, the end result is that the motor will operate at a higher-then-normal temperature, which can lead to premature failure. From a mathematical perspective, the percentage increase in temperature rise will be approximately two times the square of the percentage voltage imbalance. What this boils down is that what may seem like a small problem is actually a big problem. For example, a motor operating with a  voltage imbalance of more than 2% will experience a temperature rise that is more than 10% above normal, And, yes, a 10% excess, when it comes to motor operating temperature, is a big deal.

To understand the importance of proper phase-to-phase voltage balance, consider an example….A 220-volt, three-phase motor that is operating with the following voltage measurements.

From L1 to L2: 216 Volts        From L2 to L3: 223 Volts         From L1 to L3: 225 Volts

With accurate measurements accomplished, the next step is to find the average of the three readings. We do this by adding the three readings together, then dividing the total by 3:

216 + 223 + 225 = 664 

And….664 / 3 = 221.33

With an average calculated, we’re then going to apply that number individually via subtraction to each phase voltage reading to find out how much each individual phase is out of balance. One important factor to keep in mind about this step in the process is that we need to wind up with a positive number when we subtract. So, we need to ask the question….Is our calculated average voltage higher than any of the individual voltage readings we found?

The answer to that question is yes. One of our voltage readings (L1 to L2) was 216 volts, and our average is 221.33 volts, so our subtraction for each individual phase-to-phase reading will look like this:

221.33 – 216 =  5.33 Volts

223 – 221.33 = 1.67 Volts

225 – 221.33 = 3.67 Volts

Now, for those who easily wrap their heads around mathematics and formulas, the one that applies in our next step is:

Voltage Imbalance = 100 x Maximum Deviation From Average Voltage Divided By Average Voltage

And, for those who make sense of things from a less formulaic perspective….when you look at our calculations above, the largest imbalance is 5.33 volts, so that’s the number we’ll use in our next step in finding the amount excessive temperature we’re experiencing in our motor windings. We accomplish this by dividing 5.33 by our calculated average, multiplied by 100. We’re doing this so we’ll wind up with a percentage:

5.33 / 221.33 x 100 = 2.4%

So what we’ve determined with our basic arithmetic is that the motor in our example is operating with an imbalance beyond 2%. And, plugging that number into our next step is going to tell us what our excessive temperature rise is (in a percentage) in regard to this motor. To do this, we’ll take our calculated percentage of imbalance (2.4%) and square it:

2.4 x 2.4 = 5.76

Which brings us to our last step in calculating the percentage of excessive temperature in our motor windings. We need to plug what we know to be the maximum percentage of imbalance (as we said, 2%) into the actual imbalance percentage we calculated (2.4% squared….which gave us 5.76%), and we find:

2 x 5.76 = 11.52% Temperature Rise

An important thing for us to understand relative to this subject is that what may seem on the surface to be insignificant, is in reality a critical issue. For example, studies have shown that when a voltage imbalance reaches a level of 3%, it reduces the life of the winding insulation by one-fourth. And, if we found an imbalance situation that resulted in an excessive temperature of 50-degrees, the life of the insulation would be cut in half.

And, on this subject, I’ll leave you with a final thought:

Working from the theory that, as technical professionals, we need to invest time in studying so we can have a complete understanding of a given subject or situation, and then use the tools available to us to make things simple….in this case, not going through all the steps of calculation we just reviewed…. here is a link to a calculation tool that allows you to plug in your voltage readings and find out if the motor you’re evaluating is operating normally.


Learn From Yesterday…..Live For Today…..Look Forward To Tomorrow



If you were to ask someone in their 60’s about their experience of getting into the HVACR business and learning their craft, you would likely get a detailed story about the experience they could only get by leaving their house every day. It could be about their participation in a union apprenticeship program in which they were on the job for a period of time and attending classes a few evenings a week. It could be about their attendance at a year-long (or longer) trade school. Or, it could be about getting hired by an HVACR service company as a ‘step-and-fetchit’, starting out as a helper and working their way up through installation to service. 

In either of the above situations, the experience was intense. When you showed up for your first day of work or school, you had very little information about the HVACR industry. Even things like basic terms and what they meant, along with the names of the basic components of a refrigeration system were things that you had no idea about, hearing them for the first time from your instructor or senior technician….trying your best to understand what you were hearing, seeing or doing with no advance information whatsoever before your exposure to this new information…..kind of like a deer caught in the headlights of an 18-wheeler. 

My, how things have changed. If you’re interested in getting into the HVACR business today, the information that is available to you before you ever show up in a classroom, workshop, or on the job is staggering….. YouTube videos, blogs, discussion boards, manufacturer’s instruction manuals, etc…it, for better or worse, is out there for you. Of course, you need to know that the information you’re getting is technically and ethically correct and available from someone reputable. That’s a challenge that’s beyond just information overload. But, it’s possible to find good information before you ever show up for your first class or day of work. 

It’s often just one click away. For example, here’s a click that will take you to a series of e-books you can open, view, and learn from: 

ACHR News E Books

If you know of other good information that’s available with just one click, let me know about it and I’ll add to the list here. My email address is . 


Learn From Yesterday….Live For Today…..Look Forward To Tomorrow



Air Conditioning, Heating & Refrigeration News is a weekly newsmagazine for the HVACR contractor covering residential and commercial contracting, and the article below by Ron Rajecki, Refrigeration Editor, provides some insight on service management.


If you’re a service manager, there’s a good chance that one of the reasons you’re in that position is because you were good at something else – such as installing, servicing, or troubleshooting equipment. By demonstrating strong skills in the technical world, you were considered a good candidate to move into a management position. And that’s great.

“Unfortunately, there’s a flaw in this process,” said Jim Johnson, president, Technical Training Associates ( dealing with people is a whole different world than dealing with equipment.”

“Many service managers are promoted to their positions without a great deal of training and preparation in the areas of communication skills, customer service, dealing with different personalities, managing people, or leading a team,” Johnson said in a presentation at a recent meeting of the Refrigeration Service Engineers Society (RSES).

Johnson presented what he called some “hard facts” service managers must face:

• Management is not a popularity contest.

• Management is not easy – that’s why some people either don’t do it well or don’t do it at all.

• The biggest personal challenge many supervisors face is overcoming fears – both their own, and the fears of the people who work for them. These can include fear of change, fear of failure, and fear of not having control over one’s own life.

• People don’t want to be managed, they want a leader. And a leader must lead by example. That doesn’t mean you have to be perfect all the time, just prepare for it to be noticed when you’re not.

• Being an effective supervisor takes dedication, hard work, being open to constant self-examination, and a willingness to hear what others have to offer you in the way of advice, suggestions, or even criticism. Throughout all that, a service manager or service supervisor must be confident about his or her own skills and abilities.



According to Johnson, with most people, what you expect is exactly what you’re going to get. That’s why he suggested that service managers clearly address three items with their team.

“I think every service manager should create three memos and present them to the individuals he or she supervises,” Johnson said. “One is titled, ‘What I stand for,’ the second is titled, ‘What I won’t stand for,’ and third is, ‘What I expect from you.’”

Being clear in these three areas will help prevent surprises for you or your team, he noted, and from a service manager’s perspective, surprises are almost always good things to avoid.



Jeremy Noll oversees nearly 50 residential technicians and 38 commercial technicians in his role as service manager at Isaac Heating & Air Conditioning in Rochester, NY.
He said the formula to successfully running a service department is to hire the right people in the first place, provide excellent training, and then empower them to make the best decisions possible.

“The only way to run two large service departments like we have here is to empower our people and then enable them, and by that I mean stay out of their way,” Noll said.

“Honesty is another good quality for a service manager,” Noll added.

“Let people know where they stand and what the expectations are,” he said. “It’s a two-way relationship and relationships don’t always work, but if you’ve always been honest with a technician then there shouldn’t be any surprises. Finally, be open to change. That’s part of the culture at Isaac and it makes the service manager’s job not only easier, but more fun.”

“There’s nothing better than an employee walking into my office with a new idea,” Noll said. “Whether it works or not is another thing, but without new ideas you never move forward.”

“Communication is the key when it comes to running a service department,” said Joey Brown, service manager at Tempo Mechanical in Dallas. “You should be in regular communication with your manager,” he suggested, “because it is important first to know what’s expected of you. Then communicate clearly what you expect from your technicians.”

Joey realizes that in any workplace there’s always the possibility issues will arise, and an open communication environment becomes even more important. Technicians must know you’re available to be their “sounding board” when they need one.

“You want to make your service department a happy, healthy place to work,” Brown said. “If you hear of or sense a difficult situation in the making, or maybe just spot a technician who looks disinterested in a meeting, reach out to that person and keep the lines of communication open. It might be that that person is unhappy with something job-related such as the on-call rotation, or it could be a personal problem totally unrelated to the workplace. Either way, be proactive or let them know that you’ll do what you can to help. In many cases, all people really need to know that their voice will be heard and that you care about them as a person.”

Kim O’Connor, service manager at Air Comfort in Chicago, said ensuring great customer satisfaction is among her most important roles.

O’Connor told The NEWS she calls a customer as soon as she is made aware that a problem exists, and ask the customer to provide details of what occurred so that she has a clear point of view from the customer’s standpoint.

“I let them know I will check into and get back to them and give a specific time frame for the return call,” O’Connor said. “I contact the technician(s) involved to review information and then determine what needs to happen to get us back on track. I do my best to call the customer at least a half hour before the designated time so he or she understands that their concerns are important to us. If a return visit is needed I also make sure I call the customer back once we have completed the call to ensure everything is resolved to the customer’s satisfaction.”



Johnson concluded by offering a six-part “commitment to excellence” that service managers can live by and share with their teams. At its heart is the idea that the field personnel don’t work for the service manager, he or she works for them, and it is the service manager’s job to make sure the field team has everything they need to do their jobs well.

1. I will move heaven and earth in order to help the people on my team do what they need to do and get it done when it’s supposed to be done.

2. I will consistently work to allow each and every person on my team to learn, grow, and develop as professionals, so they will be enriched in both their professional and personal lives.

3. I will always have one person in training to replace me.

4. I will require commitments from everyone on my team and hold them accountable to those commitments.

5. I will be willing to take responsibility and make the tough decisions, no matter what the circumstances and no matter who is involved.

6. I will regularly ask everyone on my team, “How can I make your job easier?” and “How can I help you do a better job?”

There is no one answer to dealing with all the complexities of running an HVAC service department. But being clear what you want and expect from your people and understanding what they want and expect from you will go a long way toward making things run smoothly more often than not.


If you’re not a subscriber to ACHR News, the information above is a good reason for you to consider adding this weekly publication to your list of trade magazines.


Learn From Yesterday, Live For Today, Look Forward To Tomorrow




It’s a question that is almost as old as the service business itself….”Do you pay your technicians by the hour, or on a commission basis?”
And, as long as the question has been around, there have been people who are adamant about each payment method. On one side, there are those who believe that technicians should never be compensated on any system other than an hourly wage because anything that includes an incentive, bonus or commission will result in customers paying for things they don’t need or want.

On the other side, there’s the group that believes only in a performance-based pay system for technicians because the quality of the work they do is directly related to how they are compensated, and the end result of earning commissions and bonuses is an improvement in both customer service and company profitability.

And, those who express their strong beliefs about being in one camp or another on this subject are often of the opinion that when you consider the issue from the perspective of service management, you have to embrace one philosophy or the other; that there’s no middle ground. Well, like most everything else we do when we’re a leader dealing with people, there are other ways to look at this issue when we factor in human nature.

What I mean by that is that it’s part of the human condition to want to do the best job we can do.

Let’s face it. We are all, from a fundamental perspective, goal-seeking mechanisms. Once we have spent time focusing on mastering a task or achieving a goal that when we first set it was intimidating to say the least, it doesn’t take long for us to begin thinking about what we can do next. And, part of the reason this is true is that when people are just being people, we desire, and enjoy, reaping two types of benefits from accomplishing things and achieving at a high performance level. These two types of benefits are known as intrinsic (that’s on the inside…knowing that we’ve done a good job) and extrinsic (stuff we can purchase, have, see, watch our family enjoy, hold in our hand, or use as we pursue a hobby or recreational activity).

Of course, if one’s hourly wage, accompanying benefits, and working conditions are very sufficient and consistently increasing in accordance with rising living costs in order to ensure that an employee could easily and comfortably pay their basic bills for housing, utilities, groceries, etc…and also have whatever that person considers a sufficient amount left over for recreational activities, then it’s possible that those inherent human needs mentioned above will be met.

And, it’s also true that some jobs are a just a proper fit for an hourly wage, while others are a proper fit for an incentive-based payment system.

However, as you can probably guess by now, I’m of the opinion that hourly and hourly alone is not the best compensation system for a technical professional, a person whose responsibilities include not only troubleshooting HVACR equipment  and replacing parts, but also providing front-line customer service from the perspective of the autonomy that this kind of work both affords and requires.

When a competent, journeyman level technician is in a customer’s home or business, they are essentially “on their own” and “independent”. And, when they’re good at what they do, that’s just the way they like it. If this wasn’t true, then they wouldn’t have been drawn this type of career in the first place.

Sure, they enjoy working with their hands, but they also want to work with people, and they want the challenge of solving their customer’s technical problem, not just because it means that the equipment is working again, but because they know that when they’re working at their craft, they’re also providing peace of mind, convenience, and comfort for their customers. And, as a service manager, it’s our job to support them in accomplishing their mission so they can experience those intrinsic and extrinsic benefits.

Are there horror stories out there about service companies that pay (or paid because they’re not around anymore) technicians on a commission basis? Of course there are.

And one thing you can bet the farm on about these businesses is that when they have (or had) their weekly employee meetings, the service….actually, sales…. manager stomped around the room, getting in people’s faces, demanding to know “How many service contracts did you sell this week?” Or, “How many extra contactors, condenser fan motors, start capacitors or relays did you sell while you were replacing the first part that failed?” Or, “What was your add-on sales total this week?”

And part-and-parcel of this type of business environment is that if a technician’s response is that in some situations, the customer simply did not want or flat-out did not have the resources to purchase a service contract, or there were parts that they determined didn’t need replacing, the manager’s job is to hold up another technician’s numbers as an example to prove that extra revenue is always available if it’s done right.

This is not a customer service environment. It’s a revenue generating environment.

And, the fact of the matter is, a technical professional who is pursuing their mission as described above is not going to stay in this type of environment, which leaves only those technicians who are willing to go along with the revenue-and-revenue-only philosophy of doing business, which no matter how you slice it, is simply dishonesty.

No doubt, dishonesty is an issue in any business. HVACR companies that have been around for generations pride themselves on their integrity and they work hard to maintain their reputation. And when it comes to dishonesty and understanding more about it, there are books on the subject.

Here’s one example:—Especially/dp/B00J5TXATA/ref=sr_1_fkmr0_2?ie=UTF8&qid=1441382470&sr=8-2-fkmr0&keywords=%28Honest%29+Truth+About+Dishonesty%3A+How+We+Lie+to+Everyone+%E2%80%94+Especially+Ourselves%2C+by+Dan+Ariely

In this book, the author discusses the idea that people can be dishonest about anything and everything, and they can make the decision on whether or not to be honest based on an SMORC (Simple Model of Rational Crime). One example of this would be a person who is short on cash, notices a liquor store, and then does a cost-benefit calculation in regard to the risk of getting caught, which leads them to a decision to either go ahead and rob the store, or not.

I have no argument with this logic. It’s simply realistic to understand that any person could, in a particular situation supported by certain factors, along with stress, desperation, etc…could convince themselves to commit a crime. And it’s also realistic to accept that in addition to being capable of committing a violent crime, a given environment in a service company could also prompt some individuals to justify extra parts or services that may or may not be necessary.

How would you know if a particular service company could be subject to actions that might be considered dishonest?

Ask the employees this question: “What is the mission of your company?”

If the answer is “to make money” or “pay expenses and show a profit”, you have your answer. It would be possible for a technician working in an environment where commissions or spiffs are paid to ‘push’ for additional revenue.

However, if the answer you get is a clear, concise mission statement that, in as few words as possible (so that it is easily learned, remembered and recited by everyone in your company) states your mission, which is focused on customer service with integrity and honesty, then you have established the basis for an environment in which you can, with consistent management on your part, ensure that your customers will benefit from the best service possible.

In establishing this environment, you would be providing technicians an opportunity to take ownership of the service calls they perform from the perspective of doing the best job possible for the customer, which would include being aware of additional items and/or services that the customer could benefit from, and, while understanding that “sell” is not a four-letter word, let the customer know about these items/services so they can make an informed buying decision. And taking this approach to establishing a performance-based pay system for your technicians would benefit everyone involved.

Learn From Yesterday…..Live For Today…..Look Forward To Tomorrow


One of the questions frequently asked by a person considering getting into the HVACR service business is about licensing. It can be a confusing subject for several reasons. First, the process of certification is mixed into the question, when in reality, licensing and certification are really two completely different issues. And second, there’s the issue of contractor licensing, which is also a different issue that of licensing individual technicians who have no ownership of the company. And, what confounds the issue further is that technician licensing is sometimes required in some states, in others it is not. 

Sometimes, when someone calls in regard to this subject, a typical phone conversation goes something like this:

“Technical Training Associates, this is Jim. How can I help you?”

“Yes, hello, I need some information on getting my HVAC license.”

“Your HVAC license? Do you mean a license that’s required by your state?”

“Ummm….well, I’m not sure….just whatever license I need to do HVAC.”

 “Perhaps what you’re really asking about is an EPA refrigerant handling certification? We have a DVD that prepares you for taking that exam.”

And, once I bring up the subject of certification rather than licensing, the conversation can go on while I try to figure out what the caller really wants to know about (or, what I figure out is that they simply don’t really know what they want to know about) and, in the end, I usually advise them to check with the appropriate state licensing bureau, local schools and colleges, or, what we refer to here in Arizona as the Registrar of Contractors.

So, to clarify things on the subjects of licensing and certification, here’s some general information:

Certification: There are two types of certifications related to the HVACR industry. One is the type that is required by a government agency. The only one that really fits in this category in all states is the one required by the federal government….The  certification exam related to the Federal Clean Air Act, Section 608 Refrigerant Handling Certification that is focused on the rules, regulations, and fines related to the law, as well as safety, refrigerants and oils, and the fundamentals of refrigerant recovery, the basic components of a refrigeration system, and the refrigeration system cycle. There’s a manual available for study and preparation for taking that exam through ESCO Institute.

The procedure for accomplishing this closed-book certification exam means that the person accomplishing the exam needs to be proctored, and there are resources such as trade schools, colleges, and parts supply companies that are authorized to act as a proctor in cities around the country, so one would have to contact a local resource in  order to sit for the exam. With a passing score accomplished, a technician is allowed to purchase refrigerant, and access refrigeration systems for service purposes.

The second type of certification is industry related. For this type of certification there is no government agency involved, just not for profit entities that coordinate the exam process, and the simple intent here is to show the competency of the person achieving the certification. Information on this type of certification can be found here:

HVAC Excellence


Getting back to licensing….as I mentioned above, some states require an HVACR technician to be licensed, while others do not. Information on state licensing requirements can be found here:

HVAC Training Solutions

Other factors related to licensing for HVAC technicians can involve counties and/or cities that require a technician or a service company to purchase a license, so there’s that issue too.

While it may be somewhat confusing, you can figure it all out by first of all, understanding the fundamental differences between licensing and certification, and knowing what they actually refer to in regard to proving a particular competency on the part of the technician.

Learn From Yesterday…..Live For Today……Look Forward To Tomorrow


This article is based on information from RSES.

Service managers involved in conducting in-house training sessions on the ever-important issue of air flow and HVAC system performance often find that technicians are somewhat intimidated when they need to review a psychrometric chart. (Or, they’re of the opinion that they don’t need to know much about psychrometrics to do their job.) Since there are six separate sets of lines that are used to plot conditions once temperatures in a given situation are established, the chart can be daunting. However, it can be demystified by reviewing the sets of lines individually in skeletal illustrations. In Figure One are the dry bulb temperature lines of a psychrometric chart.

Figure One

Figure One



These lines are properly referred to as “Constant Dry Bulb Temperature Lines” because any point on any given line, each line represents the temperature listed on the scale at the bottom of the chart. The lines shown below in Figure Two, are also referred to as constant temperature lines, and they are identified as Wet Bulb Lines.


Figure Two

Figure Two


These lines run down from the temperature scale on the curved section of the chart at an angle of approximately 30-degrees off of horizontal. The next set of lines shown in Figure Three are the “Constant Relative Humidity Lines”

Figure Three

Figure Three


The top curved line on the chart shown as the 100% relative humidity line is also known as the saturation line, meaning that we no longer have water vapor in the air, but liquid condensing from it. In most situations, many people are comfortable when the humidity level is around 50%. It is usually recommended that the humidity level in a building remain between 40% and 60%.

These first three sets of lines are the basic ones that allows a technician to understand the process of taking both a wet bulb and dry bulb measurement in a given area, and then plotting the relative humidity conditions in the space. This is one of the most fundamental checks a technician can perform in the process of evaluating the performance of HVAC equipment and advising the customer (in language they can understand) what service may be required in order to ensure that their system is performing as efficiently as possible.

Going beyond these three sets of lines; the Constant Dry Bulb Temperature Lines that run from the bottom of the chart to the curved top, the Constant Wet Bulb Temperature Lines that run from an angle of approximately 30 degrees from the curved line to the right, and the Constant Relative Humidity Lines that follow the pattern of the curve line, the fourth set of lines we want to consider are the “Constant Dew Point Lines”. (See Figure Four)

Figure Four

Figure Four


The dew point temperature numbers are the same ones used for the wet bulb temperature scale, but the lines coming from the numbers run directly horizontal rather than at a diagonal. These lines also correspond directly to another listing to the right of the chart which expresses moisture level on the very fine scale of grains per pound. This scale is also known as the Specific Humidity Scale. This set of lines on the psychrometric chart, shown in Figure Five, run down from the curved line at an angle of about 60 degrees, and they are the “Constant Specific Volume Lines”.

Figure Five

Figure Five


The point you want to drive home in your training sessions is that these lines represent the idea that air has a certain density that changes as the temperature and water vapor level changes. And this scale is built on the fact that 1 lb. of air at a saturation temperature of 65-degrees F has a specific volume of 13.50/ft3lb (13.50 cubic feet per pound).

This brings us to the sixth set of lines on the chart that run from the curved line to points on a numbered scale above the chart, shown in Figure Six, and they are known as the “Constant Enthalpy Lines”. The term Enthalpy means “total heat content”, and these lines are simply extensions of the dew point temperature lines.

Figure Six

Figure Six

The scale shows the total heat content measured in BTU/lb. which is the common measurement of heat content used in the HVACR industry. The two kinds of heat that make up total heat are Sensible Heat, which is heat that can be measured, and Latent Heat, which is also known as “hidden heat” and is defined as heat that brings about a change in state, but not a change in temperature.

Before we explore an example of the processes of handling sensible and latent heat, we’ll bring together all the lines we’ve discussed so far; the complete psychrometric chart appears as shown in Figure Seven.

Figure Seven

Figure Seven

Once a technician has a grasp of the basic structure of the psychrometric chart (understanding that there are six separate sets of lines as we discussed) the next concept to discuss is that the chart can be used to evaluate the performance of a comfort cooling system regard to the removal of sensible and latent heat. Sensible heat, since it is simply defined as heat that can be measured, relates to the change in the temperature of an air sample. Latent heat, since it is defined as heat that brings about a change in state but not a change in temperature, is related to change in the level of water vapor in an air sample.

One simple way to explain the concept of the removal of these two kinds of heat and how the psychrometric chart can illustrate the level of a performance of a system relative to comfort via both temperature and relative humidity, is to consider something known as “State Point”, shown in Figure Eight.

Figure Eight

Figure Eight

The two temperatures plotted in this example are 80-degrees dry bulb (red line) and 67-degrees wet bulb (blue line), and the point at which the two lines converge is just above the 50% relative humidity line. The idea to keep in mind here is that once this baseline is established, the psychrometric chart can be used to illustrate the amount of sensible and latent heat that is being removed in a given situation. If the level of sensible heat removal is too high and the removal of latent heat is too low, that won’t result in maximum comfort. (See Figure Nine)

Figure Nine

Figure Nine

 In this example we’ve achieved a significant drop in dry bulb temperature all the way from 80-degrees down to 60-degrees, and from the state point of 67-degrees wet bulb down to 56.3-degrees, but what we haven’t accomplished is a balanced removal of heat. This is indicated by the fact that our relative humidity is now 80%. In Figure Ten, though, we have a more balanced removal of heat that will result in a more comfortable situation.

Figure Ten

Figure Ten

 Here, we’ve only dropped the dry bulb temperature from 80-degrees down to 75-degrees, and the wet bulb temperature from 67-degrees down to 61-degrees, but in the process, we have accomplished a more balanced removal of heat because our relative humidity is now at 45%.

When you present a simplified explanation of the psychrometric chart and add an explanation of a fundamental psychrometric process that applies to the common customer complaint of “not cooling enough”, it’s an important step toward getting the technician to understand the performance of the HVAC system from a whole building perspective, rather than just as a the ‘box’ that provides the cool air.

One of the interesting things about being in the HVACR industry and active in the technical and professional development of technicians is that you never know what inspiration will come about when you’re working on your blog. This is the fourth segment in a series on in-house training programs, and up until I read a Linked-In post by D. Brian Baker about how some people with an academic bent view the education process for trades and crafts, I had a different idea of what this installment would be about. Since I happened upon that discussion, this segment will be about what I read there.

The discussion that Brian started was about the academic community, and some of the comments that followed offered enlightening thoughts about how some think that the difference between an academic education and a trade/craft education is that with academics, people are taught to think, while in the trade/craft approach of “training” (as opposed to educating and training, which is what we in the industry consider it to be) is that people are just taught to, well, just do.

Reading some of the comments on this particular discussion, I remembered a few things…..

As somebody who ran service calls in residential and light commercial applications for many years where customer contact is on a very personal level since technicians are guests in customer’s homes (and some of their small offices that they consider to be a second home), I can attest to the fact that there are two types of customers when it comes to interaction with those who are there to provide a technical or craft service for them. One type is quick to engage in an interchange of mutual respect. A second type of person has a tendency to, as we say “look down their nose” at others. And, in accordance with the aforementioned discussion on the sometimes perceived differences between an academic and skilled craft education, it was, in my experience, that those of the second type were, far more often than not, those who either held an academic degree and worked in what could be commonly referred to as a ‘white collar’ job, or they were married to someone who held an academic degree and worked in a white collar job.

The common term that is often applied to people who act toward others in the way I’ve described is that they are a snob.

And, when I thought about that, I recalled a bit of history on the origin of that term. It came about early in the 18th century as “Sine Nobilia” ( a Latin term that means “not of nobility”) when university professors in Europe were told that they would have to offer admission to some that they considered to be lower class. This term was entered into the margin next to the person’s name in the student registry so they could be easily identified. My personal opinion is that it was noted there so professors could get ‘what they expected’ from these students, and also be able to, when one of these students dropped out, be able to say, “See I told you so” to the entities that were forcing these enrollments.

Well, as it often happens with this sort of thing, it didn’t take long for “sine nobilia” to be shortened to “snob”, and here’s where it gets even more interesting.

When some of these ‘lower class’ individuals did graduate from college in spite of what the professors thought about them, they often had a tendency to, well, treat the people in the communities that they came from differently than they treated them before they went off to school. And the term “snob” took on a new meaning….what we normally think about it today.

And, if you’ve been wondering what all this has to do with your in-house technician training program, here’s the thought that followed what I’ve noted above.

I often have to shake my head about the fact that even today, I have technicians who attend a training workshop, and in the course of our discussions on customer service, tell me that they have negative and disrespectful experiences  in which people ‘look down their nose’ at them, and it bothers them.

My response to this is a simple two-point approach.

1. One of the classic behaviors of a person with low self esteem is that, because they are unhappy with who or what they are (or aren’t), they try to make themselves feel better by putting others down.

2. When this occurs, we should have compassion for these unfortunate individuals rather than be angry or upset because of their behavior. And the reason we should take that approach is that, because we’re human, we could wind up taking some of that negative energy with us to our next call. And our customer there doesn’t deserve anything less than the best we have to offer, not just from a technical and craft approach to doing our job, but also from a customer service perspective.

Learn From Yesterday……Live For Today…..Look Forward To Tomorrow



In Part Two of the discussion on in-house training programs for HVACR technicians I touched on the subject of attitude and how it can affect a training session. In this segment I wanted to look at this subject not just from a technician’s perspective, but from an overall point-of-view.

So I decided to share something called the S.W.E.A.T Pledge.

It’s by Mike Rowe, and I think it addresses the subject of being a Technical Professional in a way that makes sense to all of us.


“The S.W.E.A.T. Pledge”

(Skill & Work Ethic Aren’t Taboo)


1. I believe that I have won the greatest lottery of all time. I am alive. I walk the Earth. I live in America. Above all things, I am grateful.


2. I believe that I am entitled to life, liberty, and the pursuit of happiness. Nothing more. I also understand that “happiness” and the “pursuit of happiness” are not the same thing.


3. I believe there is no such thing as a “bad job.” I believe that all jobs are opportunities, and it’s up to me to make the best of them.


4. I do not “follow my passion.” I bring it with me. I believe that any job can be done with passion and enthusiasm.


5. I deplore debt, and do all I can to avoid it. I would rather live in a tent and eat beans than borrow money to pay for a lifestyle I can’t afford.


6. I believe that my safety is my responsibility. I understand that being in “compliance” does not necessarily mean I’m out of danger.


7. I believe the best way to distinguish myself at work is to show up early, stay late, and cheerfully volunteer for every crappy task there is.


8. I believe the most annoying sounds in the world are whining and complaining. I will never make them. If I am unhappy in my work, I will either find a new job, or find a way to be happy.


9. I believe that my education is my responsibility, and absolutely critical to my success. I am resolved to learn as much as I can from whatever source is available to me. I will never stop learning, and understand that library cards are free.


10. I believe that I am a product of my choices – not my circumstances. I will never blame anyone for my shortcomings or the challenges I face. And I will never accept the credit for something I didn’t do.


11. I understand the world is not fair, and I’m OK with that. I do not resent the success of others.


12. I believe that all people are created equal. I also believe that all people make choices. Some choose to be lazy. Some choose to sleep in. I choose to work my butt off.


On my honor, I hereby affirm the above statements to be an accurate summation of my personal worldview. I promise to live by them.







The thrust behind this is that Mike Rowe has developed a scholarship program for high school students who plan to pursue education in a trade or craft, and in order to apply ( a $15,000 education and training opportunity here), they have to sign the S.W.E.A.T Pledge.

While I like all 12 of the points that Rowe makes in the pledge, 4, 6, 9, 11 and 12 are my favorites.

Learn From Yesterday…..Live For Today…..Look Forward To Tomorrow



More On The Perspective of Fundamentals


Beyond the understanding that new hires or installers in training to move up to service need to have a good grasp of the fundamentals of electricity, refrigeration and psychrometrics, there’s another consideration regarding this subject…..experienced technicians and a review of the basic concepts of HVACR that will help them in the continued development of their troubleshooting skills.

 As a service manager facilitating an in-house training session on this subject, we need to be aware of two important issues. The first, of course, is that we need to be creative in our approach to presenting the basic concepts of how to read wiring diagrams, troubleshoot and test components, calculate superheat and subcooling, and perform static pressure tests as part of evaluating the air flow in a system. What we ultimately want to see is the experienced technician paying attention, participating, nodding in agreement and, when prompted, even contribute information on the subject at hand in order to help bring along those in attendance who are less experienced. That would be an ideal situation; a productive training session that contributes to the professional development of everybody in attendance.

All good.


Happy employees.

Your operation running smooth.

Yes, that would be ideal, and sometimes, getting there means that we need to be aware of a second issue, and deal with it effectively. I’m talking about technicians who have been in the field for a number of years, and the possibility that they may not be as excited as you are to have them in your fundamentals training session. There could be a variety of reasons for this. Perhaps somebody who has been ‘out there’ for five years would look upon the hour spent as a waste of time, especially if they were facing a busy workday. If that’s the case, it could derail your ideal training session described above. Instead of a pleasant experience for everyone, somebody could be sitting there, arms folded, noting the time at frequent intervals, barely tolerating the experience until it will finally be over.

A situation like this not only affects you because you’re looking right at it, but the negativity, even if it’s subtle, can become pervasive, having an effect on everyone attending the session and all the subject matter being discussed. So, how would you anticipate this possibility and handle it?

One thing to consider is that if an experienced technician takes the time to contact you prior to the training to say that since it’s a fundamentals session, they would just as soon pass on attending, tread lightly. Simply dismissing their stated opinion out-of-hand and saying that the session is arbitrary, for example, is not going to be a productive route to take in this situation. My reasoning behind this is simple. I’ve been in situations where a technician may say that they have “5 years of experience” working in HVACR, when in reality, what’s closer to correct is that they have “1 year of experience 5 times over”. And, since our responsibility as a service manager and trainer is to make every effort to coach, lead, and contribute to the professional development of those who report to us, we need to anticipate this possibility and, as I said above, be creative in our approach to presenting the basic concepts, no matter who is attending our session.


Learn From Yesterday….Live For Today….Look Forward To Tomorrow


1 2 3 12

Educators and trainers may
qualify for discounts on selected
training products through
the Esco Group.

HVACR students click here
for student pricing on tools
and training materials

Appliance Repair Training Information


Technical Training Associates
PO Box 2259
Green Valley, AZ 85622-2259
Phone: 520-625-6847


Shopping Cart

Items in Your Cart

Your cart is empty


Click to View a
Training Video Sample


Appliance Repair Training Information

Link To Us

Increase your website traffic with