3 phase house wiring


Table of Contents

A 3 phase circuit is an electrical distribution method that uses three alternating currents to supply power. This type of power distribution is the most widely used in the world for transferring power from generating systems to electric supply grids.

A 3 phase circuit is also commonly used on large motors, pumps and other pieces of mechanical equipment.

Most households receive power in the form of single-phase circuits, though some may have special three-phase circuit breakers installed for appliances such as washing machines and stoves.

A three-phase system is more economical than an equivalent single-phase or two-phase system at the same voltage because it uses fewer conductor materials to transmit electrical power.

Difference between three phase and single phase power?

First,single-phase power distributes electricity for domestic uses and in residential homes.

This is because of the low power voltages, which is favourable for most appliances.

A single-phase power is best for low horsepower units amounting to 5HP. 

Unfortunately, it can’t supply bulky electronic loads as in industries.  

3 phase power can convert about 97% of electrical energy into mechanical energy. Therefore, making it efficient for motors. 

Moreover, motors using three-phase have a longer lifespan. 

Then, there’s always a continuous and non-turbulent flow of power. 

Despite being expensive, it is relatively easy to manage a three-phase supply system.  

One other important difference between 3-phase power and single-phase power is the consistency of the delivery of power.

Because of the peaks and dips in voltage, a single-phase power supply simply does not offer the same consistency as a three-phase power supply. A three-phase power supply delivers power at a steady, constant rate.

Comparing single-phase and three-phase power, three-phase power supplies are more efficient and reliable.

A three-phase power supply can transmit three times as much power as a single-phase power supply, while only needing one additional wire (that is, three wires instead of two).

Thus, three-phase power supplies, whether they have three wires or four, use less conductor material to transmit a set amount of electrical power than do single-phase power supplies.

Some three-phase power supplies do use a fourth wire, which is a neutral wire. The two most common configurations of three-phase systems are known as wye(star) and delta.

A delta configuration has only three wires, while a wye configuration has a fourth, neutral, wire.

Single-phase power supplies have a neutral wire as well.

Both single-phase and three-phase power distribution systems have roles for which they are well-suited. But the two electrical supply systems are quite different from each other.

How can I wire a three phase main distribution board?

wiring diagram of a 3 phase distribution board.
3 phase distribution board.

The process of wiring a three-phase distribution board is the same as wiring a single-phase distribution board.

The only difference is that in a 3 phase distribution board you have 3 phases or 3 wires that bring power to the distribution board.

One important fact to put in mind is that when you are wiring a 3 phase distribution board, do not combine the phases. Why because combining phases can result in a phase to phase short circuit.

How do you wire a three-phase distribution board? For me to answer this question effectively, I must tell you the components that are found in a 3 phase distribution board.

List of components found in a distribution board.

  1. 3 MCB tray or din rail.
  2. Neutral bars.
  3. Earth bar
  4. MCCB
  5. MCB.

MCB tray or din rail: This is a tray or rail where you mount MCBs on the distribution board. What determines whether to use a din rail or MCB tray is the type of mcb’s that you will mount on the distribution board.

There are MCBs that fit well on an mcb tray and others fit well on a din rail.

Neutral bars: A neutral bar is a place where you connect all the neutral wires coming into the distribution board and going out of the distribution board to various circuits in the house.

MCCB: Moulded case circuit breaker, this is the main circuit breaker that supplies electric power to the distribution board. The incoming power from the utility service provider reaches the distribution board through the MCCB.

MCB’s: Miniature circuit breaker. This is a circuit breaker that receives electric power from the MCCB in the distribution board then it supplies power to other mcb supplying power to subcircuits in the home.

Wiring a 3 phase distribution board.

I have already stated that a three-phase distribution board has three electrical wires supplying power. These Three wires currying electricity are identified using electrical wiring colour codes.

In the old wiring system, these phases were identified by the following colours, red, yellow and blue phase. While in the new wiring colour code, the phases are identified as brown, black and grey phases.

The mcb tray and din rail are arranged in three rows on the distribution board. In the first mcb tray or din rail, you mount mcb’s that are supplied by the red phase.

In the second mcb tray or din rail, you mount mcb’s that are supplied by the yellow phase. While in the third mcb tray or din rail, you mount mcb;s supplied by the blue phase.

After mounting the mcb’s on the din rail, you proceed to connect various loads to the mcbs. Here I must mention that you connect all electrical cables supplying power to various loads to the output of the mcbs. When I say loads I mean circuits like lighting, socket outlets, airconditioning systems and other appliances and machines connected in the building.

Schematic Wiring Diagram of Three Phase Distribution Board.

schematic wiring diagram of three phase distribution board.
credit electronics hub.

3 phase house wiring


4 thoughts on “

3 phase house wiring


  1. Thanks for the knowledge
    Which I have read on your site

    1. You are welcome Kay Mulenga and thanks for taking time to read through

  2. Thanks for the update on the content. I have been very much enlightened on the topic. God Bless you

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