Heater comprising several heat tubes filled with a working medium , extending preferably parallel or substantially parallel and each having a first end and a second end , and a heat source thermally coupled to the first and/or second ends of the heat tubes , the first ends of the heat tubes being designed open and fluidically connected to a first transverse connection tube and the second ends of the heat tubes being designed open and fluidically connected to a second transverse connection tube , the heat tubes and the transverse connection tubes forming a common cavity filled with the working medium , and the first transverse connection tube being thermally coupled to the heat source to receive heat from the heat source , wherein the heat source is a heating tube through which a gaseous or liquid heating medium can flow, the heating tube being arranged coaxially in the first transverse connection tube along a longitudinal axis and being surrounded by the working medium , characterized in, that connectors of the heating tube are connected to the first transverse connection tube at end face in pressure-tight and fluid-tight manner, that the heater (46; 66) has a connection system (48; 70) with a flow connection (50; 72) and a return connection (62; 86), wherein the flow being connected via a first bypass tube (52; 74) to a control valve (54; 76) which is coupled to a connector (56; 78) projecting at an end face from the second transverse connection tube and that a second bypass tube (58; 80) extends from the control valve (54; 76) preferably parallel to the first bypass tube, is in fluidic connection to the heating tube and is coupled to the return connection (62; 86). several heat tubes filled with a working medium , extending preferably parallel or substantially parallel and each having a first end and a second end , and a heat source thermally coupled to the first and/or second ends of the heat tubes , the first ends of the heat tubes being designed open and fluidically connected to a first transverse connection tube and the second ends of the heat tubes being designed open and fluidically connected to a second transverse connection tube , the heat tubes and the transverse connection tubes forming a common cavity filled with the working medium , and the first transverse connection tube being thermally coupled to the heat source to receive heat from the heat source , wherein the heat source is a heating tube through which a gaseous or liquid heating medium can flow, the heating tube being arranged coaxially in the first transverse connection tube along a longitudinal axis and being surrounded by the working medium , characterized in, that connectors of the heating tube are connected to the first transverse connection tube at end face in pressure-tight and fluid-tight manner, that the heater (46; 66) has a connection system (48; 70) with a flow connection (50; 72) and a return connection (62; 86), wherein the flow being connected via a first bypass tube (52; 74) to a control valve (54; 76) which is coupled to a connector (56; 78) projecting at an end face from the second transverse connection tube and that a second bypass tube (58; 80) extends from the control valve (54; 76) preferably parallel to the first bypass tube, is in fluidic connection to the heating tube and is coupled to the return connection (62; 86). <EOS>