Control Resources, Inc., Installation Tips

CRI Catalog and Design Guide Section

For Application and Design Information See:

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.

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 as found on the H1500 must be used on non-isolated inputs
as found on the SmartFan Nimbus.

Pressure
Positive or negative pressure can be controlled with the Nimbus or by installing a pressure transducer on the Nimbus or AC-VX. 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, see the figure below.
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 (see product pages).

Click on image for larger version

4x4 Electrical Job Box
Some units are available for mounting in a 4x4 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.