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QUEBEC CITY - The great divide between HVAC contractors and engineers is probably at its widest point where residential load calculations are concerned. Contractors don't see a practical way to do what is called a "vigorous" (i.e., complicated) load calc without losing their competitive advantage over contractors who don't perform them. Engineers don't see how a system can be installed without one.
The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) put the spotlight on contractor, OEM, and software points of view at its annual meeting. The goal of the seminar, "Practical Viewpoints on Residential Load Calculations," was to drive these concerns home to the engineers and hopefully drive research into better, more practical methods for use in the field.
"There has been a lot of controversy on residential load calculations," said Charlie Gulp, P.E., Ph.D., the session's moderator and professor of Mechanical Engineering at Texas A&M University. "This seminar offers a field of viewpoints," he said.
CONTRACTOR'S VIEWPOINT
Glenn Hourahan, engineering vice president of the Air Conditioning Contractors of America (ACCA), presented information prepared by contractor John Sedine, of Engineering Heating & Cooling, Walker, Mich. (Sedine, like many attendees, had to fight weather-related travel delays and cancellations.)
"Why are loads important to contractors?" asked Hourahan. Most national and state codes demand that when they are installing an HVAC system, contractors need to do a vigorous load calculation. "If you were to ask a group of contractors in a room, every hand would go up," Hourahan said. "When you talk to them individually, it's different." Still, load calcs play a critical role in overall comfort. Today's suburban homes - "McMansions" - are much larger and have more glass.
"Contractors know it's important," he continued. Performing load calculations can lead to contractor differentiation, pitting the good contractor against the not-so-good contractor. However, "Consumers buy on price," Hourahan said. "They need to be made aware that you may get a low price, but you may also get low value. What consumers really want...