Subsection A5.207.2.3 applies to heat rejection equipment used in comfort cooling systems such as air-cooled condensers, open cooling towers, closed-circuit cooling towers and evaporative condensers.
Each fan powered by a motor of 7.5 hp (5.6 kW) or larger shall have the capability to operate that fan at 2/3 of full speed or less and shall have controls that automatically change the fan speed to control the leaving fluid temperature or condensing temperature/pressure of the heat rejection device.
Exceptions:
- Heat rejection devices included as an integral part of the equipment listed in Tables A5.207.1-A through A5.207.1-E.
- Condenser fans serving multiple refrigerant circuits.
- Condenser fans serving flooded condensers.
- Up to 1/3 of the fans on a condenser or tower with multiple fans where the lead fans comply with the speed control requirement.
Open cooling towers configured with multiple condenser water pumps shall be designed so that all cells can be run in parallel with the larger of:
- The flow that’s produced by the smallest pump or
- 33 percent of the design flow for the cell.
Open cooling towers with a combined rated capacity of 900 gpm and greater at 95°F condenser water return, 85°F condenser water supply and 75°F outdoor wet-bulb temperature shall use propeller fans and shall not use centrifugal fans.
Exceptions:
- Cooling towers that are ducted (inlet or discharge) or have an external sound trap that requires external static pressure capability.
- Cooling towers that meet the energy efficiency requirement for propeller fan towers in Section A5.207.1, Table A5.207.1-G.