A method for identifying a deviation in a combined district heating and cooling system comprising a thermal energy circuit comprising a hot fluid conduit for transporting hot fluid, a cold fluid conduit for transporting cold fluid, and at least one thermal device (106a-f) connected to the hot fluid conduit via a hot fluid connection conduit (108a-f) and to the cold fluid conduit via a cold fluid connection conduit (110a-f), wherein, during operation, the hot fluid is warmer than the cold fluid, said method comprising: receiving a first hot fluid flow measurement from a first hot fluid flow sensor arranged in the hot fluid conduit; receiving a first cold fluid flow measurement from a first cold fluid flow sensor arranged in the cold fluid conduit; receiving a second hot fluid flow measurement from a second hot fluid flow sensor arranged in the hot fluid conduit upstream the first hot fluid flow meter; receiving a second cold fluid flow measurement from a second cold fluid flow sensor arranged in the cold fluid conduit downstream the first cold fluid flow sensor; and receiving a thermal device flow measurement (g) from a thermal device flow sensor configured to measure a thermal device flow of a thermal device connected to the hot fluid conduit downstream the first hot fluid flow sensor and upstream the second hot fluid flow sensor, and connected to the cold fluid conduit upstream the first cold fluid flow sensor and downstream the second cold fluid flow sensor, wherein the thermal device flow of the thermal device is a flow either from the cold conduit across the thermal device to the hot conduit or from the hot conduit across the thermal device to the cold conduit, wherein the method further comprises: upon the first hot fluid flow measurement is different from the second hot fluid flow measurement and the thermal device flow measurement (g) in combination, generating a first deviation signal indicating a deviation in the hot fluid conduit; and/or upon the first cold fluid flow measurement is different from the second cold fluid flow measurement and the thermal device flow measurement (g) in combination, generating a second deviation signal indicating a deviation in the cold fluid conduit. receiving a first hot fluid flow measurement from a first hot fluid flow sensor arranged in the hot fluid conduit; receiving a first cold fluid flow measurement from a first cold fluid flow sensor arranged in the cold fluid conduit; receiving a second hot fluid flow measurement from a second hot fluid flow sensor arranged in the hot fluid conduit upstream the first hot fluid flow meter; receiving a second cold fluid flow measurement from a second cold fluid flow sensor arranged in the cold fluid conduit downstream the first cold fluid flow sensor; and receiving a thermal device flow measurement (g) from a thermal device flow sensor configured to measure a thermal device flow of a thermal device connected to the hot fluid conduit downstream the first hot fluid flow sensor and upstream the second hot fluid flow sensor, and connected to the cold fluid conduit upstream the first cold fluid flow sensor and downstream the second cold fluid flow sensor, wherein the thermal device flow of the thermal device is a flow either from the cold conduit across the thermal device to the hot conduit or from the hot conduit across the thermal device to the cold conduit, wherein the method further comprises: upon the first hot fluid flow measurement is different from the second hot fluid flow measurement and the thermal device flow measurement (g) in combination, generating a first deviation signal indicating a deviation in the hot fluid conduit; and/or upon the first cold fluid flow measurement is different from the second cold fluid flow measurement and the thermal device flow measurement (g) in combination, generating a second deviation signal indicating a deviation in the cold fluid conduit. upon the first hot fluid flow measurement is different from the second hot fluid flow measurement and the thermal device flow measurement (g) in combination, generating a first deviation signal indicating a deviation in the hot fluid conduit; and/or upon the first cold fluid flow measurement is different from the second cold fluid flow measurement and the thermal device flow measurement (g) in combination, generating a second deviation signal indicating a deviation in the cold fluid conduit.