Abstract: A box for installation of an electrical apparatus in a raceway for electrical cables. The box is fixed in the raceway which is formed by association of a base section and a cover section. The base section and the cover section are formed by the extrusion of a thermoplastic insulating material, wherein the base section is provided longitudinally on the inside of the edges of the walls thereof with shaped tubular beads, longitudinally forming an upper groove for the coupling of ribs of the cover section and a lower inverted spine opposite said groove. The box is formed by an upper portion and a lower portion, wherein the upper portion is attachable to the electrical apparatus and engageable in the groove of the shaped tubular beads. The lower portion is located with a slight clearance below the upper portion, and provided with a seating for the inverted spines of the shaped tubular beads.