The air handlers on the 19th floor of the Dirksen Building in Chicago's Federal Center were reconditioned with new dampers, actuators, and LonWorks-based programmable controllers.
The Federal Center is the heart of the United States government in the city of Chicago. Comprised of the high-rise Dirksen Federal Courthouse, the Kluczynski Federal Building, and the one-story Loop Post Office pavilion, the Federal Center contains over 2.5 million sq ft of space housing 20 government agencies including the U.S. District Courts, FBI, and IRS. Designed by renowned architect Mies van der Rohe in the late 1950s, the office towers were completed in 1964 and 1972.

By 1995, the Federal Center was in need of a significant upgrade of its building systems to reflect changes in building use and function and to keep pace with changes in office environmental standards. The U.S. General Services Administration (GSA), which is the government agency responsible for maintaining and renovating these buildings, determined that a complete renovation of the systems' infrastructure was necessary and would include fire protection, life safety, electrical power, telecommunications, and hvac.

Included in this renovation was a complete overhaul of the buildings' control systems. Over the years various types of controls had been put in place - ranging from the original pneumatic to electric controls to some early direct digital control (ddc) systems. After careful evaluation of the latest technologies available, the GSA decided to convert the entire Federal Center complex to an open control system architecture.

New System Chosen

The original specification and design that went out for bid was done in the typical way; that is, 25% design accompanied by a performance specification. Proprietary and open controls companies bid on the project, and the contract was eventually awarded to an open controls company, which would install a system based on LonWorks technology. However, the minimal design specification did not clearly identify the nuances that often arise in an open control system.

This left some room for interpretation by the contractor, whose choices did not necessarily promote the level of interoperability that the GSA expected. In addition, this contractor, who was responsible for basically bringing the main mechanical systems on-line, ran into some other difficulties, which delayed Phase I completion. When the second contractor came on board to install Phase II, the architecture wasn't in place for him to tie in his devices.

As a result, there was some tension between the two contractors that ended in the hiring of Teng and Associates (Chicago). "We were brought in initially to help resolve the system integration disputes that were coming up with regards to the open systems that were going in; the existing specification and design did not address integration," says John Huston, P.E., Teng and Associates.

Teng identified the interoperability issues that were arising and was subsequently contracted to redesign the systems, and coordinate the work of the two initial contractors. "It was a fairly interesting position," says Huston. "Both contractors had a contract and a proprietary specification and design that really did not promote interoperability. The GSA was convinced that they wanted to continue the development of the open system proposed by the Phase I contractor. However, neither contract specified how to address coordination issues. Further complicating the matter, the specification for Phase II stated that the control system manufacturer for the second phase must be the same as the control system manufacturer installed in Phase I."

Teng's assignment was to provide the GSA with the open interoperable system they expected without redesigning everything that was in place. In addition, Teng wanted to find a way to have the two contractors complete their projects without having to implement major changeorders.

Table 1. This chart shows the total number and type of components added for each building.

Priorities Mapped Out

Since the original specification and design was proprietary, it became obvious that the Phase I contractor was counting on being awarded the second phase. However, a different contractor/manufacturer was awarded Phase II, and the Phase I contractor was terminated, leaving the system in disarray. Teng's scope expanded to the redesign of the remaining work.

"First of all, we performed a complete on-site investigation of the existing conditions to determine what the first phase contractor accomplished, and then we had to recover what was left," says Huston.

So Teng started a priority list. The first priority was to get the 19 air handlers, located on the 30th floor in Dirksen, under control. Each air handler controlled a specific federal courtroom. The air handlers were old and in various states of disrepair, but they weren't replaced; rather, they were fully reconditioned with new dampers and actuators. Teng quickly developed the design and construction documents to replace the control system for these air handlers with LonWorks-based programmable controllers. An emergency procurement was sent out to bid based on these documents.

Due to the deteriorating condition of pneumatic components, the operation and maintenance of the hvac system had become a 24-hr process. The O&M staff had to manually adjust the position of valves and dampers to maintain a comfortable environment. This round-the-clock effort was evident in the air handlers, where the O&M staff occasionally propped dampers open with boards and, in one case, used a table to position a large damper and keep the air moving properly.

Next on the list was to determine the heating load in the buildings. In the 40 years since the buildings were constructed, the heat load had changed dramatically due to the increased number of computers and other electronic equipment in the space. Because of this increased heat load and the capacity of the original design, Teng determined that the internal air-handling units (AHUs) did not need to provide heating. Therefore, the heating coils were removed from all the internal major AHUs, and they were replaced with cooling coils. Perimeter heat was supplied by constant variable-air volume (vav) boxes and induction units.

"The air that is now being supplied to all the internal vav boxes, which are actually mixing boxes, is dual-duct cooling," says Huston. Teng modified the control algorithms on all the mixing box controllers, which were just installed by the second-phase contractor, to be dual-duct vav as opposed to a mixing box control.

The LonWorks system was flexible enough to reprogram the mixing box controllers to dual-duct vav. Although it would have been nice to replace the existing boxes and put in all new vav boxes, that just wasn't possible. That's because it was physically impossible to get into some of the ceilings, and there was also asbestos to deal with. In the end, it turned out to be more cost effective to perform the mixing box conversion and leave the physical devices in place.

Teng also designed balancing connections between the supply ducts up the main riser to keep the pressures at the correct level. Variable-frequency drives were also added. "We ended up saving them a lot of money on that renovation," notes Huston.

New Backbone Installed

While all these renovations were going on swimmingly, a problem started to occur with the control system. The LonWorks backbone, or riser, was used in both buildings, and a network of Lon devices was installed on every floor of each building.

However, two different types of industrial operator interface packages were installed, one within Dirksen and one within Kluczynski, neither of which had a high-performance LonWorks communications driver. As more devices were added to the system, a bottleneck began to form at the user interfaces, with screen updates often taking several minutes. Machines were locking up on the operators, and the overall network performance was slowed to a crawl.

Teng knew that something had to be done, but time was working against them. These problems started to occur in December 2000, and they had to close out the contract by June 2001. They decided to call in Tridium (Milwaukee), a framework, software, and services company. Tridium's "Vykon," a Web-enabled product suite was proposed. Vykon is based on Tridium's "Niagara Framework," an open system infrastructure that has the scalability necessary for larger projects such as this.

"We weren't really sure whether it was the operator interfaces, the Lon drivers, or the existing backbone that was the problem. We suspect there might've been some limitations with the drivers or the backbone in terms of bandwidth, but it's really hard to say. This all occurred in the eleventh hour, and we needed to correct the problem immediately," says Paul Oswald, director-Midwest region for Tridium.

Oswald notes that in the final analysis, he felt the real problem was that the existing architecture was a traditional client/server architecture with all the system data being processed by a single server. That can work on a lot of jobs, but when the project is as large as this one, with its huge amount of devices and data, it can overwhelm this type of architecture. The result is slow performance, lock-ups, etc., which is what was occurring on this project.

Tridium started by replacing the LonWorks risers with standard Ethernet risers and replaced the Lon routers on each floor with its JACE(tm) controllers. The Lon devices on every floor were connected to the JACE controller, which in turn, was connected to the Ethernet riser. The graphical operator interfaces were then replaced with standard Web browsers.

Because Vykon is a multiple server/thin client architecture where each JACE device is a server and a control processor, it was able to overcome the performance problem. This architecture means that there is no single point in the system that has to process all of the data. "This system is very scaleable. The thin clients are the Web browsers the owner or user already has on their machines. No additional software is installed, and this provides two benefits. First, more users have the ability to access and use the system, and second, the cost of ownership is low since there are no client software licenses to buy," says Oswald.

The Lon devices on each floor represented numerous different manufacturers and were there for a variety of different functions - everything from hvac control to vav zone control to lighting control. Because of the various manufacturers, as well as the numerous functions involved, there was a lot of work that had to occur in the logic that existed between the various devices, notes Oswald.

"For example, the occupancy sensors had to be linked through our software, and through control logic we created to turn on and off certain lighting zones. In addition to the very graphical operator interfaces, there was a large amount of control system logic that had to exist to coordinate the nodes, to make the various Lon devices work as a system."

Indeed, besides the time crunch, Oswald says that resolving the differences between devices was the most challenging part of the job. "One of the challenges of open systems is resolving the various data types used by the different manufacturers' devices. LonMark goes a long way towards resolving most of those issues, but it doesn't resolve all the issues," says Oswald.

Then there was the sheer magnitude of the job: There were about 15,000 points in the buildings and 2,800 different graphical screens. In addition, some graphical screens were already completed for the industrial operator interfaces when Tridium arrived. The operators had had some amount of runtime with them, so the GSA wanted Tridium to create the graphics in their system to match those in the previous system.

"The good part is the GSA now has a framework in place, so they can go in and add additional open control devices, as well as software applications like electronic operation and maintenance manuals, computerized maintenance management, and energy profiling software," says Oswald of the project, which did finish on time. "These are all things that can be layered on top of the core framework that's already in place." ES