A heat exchanger assembly comprising: - at least one coil shaped heat exchanger pipe assembly for passing through a fluid to be heated, wherein the heat exchanger pipe assembly has an inlet and an outlet and wherein the heat exchanger pipe assembly comprises coil windings which extend concentrically around a coil axis, wherein the heat exchanger pipe assembly on a radial inner side bounds an inner space which comprises a burner chamber part; - a housing (20, 21) in which the heat exchanger pipe assembly is received, wherein the housing comprises: ∘ a circumferential wall which is substantially cylindrical and which defines a housing axis which substantially coincides with the coil axis, wherein an inner diameter of the circumferential wall is greater than an outer diameter of the heat exchanger pipe assembly, such that a flue gas transport gap extends between the heat exchanger pipe assembly and the circumferential wall; ∘ a first end wall which closes off a first end of the circumferential wall; ∘ a second end wall which closes off a second end of the circumferential wall at least partially and comprises a central burner cover opening; and ∘ an exhaust for flue gases; wherein the heat exchanger assembly further comprises: - a burner cover which is detachably connected with the second end wall of the housing (20, 21), which burner cover closes off the central burner cover opening and comprises an air/fuel mixture connection; - a burner which is connected with the burner cover and which extends substantially concentrically around a burner axis which substantially coincides with the housing axis and the coil axis, wherein the burner is situated in the burner chamber part, and wherein the burner is in fluid communication with the air/fuel mixture connection; wherein, in use, flue gases produced by the burner flow via the burner chamber part between said coil windings into the flue gas transport gap and wherein the flue gases eventually leave the housing (20, 21) via the exhaust; characterized in that: - the housing (20, 21) is divided in a first and a second housing part which are both made from plastic, - the first housing part includes the first end wall; - the second housing part includes the second end wall; - the first and/or the second housing part (20 and/or 21) include the circumferential wall; - the heat exchanger pipe assembly is clamped in axial direction between the first and the second plastic end wall of the housing (20, 21); wherein axial expansion forces exerted by the coil shaped heat exchanger pipe assembly, which occur in use as a result of an internal fluid pressure, are absorbed by the plastic first and second end walls (26, 36) of the housing (20, 21). - at least one coil shaped heat exchanger pipe assembly for passing through a fluid to be heated, wherein the heat exchanger pipe assembly has an inlet and an outlet and wherein the heat exchanger pipe assembly comprises coil windings which extend concentrically around a coil axis, wherein the heat exchanger pipe assembly on a radial inner side bounds an inner space which comprises a burner chamber part; - a housing (20, 21) in which the heat exchanger pipe assembly is received, wherein the housing comprises: ∘ a circumferential wall which is substantially cylindrical and which defines a housing axis which substantially coincides with the coil axis, wherein an inner diameter of the circumferential wall is greater than an outer diameter of the heat exchanger pipe assembly, such that a flue gas transport gap extends between the heat exchanger pipe assembly and the circumferential wall; ∘ a first end wall which closes off a first end of the circumferential wall; ∘ a second end wall which closes off a second end of the circumferential wall at least partially and comprises a central burner cover opening; and ∘ an exhaust for flue gases; ∘ a circumferential wall which is substantially cylindrical and which defines a housing axis which substantially coincides with the coil axis, wherein an inner diameter of the circumferential wall is greater than an outer diameter of the heat exchanger pipe assembly, such that a flue gas transport gap extends between the heat exchanger pipe assembly and the circumferential wall; ∘ a first end wall which closes off a first end of the circumferential wall; ∘ a second end wall which closes off a second end of the circumferential wall at least partially and comprises a central burner cover opening; and ∘ an exhaust for flue gases; - a burner cover which is detachably connected with the second end wall of the housing (20, 21), which burner cover closes off the central burner cover opening and comprises an air/fuel mixture connection; - a burner which is connected with the burner cover and which extends substantially concentrically around a burner axis which substantially coincides with the housing axis and the coil axis, wherein the burner is situated in the burner chamber part, and wherein the burner is in fluid communication with the air/fuel mixture connection; - the housing (20, 21) is divided in a first and a second housing part which are both made from plastic, - the first housing part includes the first end wall; - the second housing part includes the second end wall; - the first and/or the second housing part (20 and/or 21) include the circumferential wall; - the heat exchanger pipe assembly is clamped in axial direction between the first and the second plastic end wall of the housing (20, 21);