Mixing Oil and Water

Feb. 10, 2004
Today’s Climate Calls For Coordinated Control
Building owners are feeling the pressure to make their facilities more secure. But to do so requires a coordinated approach between security and heating, ventilation, and air-conditioning (HVAC).
Ideally, if an environmental hazard is detected, your staff can activate the appropriate ventilation and pressurization modes, while locking down certain doors and unlocking others to ensure a safe exit for your building’s occupants. Meanwhile, the building’s digital CCTV system is automatically recording the whole event and emergency lighting and generators have been are activated. It’s coordination that allows this type of simultaneous response to occur.
Considering today’s economic climate, this same coordination brings an additional benefit: When building equipment is shared between HVAC and security and a single operator can control both, the building owner saves money.But What About BACnet, HVAC, and Security?BACnet is a data communication protocol for building automation and control networks. In facilities that have chosen BACnet primarily for temperature control, several issues have stood in the way of progress toward a coordinated BACnet/security building management approach. First of all, the BACnet protocol lacks a usable network security model, or set of standards. Such a model becomes more essential as security systems grow larger and include various access control, intrusion detection, and digital CCTV devices. Securing these networks against tampering becomes increasingly more difficult. As a result, companies today using BACnet are looking toward a set of sanctioned guidelines on the implementation of such security measures as firewalls, user log-in procedures, and data encryption to protect particularly sensitive data as it transits their networks. Unlike building automation manufacturers who banded together with end-users to create the BACnet standard for HVAC control, there has been no successful movement amongst security vendors to do the same. The BACnet Committee is working toward standard objects and services for security; however, this effort relies upon improvements to the network security model within the BACnet standard. BACnet is making good progress in both areas; yet a published version of the standard with these improvements is several years away.But Why Wait Years?Two designs for BACnet/security systems have emerged. One “proprietary object” design extends BACnet by using proprietary BACnet objects to describe objects such as areas, doors, and personnel that don’t exist in the BACnet standard. The “bilingual” design has devices that “speak” BACnet as well as its own proprietary language, so data can be passed between their access controllers, digital video recorders (DVRs), and BACnet devices with ease. Proprietary Object or Bilingual Design?Whether you implement a proprietary object or a bilingual designed system, you will need the front-end from the manufacturer of the access control devices. A proprietary object is just that – proprietary. Unlike HVAC systems that are reprogrammed rarely, access control systems may be reprogrammed on a daily basis.However, you can still reap the benefits of BACnet when it comes to access control. Security alarms may be represented as BACnet alarms and sent to any BACnet workstation. Additionally, intrusion points may be represented as BACnet multi-state-input/value objects; and door status information may be mapped to other BACnet objects. Access events may also be used to trigger BACnet outputs and values such as a “Valid Entry,” causing the BACnet system to go into “Occupied Mode.”Oil and water can mix. Imagine seeing a summary of all key environmental systems and security status points from a single graphic. The day of coordinated BACnet/security control has arrived. Jon Williamson is a product manager at Andover, MA-based Andover Controls Corp. (www.andovercontrols.com), which designs and manufactures integrated HVAC, access control, lighting, and digital CCTV systems.

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