NEMA Enclosure Ratings Explained

An outdoor PoE switch, radio or camera power supply is only as reliable as the box around it. NEMA enclosure ratings tell you what that box is built to keep out: dirt, dust, rain, hose spray, ice and corrosion. Pick a type below what the site demands and water or salt gets in; pick far above it and you pay in weight and heat for protection the job never needed.

What NEMA enclosure ratings measure

The ratings come from NEMA 250, the standard for enclosures for electrical equipment up to 1000 volts. Each type number describes a degree of protection for people against hazardous parts and for the equipment against solid objects, water, ice and, for the X types, corrosion.

NEMA’s own summary, the NEMA Enclosure Types document, stresses that each type protects against those conditions only when the enclosure is completely and properly installed. That phrase matters on a pole or a wall: a new hole, an unrated fitting or a missing gasket can undo the rating.

The common NEMA types compared

Low-voltage work mostly uses a handful of types. The table follows the NEMA definitions; the last column shows the approximate IP code each type meets or exceeds, based on NEMA’s conversion table. Published charts differ by a digit on some rows, and the comparison only works in that one direction (see the next section).

NEMA also defines 3S and 3X variants and hazardous location Types 7 to 10, which sit outside most network and security jobs.

NEMA 4X vs IP66

This is the comparison most spec sheets raise, and the honest answer is that they overlap without being equal. An IP code from IEC 60529 has two digits: the first covers solid objects and access to hazardous parts, the second covers water. IP66 means dust tight and protected against powerful water jets.

NEMA 4X covers the same dust and hose-water ground, then goes further. NEMA notes that IEC 60529 does not address corrosion, condensation, icing or mechanical damage, while the NEMA standard tests for corrosion, rust, icing, oil and coolants and includes gasket aging tests. For that reason NEMA’s conversion table runs one way only:

• NEMA to IP: a Type 4X box meets or exceeds IP66.
• IP to NEMA: an IP66 box is not automatically Type 4X, because nothing in IP66 proves corrosion resistance or ice performance.

If a drawing calls for Type 4X, an enclosure marked only IP66 does not satisfy it. If a drawing calls for IP66, a listed Type 4 or 4X enclosure will.

Choosing an outdoor network enclosure

Match the type to the worst condition the box will actually see, not the average day.

• Under an eave or in a sheltered spot: Type 3R is usually enough, and its allowance for ventilation helps with heat.
• Open pole or rooftop with blowing dust or snow: Type 3 or Type 4.
• Areas that are hosed down, such as loading docks, barns and food plants: Type 4.
• Coastal air, pool chemicals, fertilizer or road salt: Type 4X.
• Locations that can flood: Type 6 or 6P, or better, move the box higher.

Size the box for the gear plus service loops, a surge device and air space. A cramped enclosure runs hotter and is harder to service from a ladder.

Enclosure materials and radio signals

NEMA types describe performance, not material, so a Type 4X box can be stainless steel, fiberglass or polycarbonate. Painted steel suits indoor and sheltered outdoor work; stainless and nonmetallic boxes are the usual route to corrosion resistance.

Material matters most when a radio is inside. A metal enclosure blocks radio signals, so an access point or radio with an integrated antenna must sit in a nonmetallic box or use external antennas mounted outside the enclosure. When a link is planned around a radio in a box, check the antenna position early; our guide to planning a point-to-point wireless link covers line of sight and mounting height.

Heat, condensation and cable entries

A sealed box in direct sun traps heat, and PoE switches and injectors add their own. Check every device’s operating temperature range against the hottest day on site. If you add vents or a fan, use parts rated for the same NEMA type, or the box is no longer that type.

No rating stops condensation forming when the air inside a sealed box cools overnight. Rated breather vents or drains, a desiccant pack or a small thermostatic heater help on sites with wide temperature swings.

• Bring cables in from the bottom, never the top.
• Use cable glands or liquid-tight fittings rated for the enclosure type.
• Leave a drip loop on every cable before it enters the box.
• Seal unused knockouts with rated plugs.

For outdoor runs, choose cable rated for the location, as covered in Cat5e vs Cat6 for camera and PoE runs, and check the switch load with our PoE budget guide for IP cameras.

Grounding, surge and mounting outdoors

An outdoor metal enclosure and the mast or pole it hangs on must be bonded and grounded as the electrical code and the local inspector require. The principles are the same as for antennas, set out in our guide on how to ground an outdoor antenna system.

Put surge protection on every copper line that leaves the building, and protect the indoor end as well; see power conditioner vs surge protector. Mount the box where it can be reached safely, using a mast or pole from the wireless masts category where a wall is not suitable.

Where to buy enclosures for installers

The Bursma network enclosures category includes options such as an 18 x 14 x 8 inch gray metal enclosure and a medium waterproof enclosure with an Ethernet connector. Confirm the NEMA type on the product data before you specify one. Radios, switches and cable are in the Broadband and WiFi division.

For pricing and ordering, open a Bursma dealer account or contact the Columbus, OH branch.

Frequently asked questions