What Is an Electrical Enclosure? Definition, Using, Requirements

Electrical Enclosure Definition

Electrical enclosure: an enclosure providing protection against the foreseen dangers created by electricity [defined in the IEC 60050-195-2021].

The level of protection that an enclosure can provide is determined by the value of its degree of protection. The degree of protection is specified in IEC 60529.

Each electrical enclosure has a specific IP code, which describes the degree of protection provided by the enclosure against contact with hazardous parts, penetration of external solid objects and the hazardous effects of water.

How Electrical Enclosures Are Used?

Enclosures are widely used in the electrical installations of buildings, primarily to protect humans and animals from touching live parts of electrical equipment. These parts are placed inside the enclosures and thus prevent humans from touching them with the palm of their hand, finger, tool or wire. In this application, the enclosures act as electrical enclosures, which are designed to protect against electric shock.

If hazardous mechanical parts of electrical equipment are placed inside the enclosure, the enclosure prevents access to them, thus protecting people and animals from mechanical injuries. In this case it performs the function of a mechanical enclosure.

Electrical enclosures are also used to protect the parts of electrical equipment placed in them from the hazardous effects of the environment. The enclosures are primarily designed to protect electrical equipment from external solid objects, preventing the penetration of objects greater than (equal to) 50, 12.5, 2.5 or 1.0 mm in diameter, limiting or preventing the penetration of dust. Enclosures also protect electrical equipment from the adverse effects of water in the form of water droplets, continuous splashes of water, water jets, and brief or prolonged immersion in water.

Some enclosures are designed to protect electrical equipment against mechanical shocks. The degree of protection against external mechanical shock and IK codes are specified in IEC 62262.

The enclosures of some types of electrical equipment are designed to protect against flame, electromagnetic interference and other hazardous or undesirable influences, which may be either outside or inside the enclosure.

Siemens PLC installed in an electrical enclosure
Siemens PLC installed in an electrical enclosure

Electrical Enclosure Requirements

According to the fundamental requirements of IEC 61140, enclosures are used in electrical installations and electrical equipment as one of the precautions (element of protective measure) intended to provide basic protection

The main requirements to be met by electrical enclosures are given in clause 5.2.3 “Protective barriers or enclosures” of IEC 61140.

Protective barriers or enclosures shall prevent:

  • in the case of low-voltage installations and equipment, access to hazardous-live-parts by providing a degree of protection against electric shock of at least IPXXB or IP2X of IEC 60529 and, for readily accessible horizontal top surfaces of protective barriers or enclosures, at least IPXXD or IP4X
  • in the case of high-voltage installations and equipment, entering the danger zone by providing a degree of protection of at least IPXXB or IP2X of IEC 60529, and consideration shall be given to providing a degree of protection of at least IPXXD or IP4X for readily accessible horizontal top surfaces of protective barriers or enclosures.

NOTE. The IP code applies to the enclosures of electrical equipment of rated voltage not exceeding 72,5 kV.

Protective barriers or enclosures shall have sufficient mechanical strength, stability and durability to maintain the specified degree of protection, taking account of all relevant influences from the environment and from inside the enclosure. They shall be firmly secured in place.

Where the design or construction allows for the removal of protective barriers, the opening of enclosures or the removal of parts of enclosures, access to hazardous-live-parts or entering the danger zone shall be possible only:

  • by the use of a key or tool, or
  • after isolation of hazardous-live-parts from the supply circuit where the enclosure would no longer provide protection, restoration of the supply shall become possible only after replacement of protective barriers or parts of enclosures or after the closing of doors, or
  • where an intermediate barrier still maintains the required degree of protection, such barrier being removable only by the use of a key or tool.

If, behind a barrier or in an enclosure, items of equipment are installed which may retain dangerous electrical charges after they have been switched off (capacitors, etc.), a warning label is required. Small capacitors such as those used for arc extinction, for delaying the response of relays, etc shall not be considered dangerous.

NOTE. Unintentional contact is not considered dangerous if the voltage resulting from static charges fall below 120 V d.c. in less than 5 s after disconnection from the power supply.

NOTE:

In the United States, the National Electrical Manufacturers Association (NEMA) publishes NEMA enclosure type standards for the performance of various classes of electrical enclosures. The NEMA standards cover corrosion resistance, ability to protect from rain and submersion, etc.

References

  1. IEC 60050-195-2021
  2. IEC 61140