TEMPERATURE CONTROL SYSTEM

Temperature control system (1) for a room (2, 3) with two heat exchangers (4-6). Sensors (12-18; 23-25) detect a physical characteristic of the heat carrying fluid at each heat exchanger (4-6) and an additional physical characteristic, diagnostic means detecting a kind of a malfunction of the system (1) detect a wrong size of a heat exchanger (4-6) when at least one of the following conditions are fulfilled: a) a difference between an inlet temperature and an outlet temperature of the heat exchanger (4-6) is smaller than a predetermined value and the average room temperature does not match a desired temperature, b) the outlet temperature differs more than a predetermined value from the average room temperature, c) a difference between an inlet temperature and an outlet temperature of the heat exchanger (4-6) is smaller than a predetermined value over more than a predetermined time and a desired room temperature is not reached after the predetermined time and a command has given to fully open the control valve (20-22) and the conditions are fulfilled in a predetermined number of other rooms.