Wiring diagram and structure of the refrigerator

An ordinary compression-type refrigerator operates according to the following scheme:

• The motor-driven compressor sucks the gaseous coolant from the evaporator. The coolant is then compressed, heated, and enters the condenser.
• In the condenser, the coolant is cooled to its normal temperature and liquefied.
• The liquefied coolant then enters the evaporator, where it vaporizes and cools the walls of the heat exchanger that cools the interior chambers of the refrigerator.
• From the evaporator, the vaporized coolant once again enters the compressor.
• The compressor motor is connected to an electrical circuit through a thermostat. When the temperature inside the refrigeration compartment reaches the desired level, the thermostat opens its contacts and turns off the motor.
• As time passes, and the compartment’s temperature increases, the thermoregulator will reconnect the motor by means of the starting relay.

A graphic representation of the cooling device is depicted in the figure below.

The electrical components consist of:

• motor for the compressor;
• lighting elements;
• heaters utilized in absorption-based systems;
• fans for forced air circulation.

The automation systems encompass:

• Temperature regulating devices installed in the refrigerated compartments. These devices can be either mechanical or electronic.
• Starting relays. These relays are employed to facilitate the initiation of asynchronous electric motors of the compressors and their prompt deactivation in case of an overload.
• Frost elimination systems from the surface of the evaporator.
• Incorporated automatic control systems that fulfill all aforementioned functions, in addition to monitoring the shelf life of stored merchandise and reordering them via an electronic system.

Once the appliance is plugged into the power source, electricity flows through the thermostat contacts, protective relay, starting relay’s inductive coil, and the main winding of the electric motor.

During the initial stages, while the rotor remains still, the current is higher than usual. Once the starting relay is activated, the inductive starting coil is then connected to the circuit. This causes the armature to turn, resulting in a decrease in current. As a result, the relay opens and the electric motor can run smoothly.

Once the refrigerating chamber has reached the desired temperature, the thermal relay is activated, interrupting the power supply circuit to the electric motor. As the temperature within the chamber rises beyond the set level, the motor is reconnected to resume operation. This cycle continues to repeat.

The protective relay responds to the current flow in its circuit. If the motor becomes overloaded, the current in its circuit will increase. Once it reaches the designated threshold, the protective relay will interrupt the circuit. Once the motor and relay have cooled down, the circuit will be reestablished, allowing the motor to restart. This system ensures the motor is protected against premature wear and prevents fire hazards in the room. The relay contains a sensor in the form of a bimetallic plate that is created by welding together strips of metals with differing coefficients of thermal expansion. When the plate is heated, its shape changes and causes the circuit to break. As the plate cools, it returns to its original shape and closes the circuit once again.

The image below showcases the circuit diagram for the Stinol brand compression refrigerator.

A schematic diagram of an electric compression refrigerator.

When it comes to designing the interiors of modern kitchens, one of the challenges is how to combine various shapes and colors of kitchen appliances:

• stove;
• oven
• refrigerator;
• microwave oven;
• dishwasher;
• cooker hood, etc.

One popular solution is to use fully built-in kitchen appliances. In this case, the appliances are hidden inside modular cabinets and shelves of standard sizes, with front panels designed in the same style.

Manufacturers have created special ranges of appliances designed specifically to be built into kitchen modules.

The walls and doors of these appliances are not painted with enamel, as they will be concealed inside the cabinets. The doors are equipped with special systems for attaching hinged panels.

Every user manual from manufacturers includes a diagram that outlines the installation requirements. This diagram includes the dimensions of compatible modules, the minimum depth, width, and height of the opening, the distance between the evaporator and the back wall of the cabinet, as well as the size and location of the openings for natural air circulation.

There is an option of a semi-integrated design as well. In such a scenario, a regular model of the appliance with a custom-painted door is utilized. The refrigerator is installed in a front-facing recess within the kitchen furniture. However, it is important to adhere to the requirements for proper air circulation.

The refrigerator can be connected to the power supply by simply plugging the plug into the socket.

However, there are several requirements that must be followed:

• The electrical wiring must be in good condition and capable of supporting another device.
• The socket should be securely attached to the wall and the wire fastening should be tightened. If the socket sparks or becomes hot while the refrigerator is running, it should be replaced and the wiring from the socket to the switchboard should be checked.
• It is not recommended to use extension cords or splitters to connect the refrigerator. It is more reliable to install a separate outlet.
• The electrical wiring and socket must have an earth connection.

Aside from the requirements for the electrical network, there are several general suggestions regarding the positioning and connection of the device:

• To prevent heat accumulation from sunlight, it is advisable to place the unit as far away from the window as possible.
• Avoid placing the unit in close proximity to heat sources such as stoves, ovens, heating radiators, or heated floors.
• Ensure that the refrigerator does not obstruct any passageways when its doors are open.

Adhering to these recommendations will enhance the convenience, safety, and energy efficiency of the refrigerator’s operation.

Absorption refrigerator: scheme

Aside from standard compression-type refrigerators, there has been a significant proliferation of refrigerators based on the absorption effect. These units operate without any moving parts or components, instead relying on the natural circulation of the refrigerant. This refrigerant is typically a liquid with a low boiling point, which must be easily soluble in a high boiling point liquid known as the adsorber.

Schematic diagram of an absorption device

The absorption device consists of several components that work together to achieve the desired cooling effect. The process starts with the concentrated coolant, which is stored in the tank (2). From there, it flows into the thermopump, which is designed as a copper tube heated by an electric heater. In the next step, the coolant enters the vapor generator (1), which is also heated by electricity.

Inside the vapor generator, the coolant undergoes vaporization and mixes with the vapors from the adsorber. The resulting gas mixture then passes through the condenser – deflegmator (3), where the different fractions of the mixture are separated.

The adsorbing liquid, which was present in the gas mixture, undergoes liquefaction in the condenser and is then returned to the generator for further use. On the other hand, the coolant, now in the form of gas, flows downward to the evaporator due to gravity.

As the gas flows through the evaporator, it undergoes vaporization, thereby absorbing a significant amount of energy and causing a drastic decrease in temperature. The coolant, now in the form of gas, is then returned to the adsorber tank and absorbed once again. This cycle is repeated continuously to maintain the cooling effect.

Absorption type units come with built-in features

These units are known for their extended lifespan and low noise levels. They can withstand long periods of shutdown without the risk of refrigerant leaks.

The drawback is that they consume more energy (50% higher than compression units).

These systems are commonly used in seasonal residency areas.

Schematic diagram of a refrigerator on Peltier elements

This device is essential for traveling as it does not require refrigerant. The cooling process is achieved through the Peltier effect, where different semiconductor elements are soldered together. These elements heat up on one side and cool down the chamber on the other. This device can effectively cool the chamber down to -50°C.

Schematic representation of a Peltier module

The scheme offers several benefits, including its incredibly simple and cost-effective design. Simply use a fan to cool the "hot" side of the semiconductor component, while the "cold" side is integrated into the lid of the refrigerator chamber, allowing for natural downward airflow.

Car fridge that works on the principle of the Peltier effect

One of the undeniable benefits of this design is its ability to tolerate shaking and vibration, its compact size, and the ability to quickly defrost products by simply changing the polarity of the Peltier element.

However, this design has its drawbacks, such as high power consumption and a relatively short lifespan of the semiconductor element.

Schematic diagram of relay and thermostat

When using a refrigerator, the most common sources of malfunction are relays and thermostats. However, if you’re a DIY enthusiast and skilled with a screwdriver and a tester, repairing or replacing these components is entirely possible. Unfortunately, many modern refrigerator manufacturers are opting to use unrepairable blocks that must be replaced in their entirety.

The function of the thermostat is to regulate the desired temperature in the refrigeration or freezing compartment. The bellows in the capillary tube contains a substance that expands or contracts in response to temperature changes. This causes the movable part of the thermostat to move axially, which in turn deflects the power lever and either opens or closes the contacts that control the thermal relay.

Diagram of the Stinol refrigerator’s thermal relay

Once the temperature surpasses the designated level, the contacts come together, permitting electrical current to flow through the relay’s control winding. This triggers the starting relay and initiates the compressor’s electric motor.

Once the temperature has cooled down, the bellows tube contracts and severs the relay’s control circuit. This deactivates the compressor motor. As the motor stops, the chamber’s temperature gradually increases until the thermal relay is activated again. This cycle then repeats.