EVOLUTION OF HVAC COMPUTERIZATION

EVOLUTION OF HVAC COMPUTERIZATION ©
by Bill Smith, president of Elite Software

HVAC design has been greatly aided by computers and software. Ever since the introduction of large mainframe computers, HVAC designers have used the computer to calculate peak heating and cooling loads, optimal air conditioning duct sizes, and annual heating and cooling costs. With the advent of small personal computers even more HVAC design tasks were automated. This article will discuss the evolution of HVAC software over the past twenty years and what can be expected in the next ten years.

Since the early mainframe computers operated mainly in a "batch" mode where data had to be submitted on cards or in card images, most of the

software was very difficult to use. Batch form data entry required numbers to be "key punched" on cards in certain columns with perfect alignment. Even when data was properly entered, there was always the problem of trying to understand what each number in a card deck meant.

Besides the difficulty of use, there was also the matter of expense. Very few firms could afford to have their own mainframe computer. Most firms wanting computer capabilities in those times had to subscribe to time sharing services that were expensive and relatively difficult to use.

Although the early mainframe computers certainly introduced new and powerful capabilities to the HVAC designer, many engineers were not entirely charmed by computers. Using computers at that time was so different and difficult that they were generally used on only large and complex projects.

The appearance of small microcomputers from such pioneer companies as Imsai, Intertec, North Star, Cromemco, Vector Graphics, and Radio Shack back in the middle and late seventies offered the HVAC engineer an alternative to mainframe computers. These computers were typically based on simple, "eight bit" 8080 and Z80 processors made by Intel. Although not nearly as powerful as mainframe computers, these small computers did offer tremendous price savings, better ease of use, and reasonable performance.

The first HVAC software development efforts for microcomputers were almost exclusively for the automation of HVAC load calculations. In 1980, Elite Software was one of the first to begin offering HVAC load calculation software. Carrier followed shortly thereafter in 1981 with Trane finally entering the market several years later. By today's standards, those early HVAC load calculation programs were primitive, difficult to use, and slow in computations, but still big time savers as compared to performing manual calculations or even using mainframe computers.

Although used on less powerful computers, HVAC designers generally obtained results faster with microcomputer software than with mainframe software because it was easier to input correct data. In addition, there was usually less waiting for reports. Time sharing users often had to wait for output to be mailed back, and in-house mainframe users had to coordinate printing reports with other departments of their firm such as accounting. In short, the use of microcomputers offered some real advantages over mainframe computers.

However, it was not until the introduction of the IBM personal computer (PC) back in 1982 that microcomputers really began to be used on a widespread basis. Before 1982, only the most progressive and usually smaller firms employed microcomputers. By introducing the PC, IBM essentially legitimized microcomputers, and even large firms with mainframe computers began to purchase PC's.

The advent of the IBM personal computer (PC) was a great aid in the advance of HVAC design software. The IBM PC made HVAC software much easier and faster to use. In addition, much larger and more complex projects could be handled. The IBM PC soon became an industry standard, and the Intel processor chip used by IBM has been continually improved in speed and overall capability. Some of today's microcomputers are over 30 times faster than the original IBM PC.

As time passed, both hardware and software advances were made. Modern HVAC load calculation programs are engineering marvels compared to the early microcomputer load programs. Early on, there was only a handful of HVAC load programs available. Designers now have a wide array of choices available as virtually all HVAC manufacturers and several independent software companies offer sophisticated load calculation software.

Although HVAC load calculation software remains as the single most important task that HVAC designers want performed by the computer, there are many other HVAC design functions that have been aided by the computer. As HVAC load calculation software evolved, so did the demand for automating other HVAC design tasks. Air conditioning duct sizing, chilled water pipe sizing, refrigerant line sizing, psychrometric analysis, fan, coil, and equipment selection, and building operating cost analysis were the next tasks to be automated on the microcomputer. Today, all of these tasks and more are well implemented on microcomputers.

Another benefit of IBM's entrance to the microcomputer world was an improved environment for computer aided drafting (CAD). Shortly after the IBM PC was released CAD software for microcomputers began to emerge. Programs such as AutoCAD and VersaCAD were among the first on the market. Today these programs are still the most popular CAD programs, and they are currently making a tremendous impact on the way HVAC designers work.

Besides allowing HVAC designers to quickly and easily draw finished mechanical systems, CAD programs are now also facilitating initial design work. New software has been developed that allows CAD programs to pass data directly from a computer screen drawing into a design analysis program. This type of software is called drawing aid software, and it works in conjunction with both a basic CAD package and a specific application program.

A common HVAC design task integrated with CAD is duct sizing. For example, a designer can sketch a one-line drawing of a duct system on the computer screen, and then select to have that data fed directly to a duct sizing program that can then size the ducts and automatically create a double-line duct drawing. The major advantage is that much labor is saved since the designer does not have to manually input all the data from the drawing into the design analysis program.

As concerns HVAC design tasks, duct sizing has received the most attention in regards to integration with CAD. At present, there are at least four companies that have duct sizing programs integrated with CAD. Trane has a duct sizing program that works with AutoCAD through the CaddLINK, Inc. mechanical drawing system while Carrier's duct sizing program works with AutoCAD using the Carrier DuctLINK drawing system. The American Professional Engineers Council (APEC) has a duct sizing program that works with AutoCAD through the Autodesk AEC Mechanical template system. Elite Software's duct sizing program has been interfaced to AutoCAD with HVAC drawing systems from the ArchSoft Group, CaddLINK, and Autodesk, the makers of AutoCAD.

It is interesting to note that all the duct sizing software suppliers have chosen AutoCAD as the basic CAD package to work with. The main reason that AutoCAD is so popular is that it provides a graphic programming language called AutoLISP that facilitates the integration of design programs such as duct sizing.

Besides duct sizing, all of the companies mentioned above are working on the integration of other HVAC design software with CAD. HVAC load calculations, equipment selection and specification, and water piping design are all applications that have just been interfaced to CAD or soon will be. Already, Carrier has a program called LOADLINK that allows HVAC load calculations to be made from an AutoCAD drawing. Trane, in conjunction with CaddLINK, has a water piping program integrated with AutoCAD.

In summary, there are two current trends in the evolution of HVAC design software. One is the integration of CAD with every aspect of HVAC design including load calculations, duct sizing, hot/chilled water piping design, and equipment selection. This trend will continue for some time as the surface has only just been scratched.

The other trend involves the development of HVAC utility software. Basically, these programs automate common HVAC design tasks such as wire sizing, pipe sizing, single section duct sizing, psychrometric analysis, fan law calculations, refrigerant line sizing, U-Factor calculations, and others. Although many of these tasks are simple, they can be very time consuming, and it is useful to have them automated. As time passes, more and more such HVAC design tasks will be computerized.

The rapid evolution of CAD and HVAC design software has combined to make life much easier for the HVAC engineer. With computer hardware becoming more powerful by the day, software developers are able to keep extending the capabilities and reach of their programs. The new generation HVAC software has allowed designers to obtain optimal solutions, not just satisfactory ones. Fast software allows designers to try various design alternatives without spending too much time. If trends continue, the HVAC system designer can look forward to less calculation drudgery, and more time for fun things like system design and layout.

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