Virtually 100% of the people reading drive motorized vehicles. Most of us first encountered “wheels” with a baby stroller, but hopefully that was short lived. Our first personal encounter was probably with bicycle equipped with… training wheels. These were an extra set wheels that allowed us to develop our balancing skills so that we could eventually ride easily on two wheels and go much faster, with greater maneuverability and comfort. It is a difficult skill to master, but with the help of the training wheels this process tends to take only a few short weeks. The results are nothing short of spectacular. From our humble beginnings with the bicycle, most of us advance to four wheeled pursuits like cars, trucks and the like. Some very adventuresome folks go back to two wheels albeit with a large motor (Harley’s, etc.) for greater speed and additional thrills! However, everything began with that encounter with those training wheels.
Learning to ride a bicycle is very similar to learning the basic concepts of air conditioning. The “training wheels” in this instance is the ability to accurately determine the load for both cooling and heating. From there, you advance to greater and more challenging assignments such as selecting equipment to match the load and designing ductwork and air distribution systems to provide what the customer is really asking for (and paying money to receive)…COMFORT! The ability to determine the load is not some advanced skill, but the very foundation of our business. I was truly dismayed by the number of contractors that admitted their inability to perform this elementary function as evidenced by the tremendous numbers signed up for the classes held in preparation for the 2010 Code requirements. To their credit, upon recognizing a fault in their skill level on this most basic HVAC requirement, they did seek remedial training. Hopefully, they see that the skill of determining the basic load is analogous to “training wheels.” This isn’t an “advanced skill” but a step toward all the others necessary to be able to properly design systems for their customers.
Remember that A/C is not like a refrigerator that you purchase at a store, bring home and plug-in. Air conditioning is APPLIED EQUIPMENT, by that I mean that the contractor is TOTALLY responsible for determining what is needed. Selecting the correct equipment from the multitudes of options and then correctly installing and commissioning that equipment (perhaps with ductwork) to achieve the goal of comfort and at an affordable operational cost is the sole responsibility of the contractor. The Code really doesn’t determine what should be installed… YOU DO. Some contractors appear to have needed a little push from the Code to encourage them to use the tools necessary to make that determination.
From the above, you may have surmised that I am of the opinion that a Manual J for each changeout is not asking too much. On the residential side the “typical” home in Florida is somewhere around 2100 square feet and depending on a number of factors, that home’s load could be anywhere from one and a half tons to four tons. These factors include: fenestrations (windows – numerous new choices); ceiling type (single assembly, vented or unvented above); internal loads; etc. Obviously, this is a tremendous difference in ac tonnage, but is there one “right answer” to the question. What size? You are going to install a size, what will it be? As the load fluctuates during the day (and season of the year) that “right answer” also needs to be tempered with what is best for the customer for the greatest number of hours and is “Code legal”. Friends, this is what the customer is paying YOU to determine. Many manufacturers offer systems that are “2-speed” or “variable speed” for this reason… does this job require one of them? The Code is merely demanding that you at least use the “training wheels” to aid in determining the size and type system you are going to choose to install. The argument that “it’s the size they had before” or that the load calculation is “on file at the County” just doesn’t get it. Think! You are responsible for that size, not the Code, or the municipality. If the size is wrong using one of the previous two excuses in your defense does NOT relieve YOU of responsibility for the installation. Don’t you want to be proficient in correctly determining the load, selecting and applying the right equipment? Are you willing to advance your training and skills… or are you happy with the “training wheels”?
Looking out for you,
Guest column written by Bob Cochell, a FRACCA Board member and member of the Energy Technical Advisory Committee of the Florida Building Commission. If you have questions or have feedback to give on this article, contact your local chapter office, or contact the FRACCA executive office at email@example.com or 727-576-3225.