DOE-2 Energy Modeling Summary - Courthouse
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Corridor, toilet rooms and elevator lobbies AHUs (Floors one through five)
Public lobbies, restrooms and utilitarian areas are conditioned via ducted ceiling supplies and
ceiling return plenum.
Operating parameters:
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Proportional zone thermostats for heating and cooling; throttling range 1.5F
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Minimum cfm ratio is 0.4
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Supply fan static pressure 2.0" H2O
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Return fan static pressure 0.6" H2O
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Fan efficiencies (combined: fan and motor): Supply - 50%; return - 25%
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Cooling deck temperature reset to satisfy the cooling load to the warmest zone
Mechanical rooms are served by unit ventilators with hot water heating coils. The parking area is
served by a separate constant volume ventilation system with no heating or cooling capability.
Cooling Plant
Two (2) 325-ton water cooled, centrifugal chillers (6.1 COP @ 100%), and one (1) 130-ton
water cooled screw chiller (4.45 COP @ 100%). Two (2) cooling towers with two speed fans to
cool condenser water. Chilled water economizer via strainer cycle with a heat exchanger
between chilled water and tower water.
Operating Parameters
Chiller:
Chilled water supply temperature 44F; throttling range 1.25F
Chilled water return temperature 56F (temperature rise 12F)
Design condenser water temperature rise 10F
Condenser water flow rate 3 gpm/ton
Economizer (waterside):
Strainer cycle with chilled-water/tower-water heat exchanger
Economizer operates when outdoor temperature is less than 55F
Cooling Tower:
Design wetbulb temperature 74F (per ASHRAE 1%, Washington DC)
Design approach 10F
Design range 10F
Wetbulb reset
Tower outlet water temperature 85F; throttling range 2.5F
Minimum water temperature 66F
Two speed cooling tower fans (high speed, 100%; low speed, 35%)
Tower capacity control: maximum cells possible at lowest fan speeds
Primary Chilled Water Pump
20 ft pump head
77% impeller efficiency
APPENDIX I - GSA LEED COST STUDY
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