nofrost.ru

no frost systems are commonly used in household refrigerators to prevent the formation of frost on the evaporator. The standard circuit without feedback is a relatively simple design that operates continuously, including during the defrost mode. The circuit consists of several components: 1. Timer (T): The electromechanical timer controls the alternating cooling and defrost modes of the system. It ensures cyclic operation and determines the duration of each mode. 2. Timer motor (M): The timer motor rotates the shaped drum sequencer in the electromechanical timer. This rotation allows the timer to switch between different contacts and count down the time. 3. Compressor (C): The compressor is responsible for circulating the coolant through the refrigeration unit's pipelines. It facilitates the cooling process by intensively cooling the evaporator. 4. Fan (F): The fan creates an airflow that enables heat exchange between the evaporator surface and the food products inside the refrigerator. It helps maintain a consistent temperature throughout. 5. Defrost heater (R): The defrost heater is attached to the evaporator and heats it to melt any accumulated frost. This prevents the formation of thick frost layers that could impede heat exchange. 6. Defrost thermostat (DT): The defrost thermostat monitors the temperature of the evaporator during automatic defrost cycles. It ensures that the heater is switched off when the temperature exceeds the frost melting point. The circuit operates in different modes: 1. Initial Rapid Cooling: The timer supplies power to the compressor and fan, but the defrost thermostat contacts remain open. This mode lasts for about 10 minutes until the evaporator cools down sufficiently. 2. Cooling Mode: The timer continues to supply power to the compressor and fan as the evaporator reaches the desired temperature. The defrost thermostat contacts close, and the system operates in this mode for 6 to 12 hours, gradually accumulating frost. 3. Defrost Mode: The timer de-energizes the compressor and fan while powering up the defrost heater. The defrost thermostat contacts remain closed until the evaporator temperature rises above the frost melting point. This mode typically lasts for 10 to 20 minutes, ensuring complete defrosting. 4. Rapid Cooling Mode: After the defrost phase, the timer switches over its contacts, setting the system back to rapid cooling mode. This mode lasts for 15 to 25 minutes. The standard circuit without feedback lacks a feedback mechanism to detect the end of the defrost phase accurately. This can result in a longer pause before switching to the freezing mode, affecting the temperature conditions inside the refrigerator. However, more complex feedback systems address this issue.