Central Chiller Plant Configuration Study and Central Plant Upgrade
New York, NY
The HSBC building is provided with chilled water for cooling of its office space and trading floors from a central chiller plant. The original central plant consisted of two 700 ton electric centrifugal chillers, cooling towers, and chilled water and condenser water pumps. The chillers were undersized for the load they were serving and were nearing the end of their useful life.
Multiple plate & frame heat exchangers are also located in the plant and serves various portions of the building, including the trading floors. The existing cooling towers were in poor condition and were also in need of replacement.
There also are additional condenser water circuits connected to the cooling towers and condenser water systems serving water cooled cooling units for some areas of the building.
A study was provided to review the options to replace the existing chillers.
Options included review of the feasibility of using steam driven chillers or a steam/electric hybrid plant. An operating cost model was built to evaluate the different plant configurations using hourly weather data, equipment performance, utility rates, energy escalation and eqiupment staging as inputs into the model. Equipment block layouts were also provided to evaluate the physical layout of each option.
At the conculsion of the study, it was found that electric chillers would be more cost effective than a steam driven or hybrid plant using ConEd steam.
A design was developed to replace one of the two existing 700 ton chillers with two 800 ton electric centrfigual chillers resulting in a net capacity increase of 900 tons. The two new 800 ton chillers would be used to serve the load with the remaining existing 700 ton chiller as a backup. The overall reliability of the chiller plant was greatly enhanced.
The existing cooling towers were replaced with a new four cell cooling tower, and the existing chilled water and condenser water pumps were also replaced. Variable frequency drives were provided for the new chilled water pumps as well as for the new cooling tower fans.
The chiller plant is located on the 10th floor of a high rise office building in midtown manhattan. Rigging the equipment into the plant from the street required the use of a crane and temporarily removing glass panels at the exterior of the building.
Since the plant serves the trading floors, shutdowns needed to be kept to a minimum and the plant was required to continue operating to provide chilled water during construction. Detailed construction phasing plans were developed in the design phase to minimize shutdowns and maintain service to the building during construction.
In addition, due to the nature of the spaces being served by the plant, automatic transfer switches were installed to switch plant operations to emergency power in order to maintain chilled water service to the building in case of a power failure.
Selecting chillers that fit within the space (low headroom requirements), and providing a design that could be installed with minimal shutdowns and that would allow generation of chilled water during construction presented challenges during the design of this project.