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What is meant by single-phase or three-phase connection?

The alternating electric current that supplies your home can be provided via different types of connection:

  • 2-wires: single-phase connection
  • 3- or 4-wires: three-phase connection

Each type of connection has its advantages. With a single-phase system it is easier to balance the electrical loads of the network. A three-phase connection on the other hand, is more suited to the consumption of a building that includes powerful machines (the premises of a self-employed contractor, for example) or an elevator for which a three-fase system is needed. It can, in fact, carry three times as much power.

How do I know if my home is connected via single-phase or three-phase?

Just look at your electrical service panel. You will either see 2, or 3 or 4 wires. 

2-wires: single-phase connection

If it is single-phase connection, two wires come into your electrical service panel:

  • a black or red 'live' wire
  • a blue 'neutral' wire

A voltage difference of 230 V separates these two wires.

3- or 4-wires: three-phase connection

If it is three-phase connection, 3 or 4 wires come into your electrical service panel, according to what your electrician was able to install with the available utillity network. 

  • three 'live' wires: black, red, brown or grey
  • a blue 'neutral' wire

This will allow him to properly allocate your home's power cables depending on the type of connection to maintain the balance of the electrical network.

Most of the time, a voltage difference of 230 V separates each live wire from the neutral, while there is a voltage difference of 400 V between two live wires. This makes it possible to supply both the domestic cables with 230 V and machines requiring 400 V (a car charger for example).

Note that some homes are supplied with three-phase 3 x 230 V. A voltage of 230 V separates each live wire and there is no neutral wire.

Do I need special sockets if my building is connected in three-phase?

Yes, but only for devices that operate in three-phase mode, such as an elevator motor or a commercial oven. These are round 4-pin + earth connectors, connected to 5 wires: 3 live wires + neutral + earth.

For the rest of the sockets, the standard 2-pin + earth model is suitable. These sockets have 2 wires and an earth: 2 live wires (three-phase 400 V) or 1 live wire + neutral (three-phase 230 V).

The neutral and the earth wires: not to be confused!

If your electrical system has been properly installed, your neutral wire is blue. It makes it possible to obtain the necessary voltage between two terminals.

It should not be confused with the yellow and green earth connection. This allows leaking electrical current from a faulty device or cable to be transferred to the ground, protecting you from electrocution.

Can the power of a single-phase connection be increased, or should it be changed to three-phase?

If necessary, the power of your single-phase connection can be increased to maximum 63 A. In some particular cases you may indeed have to switch to three-phase, for instance when you want your electric car to charge faster.

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