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 degrees in the office area," he said. "But that is well above the 68-degree reading we require in our computer room. Meanwhile, thermostats in the pressroom are set to maintain a constant temperature of 73 degrees."

Keeping Film Cool

The challenge to design a system that meets the diverse needs of LAGraphico fell to Ken Paschal, vice president of nearby Advanced Heating and Air Conditioning Co.

"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 York Sunline® and Predator™ single-package units were selected and sit atop the LAGraphico facility. The electric heat pumps range in size from 2 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 national mechanical engineering firm that worked with Advanced Heating and Air Conditioning on the LAGraphico 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°F. "With that many units," explained Paschal, "if one unit goes down, the others are capable of providing the necessary cooling. Cooling will not be lost while repairs are made."

In the critical computer room, two 5-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 start up and cool the room while repairs are made. "We've created a system that offers flexibility and redundancy," said Paschal, "and we've done that without sacrificing efficiency. The Sunline and Predator 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."

All Is Well That Ends Well

According to the manufacturer, the standard efficiency Predator units offer a minimum energy efficiency rating (EER) of 9.0, while the high-efficiency units reach 11.5 EER. In addition, all Predator units have two compressors with independent refrigeration circuits that are charged with R-22. If temperatures are mild and the air conditioning load is light, just one compressor turns on, providing 60 percent of the unit's cooling capacity. The second compressor is designed to provide an additional 40 percent 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.

According to Paschal, a discussion of these units would not be complete without talking about York's Simplicity® controls.

"That's one of the main reasons I recommended a York system for LAGraphico," he said. "Simplicity controls come factory-installed on both the Sunline and Predator lines 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 monitor the units from a single location becomes an important feature."

Diego Stefani, York's regional sales manager, added, "Simplicity, York's economical controls solution, protects the unit, reduces nuisance problems, and helps in troubleshooting York equipment. In the event of a lockout, LED flash codes tell the service technician exactly what caused the lockout. Additionally, the Simplicity wireless option, which can monitor up to 35 units, sends a signal via cell phone, pager, fax, or e-mail to the service company, the building owner, and the building service manager, alerting them to the lockout situation."

Installation of the units occurred with the help of a helicopter. The size of the roof and the number of units made a helicopter a less expensive option than a crane.

"We would have had to move a crane six or seven times to situate all the units where they needed to be on such a large roof," explained Wood. "By using the helicopter, we were able to line up all the units on the ground, pluck them one by one, and place them on the roof, quickly and efficiently."

That was a year ago. Today the units are functioning as advertised, providing flexibility, efficiency, and redundancy, and landing a best supporting role with LAGraphico.

Publication date: 12/13/2004