Domestic Water System Upgrade Comcast Building Application

The Comcast Center is a 58-story, 975 feet (297 m) glass skyscraper located at 17th Street and John F. Kennedy Boulevard in Center City, Philadelphia, Pennsylvania. The tower is the tallest building in Philadelphia and Pennsylvania and is the fifteenth tallest building in the United States (tenth tallest by roof height), and the tallest building built in America outside of New York City or Chicago since 1993. The building is owned and operated by Liberty Property Trust/Commerz 1701 JFK Boulevard L.P. (source: Wikipedia)

Building Domestic Water Systems

The domestic water for the building is delivered by two triplex variable speed booster pump systems, which were originally installed in 2007. The triplex Low Zone System delivers a constant 250 psi for the first 34 floors and the high zone provides 485 psi delivered directly to floors 35-52 and roof cooling towers.

Each pump system employs a series of submersible multistage centrifugal pumps with submersible motors, used commonly in the water well business. Each pump is installed into a pressurized stainless steel pipe (or a "can"). The design is selected because of the high efficiency of multistage pumps in high pressure applications, and their suitability and control in delivering water when run with a variable speed drive. The pumps are very quiet in operation, since they are, by design surrounded by the water being pumped. The design also is quite compact.

The Problem: High Zone System Controls Issues

Management at Liberty Properties wanted to upgrade the high zone system controls - a control system which controls a 25 HP jockey pump (used for lower flows) and (2) 60 HP large pumps (staged on during periods of higher water usage). The existing controls were experiencing software communications issues, unwanted pressure spikes, and problems with the sequencing and staging of the pumps.

The entire control system needed a performance upgrade to provide more efficiencies and ease-of-use for the operator. The customer wanted to simplify the controls, as the original control sequence was too complex, with information and software logic that was overly complicated and glitchy.

The trick was that all of the controls had to be replaced without losing water pressure to the building. The building had to stay "live" during the changeover. Therefore, pumping had to continue during the critical changeover to the new controls. A failure of the controls during the changeover could mean a loss of water, and closure of the building, which would be a major disruption to operations.

Controls upgrade:

Robert Brown Associates was contracted to replace the controls to address these issues. The project entailed completely revamping the control panel - new programmable logic controller (PLC) with new logic software, new communications module, variable speed drives and color touch screen Human Machine Interface (HMI) and graphics software.

Robert Brown Associates provided a proprietary SencilloTM control panel system to meet the requirements of the project. The Sencillo control system is a hardware and software package specifically designed to control a series of pumps in parallel configuration. It includes a ladder logic scheme that maintains a selected output pressure (in PSI). The logic decides which pump to run, pump speed, starting speed, acceleration and deceleration rates, sensitivity controls, and logic for staging of additional pumps to maintain the set point pressure.

All variables in the logic can be easily adjusted on the HMI to give the setup technician the ability to "fine tune" the system operation based on the building being serviced. It is a powerful software design that provides a lot of control to the technician, yet very simple design that is easy for the user to maintain.

The system also employs a series of alarm functions that are sent to the main building manager if any technical issues occur with the system. All of the data is collected at the control panel, and then the Sencillo communications package relays this information to the building manager's monitor.

The software also employs several backup functions, all designed to keep water in the building, even when internal failure of components happens.

The upgrade included new simpler internal wiring. A new dual pressure transducer was installed with an automatic switch to the backup transducer when the main transducer fails. A logic which maintains pressure even when the HMI or PLC fails is also included.

The controls were finalized with a new color HMI touch-screen to ensure ease-of-use for the operator.

The HMI screen shows a full-color, graphical representation of the entire system including:

o Piping with water flow shown

o Pump Status (Lead, Lag, Speed)

o Component Status

o Alarm Status Screen

The various screens are navigated by touch, giving the operator a complete picture of entire system at his/her fingertips.

A smooth installation...

Robert Brown Systems Manager Jose Cruz and Service Manager Jim Kelemen provided the planning, work design and installation of the system.

They began on a Thursday at 7pm and finished the installation at 5am the next day, working through the night. The newly installed controls were online and live, and worked exactly as they had planned.

After startup, complete training was provided to the building personnel on the new control system. Backup service is available and on-call 24/7 by Robert Brown technical staff.

The newly upgraded High Zone system is running smoothly and efficiently and the building owner and managers now have the confidence that the equipment and controls installed will provide domestic water pressure for years to come.

Robert Brown Associates

Tom Halley


6-C Mount Pleasant Road Aston PA 19014

Tel: 610.354.0200 | Fax: 610.354.0340

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