Monthly Archives: April 2013

OK…you’ve completed your HVACR education and now you’re looking for a job. And, maybe one of the elements of your training program was on the subject of a job search, which covered things like going beyond the classified ads to find leads, writing a resume, and wearing the right clothes for an interview.

No doubt, all that stuff is important when it comes to finding and securing a position as an HVACR technician. And, I’ll get to those things in this series, but for this segment I want to zero in on one issue relative to interviewing and understanding what the person on the other side of the desk may be thinking about you as you’re sitting there trying to make sure that you come up with the right answers to questions.

One thing that’s on their minds is  a concept known as wiffimm…actually WIIFM, which describes the idea that everybody spends a good deal of time being tuned into their favorite radio station, WIIFM…What’s In It For Me.

Selfish? No, just being human, and just doing good business. If someone is considering hiring you in order to install equipment or run service calls, the bottom line is… well, they have a bottom line. And they are trying to figure out if what happens when it’s all said and done is that you’ll be a profit center for the company.

So, once you come to an understanding that this isn’t just evil, sinister greed on the part of an employer who only thinks of you as a number and would toss you out in a heartbeat once they’ve used you up (c’mon, you know better than that), you can wait for an opening during the interview and let them know you understand how the world works when it comes to an employer/employee relationship.

Often, this opening comes in the form of that question that service managers often use during an interview, “Tell me about yourself” (a question that I, like everybody else, used to ask when I interviewed someone, but I soon learned that I could do a lot better in the interview process… but, I digress), and then they sit back and hope that they’re going to like what you have to say.

When you’re presented with this opportunity, here’s one suggestion on how you can respond:

“Well, I’m no business expert, but I’m confident that I know what it takes to be a good technician and do things right the first time so that the revenue I generate for the company will cover what I’m getting paid and then some.”

And, once you’ve responded with an answer along this line, be prepared. It’s likely that nobody has ever answered that canned question in that manner, so it will take some time for the interviewer to digest the idea that you understand what your job as a technician is: To do the work that needs to be done, serve the company’s customers in the best way you know how, and, in the end, contribute to the quarterly profit margin for the company.

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



In Part One of our discussion on the psychrometric chart we discussed 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.

In Figure One below, we’re showing a fourth set of lines, known as the Constant Dew Point Lines.

Figure One

Figure One

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.

The Dew Point Temperature 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.

 The fifth set of lines on the psychrometric chart, shown in Figure Two, run down from the curved line at an angle of about 60 degrees, and they are the Constant Specific Volume Lines.

Figure Two

Figure Two

These lines represent the idea that air has a certain density that changes as the temperature and water vapor level changes.

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).

The sixth set of lines on the chart that run from the curved line to points on a numbered scale above the chart, are shown in Figure Three Below, and they are known as the Constant Enthalpy Lines.

Figure Three

Figure Three

The term Enthalpy means “total heat content”, and these lines are simply extensions of the dew point temperature lines.

The scale shows the total heat content measured in BTU/lb (BTU, British Thermal Unit, which is the common measurement of heat content used in the HVACR industry, per pound). One BTU represents the amount of heat it takes to raise the temperature of one pound of water, one degree Fahrenheit.

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.

And, when we bring together all the lines we’ve discussed so far, the complete psychrometric chart appears as shown in Figure Four below.


Figure Four

Figure Four


In Part Three of this series, we’ll look at how the psychrometric chart is used to provide the HVAC technician with information they need to know about the properties of air as it is being handled throughout the conditioned space in a comfort cooling application.

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









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