Electric cold relay and some information about the refrigeration unit. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Electric cold relay and some information about the refrigeration unit. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches

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The electric cold relay (ERH) is designed to regulate the operation of refrigeration units, that is, to maintain the desired temperature in freezers.

In most cases, the refrigerator fails due to a malfunction of the ERC for the following reasons: refrigerant leakage from the pipe, which leads to its unusability; contamination of contacts connected to an electric heating element in absorption refrigerators or to an electric motor in compressor rooms; mechanical damage to ERH; incorrect regulation and installation of the ERC on the refrigeration unit.

The ERH connection diagram is shown in Fig.1.

ERH advantages: easy to manufacture, operate and repair; can be used for other purposes, such as adjusting the room temperature. Cons ERH: manual temperature setting.

The electrical circuits of the ERH nodes are shown in Fig. 2, the ways of connecting the ERH to the power grid are shown in Fig. 3 and Fig. 4. In this case, the device is connected through a transformer (Fig. 4), therefore, it is more overall, but also safer in operation. When connecting the device according to the scheme shown in Fig. 3, it is necessary that the insulation of the wiring and the thermistor be reliable and without damage. The complete ERH connection diagram is shown in Fig.5.

(click to enlarge)

ERH consists of a threshold device made on transistors VT1 and VT2, a mechanical relay P1 of the RES-10 type and a power supply. The temperature sensor is the thermistor R3. When the switch-off temperature is set, the transistor VT1 is closed, VT2 opens, after charging the capacitor C3, relay P1 is activated, opening the electrical circuit. With an increase in the external temperature of the chamber, the resistance of the thermistor decreases, while the transistor VT1 is open, VT2 is closed, the relay turns off, closing the electrical circuit, and the refrigeration unit works again. The relay operates in economy mode, i.e. it is disabled when the refrigeration unit is running.

Details. Resistors R1, R2, R5 type MLT-0,5. Relay P1 type RES-10 (RS4.524.302) or RSM-1 (Yu.171.81.01). Any small-sized capacitors for a voltage not less than that indicated in the diagram. Diodes VD1-VD4 type D226V. Any Tr-r transformer with a voltage on the secondary winding of 12 ... 18 V. Transistors VT1 and VT2 of the KT815A, V type.

Setting. Resistor R1 is mounted on the outer surface of the refrigerator (can be installed in place of the dismantled relay). Resistor R3 (sensor) is installed in place of the factory relay pipes. ERH is mounted on the back wall of the refrigerator case. After installation of the ERH, the refrigeration unit is turned on. After the required temperature is established in the freezer, the refrigeration unit is stopped using the tuning resistor R4. Then check the temperature maintenance of the freezer and the operation of the refrigeration unit as a whole.

If the circuit is assembled without errors from serviceable parts and the device is mounted correctly, then the ERH does not require adjustment and works immediately.

Author: R. Dobrovolsky

See other articles Section Clocks, timers, relays, load switches.

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