What Is An Electrical Control Enclosure And How Is It Rated?


August 16, 2022

In the industry, there are three different types of ratings for electrical control panel enclosures: NEMA, IP (ingress protection in the EU), and UL types (1, 3R, 4, 4x, and 12). For the sake of this blog, let’s talk solely about UL type ratings.

1 – This is an indoor-only type cabinet. It is designed to protect against falling dirt and contains enough gasketing material on doors, etc, to not allow any dirt inside enclosure.

3R – This is an indoor/outdoor enclosure. It is designed to protect against accidental contact and falling dirt, rain, sleet, and snow. It also provides protection against any natural water or splashes from a car driving by as well as external ice formation. It is required to have a weephole inside to allow any water to drain out. It features a built-in gutter system on top, so rain slides off. An example of this type of enclosure is traffic light controls.

4 – This is an indoor/outdoor enclosure. It is designed to protect against falling dirt, windblown dust, rain, snow, sleet, splashing water, and hose-directed water. It features a better seal than the 3R, so it can withstand being sprayed off and cleaned with a pressure washer or hose. Constructed with mild steel and typically painted and powder coated, this enclosure doesn’t require a weephole because water can’t get inside.

4x – With all the same characteristics as a 4, the ‘X’ means it’s corrosion proof to some level. Made out of 304 or 316 grade stainless steel, aluminum, fiberglass or plastic, these enclosures are used in extremely corrosive areas. A typical example of this type of enclosure would be found on an offshore oil rig exposed to salt air.

12 – This type of enclosure is indoor only and is designed to protect from falling dirt, windblown dust, minor dripping and splashing water, and minor dripping or splashing oil and other non-corrosive materials. It also protects against lint and other types of fibers.

When it comes to rating panels, it’s important to note that any components you add to an enclosure (such as push buttons, touch screens, A/C inside, etc.), must have the same rating as the original enclosure itself to maintain that rating. UL tests certain additional types of equipment but mixing and matching components ultimately gives you an alternate enclosure rating. For example, if you put a type 4 push button on a type 12 enclosure, then the new enclosure rating is a type 5. Similarly, when an enclosure gets installed in the field with all its conduit pipes and connections, if the enclosure leaves as a type 5, you have to have type 5 fittings to maintain the seal and rating.

With all of that being said, there are ways around using differently rated components. For example, it’s possible to buy a window kit rated 12 that goes over a lesser rated touch screen in order to maintain the original rating.

The bottom line is: you always need to read the data sheets and match specs for add-on components to ensure they will maintain the high rating of the original enclosure.

Explosion proof enclosures

There’s another type of enclosure that is designed to function in even more extreme environments: explosion proof enclosures. They’re meant to go in hazardous locations where ignitible gas or vapor is free floating in the air around where that enclosure needs to be installed. They’re constructed in such a way that they keep explosions contained inside so they don’t get outside and cause a larger explosion.

Here’s how they work: most enclosures have a single three-point latch. But explosion-proof boxes have a large flange all the way around with bolts every couple inches. They’re made of cast aluminum and you have to remove all the bolts to take the cover off. They’re designed to take an explosion without cracking internal parts. They do this by having the flanges between each bolt cool the spark so it’s too cold to ignite once it exits.

For hazardous location panels, you can use type 4 or 4x as a base. Here are two ways to do it.

  1. 1. Use nonincendive equipment. All equipment is rated for the hazard, so no arcs or sparks are possible and all contacts are contained. This option is cheaper than option 2.
  2. 2. Purging pressurization. This involves pumping compressed air into the cabinet to keep positive pressure to allow any gas from outside to migrate inside. To work efficiently, purging pressuraization requires a very good compressor with very good filtration system. For that reason, this is a more expensive option than using nonincendive equipment.

There are three types of hazardous location panels:

  •    –   Class 1/Division 1 (small minority. panel is in area with ignitible concentrations)
  •    –   Class 1/Division 2 (minority. In a gas area, but not inherently risky)
  •    –   Non-hazardous (majority)




Related Articles

Network Infrastructure Featured Product Spotlight

PBUS 14 Panduit logo 400

This webinar presented by Beth Lessard and Keith Cordero will be highlighting three Panduit solutions that will optimize network equipment and cabling to ensure that your spaces are efficiently and properly managed to support ever-evolving business needs of today and beyond. Products that will be featured include PanZone TrueEdge Wall Mount Enclsoure, Cable Managers, and Adjustable Depth 4-Post Rack.


Editor’s Pick: Featured Product News

Siemens: SIMOVAC Non-Arc-Resistant and SIMOVAC-AR Arc-Resistant Motor Controllers

The Siemens SIMOVAC medium-voltage non-arc-resistant and SIMOVAC-AR arc-resistant controllers have a modular design incorporating up to two 12SVC400 (400 A) controllers, housed in a freestanding sheet steel enclosure. Each controller is UL 347 class E2, equipped with three current-limiting fuses, a non-load-break isolating switch, and a fixed-mounted vacuum contactor (plug-in type optional for 12SVC400). The enclosure is designed for front access, allowing the equipment to be located with the rear of the equipment close to a non-combustible wall.

Read More

Sponsored Content
Electrify Your Enterprise

Power is vital to production, and well-designed control cabinets are key. Allied Electronics & Automation offers a comprehensive collection of control cabinet solutions including PLCs, HMIs, contactors, miniature circuit breakers, terminal block connectors, DIN-rail power supplies, pushbutton switches, motor starters, overloads, power relays, industrial Ethernet switches and AC drives engineered to keep your operations running safely, reliably and efficiently.

Learn more HERE.

Products for Panel Builders