Marley / MD CoolingTower / Specifications: Options
36
| Specifications |
| Specification Value |
| Vibration Limit Switch: |
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6.5 | Add the following paragraph in the |
| ■ Unless specified otherwise, a 3171 switch will |
| Mechanical Equipment section: A |
| be provided. A |
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| model is also available. If purchased in con- | |
| switch in a NEMA 4 housing shall be |
| junction with the Control System, it is also |
| installed on the mechanical equipment |
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| support for wiring into the fan motor |
| reset assures that the tower will be visited to |
| shutdown circuit. The purpose of this |
| determine the cause of excess vibration. |
| switch will be to interrupt power to the |
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| motor in the event of excessive vibra- |
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| tion. It shall be adjustable for sensitiv- |
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| ity, and shall require manual reset. |
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| Basin Heater: |
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11.2 | Add the following paragraph in the |
| ■ The Marley basin heater components described at left represent our rec- |
| Cold Water Provide an electric immer- |
| ommendation for a reliable automatic system for the prevention of basin |
| sion heater for each cell of the tower |
| freezing.They are normally shipped separately for installation at the job- |
| to prevent freezing of water in the |
| site by the installing contractor. When purchased in conjunction with the |
| collection basin during periods of shut- |
| enhanced Control System option, however, they are customarily factory- |
| down. The rod type heater is installed |
| mounted and tested. |
| in the side of the cold water basin. |
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| Each heater will include an integral |
| Submerged in basin water, in which zinc ions are present, copper |
| thermostat, set point nominally 4°C |
| immersion heaters must not be used. Insist upon stainless steel. |
| but adjustable to suit local operating |
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| requirements. |
| The ambient air temperature that you insert in the specifications should |
| Fan Motor Variable Speed Drive: |
| be the lowest 1% level of winter temperature prevalent at site. |
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6.4 | Add the following paragraph in |
| ■ Marley VFD drive systems are designed to combine absolute tempera- |
| the Mechanical Equipment section |
| ture control with ideal energy management. The cooling tower user |
| when VFD is used as a stand alone |
| selects a cold water temperature and the drive system will vary the |
| system: A complete UL listed Variable |
| fan speed to maintain that temperature. Precise temperature control is |
| Speed Drive system in a IP52 indoor or |
| accomplished with far less stress to the mechanical equipment compo- |
| IP56 3R outdoor enclosure shall be pro- |
| nents. The improved energy management provides fast payback. |
| vided. The VFD shall use PWM technol- |
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| ogy with IGBT switching and integrated |
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| bypass design. VFD output switching |
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| shall not cause mechanical issues with |
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| gearbox teeth or drive shafts. The VFD |
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| shall catch a fan spinning in the reverse |
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| direction without tripping. The panel shall |
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| include a main disconnect with short |
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| circuit protection and external operating |
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| handle, lockable in the off position for |
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| safety. The system shall include a solid |
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| state, PI temperature controller to adjust |
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| frequency output of the drive in response |
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| to the tower |
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| The temperature of the cold water and |
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| set point shall be displayed on the door |
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| of the control panel. The bypass shall |
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| include a complete magnetic bypass |
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| circuit with capability to isolate the VFD |
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| when in the bypass mode. Transfer to |
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| the bypass mode shall be automatic in |
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| the event of VFD failure or for specific |
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| trip conditions allowing safe transfer |
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