Best Supporting Role for HVAC: A Case Study

By Consulting Specifying Engineer Staff December 22, 2004

LAGraphico, a graphic imaging, pre-media and printing company, serves the Hollywood film industry. Responding to rapid growth, the company recently relocated their Burbank, Calif., operations, from 45,000 sq. ft. of space spread across three small buildings to a 75,000-sq.-ft. mixed-use facility housed in a former film warehouse. The transformed warehouse space includes a pressroom, graphic imaging and output area, computer and server room, offices and storage space that require a variety of cooling needs. The company addressed these needs by installing 35 convertible single-package rooftop units.

“Temperature and humidity control are critical to the success of our operations,” said Peter Wood, LAGraphico’s facilities manager. “In our printing and output areas, we require cool temperatures to prevent paper from shrinking or expanding. Sensitive pieces of equipment, there and in the computer room, also demand cool temperatures and low humidity. And, of course, our office areas need to be kept cool for the comfort of our employees.”

However, as Wood went on to explain, what is cool for one area may be too warm for another. “We maintain a temperature of 72

The challenge to design a system that could meet these diverse needs fell to Ken Paschal, vice president of Advanced Heating and Air Conditioning Company.

“Flexibility was probably the most important feature the people at LAGraphico were seeking in an HVAC system,” recalled Paschal. “A system composed of multiple rooftop units lends itself nicely to flexibility.”

A combination of single-package units was selected and sits atop the facility. The electric heat pumps range in size from two to 7.5 tons and give the company the ability to zone the building to meet each of the cooling needs each area demands.

“There is another issue that goes along with system flexibility,” commented Tom Rotchford, president of Solargy Inc., the mechanical engineering firm that worked with Advanced Heating and Air Conditioning on the project. “The critical nature of some of the processes at LAGraphico requires backup cooling, especially in the computer room. Rooftop units enable the company to provide redundancy far less expensively than they could with a chiller system.”

The pressroom, for example, relies on 16 single-package units to maintain a constant temperature of 73

In the critical computer room, two five-ton units alternatively run two-hour shifts. However, if one unit shuts off at anytime during its shift, the other unit is set up to kick in and cool the room while repairs are made.

“We’ve created a system that offers flexibility and redundancy,” continued Paschal, “and we’ve done that without sacrificing efficiency. The [rooftop] units offer efficiency ratings that exceed the industry standard. We also installed economizers to take advantage of the free cooling that outside air can sometimes offer.”

The standard efficiency offered by the units is a minimum energy efficiency rating (EER) of 9.0, while other, higher-efficiency units reach 11.5 EER. In addition, all units have two compressors with independent refrigeration circuits that are charged with HCFC-22. If temperatures are mild and the air conditioning load is light, just one compressor turns on, providing 60% of the unit’s cooling capacity. The second compressor provides an additional 40% when warmer temperatures demand additional cooling. As a result, the cooling or heating that the system provides is balanced, and the balance is maintained without the constant running of a single, large, more-expensive-to-operate compressor.

Finally, according to Paschal, a discussion of these units would not be complete without talking about controls. “That’s one of the main reasons I recommended [the] system for LAGraphico,” he said. “Simplicity controls come factory-installed… and offer an adaptable energy management system that is inexpensive, easy to operate and very powerful, allowing building owners to monitor their entire facility from a single location. When you have as many units as LAGraphico has, spread out across an expansive rooftop, the ability to monitorthe units from a single location becomes an important feature.”

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