Refrigerator temperature control relay knowledge

Refrigerator temperature control relay is also called temperature controller, referred to as thermostat. Commonly used thermostats include pressure thermostats and thermistor thermostats. Among them, the pressure type thermostat is simple in structure, reliable in use, long in service life and low in price, and is widely used in refrigerators. Here we focus on pressure thermostats.

Pressure thermostats include ordinary thermostats, semi-automatic frost thermostats, constant temperature reset thermostats, temperature-sensing damper thermostats, etc. Their structures and functions are different.

1. Working principle of thermostat

1. When the temperature of the evaporator rises, the pressure of the temperature-sensing agent in the temperature-sensing tube increases, so that the transmission diaphragm of the temperature-sensing chamber overcomes the tension of the spring, moves to the left, and finally pushes the quick-jump movable contact and the static The contacts are closed, and the power is turned on, and the compressor starts to run and cool.

When the surface temperature of the evaporator drops, the pressure of the temperature-sensing agent in the temperature-sensing tube also drops, and the transmission diaphragm of the temperature-sensing chamber moves to the right under the action of the spring, and finally separates the quick-jump movable contact from the static contact and cuts off Power on, compressor stopped.

2. The temperature range adjustment screw is used to adjust the temperature range. When the temperature in the box is too high, fine-tune the screw counterclockwise to lower the box temperature; when the temperature in the box is too low, fine-tune the screw clockwise to increase the box temperature.

The temperature difference adjustment screw is used to adjust the temperature difference between opening and stopping of the refrigerator. If the temperature difference between the opening and closing of the refrigerator is too small, the compressor opening and closing time will be shortened, and the opening and closing are frequent. Fine-tuning the screw counterclockwise can increase the temperature difference between opening and closing of the refrigerator and reduce the number of times of compressor opening and closing.

When the temperature difference between the opening and closing of the refrigerator is too large, the number of times of opening and closing the compressor is too small, and the cooling effect will become poor.

3. Common faults of ordinary thermostats include leakage of temperature sensing agent, poor contact or burning of contacts, and inflexibility of moving parts. When the temperature-sensing agent leaks from the thermostat, the refrigerator will have a long shutdown time, a short start-up time, and a poor freezing effect. When the contact points of the thermostat are in poor contact, the refrigerator will not start and stop regularly, and the freezing effect will be unstable. When the moving parts of the thermostat are inflexible, the refrigerator will open and stop irregularly or not stop.

Second, the difference between several temperature control

1. Semi-automatic frost thermostat

The semi-automatic frost thermostat is based on the ordinary thermostat and adds a semi-automatic frost device. There is a defrost button on the semi-automatic frost thermostat. Press this button to stop the refrigerator compressor and perform forced defrosting. When the temperature of the temperature sensing tube of the thermostat reaches 56°C, the defrost button will automatically pop up, the thermostat will be reset, the compressor will be restarted, and the thermostat will enter the same working state as the ordinary thermostat.

Because the reset temperature of the semi-automatic frost thermostat is only 56°C, the semi-automatic frost thermostat cannot perform forced defrosting at normal temperature. After the defrost button is pressed, it pops up as soon as you release it.

2. Constant temperature reset controller

The startup temperature of the constant temperature reset controller is fixed, and only the shutdown temperature can be adjusted. The constant temperature reset thermostat has three terminals, H, L and C. Between the L terminal and the C terminal is a temperature-controlled contact switch, which is similar to the contact switch in an ordinary thermostat to control the compressor's On, off. There is also a contact switch between the H terminal and the L terminal. Generally, the contact switch is always on. Only when the thermostat temperature adjustment knob is adjusted to the "stop" position, the contact switch is turned off. Contact switches can be used for the control of other electrical components.

3. Temperature sensing air door thermostat

The function of the temperature sensing damper thermostat is to automatically control the temperature of the refrigerator compartment of the intercooled refrigerator. The temperature-sensing damper thermostat is installed near the air vent between the refrigerating compartment and the freezing compartment, and is connected to the damper of the air vent through a connecting rod.

When the temperature of the refrigerator compartment rises, the thermostat will act to push the connecting rod to open the damper, and the cold air will be blown into the refrigerator compartment from the freezer compartment through the tuyere, and the temperature of the refrigerator compartment will begin to drop.

When the temperature of the refrigerating room drops to the set temperature value, the thermostat pushes the connecting rod to close the damper, and the refrigerating room is in the heat preservation state.