How to connect the motor from the refrigerator directly to a 220V network without a relay: step-by-step instructions with diagrams

The refrigerator compressor motor is the heart of the cooling system, and its connection without a standard starting relay is often required when repairing, testing or using in homemade projects (for example, to create a vacuum pump or airbrush compressor). However, direct connection to a 220V network is fraught with risks: from overheating of the windings to mechanical destruction of the piston group. In this article we will look at what circuits to use for different types of engines, and why some “folk” methods lead to breakdowns within 5 minutes of operation. how to safely start a compressor without a relay, which circuits to use for different types of engines, and why some “folk” methods lead to failure in 5 minutes of work.

It is important to understand: the starting relay in the refrigerator performs two key functions - shorts the starting winding for a split second to create the initial torque and breaks the circuit on reaching the rated speed. Without it, the engine will either not start or will work with overload. We will look at temporary solutions for testing and alternative circuits using improvised elements, but remember: long-term operation of the compressor without protection reduces its life by 3-5 times.

Why you can’t just apply 220V to the compressor

The main mistake of beginners is trying to apply voltage directly to the working winding (R), ignoring the starting winding (S). As a result, the engine either does not start (if the load is high) or begins to hum and heat up. Reasons:

• 🔹 Lack of initial torque. The compressor rotor has high inertia, and without an additional “push” from the starting winding it will not overcome the resistance of the refrigerant in the system.
• 🔹 Phase imbalance. Single-phase asynchronous motors (and these are the ones found in 99% of refrigerators) require a phase shift between the windings. The relay provides this shift for a short time.
• 🔹 Overheating of the windings. Without overload protection, the current in the working winding can exceed the rated one by 1.5–2 times, which leads to an interturn short circuit.

An exception is compressors with built-in overheating protection (thermal sensor in the winding). They can be run briefly without a relay, but the risk remains. For example, in engines Danfoss or Embraco new generation (series NTZ, EG) bimetallic fuses are often installed, which open the circuit at 130–145°C. However, this does not replace the starting relay!

⚠️ Attention: If the compressor previously worked with a relay, and now you are trying to start it without it, check the winding resistance with a multimeter. Normal values: operating winding (R) - 10–30 Ohms, starting winding (S) - 20–50 Ohms. If the resistance is below 5 Ohms or tends to zero, the winding is short-circuited, and direct connection will lead to a fire.

Types of compressors and their connection features

Before connecting the motor, determine its type. Two main options are used in refrigerators:

90% of household refrigerators (Atlant, Indesit, Stinol, Biryusa) have asynchronous compressors with three terminals: General (C), Working (R), Starting (S). They can be identified by the characteristic relay “pill” attached to the housing. Inverter compressors (in models LG, Samsung marked Inverter Linear) are useless to connect without native electronics - they require a PWM signal.

Connection diagrams without starting relay

To temporarily start an asynchronous compressor without a relay, two main schemes are used:

1. Connection via a button (short-term start)

This circuit simulates the operation of a relay: you manually close the starting winding for 1–2 seconds until the rotor picks up speed. You will need:

• 🔌 A button without fixation (for example, from a doorbell).
• 🔧 Wires with a cross-section of 1.5–2.5 mm².
• 📊 Multimeter for checking the windings.

Procedure:

1. Determine the winding terminals (by testing or marking).
2. Connect the working winding (R) directly to the 220V network.
3. Starting winding connect the winding (S) through a button parallel to the working one.
4. Press the button for 1-2 seconds - the compressor should start.

220V -----[Working winding (R)]-----
|
220V -----[Button]----[Starting winding (S)]---

⚠️ Attention: If the compressor stops after releasing the button, it means the starting torque is insufficient. Restarting is possible only after the engine has cooled down (10–15 minutes). Frequent attempts will trigger the thermal protection (if any).

Determine the type of compressor (asynchronous/inverter)|

Check the windings for open and short circuits|

Prepare a button with normally open contacts|

Make sure that there is no excess refrigerant pressure in the system|

Have a fire extinguisher on hand (in case of a short circuit)-->

2. Connection via a capacitor (permanent start)

A more reliable way is to use starting capacitor (not to be confused with the working one!). It creates a phase shift between the windings, simulating the operation of a relay. A capacitor with a capacitance 100–200 µF) is suitable. data-i="141">400V voltage 400V (for example, K78-17 or CBB60).

Connection diagram:

• 🔹 Working winding (R) is connected directly to the network.
• 🔹 Starting winding (S) is connected through a capacitor to the working one.
• 🔹 The common terminal (C) - to the second wire of the 220V network.

220V -----[Working winding (R)]-----┐
│
220V --------------------------┴--[General (C)]
│
[Capacitor]----[Starting winding (S)]---

The advantage of this method is that the compressor starts on its own, without manual intervention. However, the capacitor must be exclusively starting (not working!), otherwise the engine will overheat. For long-term operation (more than 15 minutes), an additional current relay or thermal protection is required.

Determination of compressor winding terminals

If there is no marking on the compressor or it is erased, the winding terminals are determined by testing them with a multimeter. Algorithm:

1. Ring all three outputs among themselves. The resistance between R and S must be equal to the sum of the resistances R–C and S–C (where C is the general conclusion).
2. The resistance of the working winding (R–C) is usually less than the starting winding (S–C).
3. If the resistance between any terminals tends to zero, the winding is closed, connection is prohibited!

Example for a compressor Danfoss TLX15:

• 🔹 R–C: 12 Ohm
• 🔹 S–C: 25 Ohm
• 🔹 R–S: 37 Ohm (12 + 25)

In some models (for example, Embraco EG80HLR) the common output may not be obvious. In this case, a test with a light bulb will help: connect it in series to each. pair of terminals. The pair in which the lamp burns brighter is the working winding (R–C).

What to do if the resistance of the windings is not normal?

If the resistance of any winding is below 5 Ohms or tends to infinity, this indicates:

- Interturn short circuit (resistance is too low) - rewinding is required or replacing the compressor.

- Winding break (resistance is infinite) - check the contacts and soldering of the leads. Sometimes heating with a soldering iron helps (oxidation of the contacts).

- Short circuit to the housing - ring each one. output to the compressor housing. If the resistance is not infinite, the motor is faulty and dangerous to connect.

Typical errors and their consequences

Even experienced craftsmen make mistakes when connecting the compressor directly. Here are the most common ones:

• 🔥 Using a working capacitor instead of a starting capacitor. Leads to overheating of the windings and failure within 5–10 minutes of operation.
• 💥 Supply 380V instead of 220V. Compressors of household refrigerators are designed for 220V! 380V instead of 220V
• ⚡ Lack of grounding. The compressor housing may be energized due to insulation breakdown.
• 🔌 Connection without checking the pressure in the system. If refrigerant remains under pressure in the compressor, starting under load can destroy the piston group.

One of the most dangerous mistakes is Using a capacitor that is too large. For example, if instead of 100 uF you put 400 uF, the current in the starting winding will exceed the rated one by 3-4 times. This leads to:

• 🔹 Mechanical destruction of the bearings (the rotor hits the stator).
• 🔹 Blown fuse (if any).
• 🔹 Fire hazard (overheating of windings up to 150°C+).

⚠️ Attention: If after connection the compressor hums but does not start, immediately turn off the power! This is a sign that the rotor is blocked (for example, due to lack of oil or mechanical failure). Continued supply of voltage will lead to combustion. windings.

Safety measures when working with a compressor

Connecting a compressor without a relay means working with high voltage and moving parts. Follow the rules:

• 🛠️ Turn off the power before any manipulations with it. wires.
• 🧤 Use an insulated tool and dielectric gloves.
• 🔥 Do not leave the compressor unattended during a test run.
• 💨 Work in a ventilated area — when the windings overheat, toxic gases are released.

Pay special attention grounding. The compressor housing must be reliably grounded, even if you use an RCD. parts. To check the grounding, use a tester: the resistance between the housing and the “ground” should be less than 1 Ohm.

If you use a compressor to pump air (for example, in an airbrush or for inflating wheels), be sure to install pressure reducer i pressure gauge. The pressure at the outlet of the refrigerator compressor can reach 20–30 atm, which is dangerous for most pneumatic tools.

Alternative ways to start the compressor

If standard circuits do not work, consider alternative methods:

1. Using a universal starting relay

Electrical stores sell universal relays (for example, RTK-X or DANFOSS 108N0010), which are suitable for most household compressors. They automatically connect the starting winding and turn it off after gaining speed. The cost is from 500 rubles, but it is more reliable than home-made circuits.

2. Connection via a frequency converter

For three-phase compressors (rarely found in household ones). refrigerators) you can use a frequency converter, for example VEICHI AC30. It allows you to start the engine smoothly and regulate the speed. The downside is the high cost (from 5000 rubles).

3. Starting from a 12V battery through an inverter

If you need to test the compressor in the field, you can use a car battery and inverter 12V→220V. However, keep in mind that the starting current of the compressor can reach 20–30A, so the inverter must have a power of at least 500W.

For homemade projects (for example, creating a vacuum pump) sometimes they use compressors from old refrigerators ZIL or Minsk. They are less sensitive to the connection diagram, but their efficiency is lower than that of modern models.

FAQ: Frequently asked questions about connecting a compressor

Is it possible to constantly operate a compressor without a relay?

No. Even if it starts and works, the lack of protection against overload and overheating reduces the life of the motor by 3-5 times. For permanent operation, install a new relay or use a circuit with a capacitor and a thermal one. protection.

Why does the compressor hum but does not start?

There are several reasons:

• 🔹 Insufficient starting torque (weak starting winding or low capacitor capacity).
• 🔹 Mechanical blocking rotor (piston jammed, not enough oil).
• 🔹 Low voltage in the network (less than 200V).

Check the resistance of the windings and free movement of the rotor (turn the shaft manually with the power off).

What capacitor is needed for the compressor refrigerator?

For most household compressors (power 100–300W), a starting capacitor with a capacity 100–200 uF with operating voltage 400Vis suitable. Brands: K78-17, CBB60, CD60Do not use electrolytic capacitors - they are not designed. to alternating current!

What happens if you mix up the working and starting windings?

If you switch places R and S, the compressor will either not start or will work with overheating. The starting winding is not designed for long-term load, and its constant connection will lead to failure. At best, the thermal protection will work (if there is one).

Is it possible to connect the compressor from the refrigerator to the network? 380V?

No! Household compressors are designed for 220V. Connecting to 380V will lead to an instant breakdown of the insulation and a short circuit. If you need a three-phase start, use a frequency converter or autotransformer to reduce the voltage.