Low Voltage (LV) Switchboard Form Factors

The IEC 61439 standard uses the designations

  • Form 1A,
  • Form 1B,
  • Form 2A,
  • Form 2B,
  • Form 3A,
  • Form 3B,
  • Form 4A, and
  • Form 4B

to describe the construction and arrangement of electrical panels.

These forms specify component placement, electrical circuit separation, and accessibility for upkeep and use. Below is a brief description of every form:

1). Form 1A

This form shows a simple panel with no division between the outgoing circuits and the main busbars. It is usually utilized for simple control and distribution tasks and does not offer any separation between power & control circuits.

2). Form 1B

This form has a gap between the busbars & the outgoing circuits, same like Form 1A. This form is appropriate for simple applications with modest segregation requirements since it provides minimal segregation.

3). Form 2A

Form 2A has a distinct compartment for the outgoing circuits and main busbars. Because the compartments are physically segregated, the power and control circuits are more thoroughly isolated. Maintaining outgoing circuits with the primary busbars activated is made possible by technique.

4). Form 2B

This form additionally offers distinct sections for the primary busbars & the outgoing circuits. The compartments are segregated from one another in this configuration, though, which keeps the primary busbars de-energized and permits the maintenance of outgoing circuits.

5). Form 3A

Form 3A comprises distinct sections designated for the

  • Primary busbars,
  • Inbound connections, and
  • Outbound circuits.

There is a high degree of segregation because the compartments are sealed off from one another. It makes it possible to maintain both inbound and outbound circuits without having to turn off the main busbars.

6). Form 3B

This form provides distinct compartments for the

  • Primary busbars,
  • Incoming connections, &
  • Outgoing circuits,

exactly as Form 3A does.

The division of the outgoing compartments in this way, however, enables the upkeep of the outgoing circuits while maintaining the entering compartment’s energy.

7). Form 4A

This form ensures total separation and segregation by giving separate compartments for every outgoing circuit. Complex systems that require a high degree of segregation & selective maintenance are usually the ones that adopt this design.

8). Form 4B

Form 4B is comparable to Form 4A; however, it incorporates further segregation inside the outgoing circuit compartments. Applications needing the maximum degree of flexibility and segmentation for upkeep and operation can use this type.


In order to ensure adherence to safety and operational regulations, these form identities are used to define the desired design and degree of separation in electrical panels. The particular application, system complexity, & maintenance requirements are taken into consideration when choosing the right form.