Installation Considerations
In addition, Stahlin Enclosures reports that several installation factors should be considered when selecting an enclosure:

1) Equipment mounting panel. The back panels are optional and must be selected and ordered separately. Enclosure back panels can be fabricated from aluminum, painted carbon steel, fiberglass and stainless steel. The enclosure construction material and the amount of time that an enclosure may be open and exposed to the application environment should be considered in making this selection.

2) Wiring connections. Hubs for connecting conduit to enclosures include: PVC-coated metal hubs designed for use with PVC-coated rigid metal conduit systems, PVC hubs for use with PVC conduit, and aluminum hubs for use with metal conduit. All hubs use an o-ring to seal between the hub and enclosure wall. Nylon cord-grip fittings are designed to seal out moisture, dust or other foreign material, and to form a positive sealing grip when installing an entrance cord or wire through an enclosure wall. Likewise, Sigma-form, feed-through seals provide a watertight, fume-tight seal at cable entrances to enclosures.

3) Enclosure mounting. Besides typical wall-mount and floor-mount configurations, some enclosures also are available with pedestal mounting, mounting feet and/or custom-fabricated floor mounting kits.

4) Grounding. Grounding electrical and electronic equipment in enclosures is extremely important for two reasons: to ensure safety of personnel operating the equipment and to prevent equipment damage from transient voltages generated by switching conditions, system faults and EMI/RFI. Grounding continuity must be maintained between the equipment in the enclosure and the conduits or cables entering and exiting the enclosure. Because fiberglass is an insulator, grounding must be maintained by using jumpers between internal equipment and conduit or cable connections in fiberglass enclosures. To meet this need, conduit hubs for use in fiberglass enclosures must have built-in grounding screws to comply with U L and NEC requirements.

The key to a reliable electrical system including the enclosure is a grounded system with all materials properly selected for the application and installed in accord with the recommended installation guidelines, the product listing and NEC. For more information on grounding, refer to UL’s Specification UL 50 and NEC Code's Article 250.

Selection Instructions

To help users learn to pick the most appropriate housings, Stahlin Enclosureshas compiled a 32-page guide, which is available by clicking on the "Techncal Tools" section of its website. The guide covers sizes, ratings, materials, fastenings, and other features, and even has a worksheet that users can fill out to help calculate their specifications. One of its many useful tables is presented here:

IP, NEMA Protection Categories

To protect valuable electrical and electronic components, enclosures must withstand a wide range of environmental influences, whether they're located indoors or outdoors. Rittal presents many definitions and combinations of IP and NEMA rating on its www.rittal.com. website. Visitors can click on "Technical Information" under "Services & Support," and then clock on "Protection Categories," or go to http://www.rittal.com/services_support/technical_information/protection_categories/index.html.