Project Brief

204 Second Avenue is a twelve story Verizon network building in Manhattan, full of switches and telecom equipment, cooled by a two chiller plant on the first floor and heated from district steam. KeRi was retained to study replacing the primary chiller, then to design the replacement.

The survey found a plant running on one leg. The primary machine was a 670 ton York steam absorption chiller, around thirty years old, and it was out of service: the steam control valve had failed, the solution and refrigerant pumps had failed, and spare parts for its control board were no longer available. The building was being carried entirely by what was supposed to be the standby, a five year old 670 ton Trane electric centrifugal, with nothing behind it if that machine went down.

Because the building falls under New York City Local Law 97, KeRi measured the options in carbon rather than in energy cost alone. Replacing the absorption chiller with a new 670 ton electric centrifugal came out at a 725 tCO2e annual reduction for about $1.25M. Simply reversing the roles of the two existing machines gave 242 tCO2e. A 600 ton modular electric chiller gave 579 tCO2e and removed the need for a licensed operator under the city fire code, but cost more. The gap behind all three numbers is efficiency: 0.33 kW per ton for an electric machine against 2.66 for the absorption chiller.

Alongside the chiller, KeRi recommended variable frequency drives on the chilled and condenser water pumps to convert the plant to variable flow, cooling tower repairs with new isolation valves and basin heaters, and a single interlocked power feed serving whichever chiller runs, replacing the existing 800 amp disconnect with a double throw switch. The recommendation went forward into a full design that also replaced a third floor network air handler, added seventh floor economizer fans, and carried new basement supply and exhaust fans, with KeRi staying through bid, submittals, and construction administration.

MEP Engineering Scope

What We Engineered

Feasibility study and replacement design for the plant:

• Field survey and condition assessment of both chillers and the distribution
• Three replacement options modelled and priced, each measured in tCO2e
• 670 ton electric chiller replacement carried into design
• Variable frequency drives converting the plant to variable flow
• Single interlocked power feed serving whichever chiller operates
• Network air handler, economizer fans, and basement fans in the same package

Study, Then Design

The Challenge

The primary chiller in a twelve story Manhattan network building had failed and could not be economically repaired, leaving the entire load on a machine meant to be the standby. Anything installed in its place had to go into a live building that cannot lose cooling, and because the building falls under New York City Local Law 97, the decision could not be made on energy cost alone. Carbon tonnage was the number that mattered, and the three credible options differed by a factor of three.

Our Solution

KeRi surveyed the plant, verified capacities with the manufacturers, and modelled three independent options from measured performance and real operating hours, pricing each and stating its carbon reduction against Local Law 97 so the choice could be made on the governing metric. The recommended route, a new 670 ton electric centrifugal, cuts roughly 725 tCO2e a year and restores genuine redundancy, and was carried into a design that also converted the pumps to variable flow, put both chillers on one interlocked feed, and replaced a network air handler and the economizer fans in the same package.