Tech Talk: Push System Limits With Perimeter Protection

The key to any overall security system is planning and implementing several layers of security technology. A primary element is the outdoor perimeter layers. Learn about technologies and standards you’ll need for success.

NEMA 8 — hazardous locations; NEC class 1 (circuit breaks immersed in oil).

NEMA 9 — indoor Class II, Division I hazardous locations with combustible dust atmospheres; NEC class 2.

NEMA 10 — explosion-proof; meets U.S. Bureau of Mines requirements for explosive atmospheres; designed to contain gas or vapor explosions and prevent ignition of surrounding atmospheres.

NEMA 11 — acid- or fume-resistant; provides for immersion of enclosed equipment in oil.

NEMA 12 — industrial, indoor use; resists ingress of oils, dust and moisture to satisfy individual requirements.

NEMA 13 — Oil-tight and dust-tight; intended for indoor use.

Grading Other Rating Systems

Another rating system for enclosures you might run across is the International Electrotechnical Commission (IEC) 60529 Ingress Protection (IP) standard. It has a two-digit number in which the first figure indicates the degree of protection against objects from dust to greater than 50mm in size and against moisture from water dripping, spraying, and immersion under pressure.

NEMA is more prevalent in the United States while IP prevails internationally. There is no exact equivalency between NEMA and IP ratings. However, NEMA has drafted No. 250 Appendix A as a guide to distinguish relationships among the ratings. An example would be that a NEMA 4 / 4X is similar to IP56. NEMA typically exceeds similar IP ratings.

You will also see similar UL (UL50 / UL508) and Canadian Standards Association (C22.2 No. 94) test ratings similar to what NEMA offers. While UL and CSA require enclosure testing by qualified evaluators, NEMA does not and instead leaves compliance to the manufacturers.

Bob Dolph has serv
ed in various technical management and advisory positions in the security industry for 30+ years. To share tips and installation questions, E-mail Bob at Check out his Tech Shack blog.

Tech Talk Tool Tip

[IMAGE]12235[/IMAGE]Proper protection of exterior perimeter equipment is important, and so this month I am featuring enclosures from Safety Technology Int’l ( of Waterford, Mich. The enclosure shown is the STI-7560AC. This unit has air conditioning for protecting equipment in harsh, hot environments.

Make sure to check out the wide variety of enclosures available from several manufacturers for protecting your security equipment, and your clients’ safety and investment.


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About the Author


Bob is currently a Security Sales & Integration "Tech Talk" columnist and a contributing technical writer. Bob installed his first DIY home intercom system at the age of 13, and formally started his technology career as a Navy communication electronics technician during the Vietnam War. He then attended the Milwaukee School of Engineering and went on to complete a Security Management program at Milwaukee Area Technical College. Since 1976, Bob has served in a variety of technical, training and project management positions with organizations such ADT, Rollins, National Guardian, Lockheed Martin, American Alarm Supply, Sonitrol and Ingersoll Rand. Early in his career, Bob started and operated his own alarm dealership. He has also served as treasurer of the Wisconsin Burglar and Fire Alarm Association and on Security Industry Association (SIA) standards committees. Bob also provides media and training consulting to the security industry.

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