SPX Cooling Technologies Marley MC 7012D081 - 7012H121 Engineering Data page 25

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Marley Specifications: Options
Fluid Cooler
25
Specifications Specification Value
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 fluid temperature. The
temperature of the fluid 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 temperature of
the fluid. The drive design shall be oper-
ated as a stand-alone system without
the need for a BMS system. 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 selector switch internal to the
panel allowing the fluid cooler fan motor
to be run at full speed shall be furnished.
To prevent heating problems in the fluid
cooler fan motor and to assure proper
gear box lubrication the VFD system
shall de energize the motor once 25%
motor speed is reached and cooling is
no longer required. The VFD shall include
de-icing logic with auto canceling and
adjustable time. Speed in De-Ice mode
shall not exceed 50% motor speed. The
fluid cooler 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.