The SCS can provide up to a 15-percent construction savings for just the BMS installation. A traditional installation uses a heavier gauge cable which, per foot, is typically more expensive. An SCS approach provides additional components, such as administration (cross connects), equipment cabling, and a multipair riser. These SCS components, which are part of the SCS subsystem architecture, can make it possible to reduce the number of equipment panels required for the BMS configuration. In addition, since a riser backbone is required for the voice and data, it is very cost-effective to increase the riser cable size for the BMS services.

The SCS subsystem cabling approach allows the BMS equipment to be centralized, thus fully utilizing all of the available equipment ports. Any power required to operate devices, such as FA strobes or variable volume air boxes, can be distributed from the TC locations or provided locally. This may necessitate additional BMS hardware for the SCS approach since 24–AWG cable will typically power less devices per cable. However, this situation could be alleviated if BMS power supplies were manufactured with more power taps that supplied less current per tap. The power taps could even be modular with multiple appearances on a jack, which would also simplify the installation.

On the other hand, a traditional BMS installation typically distributes the equipment panels. This leaves many unused ports scattered around a facility and usually requires more equipment panels than a centralized approach. Since the traditional installation has no administration subsystem, it is neither practical nor cost-effective to run the device cables to a central equipment location. Centralization of the BMS equipment, which can be used for most structures, is possible because of the SCS subsystem architecture. This solution can be equated to a typical private branch exchange (PBX) installation, which uses a centralized approach for providing service. A distributed PBX architecture (remote PBX cabinets) will not be used unless the distance limitations are exceeded.

Using a distributed equipment approach is typically not cost-effective for most types of equipment or systems. Sometimes the system limitations for data transmission or power require a distributed topology, but this is usually not the case for the typical low-speed and power-limited BMS equipment. Using a centralized SCS solution can reduce the combined cabling and equipment costs as well as reduce the multiple spaces typically required to house the equipment.

Figure 6. Traditional Distributed Approach versus SCS Centralized Approach

Installation, testing, and the electrical costs for the panels can also be reduced with a centralized equipment approach. Additionally, if an equipment panel fails, the ports can be easily reconnected to another equipment panel and retranslated. In a traditional installation, the panel—or components within the panel—would have to be replaced in order to restore service. Some vendors state that the panels must be placed in close proximity to the mechanical equipment for troubleshooting, but an RJ45-type outlet can provide plug-in capabilities for a remote hand-held tester. Centralization also allows ports from the same equipment panel to be dynamically alternated throughout a structure, which alleviates complete failures on any given floor or area if an equipment panel fails.

The subsystem cabling approach also makes upgrades for the BMS equipment faster and more cost-effective. In a traditional installation, devices are wired straight from the equipment panel to the device. When the panel needs to be upgraded, the cables have to be reterminated in the new panel. This is not always easy or practical, and sometimes the device cables may not be reusable. With the subsystem cabling approach, at worst, a new equipment subsystem is provided and the devices are reconfigured at the cross connect location. The SCS approach assures economical upgrades to the equipment with minimal service outages.

Data-transmission speed is rising as technology advances and more information is processed. As the BMS equipment becomes more advanced, its associated data-transmission speeds will also increase. Currently, some of the traditional BMS cabling will only support limited data rates and applications. If the right cabling is not incorporated into the structure during construction, it may require new cabling in the future.