A building hardware and software optimization upgrade performed in which existing direct digital controllers (DDC) were replaced with state-of-the-art BACnet DDC controllers is expected to save more than 400,000 kilowatt hours (kwh) a year and reduce the amount of district chilled water purchased at the Connecticut Financial Center located in New Haven, CT.

Building owners, motivated by the need to reduce energy costs and upgrade an early-generation Johnson Controls direct digital building automation system that had exceeded its maximum control potential, contracted with RCMS Controls of Wallingford, CT, to retrofit the outdated motherboards of 40 existing DSC-8500 controllers with ALC-8500 DDC controllers from Automated Logic Corp., Kennesaw, GA.

Operations at the 28 story, 530,000-square-foot commercial office building are managed by Connecticut Financial Center Management.

By more precisely matching cooling requirements to occupancy levels, the changeout should enable the end user to save $43,739 as a result of reducing chilled water use and curtailing the run times of ventilation fans and chilled water pump motors, according to building manager Richard Ziegler. Most of the predicted annual savings will come from electricity savings of 401,972 kwh a year, according to Robert Marra, with RCMS Controls, Inc., an Automated Logic strategic partner based in Wallingford, CT. The retrofit is also expected to lower annual chilled water consumption by 75,357 ton-hours, saving the company $7,239. Chilled water is purchased from local district energy provider Thermal Energy Inc.

According to Sean West, an energy services supervisor with local utility United Illuminating Co., the end user received a $44,000 incentive for implementing efficient scheduling measures under the utility's commercial, industrial, and institutional Energy Opportunities program. Payback for the replacement is estimated at just under three years once the district and utility incentives are factored in.

Ziegler reported that "This project didn't start out as a means to capture energy savings," Ziegler elaborated. "It started out because the existing energy management system was inadequate for the building's needs and was unreliable. As far as point capacity, controlling over 1000 points really stretched the limit of the old control system. It was doing weird things that nobody could really get a handle on. Once we knew we had to make a change, we started looking for a new system that could provide us with energy savings, expansion and open architecture."

Marra explained that the ALC-8500 interface is a member of Automated logic's BACnet "Connect" family of building subsystem integration products. The board is fully BACnet compliant and is outfitted with eight 0-5 volt DC binary inputs and 15 analog inputs that can be used for 0-5 volt DC signals or operation with 1,000-ohm resistive thermal devices; also, it has 16 digital outputs rated at 200 milliamps and 12 volts DC. The units were mounted using the old system's footprint and brackets. After installation, the new standalone interfaces were connected to the existing power supply via a special adapter cable. Once in place and powered, the modules' custom programming instructions were downloaded from a laptop computer.

"Basically it's a brain transplant," Marra said. "It is not a unitary module, but more of an application-specific control module that replicates the existing input/output devices."

In addition to the microprocessor, the ALC-8500 platform features an high-speed twisted-pair connection to the building's control communications trunk, an input/output expansion port, and a local diagnostic port for links to either laptops or handheld terminal devices. According to an Automated Logic applications engineer, the upgrade now enables data transmission at a rate of up to 156 KB; the prior rate was 9,600 baud.

The upgraded building automation network, which was expanded to over 1,300 control points, was primarily engineered to deliver more energy minded transitions from unoccupied to occupied modes. Normally, building engineers are charged with providing HVAC services from 8:00 A.M. to about 6:00 P.M. In the past, the building's cooling cycle had been initiated without regard to occupancy periods.

"The optimal-start-time program was an added benefit when we found out that the scheduled run time for the building and its equipment was somewhere around 3:30 A.M. until 9:00 P.M. Monday through Friday, and on Saturday from 5:00 A.M. until 1:00 P.M.," Marra observed. "The problem was that the building's actual occupancy was much less than the programmed schedule's."

With improved scheduling routines, more refined outside air measurement and damper control, and the addition of space reference temperature sensors on each floor, Ziegler was able to revamp and optimize his building's air handler startup and shutdown. Now, chilled water flow and air distribution can be initiated 15-30 minutes prior to occupancy. These new functions enabled management to significantly reduce fan and pump motor usage, which was rated at about 575 and 125 horsepower, respectively. Even through the pumps were recently outfitted with variable-speed drives, they were left in the manual bypass mode most of the time because of reliability concerns. Some of the new points were dedicated to restoring the drives to the fully automated state based on pressure signals from the penthouse, Marra related.

Because the changeover was performed in concert with a life-safety upgrade that included a floor-by-floor fire and smoke panel replacement, reducing downtime was a major factor in deciding to move forward with the retrofit. Each new interface was custom-programmed, providing almost seamless installation and startup. A new touch screen graphic fire command center console was provided in the main fire command room that provides clear intuitive monitoring and over-ride control of fans and floor pressurization. "The importance of an easy changeover was a primary concern," Ziegler commented.

Marra estimated that the decommissioning and commissioning process took about 15 minutes for each board because each ALC-8500 was downloaded with the application program in advance and fully simulated prior to installation. Down time of environmental systems and life safety systems were unacceptable

With several operator's workstations and remote access to the site building operators can quickly and easily navigate through the user-friendly ALC graphics and operating parameters and respond more readily to occupant requests, execute temporary scheduling changes, and research history trends more quickly. "We can monitor and track all points of control without limitations by pulling up a graph that shows a detailed history and respond to tenant needs in minutes verses hours," Ziegler concluded. "I find it amazing that RCMS Controls, Inc. executed the migration without any tenant complaints, no loss of life safety protection and with very few punch list items. Not only did they fulfill contract requirements, but they exceeded our expectations."