Marley / Sigma Steel CoolingTower / Specifications: Options
Specifications | Specification Value |
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Basin Heaters:
10.2Add the following paragraph in the Cold Water Basin section: Provide a system of electric immersion heaters and controls for each cell of the tower to prevent freezing of water in the collection basin during periods of shut- down. The system shall consist of one or more stainless steel electric immer- sion heaters installed in the basin. A NEMA 4 enclosure shall house a mag- netic contactor to energize heaters; a transformer to provide 24 volt control circuit power; and a solid state circuit board for temperature and low water cutoff. A control probe shall be located in the basin to monitor water level and temperature. The system shall be capable of maintaining 40°F water tem- perature at an ambient air temperature of __ °F.
Fan Motor Variable Speed Drive:
Marley All Weather ACH550 System
6.4Add the following paragraph in the Mechanical Equipment section when VFD is used with customers Building Management System: A complete UL listed Variable Speed Drive system in a NEMA 1 indoor, NEMA 12 indoor or NEMA 3R outdoor enclosure shall be provided. The VFD shall use PWM technology with IGBT switching and integrated bypass design. VFD out put 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 discon- nect with short circuit protection and external operating handle, lockable in the off position for safety. The VFD system shall receive a speed reference signal from the Building Management System monitoring the tower fluid temperature. As an option to receiving the speed reference signal from a building manage- ment system, the drive must have the capability to receive a
VFD shall have an internal PI regulator to modulate fan speed maintaining set point temperature. The drive's panel dis- play shall be able to display the
■The basin heater components described at left represent our recom- mendation for a reliable automatic system for the prevention of basin freezing. They are shipped separately for installation at the job site.
The ambient air temperature that you fill in should be the lowest 1% level of winter temperature prevalent at site.
■Marley VFD drive systems are designed to combine absolute tempera- ture control with ideal energy management. The cooling tower user selects a cold water temperature and the drive system will vary the fan speed to maintain that temperature. Precise temperature control is accomplished with far less stress to the mechanical equipment com- ponents. The improved energy management provides fast payback. Indeed, many utilities offer generous rebates for users having installed VFD drives.
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