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Starting a booster fan with a current switch.


This How To focuses on how to start and stop a booster fan (generic fan or a dryer booster fan) using a current switch like the Greystone CS-425-HC-0.

Operation:
The current switch is wired into the main fan or dryer power supply and senses when that device is drawing 1 Amp of current (or more) and then closes the output switch to activate the booster fan. With a dryer booster fan you sense the power consumption of the dryer to start the booster fan. With a generic HVAC system booster fan you sense the main blower fan current consumption.

Diagram:
The diagram below shows common wiring for clothes dryers. The same principle applies to wiring generic booster fans for HVAC systems. Note that the CS-425-HC-0 has a switch rating of 2.5 Amps maximum at 120 Volts, meaning the booster fan has to draw 2.5 Amps OR LESS.




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Here are the Greystone installation instuctions:

1. Disconnect and lock-out all power sources during installation as severe injury or death can result from electrical shock due to contact with high voltage conductors. Ensure all installations are in compliance with applicable electrical codes and that the installation is completed by qualified installers familiar with the standards and proper safety procedures for high-voltage installation. Never rely on status indicating devices only to determine if power is present in a conductor.

2. Mount sensor in a convenient location, with-in or adjacent to the breaker panel. Alternatively the sensor can be installed inside the dryer electrical compartment.

3a. (3-Phase systems) Disconnect and loop the neutral power wire, white, through the current sensor and reconnect.

3b. (220 Vac 3-wire single-phase systems) Determine which of the Hot wires is active for the dryer only. (this is necessary for stacked washer/dryer units). Verify that there is sufficient current to trip the current switch (minimum of 1 amp). If required the wire can be looped through twice to increase the current read by the switch. Loop the HOT power wire trough the current sensor and reconnect.

3c. (120 Vac systems) Verify that there is sufficient current to trip the current switch (minimum of 1 amp). If required the wire can be looped through twice to increase the current read by the switch. Loop the HOT power wire trough the current sensor and reconnect.

4. Connect the fan power supply, as shown 120 Vac max, to the top terminals of the current sensor.

5. Note that the CS-425-HC-0 has a switch rating of 2.5 Amps maximum at 120 Volts.



Parts:    CS-425-HC-0 Current Switch

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Disclaimer:
Advice and information given through our representatives is checked for usability and conformance with most codes. You as the user, however, have the responsibility for verifying conformance with local codes and standards and ensuring a safe installation. Although HVACQuick.com may employ and use professionals, their advice is not meant as substitute for professional engineering services. It is the customer's responsibility to hire and retain suitable engineering and architectural professionals as required.