Correspondence Lesson 11: Building Systems Controls

After a half-hour commute by train, Mary arrives at the office to begin her workday. As she approaches the building's front door, a smart security system identifies her and unlocks the doors. After she passes through the entrance on the ground floor, an intelligent identification system senses her entry and energizes her personal workspace on the 20th floor. The system turns on her office lights,

After a half-hour commute by train, Mary arrives at the office to begin her workday. As she approaches the building's front door, a smart security system identifies her and unlocks the doors. After she passes through the entrance on the ground floor, an intelligent identification system senses her entry and energizes her personal workspace on the 20th floor. The system turns on her office lights, starts her computer, pulls up her electronic mailbox, and adjusts the local temperature based on her personal settings.

Although this example is fictitious, it's not that far from reality. Intelligent buildings with the same capabilities, as well as many more innovative features, are just around the corner. But keep in mind, "intelligent building" means different things to different people.

To an architect, an intelligent building may be one that's energy efficient and flexible; using materials such as raised floors and movable interior walls for quick low-cost renovations. Building managers will likely dream of digital control systems and the ability to maintain temperatures within a few degrees of the thermostat setting. He or she might also want such a building to constantly monitor exterior conditions and automatically adjust for rate of air exchange and energy savings.

Still others may talk about Personal Environment Systems; where workers have the ability to customize individual work areas for temperature, acoustics, and fresh air ratios. IBM and Digital Equipment Corp. look at the this concept as a logical extension to processing opportunities, while control companies such as Honeywell and Johnson Controls focus on traditional markets with new digital solutions.

The primary features of an intelligent building include: full communications and computer network infrastructure; building security system; energy- saving equipment and controls; flexible work areas; and environmental control systems.

Selling. The demand for intelligent buildings is growing steadily, although people tend to specify types of equipment and services (since there is no standard list of equipment that makes up an intelligent building). Systems now in demand are those that give the building and its tenants greater flexibility, increased productivity, and expanded services. People tend to buy specific communications, control, energy management, and computer network systems; not some unknown package of systems sold under the tag "Intelligent Building." Your job is to tie these systems together so they become transparent to the occupants. Your first order of business should be to understand what the customer is willing to pay for.

Distributed or central intelligence. One of the key questions regarding an intelligent building is how the system will handle computing. One method is to have a central computer handle all control functions. Another is to use separate computers for various systems. Typically, a combination of the two methods works best.

For example, it's common for an office building to supply base services and for the tenants to pay for supplemental services. The building provides basic security access, fire alarm systems, and telephone and communications cabling from the point of service to every occupied space. From this point, it's up to the tenant to provide his or her own telephone system as well as supplementary security and fire protection equipment. However, for a truly intelligent building, you must tie supplemental security and fire equipment in with the central building systems.

Communications methods. Of all the pieces making up an intelligent building, none is more important than the communications system. Beyond traditional cabling like twisted pairs, coaxial, and fiber-optic, you can find almost any type of communications media in modern buildings, including: wireless infrared links (IR); radio frequency (RF) signals; microwave transmissions (usually from one building to another; not inside one building); and laser links (used in the same way as microwave links).

In most cases, communications within an intelligent building includes a mix of technologies, with each media moving signals from one place to another, or from one system to another. The signals may represent a phone call, computer file, security signal to open a door, thermostat calling for more heat, or window receiving a signal to "go-opaque."

Wiring. The distributed wire network is the primary link between all individual control systems. In most instances, it's a pair of wires looped throughout the facility. Someone must supervise the network for "loss of integrity," which is necessary for the UL listing of the life-safety systems.

There's also a design issue: the necessity for redundant cabling and using separate conduit located some distance from the initial cable. Life-safety systems don't require this redundancy for UL compliance, but consulting engineers and suppliers often consider it to be a good engineering practice. Manufacturers of integrated systems think the cost of this redundant network is not excessive in relation to the amount of additional safety it brings to the system.

For nonlife safety systems, especially for renovations or retrofits, you may have an opportunity to use existing power lines as the communication distribution network. This alternative allows easy system upgrade or installation with minimal disruption to walls or ceilings. However, manufacturers caution you to check the electrical distribution system for power line integrity before proceeding with final design.

Fire alarm. All office buildings must have a UL-approved fire-alarm system that's fully capable for stand-alone operation. All cabling from the main or distributed controllers must be supervised per UL standards. Note: This is standard for a fire alarm system. When tied into the computer, the fire alarm panel will have all of its operations overseen by the computer. Nonetheless, it must have the ability to function independently.

This type of system, supported by the CPU and the "hot backup" redundant CPU, provides an extremely reliable and safe fire-alarm system. It also allows for excellent monitoring and control, as well as flexibility for expansion or modification. Most importantly, this arrangement should be acceptable to any code authority. The power feed to the fire alarm panel is required to come from an emergency circuit, according to code.

HVAC control. You should control all HVAC equipment, from air handling devices to pumps, in an intelligent building by an energy management controller that communicates with a central computer. Standard software allows for monitoring status of the equipment, operation of equipment based on preset conditions and maintenance scheduling. This controller is the main point of control for firefighters' override capability. Most manufacturers have a built-in software check system that provides a certain level of supervision.

Many governing authorities in the United States accept the use of the HVAC controller as a code-approved firefighters' override system. Before design progresses too far, you should contact the local code-governing body for approval. An emergency power circuit must power such a controller, or any periphery device, which controls life-safety related equipment.

Work areas. As the number of automated workstations increases, housing the wires and fiber-optic cables that energize, connect, and control the various systems becomes a more vital consideration.

Systems contractors must find a way to install the equipment and its wiring wherever they can find a space. In an intelligent building, you should plan both horizontal and vertical paths for communication and control wiring from the outset with a provision for future changes. For horizontal distribution, twisted pairs of copper wires are still common while you can use fiber-optic cables for vertical and inter-building communication.

Tying it all together. Integrating various computer systems can be difficult; unless they all accept the same software and interconnections. An industry-wide effort to establish appropriate protocols for computer-aided environmental controls and energy management systems enables a "host" system to accept new subsystems.

For example, certain facilities management systems under development can control several subsystems, including HVAC controls, lighting/daylighting interface, fire alarm and life safety/fire management system, security, computer data, and communications systems; all manufactured by different companies. So although the intelligent building industry is getting better, significant challenges remain.

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