Integration: Building automation and fire alarms


How to know whether to integrate

Figure 2: In this integrated building management system display, various aspects of the facility can be reviewed in one screen. Courtesy: SiemensThere are advantages and disadvantages to consider when determining whether to integrate a BAS and a fire alarm system. The most common consideration is when the building has a complex smoke control system. An integrated system is also seen in facilities involved in process control that may be affected by a fire alarm event. For the purpose of this article, when used primarily in controlling the spread of smoke, integration of the various systems that normally have independent connections helps to facilitate improved communication, redundancy, and cost savings. Additionally, the building engineer will have the ability to determine from a single source what is causing the mechanical equipment to operate, shut down, open, or close.

Take a case of a building with separate building automation and fire alarm systems: When the building engineer receives a call from an occupant complaining about increased temperature or whistling air within the ductwork and finds that the fan is shut down or a damper is closed, the building engineer is more apt to call a controls contractor to investigate the problem before he calls their fire alarm service provider. Should the problem be related to an override of controls by the fire alarm systems, not only does the building engineer have to wait for the controls contractor to diagnose the problem, he also has to call the fire alarm contractor to come out and fix the problem. This process can take time to correct; meanwhile, building occupants are uncomfortable and inconvenienced. 

Sometimes this can even lead to finger-pointing between the two service providers as to whose problem it really is. In this scenario, the fire alarm control of a fan or a damper is required to be ahead of the hand-off-auto switch for the power to the equipment so the inadvertent shutdown of the equipment does not inhibit the operation of the fire alarm feature. A failure of the fire alarm system control relay could shut down the fan or close the damper without an alarm being present on the fire alarm system or fault condition occurring on the fire alarm control unit. 

With an integrated building automation and fire alarm system, this scenario plays out in a different manner. The BAS, when listed accordingly to UL Standard 864 UUKL listing, to provide code required smoke control functions, can rely on a digital alarm signal from the fire alarm system, passed through a gateway, as the only means outside the BAS to influence control over the building mechanical systems. The responsibility for fan and damper control is solely with the BAS and thus simplifies the troubleshooting process. 

Because many components that affect air and smoke movement within a building are shared between HVAC and fire alarm systems, let's take a step backward in the evolution of the building process. When building systems are being commissioned for proper operation by either an authority having jurisdiction (AHJ) or an independent third-party group, coordination must occur between multiple trades. At this point in the construction process, each trade is independently looking to complete its own scope of work and more often than not is under pressure to finish the specific scope in a designated timeframe. Sometimes this leaves a disconnect between the fire alarm and mechanical trades that results in disruption during start-up and commissioning. 

The integrated system approach allows for those individuals responsible for controlling air movement to be focused on proofing and balancing the mechanical system, while the fire alarm contractors focus on the detection and annunciation of the alarm events. Much in the same manner as referenced in the previous example, the problems can get resolved more expeditiously and the systems can be brought on-line. 

If we focus on the installation of a building management system (BMS) and a fire alarm system, we see many similarities. Each of these control systems is classified as low-voltage systems that communicate to their respected devices through an analog or digital signal. Their wiring methods and materials are similar, and often their respective equipment is located in the same general area and is performing the same basic functions with one significant difference: the fire alarm system uses individual point addressable monitor and control modules while the BAS uses digital input/output driver assemblies that communicate with different protocols. 

Why is this important? Because the BAS still requires individual pairs of conductors to each point being controlled or monitored by the digital input/output module, resulting in more wire being needed and longer installation time.

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