G126.96.36.199 Heat Rejection (Systems 7, 8, 9, 12, and 13)
The heat-rejection device shall be an axial-fan open-circuit cooling tower with variable-speed fan control and shall have an efficiency of 38.2 gpm/hp at the conditions specified in Table 6.8.1-7. Condenser-water design supply temperature shall be calculated using the cooling tower approach to the 0.4% evaporation design wet-bulb temperature as generated by the formula below, with a design temperature rise of 10°F;
Approach10°F Range = 25.72 — (0.24 × WB)
where WB is the 0.4% evaporation design wet-bulb temperature (°F); valid for wet bulbs from 55°F to 90°F.
The tower shall be controlled to maintain a leaving water temperature, where weather permits, per Table G188.8.131.52. floating up to the design leaving water temperature for the cooling tower. The baseline building design condenser-water pump power shall be 19 W/gpm and modeled as constant volume. For computer room systems using System 11 with an integrated fluid economizer, the baseline building design condenser-water-pump power shall be increased by 3 W/gpm for flow associated with the fluid economizer. Each chiller shall be modeled with separate condenser-water and chilled-water pumps interlocked to operate with the associated chiller.
Table G184.108.40.206 Heat-Rejection Leaving Water Temperature
|Climate Zone||Leaving Water Temperature|
|5B, 5C, 6B, 8||65°F|
|0B, 1B, 2B, 3B, 3C, 4B, 4C, 5A, 6A, 7||70°F|
|0A, 1A, 2A||80°F|