Replacement of the domestic water system in a high-rise building.
Retrofitting any installation with new equipment can be a large challenge, especially, when there are tight quarters with limited access to the installation. The replacement project must go smoothly, so the building “down time” is kept to a minimum. The key to overcoming the obstacles isn’t just design and equipment selection. It really comes down to collaboration between the customer, mechanical contractor and the pump supplier.
Two Logan Square is a high rise building, owned and operated by Brandywine Realty and located in the city of Philadelphia. The domestic water system consists of a pair of 60 HP two-stage horizontal split-case pumps and a 30 HP jockey pump. The jockey pump ran at full speed with pressure reducing valves on each pump, with the larger pumps running on variable frequency drives, to maintain a constant pressure in the building through a large range of building flow demands.
The client was ready to replace the system with a complete new system, using the latest in pump design, controls, and with technology in an integrated package that saves energy.
The challenge is that the system was tucked into the back of a mechanical room surrounded by other mechanical equipment – getting the old system out and the new system in would be a challenge.
New design through collaboration:
After several strategy meetings between Jose Cruz (RBA Systems Manager), Les Moyer (RBA Account Manager) Fluidics (Mechanical Contractor) and Brandywine (owner), the team selected a new ultra-high efficiency variable speed system, using the SENCILLO (pronounced SEN’-see- Oh) Variable Speed Control System.
The new system was to be pre-built and tested at Robert Brown Associates’ facilities in King of Prussia, to ensure that it worked perfectly when it was installed and started up. Then the entire system was to be disassembled and taken to the site in pieces, reassembled, piped and wired, and then brought on-line in a small window of time the building was scheduled to be “down” or with no water service.
Timing was a critical issue in the project. The team determined the best time frame for a scheduled shutdown was late on a Friday night, at which time the on-site crew would have to demolish the old system, bring in the new system into the building in pieces, re-assemble it in place and wire it. The entire system had to be completely operational by the following Monday morning.
A Tight Fit:
The new system had to fit on existing concrete housekeeping pad, where overhead piping was low. This limited the ability to remove the motor to service the pumps. Additionally the suction piping and discharge piping had to match the existing location and clear all the overhead piping. Needless to say, it was a tight fit, and needed detailed planning.
Sizing it up:
To get started, the pumps were sized to meet the flow and pressure requirements of the building. Careful measurements were taken and new pumps were selected to meet building demand. The current pumps had sufficient flow and pressure. However, many of the old pumping systems were over-sized, based on old fixtures which used a lot more water than the new high efficiency ones. Building flow demand will often be lower with new fixtures, which results in a smaller pump size. In addition, today’s new high efficiency pumps can often handle flow and pressure demands at a higher efficiency. This resulted in a drop in motor horsepower. The new system selected was a triplex 40 HP unit.
Before & After:
The existing system employed an old relay logic constant speed control panel with manual switches and indicating lights. These older panels have lights that are prone to fail, constant speed starters, and old style mechanical circuitry. The horsepower was 60/30, with 3 pumps installed to do the job.
The new control system maintains building pressure using variable frequency drives. A programmable logic controller (PLC) and associates software are used to guide the whole system to maintain the system pressure.
Data from a pressure transducer in the discharge header is compared to a set point pressure input at the panel. All inputs and outputs are shown on a color Human-Man Interface ( HMI) touch screen, which clearly shows the client the status on the system – water running through pipe, pump speed, amperage and run time of pumps. Any alarms show up on this screen. Also, automatic controls to respond to a component failure or a city water main break are handled by the controller. Reports to a building management system are easily incorporated into the controls to let the operator know the condition of the pump package and displays the data in their control room. Every aspect is designed to keep water in all floors of the building.
Out with the old…in with the new:
Because of the tight space in the pump room, a pre-packaged and tested pump skid was the perfect choice for this application. The mechanical contractor implemented the change from old to new in a smooth and seamless manner.
The installation started on Friday night at 10pm when the supply line was isolated. It was completed by 4am on Saturday morning. They started up the system on Saturday night at 11pm.
A smooth operation:
The entire process took approximately 2 months from start of planning to finished job. The customer is happy with the installation and no problems have been reported. This is a success story, showing how a customer, mechanical contractor and pump supplier can achieve great results through collaboration.
Robert Brown Associates