Rockwell Automation 1772-LV,D17726.6.1 A and I MNL MINI-PLC-2/15 PROCESSO - Manual (Page 26)

Assembly and Installation
Chapter 3
3Ć6
Enclosure Considerations
An enclosure is usually provided by the user for housing the Mini-PLC-2/15
Controller. The enclosure is the primary means of protecting the Controller
from atmospheric contaminants (oil, moisture, conductive dust or particles, or
any corrosive or otherwise harmful airborne substance). Standards established
by the National Electrical Manufacturer’s Association (NEMA) define
enclosure types based upon the degree of protection the enclosure provides the
components mounted inside. In general, an enclosure which conforms to the
NEMA standard for Type 12 enclosures is preferred for solid state control
devices.
The enclosure should be mounted in a position which allows the doors to be
opened fully and allows access to wiring and components for testing or
troubleshooting. Also important is the accessibility to a disconnect device in the
enclosure.
The Mini-PLC-2/15 Controller requires a minimum of 8 inches of “working
depth” in the enclosure. Working depth is the distance from the rear of the
Chassis when mounted in the enclosure to the inner-most surface of the
enclosure door when closed. This would take into account print pockets
mounted on the door. Carefully examine the vendor’s data sheets for print
pockets mounted on the door and stand off measurements when calculating the
working depth of an enclosure.
Component Spacing Considerations
Mini-PLC-2/15 Controller components must be spaced sufficiently from other
equipment and the enclosure walls to allow convection cooling. Convection
cooling draws a vertical column of air upward over the Controller module
surfaces. To keep the Controller modules within the specified temperature
limits, this cooling air, drawn in at the base of the Controller, must not exceed
60
0 C (140 0 F). Because of this vertical flow of air, the obstructed vertical
spacing above and below the Controller components is important.
The temperature of the air must not exceed 60 0 C (140 0 F) at any point
immediately below any chassis. The failure rate of the semiconductor devices
will increase significantly if the temperature is raised above 60)C.
The temperature will tend to be higher toward the top of the enclosure. Factors
which determine the level at which the temperature will be 60
0 C include the
size of the enclosure, the power dissipation within the enclosure, and the
temperature of the air outside the enclosure.
The following rules apply to the placement of Mini-PLC-2/15 Controller
components in relation to each other. Figure 3.5 and Figure 3.6 illustrate the
spacing recommendations for two Power Supply mounting configurations.