Connecting the refrigerator compressor directly without a relay: instructions and warnings

The compressor is the heart of the refrigerator, and its malfunction often causes the breakdown of all equipment. In some cases (for example, during diagnostics or temporary operation), it becomes necessary to connect the unit directly, bypassing starting relay. However, this method is fraught with risks: from overheating of the windings to failure of the motor. In this article, we will look at how to properly make a direct connection, what tools will be needed, and why this solution should be temporary.

It is important to understand: refrigerator compressors (for example, models Danfoss, Embraco or Secop) are designed to work with a starting relay that protects the windings from current surges. Connecting without it requires strict adherence to the diagram and control of the case temperature. If your goal is to check the performance of the compressor before replacing, an alternative may be to use a universal start relay RBM-1 or DFSK-09, which are suitable for most household refrigerators.

Before you begin, answer yourself the question: why do you need is this necessary? If the goal is to save on repairs, keep in mind that the cost of a new relay (from 300 to 1,500 rubles) is not comparable with the price of a compressor (from 5,000 rubles) or the risk of fire. However, for experienced craftsmen or in emergency situations (for example, in the absence of a spare part), direct starting may be justified.

Design of a refrigerator compressor and the role of a relay

A refrigerator compressor is asynchronous electric motor with starting and operating windings. Its design includes:

• 🔧 Case (sealed, filled with oil and refrigerant).
• 🔌 Three outputs: general (Common, C), starting (Start, S), working (Run, R).
• 🔄 Starting relay, which temporarily connects the starting winding to create an initial torque.

The relay performs two key functions:

1. Closes the starting winding circuit for 1–3 seconds until the rotor picks up speed.
2. Protects the compressor from overheating by opening the circuit when the current is exceeded (for example, when the shaft is jammed).

Without a relay, the starting winding remains energized constantly, which leads to its overheating and interturn short circuit.

Modern refrigerators (Samsung No Frost, Atlant, Indesit) use two types of relays:

• 🔹 Thermal (with a bimetallic plate, for example, 3TS-02).
• 🔹 Electronic (with a posistor, for example, PTC or PTR).

Electronic relays are more reliable, but they can also fail due to voltage surges.

What is a posistor in a relay?

A posistor is a thermistor with a positive temperature coefficient (PTC). When heated, its resistance increases sharply, limiting the current in the starting winding. In the relay, it replaces the mechanical bimetallic plate, providing a smoother start of the compressor.

Dangers of direct connection of the compressor

Connection. a compressor without a relay increases the risk of an interturn short circuit in 70% of cases when operating for more than 10 minutesMain threats:

Additional problem - lack of control. pressureIn normal mode, the relay turns off the compressor when the set pressure in the circuit is reached, without it the motor will work continuously, which will lead to:

• 🔥 Overload of the condenser and evaporator.
• ❄️ Freezing of tubes and deterioration of heat transfer.
• 💡 Increase in energy consumption by 1.5–2 times.

⚠️ Attention: If your refrigerator equipped with an inverter compressor (LG Linear, Samsung Digital Inverter), direct connection without an electronic control unit is impossible. Such models require specialized equipment for diagnostics.

Required tools and materials

For safe connection of the compressor without a relay. prepare:

• 🔧 Multimeter (to check the resistance of the windings).
• 🔌 Wires with a cross section of 1.5–2.5 mm² with female terminals.
• 🔨 Insulating tape or heat-shrinkable tube (for insulating connections).
• 🔋 Capacitor (if required for start-up, with a capacity of 20–40 uF).
• 🛠️ Pliers and screwdriver (for dismantling relay).

To diagnose winding resistance, use a multimeter in ohmmeter mode. Normal values for most compressors:

• C–S (starting winding): 15–30 Ohm.
• C–R (working winding): 5–15 Ohm.
• S–R (sum of windings): 20–45 Ohm.

If the resistance between any terminals tends to zero, there is a short circuit in the winding. If infinity is an open circuit.

⚠️ Attention: Do not use damaged wires to connect. insulation or twisting without soldering. In conditions of high currents (5–10 A), this can lead to fire.

Compressor connection diagram without relay

Exists two options for direct connection:

Option 1: Short-term start (for diagnostics)

Used to check the operation of the compressor. The connection is made for 5-10 seconds:

1. Connect the leads C (common) and R (working) with the phase and neutral of the 220V network.
2. Shortly (for 1–2 seconds) connect the terminal S (starting) with the terminal C.
3. If the compressor started and began to build up pressure - it is working.

Option 2: Permanent connection (highly not recommended)

For long-term operation, you need to simulate the relay function using a capacitor. Connection diagram:

220V ~
│
├───[C] (general)
│
├───[R] (working)
│
└───[Capacitor]───[S] (starting)

The capacitance of the capacitor is selected experimentally (usually 20–40 μF). Please note: this method does not provide protection against overheating!

For compressors with three leads (for example, Embraco EG80HLC) use the following pinout:

Step-by-step instructions for connection

Follow the algorithm to minimize risks:

1. Disconnect the refrigerator from network and discharge the capacitor (if it is in the circuit).
2. Remove the starting relay, remembering the location of the terminals. It is usually secured with latches or screws.
3. Ring the windings with a multimeter to make sure there are no breaks or short circuits.
4. Connect the wires according to the selected diagram (see previous section). Use terminals for reliable contact.
5. Insulate the connections with heat shrink tubing or electrical tape.
6. Turn on the power and observe the compressor. If there are signs of overheating (hot case, burning smell), immediately turn off the power.

If the compressor starts, check:

• 🔊 Noise level (should be uniform, without knocking).
• 🌡️ Case temperature (should not exceed 60–70°C).
• ⚡ Mains voltage (must be stable, 220V ±10%).

⚠️ Attention: Do not leave the compressor turned on without a relay for more than 15 minutes. Even if it works stably, the risk of winding overheating remains high. For long-term operation, be sure to install a new relay.

Common mistakes and how to avoid them

Even experienced craftsmen make mistakes when connecting directly. Let's consider typical cases:

• ❌ The leads are mixed up S and R → the compressor does not start or works in the opposite direction.

  Solution: Check the resistance of the windings with a multimeter. The starting one (C–S) always has a higher resistance than the working one (C–R).

• ❌ A capacitor of the wrong capacity is used → the compressor hums, but does not start.

  Solution: For most household compressors, a capacitor of 25–35 uF is suitable. Start with 25 uF and gradually increase the capacitance.

• ❌ Bad contact in connections → sparking, heating of wires.

  Solution: Use crimp terminals and check the reliability of fastening before turning on.

• ❌ Connection without checking the pressure in the system → the compressor operates under increased load.

  Solution: If there is no refrigerant in the system, the compressor will run “idle”, which will lead to overheating. Before starting, make sure the circuit is tight.

Another common problem - unstable voltage in the networksurges are observed, use a voltage stabilizer. The compressor is sensitive to deviations from 220V: if it drops to 190V, it may not start, and if it increases to 240V, it may overheat.

Alternative ways to start the compressor

If a direct connection seems too risky, consider alternatives:

• 🔧 Universal start relay (for example, RBM-1 or DFSK-09).

  Suitable for most compressors with a power of up to 1 kW. Cost - from 500 rubles. Advantage: reliable protection against overheating.

• 🔌 Relay with manual control (push-button).

  Allows you to manually turn on the starting winding. Suitable for temporary operation, but requires control.

• 🛠️ Replacing the standard relay with a standard one. similar.

  Find the relay by the markings on the body (for example, 3TS-02 for Atlant or RL3-221 for SamsungPrice - from 300 rubles.

• 🔋 Using a starting capacitor with a thermal relay.

  A safer option than a direct connection. The capacitor provides a phase shift, and the thermal relay protects against overheating.

For refrigerators with electronic control (for example, LG GR-B207 or Bosch KGE39AW20) may be required replacement of the control board. In this case, direct connection of the compressor will not help - comprehensive diagnostics are needed.

⚠️ Attention: If your refrigerator is still under warranty, any interventions in the electrical circuit will invalidate it.

FAQ: Frequently asked questions about connecting a compressor

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

No, household refrigerator compressors are designed for a single-phase 220V network. Connection to a three-phase network. 380V network will lead to instantaneous failure of the windings. If you need a compressor for 380V, use industrial models (for example, Bitzer or Copeland).

How to determine which terminal of the compressor is the common terminal (C) and which is the starting terminal (S)?

Using a multimeter, measure the resistance between all pairs of terminals:

• Maximum resistance - between S and R (sum of windings).
• Average resistance - between C and S (starting winding).
• Minimum resistance is between C and R (working winding).

Common terminal (C) - the one that participates in both measurements (average and minimum).

What will happen if the compressor operates without a relay for more than an hour?

When operating for a long time without a relay:

1. After 20–30 minutes, the starting winding will heat up to 100–120°C, which will lead to melting of the insulation.
2. After 40–60 minutes, an interturn short circuit or winding breakage is possible.
3. After 1–2 hours, the compressor may jam due to overheating of the oil and deformation of the bearings.

The risk of fire increases if there are flammable materials nearby (for example, plastic parts of a refrigerator).

Is it possible to use a compressor from a refrigerator to inflate tires or a spray gun?

Technically it is possible, but it is ineffective:

• 🔹 Pressure on refrigerator compressor outlet - 5-10 bar (enough for passenger car tires, but not enough for trucks).
• 🔹 The performance is low (about 5-7 l/min), so inflation will take a long time.
• 🔹 There is no receiver, so the pressure will be pulsating.

For these purposes, it is better to use a specialized compressor with a receiver.

How to check if the compressor relay is working?

Perform the following tests:

1. Test the relay contacts with a multimeter in ohmmeter mode. Between the input and output, the resistance should be close to. zero.
2. Apply 220V voltage to the relay input and check whether the contacts close (there should be a click).
3. If the relay is thermal, heat its body with a hairdryer - when the bimetallic plate is triggered, the contacts should open.

A faulty relay should be repaired Replacing it is impractical.