by Bill Smith, president of Elite Software

Desktop computers have been around since 1979. Since then, they have steadily gotten more powerful and the software that runs on them more capable. HVAC computer programs are now widespread, and exceptionally affordable, and have become powerful tools for a wide array of applications including load calculations, building energy analysis, service management and ductsizing. Increasingly, HVAC firms find that even minor computerization promotes professionalism, improves profits, and offers important competitive advantages.

One HVAC contractor making the most of the advantages afforded by computers is Air Conditioning Contractors of Alhambra, California, involved in residential and commercial work. Robert Hernandez, president, recalls what it was like in the days before computerization.

"Back then, it was all rule of thumb such as using the inefficient 'one CFM per square foot' measurement for air conditioning. We also used the ever imprecise Ductolator for most duct designs. We simply didn't know important measurements like back pressures and velocities." He admits that occasionally they were not sure of the exact air conditioning tonnage required for a given job. "We often over-engineered an inefficient system, spending more money than necessary, simply from a lack of precision. We might install a duct system that didn't last more than five years. Compressors and motors were overworked and their lives shortened; overall system efficiency was down and we had a lot of problems."

Often after the job was completed, Hernandez would have customer complaints that he would have to take valuable time to correct. "Not only did this create ill will with them, it was wasteful, and unprofitable, to constantly repair jobs that originated from bad designs," he remembers.

In 1990, Hernandez purchased Elite Software's DUCTSIZE computer program and notes some of the improvements it has offered to his business.

He remembers one of the first jobs he designed on his new computer. "It was a restaurant job where the client's ten ton air conditioning unit was not cooling properly and, in fact, had not worked right from the first day of its installation. As the system was old and worn, the client wanted it replaced so I ran the job through the computer after doing a few measurements. DUCTSIZE showed us that we would only need five tons of air conditioning but the client was skeptical. We completed the job in two weeks. The day we turned on the new system it was almost 100 degrees outside and air conditioning pulled down the inside temperature to 70 degrees within seven minutes with the restaurant full of people! With half the tonnage of the old system, the client was very happy. In addition, his first month's energy bill was half than with his old ten ton unit. And, by redesigning it with a computer the client thought I was a genius. He later wrote a beautiful testimonial letter and recommended me to many of his friends.

In bidding on new jobs, Hernandez uses the program to reveal problem areas that he'd encounter if he got the job. He notes that most of his big and important jobs are done from engineered prints and allow no deviation. He explains, "I use ductsize to check the prints to make sure they are right and nine times out of ten I find there's something wrong. I now state in my contracts, for example, that I won't be responsible for air flow or deficiencies in air cooling per the prints. This way I cover myself. In fact, when the program shows me a very serious problem I won't even ask for the job. In the old days, we would have unknowingly inherited big and expensive problems that we were stuck with - now we avoid them. Without DUCTSIZE I was lost in these kinds of jobs.

With DUCTSIZE, Hernandez found that he could actually simulate a proposed design with available velocities and pressures shown at all points in the system. He can also thoroughly evaluate an installed system before building it and document those results to the client. In this way, possible solutions to a problem can be tested with the program before any physical modifications are made. "I can predict the future by using the computer to assess the effects of things like installing insulation and using different types of materials for the walls and roof. I actually save the customer money by showing them how to remodel, what materials to use and how to install them. I can show them everything they need and why they need it. Using the program has earned me a lot of good will and repeated referrals."

Hernandez claims the program's computer printouts give his calculations and recommendations great credibility. "I can present on paper the cost alternatives before any physical obstructions are made in the field. It will also print a bill of materials for a duct layout with material and labor costs and perform an acoustic analysis. My clients regard me more professionally and rarely question my figures. They often tell me to do the job the way I see fit and often don't even ask about the price."

He admits that his days with the Ductolator are long past. "With the Ductolator you can't see what's going on with the system. DUCTSIZE shows you everything you need to know. It spells it out for you. As good as a Ductulator is, duct sizing software goes beyond it in several important ways. For example, it allows me to use other methods of sizing such as static regain, total pressure, and constant velocity which may be more appropriate for certain situations. With the Ductolator, youre just guessing."

Hernandez feels that uncomputerized firms will still make money but that their poor designs will catch up with them. "Rule of thumb is no good today. You can't design a system like that anymore - our clients are more demanding and the field is too competitive. Good designs perform better and last longer and that's good for business. And, I don't waste time later solving problems because the system wasn't designed right. In other words, I can sleep at night."

Mr. Smith welcomes your email about this article. - email

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