The holder (21) has a flange (22) consisting of a retaining plate (23) attached on the outer side of the wall (4) of the heating boiler (1) and a clamp ring (24) which is attachable on the flame tube (11). The retaining plate has one or several rear location hooks (25) and the clamp ring is provided with protrusions (26) which stands out radially from the outer cover face and can be inserted in the hooks by a rotational movement. The clamp ring is clamped to the retaining plate by means of at least one clamp screw (27) fitted in the plate axially parallel to the flame tube. The clamp ring is centred by a guide ring which engages with a groove on the rear of the holding plate.
