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:
5.5Add 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:
9.3Change 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.
■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.
