Refrigeration basic II
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In the previous post I defined and explained the main elements of the mechanical system of a domestic refrigeration system, in which I bring you next I will explain the electrical system
The elements that interact in the electric cooling system are the following:
Compressor motor, fan motor, resistors, clock, relay, bimetallic thermal and thermostat, these are necessary for the domestic cooling system to work.
In this post I will not define what the compressor engine is because I defined it in the previous article.
Fan motor: It is a common fan as we all know but of smaller size and strength. Its function is to exchange lead or extract temperatures in the refrigeration system according to the case or the place where it is positioned.
Evaporator fan motor (in refrigerators no frost): It is located inside the equipment and its function is to extract heat from the food or products stored in the refrigerator and take it to the evaporator so that the heat is absorbed and in turn circulate the cold throughout the refrigerator. Frost coolers do not have a fan motor in the evaporator.
Condenser fan motor (if any): Its function is to extract and release the heat from the condenser to the environment and in turn circulate fresh air through the condenser to cool the refrigerant that circulates inside it..
Fan motor
- Defrosting resistors (refrigerators nofrost): It can be aluminum, ceramic, or wire encapsulated in glass, is located next to the evaporator and its function in melting the ice formed in evaporator by the heat produced by the resistance to be on. This is lit by the clock in a due time and for a certain time.
Defrosting resistors
- Timer: It is a time device that determines the time and work cycles of the refrigerator. They mostly come with a specific time for each cycle depending on the model, it consists of only two cycles, the long cycle or freezing cycle where it allows the compressor to operate for a period of time (6, 8, 10 hours) and the period short where the compressor disconnects and allows it to work at the defrosting resistance for a period of time (20, 50 minutes) to melt the excess ice formed in the freezing cycle, at the end of each cycle the other begins. There are clock models where you can adjust the duration of each cycle.
Timer
- Relay: There are two types, the ptc relay and the coil relay, the ptc relay (positive temperature coefficient for its acronym) lacks contacts and moving parts and controls the starting of the compressors of the domestic equipment and works as a variable resistance that As the current circulates through a resistive material inside it increases the temperature and consequently increasing its resistivity, limiting the passage of current. The coil consists of a coil and a mobile contact in its interior that is connected or disconnected by induced magnetism when energizing the coil thus controlling the start of the compressor.
Ptc relay
Coil relay
- Bimetallic thermal: badly called "klixon" because this is just a trademark, are thermostatic switches that open or close the electrical circuit of the equipment depending on the temperature captured by it, interrupting the passage of current, to reach its normal temperature it returns to its position normal closing or opening the circuit as the case may be. A domestic refrigerator or refrigerator may have two different bimetallic thermals; connected to the compressor motor or connected to the defrosting resistor.
In the case of being connected to the compressor motor, its normal condition is closed, it keeps the circuit closed (working) and when it picks up a temperature rise due to a rise in voltage, due to lack of maintenance of the equipment or malfunction of the compressor motor it opens interrupting the work of the compressor motor as a protection measure.
In the case of being connected to the defrosting resistance, it works in reverse, its normal condition is open, being located in the evaporator connected to the resistance it freezes and closes allowing the passage of the current to the resistance in its Due to the cycle allowing the resistance to work, when melting all the ice, the bimetallic is also thawed, returning to its normal condition, interrupting the passage of the current to the resistance as protection from an over-thawing that could damage the equipment.
Bimetallic for thawing
Thermal protectors for refrigeration compressors
- Thermostat: It is another type of switch operated by temperature, it is composed of a bulb that contains inside a material that expands or contracts by the degree of temperature to which it is exposed by activating a mobile contact that opens or closes the electrical circuit of a refrigeration system. This device is adjustable and is to control the temperature we want to obtain from the equipment for food or products stored in the refrigerator.
Thermostat
Previous articles
Basic Cooling part I.
Introduction to refrigeration
Original text of: Refrigeration technician Jesús Córdova
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