The dual supply sensor contains two sensing elements within a single body. F02 indicates that one or both halves of the supply temperature sensor has failed OR the difference between the dual sensor readings is greater than 18ºF. This is a serious safety issue and the boiler will not restart until the sensor is replaced by a technician and he pushes the RESET button on the display. This situation is indicated by the red light on the display and the flashing word LOCKOUT. During this lockout fault, the pump will be on as indicated on the second line of the display.
- Check the electrical connections to each half of the thermistor on the outlet manifold. Verify 5 VDC by checking in Molex connector. If there is not 5 VDC, check the harness. If harness and sensors are OK, replace control.
NOTE: The boiler will reset automatically. Verify thermistor resistance values of each half of the dual sensor by referencing chart in this manual.
- Replace thermistor if necessary.
