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Article - May 2000
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Alerton
R BACnetTM System

Melinda Bartee
Alerton Technologies, Inc.


The Edward A. Garmatz Federal Courthouse near Baltimore's Inner Harbor is a GSA facility built in the early 1970's. Alerton's BACnet compliant system, BACtalkTM, replaced the early vintage HVAC control system that had long outlived its useful life.

The building was constructed in 1970 and the HVAC systems were comprised of 8 VAV Air Handling Units, 8 Constant Volume Air Handling Units, two centrifugal chillers, two steam/HW heat exchangers for heating, and a condensate heat recovery system that acted as a preheat for the heating hot water. The existing building automation system performed supervisory functions and equipment start/stop.

The operator's console, located in the penthouse, was a 6' x 6' x 2' deep panel that utilized pushbuttons to access system information and displayed the system graphics via a Kodak slide projector (the displays showed the code for the points and the operator would punch in the code to view the point data on an adjacent LED readout). The controls were distributed among 7 Field Panels that were connected by a 96-conductor communications trunk. Primary control of the units was accomplished via pneumatic controllers and end devices. These controls had become unreliable, service and support for the legacy controls was unavailable, and manual operation of fans, controls, and end devices had become the norm.

The GSA Region III contracted Facility Dynamics, Inc. (Columbia, MD) to design a new building automation system whose controller communications are based on the ANSI/ASHRAE 135 Standard - BACnet. The controls supplier selected for the project was Alerton Technologies of Redmond, Washington. Alerton's local representative, Advanced Power Control handled the installation.

Alerton has a BACnet compliant product line that utilizes the BACnet protocol in every controller and network device. The DDC system retrofit involved removing and replacing the existing electronic system, re-using the field cabinets and pneumatic control panels for the new controls, and performing extensive commissioning of the new controls, and re-commissioning of the existing pneumatic end-devices - with no interruption of the building use or occupancy.

All system supervisory and control functions can now be performed from a single PC Workstation. In addition to the existing control functions, monitoring of building comfort conditions and critical area alarms are also performed from the same PC. Each field cabinet was provided with a BACnet/Ethernet connection to allow a laptop PC, with all of the capabilities of the workstation, to be connected at each controller. The building staff has found day to day operations to be greatly simplified. As Mike Margolis, Building Maintenance Project Manager for HAI-WW* states, "Energy Management using a graphical interface provides real-time information so that we can be proactive when troubleshooting systems." In many cases, the maintenance personnel are able to recognize and respond to system malfunctions before the tenant becomes aware of the condition. The significant advantage to the use of BACnet on this project lies in the future capability to integrate data from multiple facilities and building systems onto a common wide-area network, and to control the systems from within a single software application.

For the GSA facilities in Baltimore, this integration will allow the facility management team to collect and respond to energy data from their buildings. According to Mike Margolis "the Energy Management System is a critical part of that process" and that BACnet and other communications standards such as IP (Internet Protocol) provide a good platform for that integration to take place. GSA has recently released a specifying guide for BACnet-based systems that can be downloaded from ASHRAE's BACnet web site www.bacnet.org. 


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