NEMA Rating? Seismic Rating? What Does it All Mean?

By: CableOrganizer®

server room

You need to set up a server room or electrical enclosure, but you don't want just any enclosure. Your enclosure may need to be resistant to dust, dirt, salt, or water…or maybe all the above. And what if you're in an area that's prone to earthquakes? How do you know your rack can stand up to environmental hazards, including tremors?

You've probably heard of NEMA ratings and seismic ratings, but maybe you're not completely clear on what those are — or how they work together.

We show you below how to rate your rack:


First, let's talk about NEMA, the acronym for the National Electrical Manufacturers Association, an organization founded in 1926 and comprised of experts in the electrical field, from businesses to engineers to scientists.

Contrary to what many people may think, NEMA isn't a testing or rating agency but publishes electrical standards that embrace energy efficiency. NEMA certification is voluntary, so not all products from a given manufacturer may meet NEMA standards. However, there is often a need in particular applications to have equipment that is certified to handle certain environmental challenges, and in such cases a NEMA rated product may be necessary. Steel and cement mills, mines, quarries, subway tunnels, shipyard docks, construction sites…these are all places that might benefit from an environmentally rated NEMA enclosure.


NEMA rated enclosures are given a numerical rating of 1-13. It is not progressive, meaning higher numbered ratings don't necessarily possess all the benefits of the numbers below it. Rather, each number is designated to be resistant to a certain array of environmental hazards. There are variations within some of the ratings denoted by letter (S, R, X, etc.) that indicate a specific level of additional resistance — or lack thereof. For our full list of NEMA enclosure ratings, read our other article here.

Here are a few of the NEMA rated enclosures offered by CableOrganizer®:


People sometimes conflate NEMA ratings and seismic ratings, but they're not actually the same. As discussed, NEMA ratings apply to (a) protecting people from possibly harmful components within an enclosure, and (b) protecting the components from various environmental hazards. Seismic rated enclosures, as the name implies, are meant to be used in areas with heavy vibration. This includes areas prone to earthquakes, but also extends to any area that might experience shaking, like near railroad tracks, power plants, airports, and tornado prone areas. There's also a national security component: an area that could potentially serve as a target for an attack would want to ensure that sensitive equipment is protected.

While anyone can use a seismic enclosure if they desire the added vibration resistance, whether or not it's required for a particular area, it boils down to an area being considered essential or non-essential. There are certain areas that need to remain functional in the event of an earthquake, to serve the population during an emergency (think hospitals, data centers, fire stations, and government agencies). If you're living or working in a particularly sensitive area and need 100% server uptime, you may strongly consider a seismic enclosure. There are other options, such as outsourcing your data to a Cloud service that provides as close to 100% uptime as possible. However, in such cases, your data may not be as secure as if it were housed on-site. You’ll need to weigh your options and determine what is best for you.


When selecting a seismic enclosure, there are certain features to keep in mind:

  • • Heavy duty doors — Rather than a single latch point (typically of non-seismic enclosures), an earthquake ready unit needs a minimum of three extra latches, plus high-quality hinges that can endure the flexing and twisting of a seismic event.
  • • Full welding — This provides an especially rigid structure. Welded equipment mounts can further reinforce a frame's strength.
  • • Mounting hardware — locking nuts and washers can help add extra strength to shelves, drawers and other rack-mounted components.

As with NEMA ratings, there are standards for seismic enclosures. But while NEMA ratings are determined by what substances and situations they provide protection against, seismic ratings are determined based on the areas most prone to earthquakes. There are four zones, with Zone 1 being the least threatened by seismic activity, and Zone 4 being the most threatened (ie. areas near an active fault line). Telcordia determines these zones and issues the standards that seismic enclosures must meet, with the Telcordia GR-63 CORE Seismic Standard. To receive this rating, an enclosure needs to have been put through a simulated seismic event without frame damage or dislodging of components. Beware of so-called "seismic-certified" enclosures that are said to meet International or Uniform Building Code (IBC & UBC) standards. Typically, these ratings are the result of calculations based on the cabinet's individual components, and not the stringent tests that Telcordia standards require.

Here are a few of the seismic enclosures available at CableOrganizer®:

When you have a need for an electronic enclosure in a sensitive area that's susceptible to hazardous conditions, whether it is salt water, an earthquake, chemicals, dust, dirt, and more, hopefully you have a better understanding of what type of enclosure rating you should be looking for, to make sure it's up to the task of protecting the components within.

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