Specifications

Specifications
Specification Value
MH Fluid Cooler — Specifications: Options
23
shall be provided for voltage isolation dur-
ing VFD maintenance. An integrated full
voltage non-reversing bypass starter shall
be furnished allowing fan motor operation
if VFD has failed. In the event of a system
fault the VFD program logic shall evaluate
type of fault determining if safe to auto-
matically transfer fan motor to the bypass
starter. Automatic bypass with an earth
ground condition shall not be allowed.
Once in bypass mode the internal con-
trols will continue to monitor cold water
temperature and cycle the fan motor on
and off maintaining cold-water set point
temperature. The drive system shall be
designed and operated as a stand-alone
system without the need for a BMS sys-
tem. Operator controls shall be mounted
on the front of the enclosure and shall
consist of Start and Stop control, Bypass/
VFD selector switch, Auto/Manual
selector switch, Manual speed control,
and solid-state temperature controller.
An emergency bypass starter selector
switch internal to the panel allowing the
fan motor to be run at full speed shall be
furnished. The system shall include a solid
state PI temperature controller to adjust
frequency output of the drive in response
to the tower cold-water temperature. A
four-wire RTD with dry well shall be fur-
nished with the VFD and field installed
into the cold-water discharge pipe coming
from the fluid cooler cell. The temperature
of the cold-water and set point shall be
displayed on the door of the control panel.
The bypass starter shall be integrated into
the same enclosure as the VFD includ-
ing complete circuitry to isolate the VFD
when in the bypass mode. To prevent
heating problems in the fan motor the
VFD system shall de-energize the motor
once 25% motor speed is reached and
cooling is no longer required. The VFD
shall include deicing logic and manual
control with the ability to reverse fan rota-
tion including auto canceling with adjust-
able time. Speed in deice mode shall not
exceed 50% motor speed. The manufac-
turer shall supply VFD start-up assistance
by a certified technician.
WITH MARLEY
PREMIUM VFD
SINGLE
SPEED MOTOR
$300,000
$100,000
FIVE YEAR AVERAGE ENERGY COST
$200,000
20% reduction in fan speed will typically save 50% of electrical energy