3 Phase Electrical Distribution Board DB Wiring Procedure
To understand and wiring an electrical distribution board, first of all you have to clear understanding about DB or Distribution Board wiring definition and systems as per international and local standard. Here you will find some basic idea about Distribution Board and its types.

Electrical Distribution Board wiring system

What Distribution Board (DB) Is?

A safe electrical system designed for a house or premises that included isolation switches, protective devices, connecting of multiple cable circuits including their associated neutral and earth conductors. Distribution Boards are normally following three (3) types-

 Main Distribution Board (MDB):

The Distribution Board which in generally receive incoming source of Low Voltage (LV) from transformer secondary of customer or the distribution company’s service outlets. MDB is the first receiving point (bus bar) from Transformer or Distribution Company.

The MDB may also be known as the ‘Consumer Unit’ where the main isolation device and Protective Devices are integrated.

Sub Distribution Board (SDB):

The Distribution Board which is supplied from the Main Distribution Board in a building and which is used to distribute wiring and circuits within a selected area, e.g.  floor in a multi-storey building.

Final Distribution Board (FDB):

The Distribution Board which supplies to Final Circuits. From FDB power goes to switching board from where switch uses for power on/off particular devices.

Wiring Accessories for 3 Phase Distribution Board:
The Distribution Board or Fuse Boards usually contains following three things to control and distribute electric supply safely:

v DP or Double Pole MCB  as main switch or main isolator;
v RCD (also DP) Residual Current Devices for safety;
v SP or Single Pole MCB as Circuit Breakers and Fuses.

Double Pole (DP) MCB (The main switch or Isolator):

This the main operating switch to control electric supply in the premises, to turn off and on the electric supply immediately due to any emergency like electric shock, fire or  while working on main board. Multiple mains switch may use if one have more supply units.

RCD- DP, Residual Current Devices:

Residual Current Device, (RCD) or Residual Current Circuit Breaker (RCCB) is an electrical wiring device or switch that disconnects or trip a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor. Then instantly go safe mode disconnecting the electric circuit.

Circuit Breakers (CB)

Circuit breaker is a device which switches on at normal condition and off automatically electricity at any abnormal condition. Alternately we can say these are automatic protection devices in DB that switch off a circuit if they detect a fault. Circuit Breaker may be SP-Single Pole, DP-Double Pole and TP-Triple Pole.

In the wiring diagram shown that 3 phase Read-Yellow-Blue receiving from a MCCB, these 3 phases are feeding 3 individual DP-MCB isolator switches, all SP-MCB receiving through a common RCCB-DP and feeding to final distribution board. Please check the above 3-ph to 1-ph wiring diagram where 3 phase electrical distribution board wiring procedure with accessories are shown details.


  1. good, very helpful post.
    we desire more like this

  2. thanx a lot that was very helpful in clearing my doubts.


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