Installation Tips

Fan Installation and Vibration

Most fan noise is caused by the fan blades. Another noise component is motor vibration transmitted to the mounting plate. At slower speeds, depending on the design of the mount, the motor component may become a significant contributor. Should this situation be encountered, vibration isolation may help. Rubber grommets or wellnuts may be used.

For some AC fans, you may notice a humming noise or excessive heat coming from the motor especially at low speeds. This may be a sign of motor incompatibility. Try other motors or contact CRI customer service for further testing recommendations. Click here for our AC Motor Compatibility checklist.

Positioning the Sensor or Sensors

  • Temperature
    For applications with one heat source, the logical location to sense temperature would be the surface of the heat source or the air stream just above the heat source. In applications with multiple heat sources, multiple sensors can be used to sense several locations or one sensor can be placed at the exhaust. In either case consider the implications of the sensed temperature during a fan failure.In dwellings, where sensing the average temperature is important, consider placing the sensor in a central location where there is some air circulation.
  • Humidity
    The key to good humidity control is locating the sensor in a central location where there is some air circulation and very little chance for direct splashing or submersion. When a humidity sensor gets soaked it will not control properly. A jacketed cable must be used on non-isolated inputs as found on the SmartFan Nimbus II or Nimbus-HP.
  • Pressure
    Positive or negative pressure can be controlled by connecting a pressure transducer to the Nimbus II or Nimbus-HP. Whether controlling positive or negative pressure, tubing is required on at least one port to create a pressure differential. To differentiate static pressure from dynamic pressure, the use of a pitot tube at the sense point is recommended.

Mounting and Derating

  • Circuit Boards
    To achieve maximum power ratings, units should be mounted in an air stream. Note change in power ratings when in still air. Circuit boards may be mounted with snap in plastic spacers such as Richco CBS-4-19 or equivalent. Units with grounding pads should be mounted using metal spacers at these pads to minimize EMI (electrical noise). Hardware packs, that include typical mounting and connecting hardware, are available. For hardware pack part numbers and a list of components, see the Product PDF pages in our Technical Data section.
  • 4×4 Electrical Job Box
    Some units are available for mounting in a 4×4 electrical job box. When using a job box in a dwelling, consult local electrical codes for placement and hookup.
  • Nema 4X Enclosures
    For outdoor or wet indoor environments, some controls can be supplied in a Nema 4X enclosure. For best protection against the elements, mount wire side down using existing mounting holes.

Testing Tips

  • Avoid Heat Guns
    Using a heat gun or hair dryer directly on a temperature sensor forces its temperature from below the control temperature to above so quickly that the fan may seem to “switch speed”. The hot air is not being forced by the fan but by the hair dryer, and the fan, therefore, cannot control it. For best results, test the control in a complete cooling or ventilating system and change the sensor environment to simulate extreme but realistic conditions.
  • True RMS Meters
    When checking voltage in an AC system, make sure the voltmeter used is a true RMS meter. Readings taken with a meter that is not true RMS will be artificially low.
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