Outdoor Rated NEMA Enclosures Selection Guide
Choosing the right outdoor rated NEMA enclosure will help keep sensitive devices safe from flying dust, pounding rainstorms and the many other kinds of environmental hazards present outdoors. So, what’s the first step to ensuring that you choose the best electronics enclosure for your outdoor application? Being familiar with the many factors that will influence your selection.Polycase prides itself on offering a huge selection of outdoor enclosures to our customers. At the same time, we understand that it can be challenging to select the right model from such a wide variety. That’s why we’ve assembled this brief guide to outdoor rated NEMA enclosures.Our outdoor NEMA enclosure guide presents the many options that we have available for rugged outdoor grade enclosures. With a thorough understanding of each aspect of the enclosure selection process, you’ll be able to evaluate your many choices and select the right enclosure. First up: Let’s discuss how to determine the necessary qualities and features for your outdoor NEMA enclosure. 

Considering Your Application

Before you investigate enclosure options, think through the qualities that your outdoor rated enclosure needs to have. An outdoor electrical junction box will have different needs from an outdoor network enclosure compared to a lockable electrical box. Consider all of these application factors when choosing an enclosure:
  • The temperatures to which the device will be exposed
  • The weather conditions to which the device will be exposed
  • Whether the device will be subject to submersion
  • Whether the device will be exposed to corrosive substances (including salt water)
  • Whether the device will be exposed to flying particulates like dirt, dust and debris
  • Whether the enclosure will need a hinged cover or door for easy access
  • Whether the enclosure will need to be a locking electrical box
  • Whether the enclosure will need a clear cover for easy instrument reading
  • The amount of heat that the components in the enclosure will generate
  • What kind of mounting features (such as mounting feet or PCB bosses) the enclosure will need
We’ll give a brief overview of each of these factors here. We can address the weather- and environment-related factors through a relatively simple and widely used system called NEMA ratings.

What Is a NEMA Rating?

The NEMA rating scale is a critically important tool developed by the National Electrical Manufacturers Association. This scale uses numbers and letters to rate an enclosure’s protective qualities against environmental hazards. NEMA ratings are the most widely used enclosure rating system in the United States. The NEMA rating system includes factors such as:
  • Protection from flying particulate matter, such as dust and debris
  • Protection from water, oil or coolant ingress
  • Protection from corrosion 
  • Protection from ice formation on the enclosure
  • Protection from incidental contact by employees or objects
NEMA ratings use a roughly ascending order, starting at the lowest level of protection with NEMA 1 enclosures. However, it’s important to note that some numerically higher ratings are actually not the highest available. For example, NEMA 12 and NEMA 13 enclosures, despite their higher numbers, are actually lower-rated enclosures that are suitable only for indoor applications. An enclosure with a higher NEMA rating will usually also carry the ratings below it. For example, most of our NEMA 6P enclosures also include NEMA 4X, NEMA 12 and NEMA 13 ratings. However, you should still be sure to check each enclosure’s ratings thoroughly. 

Which Enclosure Material Should You Choose?

Polycase offers several choices for outdoor NEMA rated enclosure materials. Each material offers its own combination of features, so the best choice depends on your intended application. Which Enclosure Material Should You Choose
  • Stainless Steel: A famously durable and attractive material created by alloying steel with other elements like molybdenum and chromium. It’s pricier than other materials, but provides outstanding performance for most applications. 
  • Carbon Steel: Steel with a higher carbon content that’s used around the world for a variety of industrial applications. It doesn’t provide the same level of corrosion resistance and aesthetic excellence as stainless steel, but it’s less expensive and still provides great protection. 
  • Polycarbonate: A versatile hard plastic material that’s resistant to almost every environmental condition and offers many design options. For many applications, polycarbonate offers an ideal balance of price, aesthetics and durability. 
  • Aluminum: Another extremely durable and attractive metal material that offers natural radio frequency shielding. Aluminum provides great all-around performance, although it costs more and can be vulnerable to denting. 
We also offer ABS plastic enclosures, but they’re generally rated only for indoor use. For a detailed analysis of the pros and cons of each material, see our enclosure material selection guide. 

Mounting Hardware for Outdoor Rated NEMA Enclosures

Most electronics enclosures will be mounted on a surface, such as a wall or control panel. In addition, many applications require a place in the enclosure to mount internal components, such as printed circuit boards (PCBs). That means that you’ll need to pay attention to the external and internal mounting hardware that’s available for each model of enclosure. Mounting Hardware for Outdoor Rated NEMA Enclosures
  • External Mounting Hardware
    • Mounting feet and mounting flanges are the most common types of external mounting hardware. Mounting feet are a set of four small attachments on the exterior of an enclosure that allow it to be mounted using screws, while mounting flanges are sets of two larger pieces with the same function. Many of our enclosures offer built-in mounting feet or flanges, but we also offer screw-on mounting feet. If you need to mount your device on a utility pole, make sure to choose a pole mount kit compatible with your enclosure. 
  • Internal Mounting Hardware
    • Many enclosures also need internal hardware to allow device components to be mounted. DIN rails and panels are two of the most common kinds of internal mounting hardware. A DIN rail is a metal rail inside an enclosure that allows for the easy mounting of equipment like circuit breakers. We offer DIN rail kits that are compatible with some of our most popular enclosures. Many Polycase enclosures offer internal mounting panels to assemble components to. The panels are then secured with screws to internal mounting bosses molded inside the enclosure’s base or cover.  We also offer adhesive PCB mounting standoffs for custom mounting configurations. 
Polycase SA-49 with Hinged Locking Cover

Polycase SA-49 with Hinged Locking Cover

Hinged and Transparent Covers for Outdoor NEMA Enclosures

Enclosures that house devices like control panels and circuit breakers often need to have a hinged cover for quick access. Many of our enclosure models, such as the Polycase SA Series and Polycase ZH Series, offer hinged covers. These covers are designed with sealing  waterproof gaskets, so the enclosures still offer professional-grade outdoor performance. If you choose an enclosure with a hinged cover, make sure that it includes a locking mechanism to protect access. Some Polycase lockable electrical enclosures, like the SA Series, come with their own built-in keyed mechanism. Others, like the ZH Series, include a lock staple on their latch where a padlock can easily be attached. Both options are a great fit for a lockable junction box.Finally, some applications (such as electrical meters) require an easy way to examine a device without opening the enclosure. For these applications, many of our enclosures are available with optional transparent covers. The Polycase ML Series and Polycase WC Series are two of our most popular clear cover enclosures.  

Heat Dissipation and Venting in Outdoor NEMA Enclosures

If the device components in your enclosure generate heat, remember that you’ll have to consider heat dissipation methods. In some enclosures, passive ventilation will be enough, while others will require active ventilation measures. First, you’ll need to determine how much the heat from your components will raise the temperature inside your enclosure. Our guide to calculating heat rise in an enclosure provides an in-depth look at how to perform this critical calculation. Determining your heat rise level will allow you to evaluate what kind of ventilation your enclosure will need. If you need active ventilation, make sure to leave room for motors, blower fans and any other forced air elements that may be required. No matter which type you use, make sure to also pick up any enclosure venting accessories that you might need. 

Polycase’s Best Outdoor NEMA Rated Enclosures

Polycase has our industry’s widest selection of outdoor weatherproof enclosures models in many different materials and designs. In this section, we’ll give a brief overview of four of the top outdoor NEMA enclosure options from Polycase: Polycase SA Series
  • NEMA 4X Outdoor Enclosures
    • Polycase SA Series: Our stainless steel enclosures are some of our most rugged and sharpest-looking models. SA Series models feature a hinged and gasketed steel door with a keyed quarter turn latch closure for easy and secure access to your locking electrical box. 
    • Polycase HD Series: These polycarbonate enclosures are designed for powerful outdoor performance. The HD Series is equipped with key built-in features, such as a silicone rubber gasket that makes these models highly resistant to both liquid and dust ingress.
  • NEMA 6P Outdoor Enclosures
    • Polycase AN Series: The AN Series are as elegant as they are functional. These aluminum enclosures are rated for extreme watertight performance that keeps devices safe–even in the most hostile conditions.
    • Polycase ML Series: Our most protective and durable polycarbonate enclosures, the ML Series is precision-molded for an ultra-tight fit. Includes gray or clear cover options and features an impact-resistant design.

Common Mistakes to Avoid When Choosing Outdoor NEMA Enclosures

It’s important to know the common missteps in the enclosure selection process so that you can avoid them. Here are some typical enclosure selection errors that you’ll want to be aware of: 
  • Choosing a NEMA 12 or NEMA 13 enclosure for an outdoor application. Remember that NEMA 12 and NEMA 13 enclosures are actually rated only for indoor use, despite being numerically higher than some outdoor NEMA ratings. 
  • Assuming that enclosures listed as “NEMA rated” have been approved by a testing authority. NEMA does not perform tests itself, and any manufacturer can claim that their products satisfy NEMA rating conditions. Polycase independently tests all of our enclosures via Underwriters Laboratories, the gold standard for product safety laboratories. 
  • Choosing an RF-shielded material for devices with internal antennas. The natural RF shielding found in enclosure materials like aluminum and stainless steel can be useful in outdoor network enclosures that need to protect their devices from electrical interference. However, it also blocks transmission from Wi-Fi antennas inside the device. In such a case, you’ll want to either use an external antenna for your device or choose a non-shielded material such as polycarbonate. 
  • Choosing a stainless steel enclosure for an application that needs machined cutouts. Machining stainless steel requires expensive specialized tools because the material is so hard. Choose another material like polycarbonate or aluminum instead. 
  • Choosing an enclosure that’s too small. Just because an enclosure is big enough to fit all of your device components doesn’t mean it’s actually as big as it needs to be for your application. Choose an enclosure that’s big enough to accommodate your heat dissipation needs and provides enough space for safe and efficient assembly. 

Customizing Your Outdoor NEMA Rated Enclosure

Outdoor NEMA enclosures often require a variety of features, such as machined cutouts and custom printing. With Polycase’s enclosure customization options, our customers can turn a stock enclosure into a turn-key custom enclosure ready to go to the assembly line. Polycase’s custom CNC machining service offers precision-machined cutouts to most of our enclosure models. We use state-of-the-art machining tools that cut with a tolerance of just +/- 0.005”, and our efficient manufacturing process reduces scrap costs. If you’re including cutouts for vents and cable glands on your enclosure, make sure to also browse our selection of enclosure accessories to keep your enclosure weathertight.Our custom digital printing, meanwhile, creates bright and attractive images on your enclosure, and our printing process ensures that the graphics won’t crack or peel like other labeling  methods do. It’s an easy way to provide key operating information on your device enclosure or simply to give your device an eye-catching and on-brand look. Polycase ML-47F Polycarbonate Outdoor NEMA Enclosure

Polycase ML-47F Polycarbonate Outdoor NEMA Enclosure

Polycase’s experts are always glad to assist our customers with choosing an outdoor rated NEMA enclosure model. Just call us at 1-800-248-1233 for a free consultation or contact us online for more information. 
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