Patent ID: 8122855

Claim:
A boiler, comprising a combustion chamber ( 1 ) with a heat insulating block ( 13 ), wherein said combustion chamber ( 1 ) is surrounded at least in part by a combustion gas flue ( 2 ) that is embodied as a primary heat exchanger, wherein said combustion gas flue ( 2 ) is surrounded at least in part by a water-conducting housing ( 3 ), wherein a water-conducting secondary heat exchanger ( 4 ) that is hydraulically connected to the housing ( 3 ) and through which heating gas flows is mounted downstream of the combustion gas flue ( 2 ), characterised in that the combustion chamber ( 1 ) is surrounded at least in part by the secondary heat exchanger ( 4 ), wherein the combustion chamber ( 1 ) comprises a combustion chamber sleeve ( 14 ) which is configured as withdrawable from the combustion chamber ( 1 ) in the axial direction.