Jim’s Blog

HVAC technicians in training are often intimidated when they see a psychrometric chart for the first time since there are six separate sets of lines that are used to plot conditions once temperatures in a given situation are established. However, the chart can be demystified by reviewing the sets of lines individually in skeletal illustrations.

In Figure One below, 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 has the temperature listed on the scale.

The lines shown below in Figure Two, are also 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 allow a technician to take both a wet bulb and dry bulb measurement in a given area, and then plot the relative humidity conditions in the space.

In Part Two, we’ll look at three more sets of lines on the psychrometric chart.

Learn from yesterday…Live for today…Look forward to tomorrow










One of the things that technicians-turned-service-mangers-turned-trainers will discover is that once they’re in the training mode, they will notice things that they didn’t see before….things that help them better understand the process of training overall. I stumbled upon something recently that I didn’t know about training in the restaurant business. Take a look at the illustration below:

 Restaurant Order Ticket2

Can you guess what it is?

Unless you are familiar with Cracker Barrel restaurants, you probably can’t. But, if you’ve ever eaten at one of this chain’s locations, you may be able to figure this drawing out due to the reference to “Peg Game” near the left side of the illustration. And, if I explain further that the “7 and 8” numbers represent “spot/seat” and the two blank boxes to the right represent “Drink/Appetizer” and “Meal”, you might be able to guess what this partial illustration is representing. I say ‘partial’ because it’s a bit too large to show all of it here and make sure you can make out the important part of it, which are the numbered boxes, standing position and the circle.

What you’re looking at here is the bottom section of a page from the tablet you don’t pay much attention to when you are ordering in a restaurant. The entire page is numbered from 1 through 8, which means it’s designed to accommodate up to eight guests at a table. Note the “You Are Here” reference and the positioning of the feet. If you are the server, and you’re taking care of a table that has only two people, the diagram shows how you number the guests based on how you’re facing the table. And, if it’s, as they say in the restaurant business, a four-top, the illustration shows how to list the four guests there correctly. And, if a server is taking care of a table of eight…well, you get the idea.

So, what is all this about? It’s about preventing something that shouldn’t happen in a restaurant when the meals are being delivered. With this simple system, the server is not only training when they start work, but they have ready reference every time they approach a table (until it becomes a familiar habit). And, what is being prevented here is a server, or a server being helped by other servers in a situation where there are several guests, mixing up the delivery.

Think about it….you’re out for breakfast, lunch or dinner, and you place your order. Then, while you’re enjoying a conversation with your partners at the table, the food arrives, and the server sets your order down in front of somebody else, and what winds up in front of you is the order for somebody else, and….now, you’re not enjoying your experience at this restaurant.

However, with the graphic reminder at the bottom of the order ticket page, the odds of this happening are reduced, not only if your server is new on the job, but also if they have more experience, and they make it  habit use the graphic they are so familiar with to keep themselves on track as far as not mixing up orders.

For a service manager who is tasked with maintaining a proactive in-house training program, the same idea applies. Presenting a training session is one thing….making sure that technicians have access to information they need in the field to keep them on track and doing the best job they can do is another.

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


One of the premier HVACR publications conducts an annual contest to name the best contractors to work for. In order for the contest to be fair, there are several size categories because, after all, an HVACR company that has 125 employees can do things differently than a company that has less than ten technicians in the field. And, the contractors that compete for the top award in each category are evaluated on many different points relative to the management of their business and the systems they set up so their employees can do their job, because, like I said, there are several different size categories, and large companies do things differently than smaller organizations. However, when you review the list of winners every year, there is one common thread that stands out for each of the companies…large, medium or small…that win the top prize.

Each and every one of them has an active, well-structured, in-house training program.

Of course, setting up an in-house training program is often easier for larger contractors. They have more resources and often have a person on staff whose only job is to develop and manage the in-house training, and, more often that not, be the main presenter for the regularly scheduled sessions. However, when it comes to smaller contractors, the harsh reality is that they just don’t have the same resources at hand. And establishing a program is more difficult, with the task often becoming the responsibility of  an already very busy service manager, or the service company owner.

And, more often than not, the service manager or service company owner with fewer than 10 technicians is not an instructor by craft. They’re former technicians who made the transition to ownership and management. Which means that they need to learn some things about being an instructor and how an adult as a student (which is what technicians are during a training session, whether they want to admit it or not) responds to or connects with the person at the front of the room.

Among them:

1. Never waste an adult learner’s time. Do your homework in order to ensure that the session moves at a brisk pace and provides a wealth of information in a short length of time. I’ve been in situations where I’ve invested several hours in  preparing a 30-minute presentation.

2. Remember that you’re an instructor here, and that means that your responsibility is to manage the session. If a particular individual is dominating the conversation, do what you need to do in order to minimize that situation.

3. Just because you’re dealing with adults, that doesn’t mean that you avoid positive reinforcement. Remember, just being there in a training session (whether the person appears to be super confident or not) is a stressful situation for the an adult in a learning environment. So, by all means be prepared to praise somebody for getting it right or making a meaningful contribution.

Keeping these three simple points in mind when preparing for an in-house training session will make the the event more pleasant for those attending…and for you.

Learn from yesterday….Live for today….Look forward to tomorrow


HVAC technicians are people too.

Yeah, I know that the opening line above is similar to the cutieism that often appears on bumper stickers about dogs or cats, or whatever it is that the driver of that particular vehicle is expressing their devotion to and love for, but I thought it was appropriate; simply because it’s true. And what’s also true is that service managers sometimes forget this basic fact when it comes to supervising technicians. For some reason, it’s easy for people in management positions to think that a person with technical skills…especially a technician who pretty much functions independently as we do in the world of HVACR service…doesn’t require the same amount of coaching as others do in other professions.

Not true.

I’ve said before that part of our job as a service manager is to, well, manage things. Things like schedules, supplies, paperwork flow, etc…but when it comes to managing people, it’s not just management. It’s teaching, leading, and uiltimately, coaching. And part of coaching is asking the right questions. Learning to do this takes a lot of time, effort, study, and learning from your mistakes, but it’s worth it.

Here’s a situation where a coaching question can be part of leading and teaching:

You’re about to send a technician out on something that he or she may not be totally familiar with, and you know you need to help them not only build their self-confidence, but also give them an opportunity to motivate themselves. So, you ask if they’re sure about what they need to do, and you get one of those stock answers like, “Well, I’m not sure”, or “I don’t know.”

And here’s your coaching opportunity. Instead of just giving them a verbal pat on the back by telling them you know they’ll be able to figure things out, and that if they need help, they can also check in with you (trust me, if you tell them that, your phone will ring even if they don’t really need to talk to you, but just need to confirm what they already know before they go ahead), ask…

“If you did know, what do you think the answer would be?”

And there you have it; the difference between managing and coaching. It’s giving them an opportunity to think, which is what any person needs to be able to do in order to grow and develop their skills as a professional. Like I said, technicians are people too.

When you ask this question, be prepared to be very patient in what will seem to be a suddenly painful situation in which you’ve made a grave mistake. The seemingly endless silence will be deafening, but, wait…wait…wait, take a deep breath if you have to, and then wait some more. You could cock you head to one side, blink a few times and show your best friendly smile (remember, a genuine smile is one that reaches your eyes) if you have to, but wait. Nine times out of ten you’ll get either a thoughtful response that absoultely nails it, or honest and intelligent questions that will eventually help you lead them to the place you want them to be.

There are many other good coaching questions we can ask that begin with….

Who do you need to be in order to…..?

What do you think is the best way to….?

How do you think we should handle…..?

Or, my favorite: What if….?

Learn from yesterday…Live for today…Look forward to tomorrow



When considering the fresh air requirements in a residence, we can go beyond the 15 CFM per person/1 person per bedroom plus 1 rule of thumb, and use the Total Heat Formula to calculate how much additional load is being introduced into the building. Of course, the reason this is important is that it results in proper sizing of the equipment, enabling it to handle the total heating load in the structure.

Here’s an example….

If a tight 2,000 square foot home with 8-ft ceilings needs to change 25% of the air per hour during the heating season, and there is a temperature difference of 53 degrees between the outdoor air temperature and the indoor air temperature that is being maintained, the following formula calculations will tell you how many BTU’s per hour need to be added to offset the colder air being introduced into the building to satisfy the fresh air requirement.

First, the CFM is calculated based on the cubic foot area of the building and the percentage of hourly air change that is necessary.

So, we can calculate the total CFM necessary in our specific example by plugging in the following numbers:

2,000 x 8 x 0.25 = 4000 ft3/h (cubic feet per hour)

And, then our next step is to refine our concept of time relative to the situation by employing another simple arithmetic step:

4,000 /  (Divided By) 60 minutes   = 67 CFM

And, with the temperature difference….TD…. (53, as mentioned above) and the CFM (67, as we calculated) known, the Total Heat formula will provide the BTU requirement information we are looking for.

By the way, the TD in situations such as this is calculated based on what is known as a “worst case scenario” and is derived from the outdoor design temperature. For example, if the outdoor design temperature in Tucson, Arizona was 20-degrees (“worst case scenario”) and the temperature to be maintained inside the building was 73 degrees, then the temperature difference would be listed as 53 degrees. You can plug your numbers into the formulae mentioned above and research the design temperature information for your particular situation to perform a calculation on any building.

On to our final calculation….

Our Total Heat Formula…..Qs (Total Heat) = 1.08 x CFM x TD…..when employed in our specific example…..shows:

Qs = 1.08 x 67 x 53 = 3,835 Btu/hr.

Which means that when the furnace size is determined for our example residence, we would have to consider an additional heating load of 3,835 BTU’s because our building is tightly constructed, and the HVAC system is designed to control the amount fresh air being introduced into the living space.

Until next time…

Learn from yesterday….Live for today….Look forward to tomorrow.


Fresh air is a necessary component of human health. That’s a biological no-brainer. And, decades ago when a person was inside their home, they still got a lot of fresh air  through the process of infiltration. Air leaked into the house through cracks near doors and windows and other places in the building, and infiltrated into the living space.  So, infiltration is a nice way of saying that the contruction of buildings wasn’t exactly tremendous, and they leaked a lot. I recall one place I lived in. On cold winter days, if you held a match up next to an electrical outlet on a exterior wall, it would go out. Yes, we were very healthy. Cold and shivering maybe, but healthy.

But, of course, time has moved on and buildings are built much tighter now, which means that we still need fresh air to be brought brought into a building; it’s just that now, we have to do it on purpose.

And, of course, the question that is often raised is, “How much fresh air do we need?”

In commercial buildings, there are specific numbers relative to the amount of fresh air an HVAC system needs to bring from the outside and circulate along with the return air throughout the structure. In the case of residential applications, though, things are somewhat different. Since there is really no specific requirement that states the exact amount of fresh air necessary, a ‘rule of thumb’, which says that it’s generally accepted that a person needs 15 CFM (cubic feet of air per minute) of fresh air, applies. And, when it comes to applying another rule of thumb to the building itself, another generally accepted factor is that the number of occupants in a building will be calculated as 1 per bedroom, plus 1.

So, what this boils down to is that in a three-bedroom home, we would consider that there will be four people that need fresh air.

And, 15 x 4 = 60 so the total fresh air requirement for the building would be 60 CFM.

So, when you remove the filter from a return plenum in a gas furnace installation in a new home and look closely, you’ll likely note some kind of system that allows fresh air to be drawn directly from the outside and delivered into the return of the furnace cabinet. It’s quite common to see a 6-inch round flex duct of some sort connected to the return, and the other end is just open (screened in order to keep critters out) to the outside.

Of course, when this outside air is drawn into the structure while the furnace is operating in the  heating mode, the air that’s coming is a going to be cold. And, that means that we need to account for that additional load on the furnace when it’s sized so that it will be able to handle raising the temprature correctly even though we may be bringing in outside air that’s 20-degrees (which is what we consider pretty cold here in Arizona), so that’s the number we would use in a total heat formula in order to determine just how much of an additional load we’re creating with the building’s fresh air system.

I’ll give you an example of that next time.

Learn from yesterday….Live for today…..Look forward to tomorrow.


Depending on which study you read, it’s been estimated that somewhere between 58 and 72 Percent of air conditioning systems are not functioning as designed due to problems with the air handling system. Regardless of whether or not we accept any given number presented by any given study at the time, we have to admit that it’s important that the air flow through any HVAC system be proper in order to accomplish the necessary heat exchange and achieve the desired comfort level. And when it comes to forced-air gas heating systems, technicians can accomplish the task of ‘wrapping their head around’ the concept of proper air flow by understanding the fundamentals of the properties of air….and two formulas.

As far as the properties concept goes, since we always have to start somewhere with a standard, when we consider the properties of air we understand that two of these standard points are:

1. Sea level (14.7 PSI….meaning 14.7 pounds per square inch of atmospheric pressure pressing down on the earth, referred to as 1 Atmosphere of Barometric Pressure). 

2. A temperature of 68-degrees Fahrenheit.

Of course, a change in temperature or pressure will bring about a change in the air itself, but at the standard conditions mentioned above, we can derive two factors, which are:

1. Air will have a Density of 0.075 lbs. per cubic foot.

2. Air will have a Specific Heat of 0.24 BTU’s.

Which brings us to our first formula that HVAC technicians need to understand relative to air flow. When we apply these two factors in a formula along with a factor of time (one hour….expressed as 60 minutes in the formula), we can calculate what is known as The Sensible Heat Factor of Air.

0.075 x 0.24 x 60 = 1.08

And, that number that we arrived at can now be applied within the second formula, which is:

CFM = Qs / 1.08 x TD

And, once we are reminded that the factors in the formula are:

CFM = Cubic Feet Per Minute

Qs = Sensible Heat In BTU’s Per Hour

1.08 = Sensible Heat Factor of Air

TD = Temperature Difference Between Return and Supply Air….

….We can undersand that a manufacturer designs a gas furnace, this formula, along with other factors, are used to determine the size of the squirrel-cage blower and the horsepower rating and speed of the motor that ultimately determines the amount of air flow through the furnace cabinet.

To illustrate the formula, we’ll consider a specific gas furnace and plug in the necessary numbers to make it work.

Our equipment will be an 80,000 BTU furnace that has an efficiency rating of 80%, which means that the actual heat output (Sensible Heat Factor in BTU’s Per Hour) can be calculated as follows:

80,000 x 0.80 = 64,000

And we’ll also determine that our return air temperature will be 70-degrees, and that our supply air temperature will be 130-degrees, which means we can calculate our TD as follows:

130 – 70 = 60

As our next step in explaining the process, we’ll again present the original formula as….

CFM = Qs / 1.08 x TD

 …Which means that with our numbers plugged in, it reads as:

CFM = 64,000 / 1.08 x 60

…Which works out to:

CFM = 64,000 / 64.8

…Which means that what we have to do is divide 64,000 by 64.8, in order to arrive at:

987.65432 Cubic Feet of Air Per Minute

All of which boils down to the fact that this particular furnace needs 988 CFM traveling through its cabinet, along with properly designed and installed duct system, in order to accomplish the proper temperature rise, which accomplishes the intended goal of proper operation and achievement of the desired comfort level in the building.

In America, medical doctors see a patient and go through a series of procedures to make a diagnosis. And, HVACR technicians also go through a series of procedures in order to make a diagnosis…..in other words, troubleshoot to find the source of the problem with a given piece of equipment.

In other cultures, which we would describe as “Third World Countries”, a medical doctor doesn’t accomplish their diagnosis of a patient in the same way we do in America. Instead of of seeing a patient in an office, the doctor moves in with the patient and their family. The simple theory here is that the doctor can observe the patient’s entire life experiences and find out the real root of the problem.

And, sometimes, taking this simple approach can work in troubleshooting an HVACR equipment problem.

As an example, here’s a troubleshooting story that Chuck Peltz of Clermont, Florida shared with us.

“About 20 years ago,  I had a temp job with a national motel chain, servicing their AC units. There was restaurant attached to the motel, and I was approach by the food manager to see if I could find out why they were not able to keep products frozen in the freezers.

I did a quick basic check of the temperatures/pressures, check for dirty evaporator and condenser coils. Nothing seemed unusual at the time I was checking. I stopped by every couple of days to do a quick visual, and the problem was still apparent.

On about the 5th visit at about 2.00 in the afternoon, I noticed that the freezer door was wedged wide open by a wooden chair.

Seated in the chair was a very large, middle-aged female, Southern-type cook, snapping beans and peeling potatoes for the next meal. A casual conversation followed, and I learned that this was an almost daily routine, as the kitchen was ‘too darn hot’ to work comfortably.

 My findings were passed on to the food manager.”

Yes, troubleshooting is sometimes so very simple.

If you have a troubleshooting story you would like to share, get in touch.

Learn from yesterday…..Live for today…..Look forward to tomorrow



Mankind, for many hundreds of thousands of years, has been involved in relationships of all kinds. Some related to survival in our early existence, and today, some relationships are romantic, some are business-related, etc…. Whatever the relationship, one of the innate qualities of mankind is that we want all relationships to be based in honesty. But, sometimes, when a relationship isn’t all that important to us, we let the honesty thing slide because it’s more effort that it’s worth to deal with (and certainly not a productive use of our time to dwell on it), while in other cases, we absolutely insist on total honesty in our relationships.

One case in which we can all understand we should just let go and move on regarding honesty in a relationship is when you go on a cruise. Cruise lines have a rule about passengers bringing their own liquor on board, whether it’s brought on when you first board the ship, or if you happen to purchase liquor at a port-of-call so you can take it home with you. The rule is a simple one….you can’t bring it on at the beginning of your journey, and if you purchase some along the way, you can’t keep it with you when you come back on board.

And, the explanation that the cruise lines offer relative to this rule is that it could result in an unsafe situation for a passenger who consumed too much alcohol….things like, they would be more apt to stumble and fall on a moving ship in rough seas, or they may even fall overboard if they had too much to drink. So, based on that explanation, if anybody tries to bring liquor such as vodka or gin on board a cruise ship by hiding it in a water bottle, security personnel know how to check for that scam and confiscate the contraband. And, if you decide to purchase a bottle of a rum in Panama that you can’t get in the United States, or a specialty tequila in Mexico that you can only find there, when you re-board the ship, your purchases will be confiscated for the duration of the cruise, and then returned to you some time after 8PM on your last night on board.

So, everybody who has ever been on a  cruise knows the rules, and they know what the cruise line explanation is. However, everybody also knows that the real reason for the liquor rules is that the cruise lines sell alcolholic drinks, and if passengers could either BYOB or purchase liquor in a foreign port and take it to their cabin, then the cruise line would wind up selling fewer drinks. And, if a person was hell-bent on getting so snockered on a cruise ship to the point where it would be “unsafe” for them, they could certainly do so by purchasing alcoholic drinks on board. Which means that the cruise line isn’t being honest. They’re creating a situation that allows them to generate more revenue under the guise of ‘passenger safety’.

And, there’s no sense in wasting any time and energy on this rule that is based in a less-than-honest motive. After all, you’re on a cruise to have a good time, and no matter how right you are about the truth in this case, it’s not going to change. So, sit back, enjoy yourself, and let the dishonesty go. Have a few drinks if you want, and turn in your foreign port liquor purchases so you can enjoy them at your leisure when you get back home. Yes, somebody is being less-than-honest with you, but it’s no big deal.

But, don’t let this study in cruise line policy diminish the importance of your dealings with your customers. They will live with the unimportant dishonesty they encounter on a cruise line, but they will have zero tolerance for it when it comes to entering into a business agreement with you to maintain or repair their HVACR equipment. Keep in mind that the number one thing that prompts some one to call a service company is the word-of-mouth advertising they hear from their family, and friends and neighbors. If you are honest with your customer, they’ll tell 10 people about you. If you’re dishonest (of they perceive that you were dishonest in any way with them, which makes it your job to make sure that doesn’t happen) they’ll tell 100 people about you.

Until next time….

Learn from yesterday….Live for today….Look forward to tomorrow




This is a story about a FedEx driver/delivery person who decided getting paid was more important than doing the job properly.

A young couple in Nashville, Tennessee, like many 30-something couples these days, are into juicing….fresh vegetables and fruits fed into what is basically a seriously beefed-up blender, creating an end product that is healthy and pretty much free of chemicals and other things that aren’t good for us. So, since a sister in Tucson, Arizona had a birthday coming up, the couple decided to send her a juicer.

And, so they ordered it on-line, and it was shipped via FedEx Ground….

And FedEx delivered it…..by throwing over the fence into the yard.

Now, on the surface, this story might seem to be about nothing more than an un-motivated, lazy employee, but as you can see by my title and opening line, there could be more to this story, and based on what I know about the shipping business (which, I admit isn’t a great deal) I’m betting that there is more to it than just laziness and inexcusable behavior on the part of an employee.

The reasoning behind my opinion is that since I am regularly on the receiving end of shipments due to on-line purchases and business purchase situations, I’ve had a few brief discussions with drivers and discovered some things that aren’t necessarily common knowledge. For example, while some companies that deliver things to your home or place of business (UPS for example) employ drivers who are just that….employees who are paid an hourly wage plus benefits to drive a company-owned truck and deliver packages to their customers, other companies have a system in which not all drivers are exactly an employee, and not all trucks are exactly company-owned.

Instead, the truck that shows up in your driveway or in front of your store or shop is owned or leased by the person doing the driving, and, under contract with a major, branded, well-known shipping company, is paid by the package. Which, by the way, is a system that I’m all for…I think it’s truly a wonderful idea to create opportunities for small business of all kinds. Heck, that’s how it works for most of us in the HVACR business, and I personally wouldn’t take back 99% of the experiences I’ve had as an independent service company owner. So, like like I said…..bravo….let people have opportunities for independent employment. It’s an essential element of the heartbeat of American business and I think it’s one of the greatest things we have going for us in the United States.

But, in this case, I’m convinced the system broke down and resulted in horrible, inexcusable, unbelievably bad behavior on the part of a FedEx driver/delivery person.

Sure, there was a fence and closed gate around the property. And sure, there was nobody right there in the yard at the moment so the gate could be quickly opened, allowing for a speedy and efficient delivery of the package (which wasn’t ‘just a package’, it was a gift that somebody decided to send to somebody else, and they trusted that it would be delivered in a professional manner that would ensure that it got there safe and sound, because as the customer in this scenario, that’s what they had every right to expect would happen regardless of the structure of the delivery system) but, what I’m convinced happened here is that somebody decided it was more important to get paid for that package right then and there rather than leave a notice that would result in a return trip to get the job done correctly.

(Author’s Note: In order that you understand just how I feel about this type of situation, re-read the above paragraph, note again the italics, and imagine that the well-known comedian Lewis Black is telling this story.)

So, what is the lesson here for HVACR technicians who provide a service to customers and, as an arrangement with their employer, part of their compensation package is based on commission or bonuses?

Never lose sight of what your responsibility is to your customer. Never cut corners. Always do the right thing for your customer, even if it doesn’t result in getting compensated immediately.

Because, there’s more to your job than just getting paid.

(Another Author’s Note: If somebody from FedEx wants to tell me that I’m wrong about what happened regarding that juicer delivery, by all means, get in touch. I’ll be happy to make sure I’m correct.)

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



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