Magnetic separator of impurities for a heating and/or cooling plant, comprising: - wall means (3, 4, 7, 8) defining a first hollow body delimiting a separation chamber for separating ferrous and non-ferrous particles from a fluid circulating in said heating and/or cooling plant, and a second hollow body delimiting a quieting and collecting chamber defined inferiorly by a bottom wall of said wall means (3, 4, 7) and suitable for receiving and storing, on an inner collecting surface provided on said bottom wall, said ferrous and non-ferrous particles, said separation chamber being configured to house a filtering cartridge suitable to hinder said particles and to cause the decantation thereof towards said quieting and collecting chamber; - said first hollow body and said second hollow body being mutually connected by a sealed threaded coupling so as to be arranged, during operation, one on top of the other thus defining a vertical longitudinal axis, with said separation chamber being located superiorly to said quieting and collecting chamber, - an inlet and an outlet for said fluid, obtained in the proximity of said separation chamber and a discharge outlet provided at a lower end of said wall means (3, 4, 7, 8) for evacuating said ferrous and non-ferrous particles from said quieting and collecting chamber; - said inlet and said outlet being arranged on opposite sides with respect to said separation chamber, and both in a zone farther from said quieting and collecting chamber; - said inlet and said outlet facing a higher region of said separation chamber and being mutually aligned along a direction that is orthogonally incident on said longitudinal axis; - magnet means for attracting and holding the ferrous particles transported by said fluid; CHARACTERIZED IN THAT said magnet means are removably enclosed in said wall means by engaging with respective seat means obtained in said bottom wall of said second hollow body so as to be, during operation, removably incorporated in said bottom wall and located externally under said quieting and collecting chamber and so as to attract said ferrous particles in a region farther from said separation chamber, far from turbulence and dragging actions of said fluid, wherein said first hollow body and second hollow body, and, consequently, said separation chamber and said quieting and collecting chamber defined thereby, are shaped so that the advancing of the fluid-flow and the turbulent movement thereof substantially affect an upper portion of said separation chamber, far from said quieting and collecting chamber, so that said quieting and collecting chamber, particularly said inner collecting surface, does not suffer from the turbulence and dragging effects of the circulating fluid, thus enabling an evacuation of the impurities from said quieting and collecting chamber through said discharge outlet without necessarily stopping the fluid circulation in the plant. - wall means (3, 4, 7, 8) defining a first hollow body delimiting a separation chamber for separating ferrous and non-ferrous particles from a fluid circulating in said heating and/or cooling plant, and a second hollow body delimiting a quieting and collecting chamber defined inferiorly by a bottom wall of said wall means (3, 4, 7) and suitable for receiving and storing, on an inner collecting surface provided on said bottom wall, said ferrous and non-ferrous particles, said separation chamber being configured to house a filtering cartridge suitable to hinder said particles and to cause the decantation thereof towards said quieting and collecting chamber; - said first hollow body and said second hollow body being mutually connected by a sealed threaded coupling so as to be arranged, during operation, one on top of the other thus defining a vertical longitudinal axis, with said separation chamber being located superiorly to said quieting and collecting chamber, - an inlet and an outlet for said fluid, obtained in the proximity of said separation chamber and a discharge outlet provided at a lower end of said wall means (3, 4, 7, 8) for evacuating said ferrous and non-ferrous particles from said quieting and collecting chamber; - said inlet and said outlet being arranged on opposite sides with respect to said separation chamber, and both in a zone farther from said quieting and collecting chamber; - said inlet and said outlet facing a higher region of said separation chamber and being mutually aligned along a direction that is orthogonally incident on said longitudinal axis; - magnet means for attracting and holding the ferrous particles transported by said fluid;