The invention relates to a heating or cooling system comprising at least one heat/cold generator (7, 21, 70) and at least one partial system unit (95). The partial system unit comprises a heat/cold exchanger (11) used as a system separator, a mixing device (13, 13a, 61) comprising two inputs (E1, E2, or E3) and an output, and a pump (15, 65). The output of the mixing device (13, 13a, 61) is thereby connected to a mixer-side input of the heat/cold exchanger (11) via an unbranched input line (91), and a mixer-side output of the heat/cold exchanger (11) is connected to a feed or return of a heat/cold source (7, 30, 66, 80, 82) and/or a heat/cold sink (10, 30) via an unbranched output line (90). The invention is characterized in that a pump (15, 65) is provided in the unbranched input line (91) or in the unbranched output line (90) of the heat/cold exchanger (11). A low delivery head of preferably 100 mbar to 200 mbar is advantageously provided for the pump (15, 65).
