Case Study

25 Burlington Mall Road - Burlington, MA

25 Burlington Mall Road is a six story multi-tenant office building located adjacent to I-95/Rt. 128 in Burlington, Massachusetts.

The building's major mechanical systems include:

1. Minimize operating and energy expenses.
2. Track the buildings mechanical performance.
3. Automate the present zone control system.
4. Interface to the chiller system to control leaving water temperature and motor current limits.
5. Maintain the integrity of the pneumatic control system for back-up control.
6. Install a Graphical Operator Interface.
7. Reduce the operator workload in the day-to-day operations of the HVAC system.

The first phase of this multi-phase project involved the installation of a Delta Controls Intelli-Sys Control System to replace both the old DDC and EMS systems. Four space temperature sensors were installed per floor that transmit space temperatures to a Delta Intelli-Con Micro Panel located on each floor. Additionally, two duct static pressure sensors were installed on each floor to monitor duct static pressure at the ends of each floor. Correct static pressure is critical to proper air balancing and VAV box control. These sensors would enable the maintenance personnel to make adjustments and track performance.

The Micro Panels exchange data with one of the two Delta Intelli-Con Turbo Panels located in the Mechanical Penthouse above the sixth floor. This is accomplished using a 38.4K RS-485 twisted pair trunk wire. Micro Panels were selected for this project over traditional zone multiplexors because of their trend logging capability.

The two Delta Turbo Panels control the following:

Each Delta Turbo Panel is a multi-ported, memory enhanced, dual processor field panel. At 25 Burlington Mall Road, Turbo #1 connects to a printer and color host computer located in the Maintenance Office on the First Floor. Turbo #2 is connected to a computer and high-speed modem located in the Mechanical Penthouse. The modem is used for off-site diagnostics, data retrieval and operator paging. The two Delta Turbo Panels share information over a proprietary 1,000,000 baud network, Intelli-Net.

Special software was written by R. L. Shields Associates, Inc. to accomplish several of the tasks designated as goals. Custom software included:

1. Zone Control Software - This software was unique because sequencing the zones in conjunction with the static pressure control was critical. If static pressure was not unloaded completely prior to the zones transitioning from occupied to unoccupied could result in duct over-pressure. In essence, the static pressure anticipates the change in zone status. After the zones transition, the software then makes a decision whether to run one air handler unit or two, based on the number of zones. The approximate vane control output signal is calculated and sent to the static pressure vanes at which time the normal static pressure control algorithm is restarted.
2. Demand Side Management Software - This software is used to calculate the electrical demand, consumption and projects demand based on a minute by minute calculation. This enables the computer and operator to make changes in operation to avoid setting demand peaks. At 25 Burlington Mall Road, demand is approximately $10.00 per kilo watt in the winter months and approximately $27.00 per kilo watt in the summer months. A reduction in the peak kilowatts of 100 in the summer can result in a monthly savings of $2,700.00. This software also unloads the static pressure in the building while starting the chillers. This reduces the initial demand spike. To better understand Electric Demand, click here.
3. Chiller Motor Current Limits - This software controls the chiller motor current limits. For example, if the chiller is running at 100% motor current, the load on the chiller is approximately 370 tons (1 ton equals 12,000 BTU's). Normally the chiller would start under no cooling load, transition to 100% load to cool the water to normal limits and then reduce to a sustained value matching the building load. By anticipating the building load and then limiting the maximum current the chiller can draw, the electrical demand is controlled.
4. Chiller Leaving Water Temperature Control - This software resets the temperature of the leaving water on cool, dry days to further reduce the electric consumption of the building.
5. Building Performance Tracking Software - Software was written to take the trended information and store it on the hard drive located on the PC in the Maintenance Office. This includes electrical demand and consumption information, temperature data and other items that the maintenance personnel thought was important and storing it in a database. This database has some custom software that allows for automatic creation of management reports using the standard spread sheet programs.
6. Sunrise/Sunset Time Calculation - This controls the parking lot and building exterior lighting based on Sunrise and Sunset. The eliminates the problems associated with power failures skewing the time clocks and provides for the adjustment to Daylight Savings Time and Daylight Standard Time.
7. Degree Day Tracking - This software computes the heating and cooling degree days and the same manner used by the National Weather Service. Heating and Cooling Utility costs can be tracked in conjunction with heating and cooling degree day totals. This provide a means of tracking performance based on changing climatic conditions.  To better understand degree days, click here.

As previously mentioned, the Delta Turbo Panel is connected to a color host PC. The host system features Delta's IGRAPHW software. This "state-of-the-art" software package provides the user with both text information as well as providing a graphical interface. This software is also installed on the mechanical staff's personal computers to be used for off-site, after hours, operating changes. This helps the management company resolve problems and avoid some of the after hours call-ins. The maintenance staff has the ability to view all data and graphics from their home computers as they would see from their on-site computers.

Future phases of this project will include automating the tenant Variable Air Volume (VAV) Boxes and adding Carbon Dioxide sensors to monitor indoor air quality.

What do the Operators say about the project?

I was an active participant in the decision making process. I was told to pick a system that I was comfortable with, since I had to live with it. We were considering two vendors, both of which were involved with systems within this building. I chose Delta over the other system because I was sold on the reputation of the vendor, R. L. Shields Associates, Inc. My past experience has shown me that Bob Shields will not settle for anything less than the best. He has a reputation for giving the job 200%. His reputation is very important to him. If he says that Delta is the way to go, I trust his judgment. The system has done everything that he promised and more.

Robert Wolske, M.C.L.P. - Building Technology Engineers, Inc. - Boston, MA

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Intelli-Sys, Intelli-Con, Intelli-Net, and Intelli-Stat are trademarks of Delta Controls, Inc.