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7

operation

A slight difference of 1/16" either way creates a large change in the trip 
point setting.

Turning the adjustment screw clockwise increases the trip point making the 
switch less sensitive to shock. Turning the adjustment screw counter clockwise 
decreases the trip point making the switch more sensitive to shock.

Adjustment — If Required

Make sure the switch is set per “Factory Setting” before making any 
adjustments.

Operate fan motor as follows:

Motor starter operation (full voltage or DOL start):

•   Start the fan motor. If the switch trips rotate the adjustment screw clockwise 

1/4 turn, reset the switch and restart the motor.

VFD operation:

•   If the VFD has a bypass motor starter follow the above procedure first using 

the bypass motor starter.

•   Using the VFD speed control, slowly ramp up the motor speed to full speed 

allowing 5 seconds for every 2 hertz of speed change. If the switch trips 
during the ramp up procedure, consider performing a vibration analysis on 
the tower operation. 

Rotating the adjustment screw clockwise increases the trip point. Turning 
counter clockwise decreases the trip point

Note

Note

Note

Figure 3

Summary of Contents for 685a

Page 1: ...IMI vibration switch I N STALLATION OPE RATION MAI NTE NANCE Z0929039_A I SSU E D 03 2017 READ AND UNDERSTAND THIS MANUAL PRIOR TO OPERATING OR SERVICING THIS PRODUCT US E R MAN UAL...

Page 2: ...s Overview General Features 3 Warnings 3 Installation Field Wiring 5 Internal Switch Rating 5 Operation Switch Setup 6 Adjustment 7 Switches with Remote Reset 8 Commissioning 10 Specifications 11 Dime...

Page 3: ...IP66 rated enclosure Remote options 24VDC Remote Reset 120VAC 60Hz Remote Reset 240VAC 50Hz Remote Reset Top cover is secured with socket head cap screws for easy access to wiring terminals If using a...

Page 4: ...s below Replacement mounting plate and hardware can also be purchased through SPX if desired 4 Make the necessary electrical connections to the vibration switch See Figure 1 for electrical terminal lo...

Page 5: ...The NO contact of Sw 2 may be used to complete the alarm circuit When the switch trips this contact will close and complete the alarm circuit Internal Switch Contact Ratings The vibration switch uses...

Page 6: ...s depressed If it does not remain depressed turn the sensitivity adjustment screw clockwise until it does Figure 3 Turning the adjustment screw clockwise increases the set point at which the switch wi...

Page 7: ...ter operation full voltage or DOL start Start the fan motor If the switch trips rotate the adjustment screw clockwise 1 4 turn reset the switch and restart the motor VFD operation If the VFD has a byp...

Page 8: ...ton station A mechanical switch is designed to sense a high shock or severe vibration event and cannot sense low vibration frequencies sometimes associated with cooling towers When the switch trips it...

Page 9: ...f the reset coil was recently energized Since the coil needs the peak current only for a short period of time the thermistor lowers the current but it is still strong enough to hold the switch in rese...

Page 10: ...s 6 Minutes 8 Minutes 1 Minute 3 Minutes 4 Minutes 30 seconds 1 5 Minutes 2 Minutes A power ON delay may be required when starting tower fan motor across the line DOL A 15 second delay is suggested to...

Page 11: ...id 2442496 Manual external reset button and 240 VAC 50 Hz remote reset solenoid Model Startup Delay Trip indication Enclosure type Conduit fitting Electrical Certification 2396245 No External red indi...

Page 12: ...terest of technological progress all products are subject to design and or material change without notice IMI vibration switch US E R MAN UAL SPX COOLING TECHNOLOGIES INC 7401 WEST 129 STREET OVERLAND...

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