Refrigerator relay: device, principle of operation and types of faults

The refrigerator relay is a small but critical element on which the operation of the entire unit depends. Without it, the compressor simply will not be able to start or will work intermittently, which will lead to food spoilage, overheating of the motor and even complete failure of the equipment. Many users are not even aware of the existence of this part until they encounter characteristic clicks, lack of cold or a constant hum without cooling.

In this article we will look at how the refrigerator relay works, what functions it performs and why it is often called the “heart” of the starting system. You will learn about the two main types of relays - start-up protection and thermal, their design differences, as well as how to recognize a malfunction by indirect signs. We will pay special attention to the connection diagram, the operating principle and whether it is possible to repair the relay with your own hands or is it better to immediately replace it with a new one.

The material will be useful for both novice craftsmen and ordinary users who want to understand the structure of their equipment. We avoid complex terminology, but at the same time we give precise technical explanations - so that you can not only understand the problem, but also competently explain it to a specialist if necessary.

What is a relay in a refrigerator and why is it needed?

A relay in a refrigerator is an electromechanical (or electronic) device that controls the operation compressor. Its main tasks:

• 🔌 Starting the compressor —supplying a short-term high current pulse to the starting winding of the motor.
• 🛡️ Overload protection —turning off the power in case of overheating, jamming or power surges.
• ⚡ Operation stabilization —maintaining the optimal mode of turning on/off the compressor.

Without a relay, the compressor will either not start at all or will work continuously, which will lead to its rapid wear. In modern refrigerators (Indesit, Samsung, Atlant, LG) most often used starting protection relay (PZR), which combines both functions. In older models (for example, ZIL or Minsk) separate starting and protective relays could be installed.

It is interesting that in inverter refrigerators (for example, Samsung Digital Inverter or LG InstaView), the classic relay is often replaced electronic control unit, which smoothly regulates the speed of the compressor without sudden starts. However, even in such models, protection elements similar to traditional relays can be retained.

Design of a refrigerator start-protection relay: design analysis

The classic start-protection relay (PPR) consists of several key elements, each of which performs its own role. Let's consider its device using the example of the most common type - induction relay with thermal protection (installed in 80% of household refrigerators).

Main components:

• 🧲 Coil (solenoid) - creates a magnetic field when passing current that attracts the core to close the contacts.
• ⚙️ Core (armature) —a moving element that closes/opens the contacts of the starting winding.
• 🔥 Bimetallic plate —triggered when overheated, opening the circuit (protective function).
• 🔌 Contact - movable and fixed plates through which current passes to the compressor.
• 📦 Case - usually made of plastic or metal, protects internal parts from dust and moisture.

Inside the case there is also springwhich returns the core to its original position after starting the compressor. In some models (for example, a relay Danfoss or Embraco) an additional posistor thermistor is installed, which limits the starting current.

Important: in the relay of refrigerators with a No Frost system (for example, Bosch KAN92VI20 or Liebherr CNef 4315), more sensitive bimetallic plates are often installed, since the compressor operates in intensive mode.

The principle of the relay: how it starts the compressor

The operation of the refrigerator relay is based on electromagnetic and thermal principles. Let's figure out how this happens step by step:

1. Power supply. When the thermostat detects an increase in temperature in the chamber, it closes the circuit and voltage is supplied to the working winding of the compressor i to the relay coil.
2. Triggering mechanism. The current in the coil creates a magnetic field that attracts the core. That, in turn, closes the contacts starting winding of the compressor. Now the motor receives an increased current (2-3 times higher than the rated current), necessary to overcome the inertia of rest.
3. Starting the compressor works. The rotor begins to rotate, and after 1-3 seconds it reaches operating speed. At this moment, the relay core returns to its original position (due to a spring or a decrease in current), and the starting winding is turned off. Then only working winding.
4. Control and protection. If the compressor overheats (for example, due to jamming or a power surge), the bimetallic plate opens the circuit, cutting off the power. After cooling, the contacts close again and the cycle repeats.

The whole process takes a split second, but without the relay the compressor simply would not be able to start - it would not have enough power to overcome the starting load. In refrigerators with linear compressors (for example, Secop or Embraco), the relay is activated every time it is turned on, and in inverter models its role is played by an electronic unit that smoothly regulates the motor speed.

Why does the relay click when starting?

Clicks are the normal sound of the relay core operating. When voltage is applied, the coil attracts an armature, which closes the contacts with a characteristic sound. If the clicks are repeated many times in a row (the compressor does not start), this is a sign of a malfunction of the relay or the motor itself.

Interesting fact: in some industrial refrigerators (for example, for shops) relays are used restart delay (up to 5-10 minutes). This protects the compressor from frequent starts, which can lead to overheating of the windings.

Types of relays in refrigerators: how they differ

Depending on the model of the refrigerator and the type of compressor, different types of relays can be installed. They can be classified according to several criteria:

1. According to the principle of operation

• 🔄 Induction (electromagnetic) the most common ones operate due to the magnetic field of the coil. Installed in 90% of household refrigerators.
• 🔥 Thermal (with a bimetallic plate) - triggered when heated, often combined with induction in the same housing.
• 📱 Electronic — used in inverter models, controlled by a microcontroller.

2. By design

• 📦 External (mounted) - mounted on the compressor housing (for example, relay Danfoss 103N0017 or Embraco ER24-1).
• 🔌 Built-in - placed inside the compressor (typical for some models Samsung i LG).

3. For purpose

• 🚀 Starting —only for starting the compressor.
• 🛡️ Protective —only for shutting down when overloads.
• ⚡ Start-protective (PZR) - combine both functions (the most common option).

The table below shows examples of relays for popular brands of refrigerators:

If you are not sure which relay is installed in your refrigerator, pay attention to the markings on its case. Usually the model (for example, R3-1B or KLIXON 3AM-15G) and rated current (for example, 10A). This information will be useful when purchasing a replacement.

Signs of a faulty refrigerator relay

The relay is one of the most vulnerable parts of the refrigerator, so how it works under conditions of constant loads and temperature changes. You can recognize its malfunction by the following signs:

• 🔊 The refrigerator does not turn on - the compressor is silent, but the light inside the chamber is on. This may mean that the relay does not supply voltage to the motor.
• ⚡ The compressor tries to start, but turns off - repeating clicks are heard. (the relay is activated, but the motor does not rotate). The reason may be burnt contacts or a faulty coil.
• ❄️ Refrigerator is not cooling —the compressor runs continuously, but the temperature in the chambers does not drop. Perhaps the relay does not turn off the starting winding, and the motor overheats. data-i="204">The refrigerator does not cool
• 🔥 The relay body is hot —if you feel strong heating when touching the relay, this is a sign of an overload or an interturn short circuit in the coil.
• 💥 Sparking or burning smell —indicates burnt contacts or breakdown insulation.

It is important to distinguish a relay malfunction from problems with the compressor or thermostat itself. For example, if the refrigerator does not respond at all when plugged into the network, not only the relay, but also supply filter, fuse or control unit may be to blame. modern models).

⚠️ Attention: if the relay clicks, but the compressor does not start, DO NOT try to turn on the refrigerator multiple times in a row. Each start without successfully starting the motor increases the risk of an interturn short circuit. compressor windings!

For accurate diagnostics you will need testing the relay with a multimeter checking the resistance of the compressor windings. We will talk about this in the next section.

How to test a refrigerator relay with a multimeter

Checking a relay is a task that you can handle yourself if you have a multimeter and skills in working with electricity. We will describe step-by-step instructions for the most common type - a start-up relay with a coil and a bimetallic plate..

First, unplug the refrigerator and remove the relay. It is usually attached to the compressor housing using latches or screws. On the relay body you will see 3-4 contacts marked:

• S (Start) - starting winding,
• R (Run) - working. winding,
• C (Common) - common contact,
• L (Line) - phase input (if any).

Next follow the instructions:

Disconnect the refrigerator from the network and discharge the capacitors (if any)

Remove the relay from the compressor

Ring the relay coil (resistance should be 10–100 Ohms)

Ring the contacts in normal condition (without voltage supply)

Apply voltage to the coil and check the circuit contacts

Ring the bimetallic plate (in a cold state it should pass current)

Check that there is no short circuit between the contacts and the body-->

More details about each step:

1. Coil continuity. Connect the multimeter probes to coil terminals (usually contacts S and C or L and C. The resistance should be within the limits 10–100 Ohm. data-i="243">) or short circuit (OL) or short circuit (0 Ohm), the coil is faulty.
2. Checking the contacts. V in normal condition (without voltage supply), the contacts of the starting winding should be open. If the multimeter shows conductivity, then the contacts are “stuck” and require cleaning or replacement.
3. Operation test. Apply voltage to the coil 220V (through an extension cord with a plug, observing safety precautions!). You should hear a click - this is the core being pulled in and closing the contacts. If there is no click, the relay is faulty.
4. Checking the bimetallic plate. In a cold state, it should pass current (resistance ~0 Ohm). (carefully!) - when triggered, the circuit should open.

If the relay passes all the tests, but the refrigerator still does not work, the problem may be in compressor or thermostat. In this case, a deeper one will be required. diagnostics.

⚠️ Attention: When checking the relay under voltage, be careful not to touch the exposed contacts and use insulated tools. It is better to carry out tests on a table away from the refrigerator.

Can the relay be repaired or just replaced

In most cases, the refrigerator relay cannot be repaired - it is easier and more reliable to replace it, however, there are several situations when you can try to restore the functionality of the part:

• 🔧 Oxidation or burning of contacts. They can be cleaned with fine sandpaper. paper (zero) or a file. After cleaning, wipe the contacts with alcohol.
• 🧲 Sticking of the core. Sometimes disassembling the relay and cleaning the core guides from dirt is not recommended. It is not recommended to lubricate the parts. - this can lead to dust accumulation.
• 🔥 False triggering of the bimetallic plate. If the plate triggers too often, it can be bent (very carefully!) to change the trigger threshold.

In all other cases (coil breakage, cracks in the housing, insulation breakdown), the relay must be replaced. The cost of a new relay for most refrigerator models is 500–2000 rubles, depending on the brand and type:

• Relay Danfoss 103N0017 — ~1200 rub.,
• Relay RTK-X (for Atlant) — ~600 rub.,
• Relay KLIXON 3AM-15G — ~1500 RUR.

When replacing a relay, pay attention to:

• 🔌 Compatibility with compressor. The relay must be suitable for current, voltage and type of mounting.
• 📏 Dimensions. The new relay must physically fit in place of the old one.
• 🔧 Connection polarity. Do not mix up the contacts S, R and C!

If you are not sure of the choice, show the old relay to the seller at the spare parts store - he will help you choose an analogue. You can install relays from another refrigerator model only if their technical parameters completely match.

FAQ: Frequently asked questions about the refrigerator relay

Why does the relay click, but the compressor does not start?

This is a typical sign that the relay is activated, but the compressor cannot start rotating. The reasons may be the following:

• Compressor jamming (mechanical blocking).
• Breakage of the motor starting winding.
• Low voltage in the network (less than 180V).
• Failure of the capacitor (if any in the circuit).

For diagnostics, turn off the relay and apply voltage directly to the compressor (to contacts S and C). If the motor does not start, the problem is in itself.

Is it possible to start a refrigerator without a relay?

Technically yes, but highly not recommended. Without a relay, the compressor will not receive the necessary starting current and will not be able to start. If you temporarily close the contacts manually (for example, with a screwdriver), the motor may burn out due to the lack of overload protection.

An exception is a short-term check of the compressor during diagnostics. In this case, you can apply voltage to the working winding (R i C), but for no more than 1-2 seconds!

How often do you need to change the relay?

The relay does not have a fixed service life, but on average it lasts 5–10 years. Its service life is affected by:

• The quality of the voltage in the network (frequent surges shorten the service life).
• The frequency of compressor switching on (in hot climates or if the thermostat is not set correctly, the relay wears out faster).
• Dust and humidity (lead to oxidation of contacts).

If the refrigerator operates stably, the relay does not make any extraneous sounds and does not get hot, there is no need to replace it “prophylactically.”

What to do if the new relay burns out immediately?

If the installed one the new relay immediately failed, the reason, most likely, is:

• Faulty compressor (interturn short circuit or jamming).
• Incorrect connection (contacts are mixed up S and R).
• Power surges in the network (the relay burns out due to overvoltage).

Before installing a new relay, check the resistance of the compressor windings and the voltage in the socket. If the problem persists, contact a specialist to diagnose the compressor.

Can I use a relay from another refrigerator?

It is possible, but only if:

• The rated current of the relay corresponds to the compressor current (indicated on the motor nameplate).
• The type of relay is suitable (induction, thermal or start-protective).
• The connection diagram (contact arrangement) matches data-i="331">For example, a relay from S, R, C).

For example, a relay from Indesit with a compressor Embraco can be installed on Atlantif it has the same motor, but a relay from an inverter Samsung is not suitable for a regular compressor. refrigerator.