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Single-phase or three-phase power, what have I got?

19 Mayo 2017
Instalación monofásica o trifásica, ¿cuál tengo?

In order to calculate the power required in your household, you have to know if you have a single-phase or three-phase system installed. It sounds technical and complicated, but once you have read this, you will be able to recognise each system at a glance. You will know more about your bill and you will come across as a professional electrician!

What electricity do I have in my home? Single-phase? Or is it three-phase? What are the differences? Which should I have?

You have probably asked yourself some of these questions before, or all of them, while checking your bill or trying to calculate the power required in your home.

We will answer all your questions once and for all.

What is a single-phase system?

This is the system used in most houses and apartments.

These systems use a single phase and a single alternating current. Their normalised tensions are established at 220 or 230 volts and hence a maximum contracted power of 13,86 kW for 220 volts and 14,49 kW for 230 volts. 

These systems are normally used in households and the size of the house is irrelevant, since a detached house with a swimming pool can have a single-phase system without any problem.

If you want to find out if you are single-phase, check your electrical panel in your house (normally next to the front door). 

If it looks like this (a double device), it means your system is single-phase:

Imagen de instalación eléctrica monofásica

What is a three-phase system?

Three-phase systems are normally installed in commercial buildings. They are made up of three phases, i.e., three different alternating currents that divide the power into three parts. Their normalised tension is generally around 380 or 400 volts.

The power contracted for this type of installation starts from 15 kW in a mandatory way, which makes it the most suitable for installations with three-phase equipment (the ones usually used by companies).

If your ICP looks like this (triple device or higher), it means you have a three-phase system:

Imagen de instalación eléctrica trifásica

Which should I have?

When choosing a system, the first thing you have to do is calculate the approximate power used by the electrical appliances in your home.

If you do not need a contracted power above 13,86 kW, we recommend a single-phase system. You will pay less and you won’t trip the fuses.

If 13,86 kW is not enough, you should install a three-phase system. In which case, you must make sure your electrical appliances are three-phase (they are normally single-phase).

The main inconvenience of a three-phase system is that the contracted power is distributed among three phases; therefore if your electrical appliances are single-phase, you will find that you often exceed your limit and trip the fuses.

What if I wat to change my power?

When changing your power it is important to take into account the type of system you have. Particularly if you have a power above 13,86 kW and you want to drop it, since this could cause some problems.

For example, if you dropped a single-phase system with a power in excess of 13,86 kW to 9.2 kW, this would save you considerable money on your electricity bill and your real power would barely vary. However, with a three-phase system you would have to drop it to at least 6.9 kW, a considerable drop that may leave you short of power.

All these processes entail a series of costs, therefore we recommend seeking more information before requesting a change of power:


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