| 摘要 |
In a control circuit of an electric flow heater, it is desired to restrict the delayed switching on of the heating elements in the case of air bubbles in the line of water to dangerous cases. A sensor is attached to a microprocessor that controls the heating elements; this monitors the flow heater's operating voltage. After initial application of the operating voltage and after an outage of operating voltage, the microprocessor does not switch on the heating elements at the first subsequent drawing of water until after a delay. The same applies to an outage of the water mains pressure.
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