In the electric heaters sector there can be different types of electrical connection:

SERIAL, STAR and TRIANGLE connections.

Serial and parallel circuits

A serial connection is when two or more components are connected in order to make a single itinerary for the power which passes through them; in case of electric components with two terminals, in the serial connection every extremity is connected with only one end of the other and the power can be supplied through the free terminals of the first and of the last dipole.

circuiti in serie

A parallel connection  is when the components are connected to a couple of conductors so that the tension can be applied to each one in the same way. The heaters are parallel and their function is independent: if one heater does not work, the others work.

circuiti in parallelo

Three-phase star and triangle connections

There are two types of connections for  the three-phase.

The first one can be made connecting the two extremities of three wrappings and bringing the other extremities to the power, as it was an Y.

The second connection, always used in the three-phase, can be made connecting the wrappings in order to shape a triangle and then the power will be brought to the triangle’s vertexes.

These types of connections are made in three-phase systems.

In the star connection every single phase is connected to the extremities of the three heaters, applying to each one a voltage of 230V. The other three ends are connected among them to make the star centre. The sum of the three currents  flows on the neutral but three equal currents, 120° out of phase, give a sum of a null value.

It is called star connection because, if you try to draw the connection plan, you will obtain a three-ends star. With reference to the electricity, the star centre has free potential,  while the potential difference between the star centre and every phase will be 400V (three-phase) or 230V.

In the triangle connection there are always three electric heaters but they will be connected among them (the extremity of the first wrapping will be connected to the end of the second one; the other extremity of the second one will be connected to the end of the third one and the other  end of the third one to the other extremity of the first one). If  you try to draw this connection you will obtain a triangle.  With reference to the electricity, to each of the three junctions ends is connected, always individually, each of the three phases . In this way the potential difference at the extremities of every wrapping will be of 400V. You don’t need the neutral.
In the triangle connections the developed power is bigger than in star connections.

Below some example of three-phase connections with more elements (ELMITI’ drawings)





ST 1ST 12E


ST 2ST 18E


ST 2ST 48E


TR 1ST 30E


TR 3ST 18E


TR 3ST 45E


TR 6ST 72E