In a system for non-contact transmission of electrical energy to a mobile part movably arranged on a facility floor, a charge unit is situated in a recess of the floor, the charge unit has a receiving part having upper and lower cover parts, a primary winding is accommodated in the upper cover part, the receiving part at least partially restricts a space region that accommodates an electronic circuit, a bore penetrates the lower cover part, and terminates via its first end region in the space region and terminates via its other end region in a further space region which is at least partially restricted by a dome wall provided on the lower cover part, and a diaphragm is situated on the bore.