Understanding Psychometrics is the entire basis for this business. The chart, the process and the intimidation with regard to the understanding of this fundamental part of our business is what is keeping the widespread application of this valuable service tool from being used to its full potential.

If you own a service company, this chart and the ability to use it in everyday situations is absolutely vital for every technician. I have been all over the country settling disputes between contractors and business owners who have felt that equipment is not performing to its full potential. Sadly, it’s usually only when attorneys get involved that this tool is even considered. In reality, start-up is when its true simplicity and ability to absolutely zero in on system operation can be readily appreciated.

This is why, as a business owner, it is in your best interest to have the work force you command trained in the everyday uses of this valuable service tool. I find it entertaining when I show up on a job site that is in dispute and pull out the chart, place it on the table and get out a sling Psychrometer that the room gets silent and the other parties take a step back, hence, Air conditioning Voodoo. It’s not understood, so it must be magic. The only things missing are the chicken bones. The truly great thing, though, is that it’s simple!

The basic chart is broken into dry bulb temperatures, wet bulb temperatures, and has a cross reference for relative humidity and grains of moisture or water content—all components of our business. A technician starts with a simple thermometer and takes a dry bulb temperature, meaning the bulb on the thermometer is dry. Next he takes a wet bulb temperature—this is a thermometer with a sock on it that is wet. This causes an evaporation or cooling effect on the thermometer allowing you to have two reference points to plot on the chart.

Do this for return air and again for supply air, and you now have four points from which to plot and to use to help determine true enthalpy removal and the capacity of the equipment you just installed. This is a good thing to know, otherwise, how you can protect yourself against customers who say “the equipment doesn’t work, take it out”? What about salesmen who either oversell or undersell a piece of equipment? They should know how this works as well.

The other determining factor for the overall result is for the technician to be able to find true CFM. This is a measurement that has to be accurate because the base line is total delivered CFM. I cannot tell you how many times I have been in the field and the standard answer is, “the air flow is good”. What does that mean? Will it blow your uncle’s toupee off his head or blow the cat off the register? How can you determine how something is working if you do not know the proper way to determine it? This entire business is subject to air flow. Too much, too little or poor design.

With the advent of higher and higher SEER equipment it is crucial to get it right on the installation with regard to air flow because, if you do, the capacity will follow. Train your People! Expect craftsmanship! Those that know why lead those that know how.

Bruce Porter is a Senior Application Engineer with Johnson Controls, Inc. York division, and an instructor at Metro Technology Center, Oklahoma City. He can be reached at Bruce.L.Porter@jci.com