Types of Panelboards
There are two main types of panelboards, distribution or lighting and appliance. The primary focus of this article is distribution panelboards. They can be enclosed or open although the vast majority of distribution panels encountered in the real world are enclosed. There are six NEMA type specifications for enclosures. These NEMA enclosure types apply to all enclosures – not just panelboard enclosures.
NEMA Spec Panelboards
Type 1 enclosures are designated for indoor use to keep people out of the electrical components and to protect the inside components from falling dirt or solid foreign objects. These are not waterproof or water resistant and usually have knockouts on the ends for wiring and conduit connections. These are not seen very often in industrial environments.
Type 3R enclosures are intended for either indoor or outdoor use and provide the same basic protection to personnel as the Type 1 with better resistance to water, rain, sleet, etc. They are also tolerant of ice formation on the outside of the enclosure.
Type 4 enclosures are designed to protect people from hazardous, electrically live components and to protect the inside components from windblown dust and dirt. These are more resistant to water including splashing and hose-directed water than the previous types. Ice on the outside is not a problem.
Type 4X encompasses the protection features of type 4 and adds a resistance to corrosion. These are often stainless steel or non-metallic and are found in food and pharmaceutical industries where wash -downs are common.
Type 5 has the standard protection to keep people separated from hazardous parts. They are intended for indoor use with protection against airborne dust, lint and against light splashing and dripping water.
Type 12 enclosures are indoor boxes without knockouts and protect people against access to electrically live components. Like type 5 they protect against circulating dust, fibers and lint as well as dripping water or light splashing.
Panelboards are dead front electrical devices. This means the person operating a circuit breaker cannot contact electrically live parts when the cover is installed. In industrial applications most panelboards are three-phase and are wired with either 208/240V or 480V. These are considered low voltage. Some medium voltage (600 – 2500V) panels may be found and in rare cases a high voltage (over 2500V) panel may be encountered.
When specifying a panelboard for a new installation it is important to have all the information about the application. Most manufacturers will help with specifying the panel to order and help with all the accessories needed to complete the installation.
Once installed, panelboards rarely contribute to problems. They are usually never a subject of conversation or consideration until someone destroys one with a lift truck. Fires or explosions in panels are almost always the result of improper maintenance. Proper maintenance includes regular inspection for loose or overheating wiring connections, properly seated breakers and dirt, lint or liquids in the enclosure. As with all things industrial, some time spent on maintenance will be repaid with a dramatic reduction in downtime.
