The invention relates to a heat exchanger assembly with at least one multi-pass heat exchanger, comprising a first distributor (1) with a first connection part (1a) for connecting to a fluid line (9), a second distributor (2) with a second connection part (2a) for connecting to a fluid line (9), and at least one first deflection distributor (4), as well as a plurality of tube lines (5) through which a fluid, in particular water, can flow, wherein the first distributor (1) and the second distributor (2) are arranged at one end (A) of the heat exchanger assembly, the deflection distributor (4) is arranged at the opposite end (B) and the tube lines (5) extend from the one end (A) to the opposite end (B), and wherein the first connection part (1a) is arranged at a lowest point (T) or at least near to the lowest point (T) of the first distributor (1) and the second connection piece (2a) is arranged at a lowest point (T) or at least near to the lowest point (T) of the second distributor (2). In order to allow for the heat exchanger assembly to be quickly filled with the fluid and quickly emptied, a third connection part (3) is arranged on the first distributor (1) and/or on the second distributor (2) at a highest point (H) or at least near to the highest point (H) of the respective distributor (1 or 2), and at least one ventilation opening (10) is provided at a highest point (T) or at least near to the highest point (T) of the deflection distributor (4) for pressure equalisation with the environment.