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Marley
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Sigma F Series Cooling Tower
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Specifications: Options
27
Specification Value
■ Unless specified otherwise, a Robertshaw or Metrix switch will
be provided. Double-pole, double-throw models are also avail-
able. 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.
■ This option is for those customers who either prefer steel lad-
ders, or whose atmospheric conditions at the cooling tower loca-
tion would be detrimental to aluminum.
consist of start and stop control, bypass/
VFD selector switch, Auto/Manual selec-
tor switch, manual speed control, and
solid-state temperature controller. An
emergency bypass selector switch inter-
nal 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 sys-
tem shall de energize the motor once
25% motor speed is reached and cool-
ing 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 natural frequency vibration
levels which may exceed CTI guidelines.
Vibration Limit Switch:
5.5 Add the following paragraph in the
Mechanical Equipment Section: A
single-pole, double-throw vibration
limit switch in the NEMA 4 housing
shall be installed on the mechanical
equipment support for wiring into the
owner's control panel. The purpose of
this switch will be to interrupt power
to the motor in the event of excessive
vibration. It shall be adjustable for sen-
sitivity, and shall require manual reset.
Miscellaneous Options
Galvanized Steel Ladder:
9.3 Change paragraph 9.3 to read as fol-
lows: One endwall of the tower shall
be equipped with an 18" (457 mm)
wide hot-dip galvanized steel vertical
ladder, supported by hot-dip galva-
nized steel brackets through-bolted
to the endwall structure. Ladder shall
rise from the cold water basin level
to the top of the fan deck guardrail,
and shall be designed and installed in
conformance with OSHA standards. A
horizontal-swing, gravity-closing safety
bar shall be provided across the ladder
opening at the fan deck.