Understanding Control Panel Enclosure Ratings

As manufacturers increasingly rely on automated and mechanical equipment to more efficiently produce products, control panels provide a reliable and effective means to control this equipment. However, because control panels contain sensitive circuitry and electronic components and are often located in dirty, wet, corrosive, or hazardous factory environments, it’s imperative that the control panel enclosure can not only safely accommodate and protect the enclosed electronics from the potentially harmful effects of the plant’s environment but also can withstand the external conditions in which it is installed. For this reason, electrical control panel enclosures are rated by a variety of agencies and organizations, including the National Electrical Manufacturers Association (NEMA) and Underwriters’ Laboratories (UL), to ensure safety. 

What’s in a Control Panel? 

To understand why safety is paramount when it comes to control panel enclosures, let’s look at the components that are commonly found within the unit: 

  • Power Components: Used to regulate the flow of power to the physical equipment, power components typically include items such as circuit breakers, fuses, motor starters, and variable frequency drives. 
  • Control Components: Used to control and operate the motion sequence of the automated and mechanical equipment in the plant, control components might include control and/or timing relays and programmable logic controllers. 
  • Other Devices: A control panel may also contain devices such as digital meters to monitor electricity use, touchscreens or displays, and other devices such as pushbuttons. 

Since these components are used to operate and control the mechanical equipment that keeps the plant up and running, it’s important that they remain reliable. However, control panels can get hot due to the heat generated by the electronics contained within and are often sensitive to environmental debris, moisture, and fire hazards. For this reason, it is crucial that the control panel enclosure is tested and rated to safely function in the environment in which it is placed. 

Control Panel Enclosure Ratings Ensure Safety and Reliability 

While both NEMA and UL agencies have ratings for various components within the control panel, the organizations also offer standards and ratings specifically for control panel enclosures. Although NEMA ratings are often used to determine UL Enclosure Ratings, this article will focus on the UL Enclosure Ratings because it is the most commonly referenced enclosure rating. A UL-listed enclosure bearing the UL-listing emblem has been subjected to stringent testing and was found to meet nationally recognized safety standards. Therefore, the following UL Enclosure Ratings will be helpful in determining whether your control panel enclosure will effectively and safely keep the contained components reliably running within your application and environment. 

Type 1: Type 1 enclosures are rated for indoor use only and are designed to provide protection against accidental contact with the enclosed equipment and from a limited amount of falling dirt. 

Type 2: Type 2 enclosures are rated for indoor use only and are designed to provide protection against limited amounts of falling water and dirt. 

Type 3: Type 3 enclosures are rated for indoor or outdoor use and are designed to provide protection against windblown dust, rain, snow and sleet and will not be damaged by external ice formation on the enclosure. 

Type 3R: Type 3R enclosures are rated for indoor or outdoor use and provide protection against accidental contact, as well as falling dirt, rain, sleet and snow and will not be damaged by external ice formation on the enclosure. 

Type 3S: Type 3S enclosures are rated for indoor or outdoor use and are designed to provide protection against accidental contact, as well as windblown dust, rain, snow and sleet. The external mechanisms are designed to remain operable when covered in ice. 

Type 4: Type 4 enclosures are rated for indoor or outdoor use and are designed to provide protection against splashing water, windblown dust, rain, sleet and snow, as well as hose-directed water and will remain undamaged by the formation of ice on the enclosure. 

Type 4X: Type 4X enclosures are rated for indoor or outdoor use and provide protection from splashing water, windblown dust, rain, sleet and snow, as well as hose-directed water. They remain undamaged by the formation of ice on the enclosure. The “X” means they are designed to resist corrosion, so they are typically made from stainless steel, aluminum, fiberglass or plastic. 

Type 6: Type 6 enclosures provide protection against the entry of water during temporary submersion at a limited depth. The enclosure will remain undamaged by external ice formation on the enclosure. 

Type 6P: Type 6P enclosures are designed and rated to protect against the entry of water during prolonged submersion at a limited depth. 

Type 11: Type 11 enclosures are rated for indoor use only and are designed to provide protection of the enclosed equipment against the effects of corrosive liquids and gases. 

Type 12: Type 12 enclosures are rated for indoor use only and are designed to provide protection from windblown dust, falling dirt, minor dripping and splashing water and minor dripping and splashing oil and non-corrosive liquids, with no knockouts. 

Type 12K: Type 12K enclosures are rated for indoor use only and are designed to provide protection from windblown dust, falling dirt, minor dripping and splashing water and minor dripping and splashing oil and non-corrosive liquids, with knockouts. 

Type 13: Type 13 enclosures are rated for indoor use to provide protection against dust and spraying of water, oil and non-corrosive coolants. 

Explosion-Proof Enclosures 

Designed to function in more extreme environments, explosion-proof enclosures are suitable for hazardous environments where there is free-floating ignitable gas or vapor. Explosion-proof control panel enclosures are constructed so that any potential explosions remain contained inside the enclosure in order to prevent a larger explosion within the facility. 

While standard control panel enclosures have a latching mechanism, explosion-proof enclosures offer a flange around the box that is held in place by bolts. The flanges between each bolt are designed to cool any sparks, preventing ignition if there is an explosion inside the enclosure and containing the explosion without cracking the internals. 

The two most common types of hazardous location panels include: 

Class 1/Division 1: This enclosure is designed for safe use in areas where ignitable concentrations of flammable gases, vapors or liquids are continuously present during normal operating conditions. 

Class 1/Division 2: This enclosure is suitable for use in facilities that deal with flammable gases, vapors, and liquids. Additionally, the facility handling, processing, or using the materials in the defined hazardous location contains concentrations that are considered insufficient to be ignitable. 

Class 2/Division 1: Suited for situations where combustible dust (like metal dust, carbon dust, and grain dust) is a consistent hazard within the facility. Common locations are grain elevators, ethanol plants, hay grinding plants, etc. 

Class 2/Division 2: This enclosure is made for facilities that contain combustible dust, but the dust doesn’t normally reach the concentration needed for ignition. Dangerous concentrations might form under abnormal circumstances and could interfere with the equipment. 

Due to the importance of safely containing and protecting the sensitive electronic components within a control panel enclosure, it’s important to talk to an expert when creating a control panel to ensure that the selected enclosure will keep the panel internals and the equipment being controlled up and running in a reliable and safe manner. Please reach out to an expert at JHFoster for assistance with control panel enclosure selection.