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:
- 2 - 370 ton York Centrifugal Chillers
- 2 - Large Air Handlers that utilize 3 Joy axial fans
each, 2 supply fans and one return fan
- 2 - Marley Cooling Towers
- 1 - Evapco Cooling Towers (For Computer Room A/C Units)
- VAV Boxes (Exterior boxes have electric heat coils)
- Pneumatic Controls
- DDC System Interface to the Pneumatic Controls
- EMS System Interface to the DDC System Interface
The initial project involved replacing both the DDC and
EMS systems since both were approximately 10 years old and parts were very hard,
if not impossible to obtain. While updating the equipment, management put forth
a list of goals that they wanted to accomplish during the replacement. These
- Minimize operating and energy expenses.
- Track the buildings mechanical performance.
- Automate the present zone control system.
- Interface to the chiller system to control leaving water temperature and
motor current limits.
- Maintain the integrity of the pneumatic control system for back-up control.
- Install a Graphical Operator Interface.
- 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
The two Delta Turbo Panels control the following:
- Supply and Return Air Handler Fans
- Inlet Vanes on the Air Handler Fans to Duct Maintain
- Modulate Valves and Dampers to maintain correct discharge
- Start and Stop the two York Centrifugal Chillers
- Motor current limits and leaving water temperature for
- Modulate bypass valves to maintain correct hot and cold
deck temperatures and flow rates.
- Control the Speed of the Evapco Cooling Tower Fans
- Start and Stop make-up water to the cooling towers
- Control eleven floor zones (Occupied/Unoccupied)
- Monitor Electrical Consumption and Demand and performs
Demand Management Control
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
Special software was written by R. L. Shields Associates, Inc. to accomplish
several of the tasks designated as goals. Custom software included:
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
Links to additional graphics
for this project
AIR HANDLER GRAPHIC
VAV BOX GRAPHIC
TYPICAL FLOOR PLAN
CHILLER CONTROL GRAPHIC
COOLING TOWER GRAPHIC
ELECTRICAL DATA DISPLAY
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
For more information on this project or Delta Controls, contact:
R. L. Shields Associates, Inc.
27 Wentworth Drive
Bedford, NH 03110
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