How to apply panel cooling systems

Control system electronic components have temperature limits that must not be exceeded if proper system operation is to be maintained. Ensuring proper operation of electronic components requires that the temperature inside their enclosures be controlled within operational temperature limits of these devices.

By Tracy J. Coates September 1, 2001

Control system electronic components have temperature limits that must not be exceeded if proper system operation is to be maintained. Ensuring proper operation of electronic components requires that the temperature inside their enclosures be controlled within operational temperature limits of these devices. Obviously, location of each enclosure in the control system must be taken into account.

In estimating the operating temperature of an enclosed panel, specific sources of heat generation and loss must be considered. These include ambient heat gain and loss, solar load, and heat generated by the components. All these heat sources may serve to increase the internal temperature of an enclosure to a point well above ambient in many cases. If internal temperature increases unabated, a very real possibility exists that the maximum operating temperature of some of the electronic components will be exceeded.

Turn up the heat

Not all enclosure applications are located where component overheating may become a problem. Outside applications, especially in northern climates, can be subjected to below freezing temperatures that could drive internal temperatures below the minimum for proper system operation. Of particular concern, in addition to low temperatures, is that dew point might cause condensation within the enclosure. This moisture can cause device failure.

To estimate enclosure temperature extremes, determination of heat loss/gain rate must be made. This value is a complex function of enclosure size, ambient temperature, materials of construction, exterior paint color, sun exposure time, and availability of air circulation around the enclosure’s exterior.

While the required equations, physical values, and related factors are available in standard reference works, many users are probably unfamiliar with their setup and use. However, Climate Control, a software package from Hoffman Engineering Co. (Anoka, Minn.) is available for performing these calculations. Climate Control permits users to enter the panel installation parameters needed to estimate an enclosure’s internal temperature. The package works for any vendor’s enclosure.

Climate Control steps a user through a series of screens where basic design questions are asked. On each screen, a help button is available to bring up explanations of the questions/ fields on that page. The application includes solutions for metal enclosures installed both indoors or outdoors of either NEMA 12 or NEMA 4 design. In addition, a user can specify if the system will allow ventilation of the enclosure. However, the package does not allow selection of heaters and pass-through ventilation of a system.

Using the software creates recommendations for the Hoffman devices needed for maintaining the desired temperature range within the enclosure. This includes cooling and heating devices, based upon system requirements. The software provides both the Hoffman part number and drawing information of the specified devices for installation into a panel.

Adding in the Internet

When used with the Hoffman Helps electronic catalog or its website, the output from this program provides the needed information for design, specification, and purchase of the heating and cooling equipment. Availability of these extra resources is an additional help in terms of enclosure selection and technical explanation of the mechanisms of enclosure temperature control.

This review is based upon revision 2.5 of Climate Control, operating under Microsoft Windows 98. This package is available as a download file from the Hoffman web site. www.hoffmanonline.com .

For more information on Climate Control, go online at www.controleng.com/freeinfo .

Author Information
Contributing Editor, Tracy J. Coates P.E. is a consulting engineer at PCE Engineering, Johnson City, Tenn.