SPX Cooling Technologies SS-NC-08A Specifications, Specification Value, Marley Premium VFD System

Marley / NC Class Stainless CoolingTower / Specifications: Options 17

Specifications Specification Value

cold-water temperature. The application must be able to handle very cold water while VFD is in a by-pass mode. Operator controls shall be mounted on the front of the enclosure and shall consist of start and stop control, bypass/VFD selection, Auto/Manual selections, manual speed control. To prevent heating problems

in the cooling tower fan motor and to assure proper gear reducer lubrication the VFD system shall de energize the motor once 25% motor speed is reached and cooling is no longer required. The cooling tower manufacturer shall supply VFD start-up assistance. Tower vibration testing throughout the speed range is required to identify and lockout any natu- ral frequency vibration levels which may exceed CTI guidelines.

Marley Premium VFD System

6.4Add the following paragraph in the Mechanical Equipment section when VFD is used as a stand alone system: A complete UL listed Variable Speed Drive system in a IP52 indoor or IP14 outdoor enclosure shall be provided. The VFD shall use PWM technology with IGBT switching and integrated bypass design. VFD output switching shall not cause mechanical issues with gearbox teeth or drive shafts. The VFD shall catch a fan spinning in the reverse direction without tripping. The panel shall include a main disconnect with short circuit pro- tection and external operating handle, lockable in the off position for safety. The system shall include a solid state, PI temperature controller to adjust fre- quency output of the drive in response to the tower cold-water temperature. The temperature of the cold water and set point shall be displayed on the door of the control panel. The bypass shall include a complete magnetic bypass circuit with capability to isolate the VFD when in the bypass mode. Transfer to the bypass mode shall be automatic in the event of VFD failure or for specific trip conditions allowing safe transfer of utility voltage to the motor. Automatic bypass with an earth ground condition is not allowed. The bypass contactor shall be cycled on and off while operating in bypass, to maintain the set-point temper- ature of the cold water. The drive design