8.14 Heat exchanger 8.14.1 General characteristics 1. External casing 2. Heat exchanger 3. Heating element 4. Thermostat In certain Jetsystem models, the water is heated by a heat exchanger (not recent models). The heat exchanger consists of a cylindrical body in aluminium alloy, lined with a layer of "teflon" to prevent the formation of scale. The water to be heated flows through the heat exchanger. The armoured spiral-shaped heating element is located inside the cylinder. A safety thermostat is positioned in close contact with the heat exchanger. The thermostat (normally-closed) is calibrated to intervene at a temperature of 220°C, and is connected in series to the heating element.
The external casing protects the heat exchanger unit. 8.14.2 Electrical symbol 8.14.3 Checking for efficiency DOES NOT HEAT: - check that the heating element is not broken: measure the resistance across the two terminals. - check that the safety thermostat is normally closed. INTERVENTION OF ELECTRICAL SAFETY CUT-OUTS: - use an ohmmeter to check that the heating element is not connected to mass and check for current leakage (40 M Ω ) WATER LEAKS: - check that the seal is correctly positioned and fitted. NO RE-CIRCULATION/DOES NOT HEAT: - check that the heat exchanger is not blocked. SOI/DT 2002-05 eb 85 599 35 23-17