Abstract: An intermediate housing that is, preferably, developed as a cast part and combines several functions and objectives in itself. The intermediate housing not only houses a driving motor for a combustion air blower and a heating air fan, but the driving motor is also disposed by means of a circumferential support developed in the intermediate housing which, at the same time, serves as a stop during the mounting. By means of an elastic bearing of the driving motor, structure-born noise transmission can be avoided. On one side, a combustion air intake connection piece, a fuel supply pipe receiving opening and an exhaust gas outlet connection piece are integrally formed. For the mounting of the heater at a mounting arrangement, the intermediate housing also has passages for fastening screws that are accessible from the direction of the top side of the heater.