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What does a single or three-phase connection mean?

Your home can be connected to the energy grid in two ways:

  • with a 2-wire connection, i.e. single-phase
  • with a 3- or 4-wire connection, i.e. 3-phase

Single-phase or three-phase: which is better?

Both types of connection have their advantages:

  • a single-phase connection is perfectly suited for domestic use, as all appliances are connected to a single circuit for the whole house;
  • the three-phase connection is more suitable to power a building with energy-guzzling machines (e.g. in a self-employed person's house) or a lift. The reason being that it can supply more power. It can also be used to power appliances that require different voltages.

In both cases, it will be up to your electrician to correctly distribute the power lines in your home according to the type of connection, in order to maintain the balance of the energy network.

How do I know if my home is connected to a single or three-phase power supply?

In theory, the easiest way to answer this question would be to observe the number of wires coming from the meter on your electrical panel: 2 wires point to single phase, 3 or 4 wires point to three-phase.

In practice, it is not so simple, as the connection between the meter and the switchboard is not always visible. At the meter, you can't always see the wires either. 

So what should you do? Look at your meter: a diagram or wording usually indicates the number of phases.

  Single-phase Three-phase
Network All 230 V 400 V
Number of wires from the meter 2 3 4
Available power for 16 A 3,7 kW 6,3 kW 11 kW

How do you distinguish between three-phase 230 V and three-phase 400 V?

  1. Look for a yellow "400 V" sticker on the meter.
  2. No visible sticker? Check your switchboard. If you have a circuit breaker, 3 combined modules point to 230V (3 x 230V), 4 point to 400V (3 x 400V + 1 neutral).
  3. If your installation is fuse-based, look at the wires connected to the electricity meter. A total of 6 wires points to 230 V, a total of 8 wires points to 400 V
  4. If none of these methods work, look at the wires connected to your protection module: if there is a blue wire, it's 400V. If not, it's 230 V.

What do the connection wires correspond to?

A single-phase connection has 2 wires: a neutral wire (blue) and a phase conductor.

A three-phase connection has 3 to 4 wires:

  • in three-phase 400 V, there are 4 wires (3 phases + 1 neutral);

In three-phase 230 V, there are 3 wires. In a 3x400 V three-phase system, the voltage difference between each phase wire and the neutral is always 230 V, while the voltage difference between two phase wires is 400 V. This makes it possible to supply both the house with 230 V and machines that require 400 V (some electric car chargers for example).

In a 3 x 230 V three-phase system, the voltage difference between each phase wire is 230 V and there is no neutral conductor.

Be careful not to confuse the neutral wire with the earth connection which is yellow and green. The latter allows electrical current leaking from a faulty appliance or cable to be grounded to earth. It protects you from electrocution.

Can the power of a single-phase connection be increased? Or is it necessary to switch to three-phase?

If required, the power of your single-phase connection can be increased to a maximum of 63 A.

If you need more power, or if you have appliances that require a three-phase connection, there is no alternative to switching to a three-phase connection. For example, if you have an electric vehicle and a single-phase connection and you want to charge your vehicle more quickly, you will need to switch to a three-phase connection.

Do I need special plugs if my home has a three-phase connection?

No, the ordinary 2-pin + earth model is perfectly suitable for domestic appliances.

A three-phase socket is only required for appliances that operate in three-phase, such as a professional oven or a lift. These are round 4-pin + earth sockets, connected to 5 wires: 3 phases + neutral + earth.

Note that since most three-phase appliances are fixed (lift, circulator, etc.), they are connected directly to the installation, without a plug.

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