HVAC Projects


A retrofit of the central-plant equipment and air-handling equipment in the commercial and common spaces reduces overall energy use.
A retrofit of the central-plant equipment and air-handling equipment in the commercial and common spaces reduces overall energy use.

Retrofit Team

PROJECT LEAD: Xylem Inc./Bell & Gossett
RESEARCHER: Michael Waite, Sustainable Engineering Lab, Columbia University, New York
MANUFACTURER’S REPRESENTATIVE: Wallace Eannace Associates Inc., Plainview, N.Y.
CONSULTANT: Steven Winter Associates Inc., New York
MECHANICAL CONTRACTOR: Fresh Meadow Mechanical Corp., Fresh Meadows, N.Y.
BUILDING AUTOMATION CONTRACTOR: Advanced Control Solutions, Bayshore, N.Y.
ELECTRICAL AND HVAC CONTRACTOR: Blake Electrical Contracting & HVAC, Bronx, N.Y., (718) 292-8080

The Retrofit

The 21-story Astor Place tower in New York City was completed by Related Cos. in 2005. It includes 39 residential units with commercial space on the building’s first and second floors. The HVAC system used hydronic space heating through boilers and cooling with central absorption chillers. Fan-coil units provide HVAC to residential floors; HVAC in the common and commercial spaces employs air-handling units. A retrofit of the central-plant equipment and air-handling equipment in the commercial and common spaces was conducted to reduce overall energy use with the data aiding Columbia University researchers as they tested assumptions on energy efficiency.

Xylem/Bell & Gossett provided engineering expertise, along with the pumps, drives and monitoring equipment for the project conducted in partnership with Related and Columbia University’s Sustainable Engineering Lab.

On the cooling side, the original 30-horsepower condenser water pumps were replaced with Xylem Bell & Gossett e-1510 20-hp pumps. The lower horsepower but more technologically advanced pumps immediately delivered savings in electricity use—from 25.3 kW to 18.0 kW.

Other modifications included new piping to create primary/secondary chilled water loops out of the original primary only system and the addition of Bell & Gossett Series 80 7.5-hp primary pumps. Constant primary chilled water flow optimizes chiller performance. Decoupling the loops in the original one-loop system allowed for the installation of variable flow technologies on the secondary loop. Bell & Gossett e-1510 15-hp pumps replaced the original 20-hp distribution pumps and were outfitted with variable frequency drives.

The Astor Place Energy Improvement Project consisted of three primary steps: conducting an initial energy assessment of the hydronic system, updating the system with technologically advanced pumps and controls, and adjusting the system in real time to evaluate the effects of the HVAC modifications.

Monitoring system behavior at Astor Place yielded three primary benefits: It determined whether equipment was operating as designed, assessed the amount of energy being used and the dynamic adjustments to the load’s demands, and gained a broader understanding of system behavior.

Prior to the retrofit, nearly 30 percent of the building’s common system utility costs were for pumping electricity, primarily because of the pumps being oversized for the demands of the system and the constant-speed operation at partial loads. Oversized pumps were found to cause unnecessarily high pressure differentials and flow rates in the system. Right-sized pumps paired with VFDs powering the chilled-water portion of a hydraulically balanced system delivered a dramatic 95 percent reduction in pumping energy.

When considering heating and cooling, the retrofit resulted in a computed annual pumping electricity usage of 316 MWh, a 41 percent improvement in pumping energy requirements and an estimated 12 percent reduction in the building’s central operations’ energy bills. The results from the Astor Place Energy Improvement Project can help inform decisions about new equipment and its energy-savings potential.



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