On the Boards | The Season of the Chiller
Bailey Edward had the privilege of working on four different chiller replacement projects in 2016-2017 for the U.S. Geological Service Upper Midwest Environmental Service Center, the U.S. Department of Agriculture National Centers for Animal Health, Veterans Affairs, and the General Services Administration E. Ross Adair Federal Courthouse. Each project included initial reports to determine the issues and solutions and progressed through design, construction, and commissioning.
USGS Upper Midwest Environmental Sciences Center (UMESC) Chiller Replacement – Lacrosse, WI
The existing chiller plant was reaching the end of its useful life and needed to be replaced. Comprised of two water-cooled chillers, a Multistack (200 ton) and a Carrier screw chiller (250 ton) connected in a series, during design days the central plant did not have enough capacity to maintain the building requirements.
Therefore, a larger (290 ton) Multistack chiller and a smaller (60 ton) Multistack heat recovery chiller were installed. This chiller rejects the heat to the building heating system used for the reheat function to control temperature / humidity, so the gas boilers do not have to operate. The existing series chilled water piping configuration was changed to a parallel configuration.
USDA National Centers for Animal Health (NCAH) Chiller Replacement – Ames, IA
The scope was to replace the existing combination central plant (electric, steam absorption and natural-gas-driven) with an absorption chiller, the largest available at that time. The existing condenser water and cooling tower had excess capacity to support the new chiller’s additional condenser water requirements.
Different orientations of the new chiller, associated required clearances, and piping connections within the existing space constraints ultimately required removal of a wall. As well, a 10’ x 16’ opening/overhead door in the existing precast exterior wall was made to install the chiller.
The temperature controls were carefully coordinated to provide the amount of information and in the correct form (graphics) to match the previous installation. A new high-pressure steam line needed to be extended from the existing high-pressure system (125 psi) along with a new condensate return system, receiver and pump. The chiller required 5 psi steam pressure, so a pressure reducing station with sound attenuator to reduce the pressure from 125 psi to 5 psi was added.
VA Chiller Replacement - North Chicago
Chiller #3 in the central plant was damaged beyond repair and needed to be replaced. The replacement had to modulate below 100 tons, which is the plant minimum load. The existing central plant consisted of (5) 1,000 ton electric chillers and (1) 1,500 ton steam chiller (able to modulate down to 500 tons) connected to five, 1000 ton cooling towers.
BE performed a life-cycle analysis to compare an electric to a steam chiller. Specifically, a 750 ton electric with VFD was compared to a 1,500 ton steam absorption chiller to determine payback time if the steam chiller was used. The steam chiller’s payback was nine years and electric chiller solution was selected by the client.
GSA E. Ross Adair Federal Courthouse Chiller Replacement - Fort Wayne, IN
The existing chiller plant (2-120 ton McQuay water chillers with air-cooled condensers) was nearing the end of its useful life and needed replacement. The existing pumps were secured to the concrete without spring-isolated floating bases, chillers without flexible connections, and standard hangers in lieu of spring isolated hangers were creating some noise issues.
A life-cycle analysis for a 25-year period compared chillers with air-cooled condensers; chillers with evaporative condensers; and centrifugal magnetic bearing chillers with cooling towers. Due to building restraints, noise/visual restraints, and location of the proposed condenser/cooling tower location, the air-cooled condenser option was selected.
Two, 168 ton water chillers with remote air-cooled condensers were installed to provide additional capacity during extreme design days. To solve visual and air noise issues, the air-cooled condensers were moved to a different area of the roof. A new structural beam/station/grating system was designed to support the condensers and provide proper clearances and access for maintenance. Direct digital controls (DDC) were upgraded with additional control/monitoring points and associated sequences to provide the flexibility the user required.