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Marley
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MCW Cooling Tower
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Specifications: Options
29
Vibration Limit Switch:
6.5 Add the following paragraph in the
Mechanical Equipment section: A
single-pole, double-throw vibration
limit switch in a IP56 housing shall be
installed on the mechanical equipment
support for wiring into the fan motor
shutdown circuit. The purpose of this
switch will be to interrupt power to the
motor in the event of excessive vibra-
tion. It shall be adjustable for sensitiv-
ity, and shall require manual reset.
Basin Heater:
11.2 Add 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 threaded cou-
plings provided in the side of the basin.
A IP56 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
cut-off. A control probe shall be located
in the basin to monitor water level
and temperature. The system shall be
capable of maintaining 5°C water tem-
perature at an ambient air temperature
of _____ °C.
Fan Motor Variable Speed Drive:
Marley All Weather ACH550 System
6.4 Add 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
IP10 indoor, IP52 indoor or IP14 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
disconnect 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
■ Unless specified otherwise, a Metrix switch will be provided. A
double-pole, double-throw model is also available. If purchased in
conjunction with the Control System, it is also factory-wired. The
requirement for manual reset assures that the tower will be visited to
determine the cause of excess vibration.
■ The Marley basin heater components described at left represent our
recommendation for a reliable automatic system for the prevention of
basin freezing. They are normally shipped separately for installation at
the jobsite by the installing contractor. When purchased in conjunction
with the enhanced Control System option, however, they are customar-
ily factory-mounted and tested.
Submerged in basin water, in which zinc ions are present, copper
immersion heaters must not be used. Insist upon stainless steel.
The ambient air temperature that you insert in the specifications
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
components. The improved energy management provides fast pay-
back.
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