1. A function component upper part for placing onto a function component lower part of a function component of a component construction system comprising:a housing;
a mechanical interface formed in the housing for mechanical connection to the function component lower part; and
socket receptacles to accept a plug of the function component lower part which is arranged at a lower side of the housing of the function component upper part,
wherein the function component upper part comprises a connecting apparatus for the connection of an inserted electrical cable;
wherein the housing comprises a surrounding recess for an insertion of a sealing element to seal the function component upper part against at least one of the function component lower part and against the housing upper part,
wherein the housing comprises at least one recess for inserting a corresponding segment of the sealing element, such that guidance and coding is achieved when the housing parts are brought together in the correct position, and
wherein the housing comprises an internal thread for screwing on the sealing element by means of a screw.