Plant Controls in the Home Office?
-- Consulting-Specifying Engineer, 12/1/2000
Building-automation system (BAS) specification for commercial buildings has a long history of borrowing from more advanced concepts developed for the process industries. Yet, Southern California Edison (SCE) was making a novel-if quite logical-choice when they selected a BAS model for their general offices that more closely resembled the controls schemes used for their generation and transmission assets.
According to Stephen Long, P.E., systems integrator with Anaheim, Calif,-based Consolidated Data Systems, SCE moved away from a standard, single-source BAS approach in favor of a highly fault-tolerant open system that could control mechanical systems as well as fire- and life-safety equipment in its data-processing center.
The specified system employs a Windows-based human-machine interface (HMI) and an I/O server that sits between the HMI and all field controllers, says Long.
"SCE can go with any manufacturer of PLCs [programmable-logic controllers]," says Long of the open architecture. "They have tremendous flexibility, and can choose from multiple levels of very price-competitive PLCs that can be tailored to each application," regardless of whether it needs a high- or low-level controller.
According to David L. Toth, manager of design and construction with SCE, the decision mainly hinged on the system's track record and the utility's previous experience with it. "We basically used [this BAS system] because it worked," he recalls. "We had it in place in other areas and we had already researched it."
The automation system is laced through the entire complex via fiber-optic cabling, adds Rodney A. Sleeter, facility manager with SCE, which is uncommon for mechanical-system controls. "We have four operator stations, and they're hanging on [uninterruptible power-supply] units to keep the network up and alive at all times," he adds. "The HMI is very user-friendly, and the system lets us work with industrial process-control devices, which we are already familiar with."
