| 摘要 |
PURPOSE:To provide a safety circuit which detects the failure of a temperature detecting sensor, immediately cut off a relay circuit, and stop supplies of hot-water and electric power to a floor panel, when the temperature detecting sensor consisting of a thermistor of negative characteristics fails, to the temperature controlling circuit for a floor heating device. CONSTITUTION:The serial circuit of a floor temperature sensor 6 and a resistor RA, and the serial circuit of resistors RB and RC are provided in a temperature controlling device. The contact point of a resistor RA and a floor temperature sensor 6 is connected to the inverted input terminal of a comparator OP2, while the contact point of resistors RB and RC is connected to the non-inverted input terminal of a comparator OP2. The output terminal of a comparator OP2 is connected to the base of a transistor Tr1 which drives a relay by the output from said comparator. With such an arrangement, when the floor temperature sensor 6 fails, the inverted input voltage VA to the comparator OP2 becomes equal to the circuit power supply voltage VCC, forming a relation with VA>VB, and an output voltage from the comparator OP2 drops low. The low level voltage is held when the sensor 6 fails, regardless of high or low output level from a comparator OP1. The transistor Tr1 which drives the relay is turned OFF, a thermal valve is closed, and circulation of hot-water is stopped. In such a manner, safety function is secured when the sensor 6 fails. |
