The principle of operation of the refrigerator
When turned on, the compressor compresses the refrigerant with a piston and pushes it into the condenser, which is a coil of tubes on the back of the refrigerator.
Unstable network - the cause of compressor failure
In the condenser, the refrigerant vapors are cooled and condensed into a liquid. There is high pressure in the condenser section. The cooled liquid refrigerant is injected under pressure through a capillary tube into the evaporator, where it evaporates and takes the heat from the refrigerator.
And then everything repeats, the compressor pumps the refrigerant into the condenser and creates a vacuum in the evaporator. The compressor is arranged in the same way as a gasoline engine, where the pistons spin the crankshaft, and in the compressor, on the contrary, the electric motor spins the piston, which creates pressure on the refrigerant at the outlet, and vacuum at the compressor inlet.
As soon as the required temperature in the refrigerator is reached, the compressor turns off and the pressure equalization of the refrigerant begins, the process of which can be heard by putting your ear to the refrigerator.
Malfunctions of modern refrigerators during power surges
If Soviet refrigerators were designed to work in conditions of a voltage drop in the network, then this cannot be said about modern refrigerators. The compressors of older refrigerators were powerful and had no difficulty in overcoming the high pressure in the system when restarted.
True, they did not have any energy savings. The energy savings of modern refrigerators are divided into several groups and the lowest energy consumption is in the A+++ group. Energy consumption is reduced by improving the thermal insulation, which reduces the compressor running time, and by reducing the compressor power.
The small power of the electric motor negatively affects when working in our poor-quality electrical network. If in the countries where these refrigerators are produced, the power grid is stable and this compressor power is quite enough, then in the CIS countries things are much worse.
Frequent voltage drops in the network with short-term outages lead to the failure of the compressor and refrigerator electronics. When the mains voltage is low, the motor current increases sharply, the current protection is triggered. This can be repeated until the compressor fails completely.
A sharp increase in voltage provokes an increase in the pressure of the refrigerant on the piston, and the current also increases sharply. After a short time, protection is triggered. Such repetitive processes lead to compressor failure. And a third option is also possible, when a short-term network outage occurs.
The compressor stops during operation and restarts. During operation, some refrigerant pressure has already been created in the refrigerator condenser, and it will be difficult for the compressor to overcome it. In addition to the high starting currents of the motor, an even higher refrigerant resistance is added.
Voltage relay RN - 101M
The current protection trips and turns off the compressor. Having cooled down a little, the protection turns on the compressor again, and the cycle repeats until the motor winding burns out. After a short-term power outage, the delay time for turning on the refrigerator must be at least 5 minutes, or you must pull the plug out of the socket yourself. And if at that moment no one is at home or simply did not notice a short-term blinker?
Ways to protect the refrigerator from power surges
In expensive refrigeration units, the electronics already provide protection for the refrigerator from power surges and a turn-on delay time is set. In the majority, popular and inexpensive refrigerators and freezers are sold without protection.
To extend the life of refrigerators, the best option would be to install a voltage relay RN-101M with a turn-on delay time function from 0 to 15 minutes. Such a device can withstand load power up to 3 kW. If there is a refrigerator and a freezer, they can be powered from one PH-101M.
It is better to set the voltage threshold to 180-260 V. Further, after following the network indication on the voltage relay display for some time, you can narrow the voltage limits to 190-250 V. The delay time for turning on the refrigerator is set to 5 minutes, and individual freezers 10 minutes.
You can put one voltage relay in the electrical panel of the apartment and set the time to turn on the refrigerator again for 10 minutes. But such an inclusion creates inconvenience. It will take 10 minutes to wait for the network to turn on in the apartment after it is submitted.
If it is not possible to purchase a voltage control relay, you can assemble a do-it-yourself time relay circuit for a refrigerator.
A diagram of such a reclosing relay is shown below. With these element ratings, the delay time is 5 minutes 30 seconds. Since modern refrigeration units are sensitive to the quality of the network, a JFV series capacitor must be installed in this time relay. In the diagram, it is designated X2 and is designed to suppress all types of impulse noise from various power and switching devices (generators, welding machines, powerful industrial installations) with an amplitude of up to 2.5 kV. They can be found on the circuit boards of faulty washing machines.
In itself, a power outage is not so scary, sharp drops are dangerous. If the device is de-energized, the compressor stops working, the movement of the refrigerant stops, but the isothermal walls of the device retain products for several hours (up to a day, depending on the climatic version of the model and the temperature in the room). Three other power problems are much more dangerous:
- A sharp increase in voltage. Appears due to the simultaneous shutdown of several powerful consumers, zero break in the shield, accidents at the substation, lightning strikes. Usually, overvoltage lasts a fraction of a second and during this period it can disable all electrical appliances plugged into sockets. In refrigerators, sensors, electronic control break down, compressor windings burn, insulation collapses - the result depends on the weak points of a particular model.
- Long-term undervoltage. Starting currents increase and disable the power supply, compressor and electronics. The device works for some time for wear and tear, and then fails. If the voltage is not enough even to start the compressor, then the start-up relay breaks first, which unsuccessfully works and finally burns out.
- Brief power outages. The cooling system is very inertial, the liquid accelerates slowly. During a stop, the compressor piston freezes, the residual pressure of freon blocks its movement forward. Imagine that you turned on the device and the motor abruptly pushes the resisting medium with force: there is too much pressure on the piston, shaft and other parts of the compressor. If the refrigerator continues to work after such an attempt, then the model is really reliable. But it’s not worth experimenting - it’s better to give the device 10 minutes to equalize the pressure, it will cost less than repairing or replacing the compressor.
Devices to protect the refrigerator from power surges
| Surely in the economy of each family there is a “power surge protector” that should be turned off during an overvoltage. In fact, this device reacts rather to exceeding the power of the electrical appliance itself - for example, if you connect a welding machine or a washing machine, a kettle and an iron to such an extension cord, the fuse will work and the wiring in the apartment will not be damaged. The “filter” can skip the power surge, but it’s generally useless against drops and sudden switching on of the network. |
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| Voltage regulator. The device is great for protecting expensive equipment - it constantly equalizes the voltage to 220, and turns it off when it rises sharply. After normalizing the voltage in the network, the device automatically restores power. In the case of the refrigerator, two problems are solved - sharp jumps and a long decrease. To protect yourself from short breaks also, make sure that the start delay function is available. |
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| Voltage control relay. Turn off the power when the voltage drops, and when the voltage rises. They are usually installed as a block for different sections of residential electrical wiring. For an area with a refrigerator, select a relay with a restart pause of at least 5 minutes. |
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| Uninterruptible power supply (UPS) for the refrigerator. Electricity passes through the device and charges its battery, and the refrigerator, computers and other equipment are already connected to the battery. Jumps and shutdowns do not affect the operation of the equipment. |
Quite often, the reason for calling a refrigerator repairman is the failure of the electric motor due to instability of the voltage in the mains. There are situations when requests for urgent repairs are received from several residents of the same entrance at once, affected by its sharp increase or decrease.
Indeed, modern household refrigerators are designed to operate with a voltage of 220V (nominal value). Maximum permissible deviations range from 187V to 242V.
What happens to the refrigerator when these tolerances are exceeded?
A voltage jump above 242V for a sufficiently long period of time threatens with excessive heating of the starting winding. As a result - insulation melting, short circuit and inevitable repair with replacement of units.
In Russian practice, the opposite situation occurs much more often - when the voltage of the electric current in the network drops below the permissible 187V and keeps at such an underestimated level for a very, very long time. If its value is too low, the start-protective relay may not work, and the starting winding will not turn on. This is fraught primarily with heating of the working winding of the electric motor, which will provide expensive repairs to refrigerators. Moscow is no exception, and power surges are quite frequent in our capital.
You can avoid such problems! You just need to take some precautions.
- Firstly, ensure high-quality contact - no loose sockets and plugs twisted with electrical tape. The reliability of contact between the plug and the socket is a mandatory requirement for the operating rules of any refrigeration unit, whether it is an old Saratov refrigerator that has served you for decades, or the latest Indesit with the No Frost system and a lot of electronics.
- Secondly, allocate a separate outlet for the refrigerator. All other kitchen appliances must be connected to a different power point.
- And finally third, and most importantly: if systematic fluctuations in voltage and power outages are observed in your home, purchase an electric voltage stabilizer. Instead of spending money on refrigerator repairs every time, invest in a stabilizer and forget about such problems.
Remember, your refrigerator will work for a long time and properly only if it is properly maintained. Otherwise, the repair of refrigeration equipment will become a constant cost item in your family budget.
A simple home-made refrigerator turn-on delay relay will help protect the compressor from breakdown.
The operating instructions for the refrigerator indicate that even after briefly disconnecting it from the mains, for example, you decide to switch the refrigerator to another outlet, you can turn it on again no sooner than after 10 minutes.
The refrigerator operates in a cyclic mode, which is determined by the installation and environmental conditions.
When the refrigerator is turned on, the refrigerant pressure in the system increases to almost seven atmospheres, and when turned off, it drops to one and a half atmospheres or less (curve 1 on the pressure graph).
These pressure drops are very dangerous for refrigerators, especially older models.
The pressure in the system acts on the compressor piston, loading the electric motor. Imagine that the compressor was turned off at a high pressure, for example, at 6.5 atmospheres and tried to turn it on again. Now the engine will work against high pressure in starting mode and its power will not be enough to move the compressor piston. Probably it is not necessary to explain what can happen with a jammed rotor of an electric motor.
However, if you wait a few minutes, the pressure in the system will decrease, and the pressure on the piston will also decrease. The compressor will start easily.
A general rule has been developed: when turning off the refrigerator, wait a ten-minute pause before turning it on again.
Modern refrigerators of new models contain posistor starting relays instead of traditional mechanical ones. The thermistor relay after stopping the compressor needs some time to turn on the engine again.
Protection allows you to avoid trouble with a blocked engine rotor, but experts believe that it is not worth bringing the matter to the point of protection. In addition, older refrigerators and refrigerators with electromechanical control do not have delay systems, so they can fail. But these refrigerators most often live in villages and dachas. And it is there that situations happen when the light goes out and literally immediately turns on again. No one will even notice this or no one at all, and the refrigerator is trying to turn on until the pressure in the system stabilizes or the engine burns out.
To protect such refrigerators, a switch-on delay device was made after disconnecting the refrigerator from the mains, which is switched on between the mains socket and the refrigerator plug. The circuit is simple, this is a conventional time relay that starts when you turn on the network. devices through a small-sized transformer, a standard bridge and a stabilizer. The turn-on delay is determined by a 47 micron capacitor. and a 5.8 ohm resistor. (2.4 mΩ resistors connected in series and a 1 mΩ resistor).
Indicators signal one of the inclusion of the device in the network, and the second of the connection of the load. Of particular note is the relay that turns on the refrigerator compressor. The relay contacts must be able to withstand the starting current of the compressor motor. In old Soviet refrigerators, the compressor motor power was 300 - 400 watts. Accordingly, the current in the operating mode is 1.8 amperes. The starting current is seven times more than the working 12.6 amperes!
The device uses a relay with contacts rated not 16 amperes.
The relay winding must be designed for a voltage of 12 volts, while the current through it must not exceed 200 milliamps (allowable for the microcircuit). For the selected 175 ohm relay, all these requirements are met. Structurally, the device is made in a housing on which there is a socket for connecting a refrigerator and two indicators (LEDs).
The operation of the device is shown in the photo. On the left, the device is turned on. The stopwatch has just started counting down the time. Bulb loading is not included. The "network" indicator is on, and the "load" indicator is off.
With an increase, as well as a decrease in the voltage in the network, which occurs as a result of accidents or a break in power lines, household appliances can completely fail. Often, power surges are also accompanied by a short circuit, which is a danger not only for various units, but also for people's lives.
Causes of power surges:
- often this happens due to the constant turning off or on of household appliances. For example, during an emergency shutdown of machines in a large factory, there will be a serious power surge that can lead to the breakdown of a large number of electronics;
- overvoltage in the network also occurs due to breaks in power lines or during a thunderstorm, when lightning discharges are observed near power lines. Therefore, the documentation for electrical appliances has advice on turning off household electrical appliances during a thunderstorm;
- consumer electronics break down due to increased voltage, which exceeds the norms for a particular device. This leads to uneven consumption of electricity.
The consequences of power surges
The problem of protecting household appliances from power surges is very important due to the high cost of most electrical appliances. In electrical networks of poor quality, the voltage may increase up to 250 V and fall below 180 V which is against the rules. If household appliances operate under overvoltage for a long time, this reduces the life of the devices, leads to insulation breakdown and various malfunctions.
Almost all manufacturers of household appliances strive to protect electrical appliances from unexpected surprises of overvoltage and network fluctuations by introducing protective elements into the design itself. For example, some refrigerators simply stop working when the voltage drops to 180V.
In refrigerators, as a result of unstable voltage in the mains, first of all, the electric motor fails. Moreover, at the same time, all residents of the entrance, whose household appliances have suffered from a sharp change in voltage, can simultaneously declare the problem. for example, it is designed to work with a voltage of 220V, and possible deviations may be 187V -242V. If the voltage is more than 242V for a long time, excessive heating of the starting winding may occur, which will lead to melting of the insulation and a short circuit. The result of all this will be a repair, in which all the main parts of the unit will have to be changed.
In Russia, the voltage of the electric current in the network is often low, below 187V, and also remains at this level for too long. In this case, the start-protective relay does not work, and the starting winding does not turn on. This leads to heating of the working winding of the electric motor, which necessitates an expensive one.
To prevent these problems, you must take the following measures:
- 1. Qualitatively make contact, which is expressed in the absence of loose sockets and plugs. First of all, it is necessary to ensure reliable contact between the plug and the socket, as this is a mandatory requirement for the operating rules of any type of refrigeration unit.
- 2. For you need to make a separate outlet, and connect other appliances in the kitchen to the rest of the power points.
- 3. In case of systematic voltage fluctuations, as well as power outages, it is worth buying an electric voltage stabilizer. This will save you money on ongoing refrigerator repairs.
In this case, it will always work without problems for many years, since the life of household appliances largely depends on high-quality power supply. Constant shutdowns and power surges are often accompanied by breakdowns of such equipment.
