How to start a refrigerator compressor without a relay: operating diagrams and risks

Starting a refrigerator compressor without a starting relay is a necessary measure, which is resorted to when the standard starting device breaks down or for troubleshooting. This method allows you to temporarily restore the functionality of the unit, but requires strict adherence to the connection diagrams and precautions. In this article we will look at how to correctly connect a compressor directly to a 220V networkwhat tools will be needed, and why this method is not intended for constant use.

It is important to understand: the starting relay performs two critical functions - it protects the compressor windings from overheating and ensures correct starting due to a short-term connection starting winding. With a direct connection the risk of compressor failure increases significantly, especially if you make mistakes in assembling the circuit or mix up the contacts. Therefore, this method is used only to check the performance of the compressor or as a temporary solution until the relay is replaced.

If you have never worked with electrical circuits, it is better to entrust the diagnostics to a specialist. The article provides diagrams and instructions for experienced users who are ready to take responsibility for possible consequences. For beginners, we recommend starting by studying common mistakes at the end of the material.

When is it necessary to start a compressor without a relay?

The main situations in which you have to do without a starting relay:

• 🔧 Fault diagnosis: you need to check if it works whether the compressor is on its own, or the problem lies within itself (for example, an interturn short circuit or a break in the windings).
• 💥 Failure relay: if the starting device is burnt out and there is no new one at hand, a temporary connection will help preserve the products until a replacement is purchased.
• ⚡ Check after repair: after rewinding the windings or changing the oil in the compressor, a test run without load is required.
• 🔍 Finding the cause of the unstable operation: if the refrigerator turns on and immediately turns off, direct voltage supply helps to localize the problem.

However, there are cases when starting without a relay is strictly prohibited:

• 🚫 The compressor had previously overheated or had signs of a short circuit (darkening of the housing, a burning smell).
• 🚫 Absent on the compressor terminals marking of contacts (risk of mixing up windings).
• 🚫 The refrigerator is equipped with an inverter compressor (for example, LG Linear Compressor or Samsung Digital Inverter) - such models require special control boards.

Refrigerator compressor design: which contacts are responsible for what

Before connecting the compressor directly, you need to understand the purpose of its terminals. A standard refrigerator compressor has three outputs:

1. C (Common) —a common contact connected to both windings.
2. S (Start) —a starting winding, used only at the moment of startup.
3. R (Run) —a working winding, ensures continuous operation of the compressor.

In some models (for example Danfoss or Secop) the terminals may be designated differently:

• M (Main) - analog C,
• A (Auxiliary) - analog S.

The connection diagram is usually marked on the compressor body - it needs to be photographed or sketch before starting work.

If the resistance between any terminals is equal to 0 Ohm (short circuit) or ∞ (open), the compressor is faulty and requires repair or replacement. Before connecting, be sure to check the circuit with a multimeter!

Compressor connection diagrams without relay

There are two main schemes for direct connection of a refrigerator compressor:

1. Connection via a button (temporary start)

This method simulates the operation of a starting relay: the button closes the starting winding S for a few seconds, after which the compressor continues to operate only on the working winding R.

220V ~
│
├───┬───[Button]─── S (Start)
│  │
│  └────────────── R (Run)
│
└───────────────── C (Common)

Procedure:

Disconnect the refrigerator from the network and discharge the capacitors (short-circuit the terminals with an insulated screwdriver handle)|

Connect the wire from the 220V phase to the terminal C|

Connect the second wire from the phase to the terminal R via a permanent connection|

Parallel R connect the button, the second contact of which goes to S|

Turn on the power and hold the button for 1-3 seconds (until the characteristic start click)|

Release the button - the compressor should continue to work on R i C

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2. Connection via a capacitor (for long-term operation)

This circuit is used if you need to operate the refrigerator without a relay for several days. A capacitor (for example, 25–40 μF, 450V) provides a phase shift for the starting winding.

220V ~
│
├───┬───[Condenser]─── S (Start)
│  │
│  └─────────────────── R (Run)
│
└────────────────────── C (Common)

Important: the capacitor capacity is selected according to the power of the compressor. For most household refrigerators (Atlant, Indesit, Samsung), a capacitor for 30–35 μFis suitable. Exceeding the capacitance will lead to overheating of the windings!

How to check the functionality of the capacitor?

Use a multimeter in capacitance measurement mode (or a special tester). Connect the probes to the terminals of the capacitor - the readings should correspond to the markings with an error of ±5%. If the device shows 0 or ∞, the capacitor is faulty and requires replacement.

Step-by-step instructions for starting a compressor without a relay

For work you will need:

• 🔧 Screwdriver with an insulated handle.
• 📊 Multimeter (for checking resistance and voltage).
• 🔌 Wires with a cross-section of at least 1.5 mm² with terminals.
• 🔘 A non-latching button (for example, from a doorbell) or a capacitor.
• 🛠 Pliers and electrical tape.

Step 1. Disconnection and preparation

Disconnect the refrigerator from the network. Remove the start relay from the compressor (usually it is secured with clips or screws). Inspect the compressor terminals for oxidation or damage - if necessary, clean the contacts with sandpaper.

Step 2. Checking the compressor

Measure the resistance between the terminals:

• C-R: should be within limits 5–15 Ohm.
• C-S: 15–40 Ohm.
• S-R: the sum of the two previous values.

If the parameters do not match, the compressor is faulty.

Step 3. Assembling the circuit

Select one of the circuits (with a button or a capacitor) and assemble the circuit according to the figures above. All connections must be securely insulated, and exposed wires are excluded. For temporary connections, you can use terminal blocks.

Step 4. Test run

Turn on the power. When using the button, hold it for no longer than 3 seconds. The compressor should start with a characteristic hum. If you hear clicks or the machine in the control panel is triggered, immediately turn off the power and check the circuit!

Dangers and risks when starting without a relay

Even if the compressor has started successfully, long-term operation without a starting relay is fraught with serious consequences:

⚠️ Attention: Without relay protection, the compressor windings overheat 2-3 times faster. This leads to destruction of insulation, interturn short circuit and complete failure of the unit. The average service life of a compressor in this mode is from several hours to 2-3 days.

Main risks:

• 🔥 Overheating of the windings: without thermal protection of the relay, the temperature may exceed 120°Cwhich will lead to melting of the varnish on wires.
• ⚡ Insulation damage: breakdown on the compressor housing can cause current leakage and electric shock.
• 💸 Increased energy consumption: the compressor operates less efficiently, spending 20–30% more electricity.
• 🚨 Tripping of automatic machines: when overloaded, current surges are possible, leading to a shutdown of the electrical network in the house.

If you had to resort to this method, monitor the temperature of the compressor housing (it does not should heat up higher 60–70°C) and do not leave the refrigerator unattended. The optimal solution is to install a new relay as quickly as possible.

How to choose a new starting relay?

If the diagnostics showed that the compressor is working, but the problem was in the relay, it needs to be replaced. When choosing a new device, consider:

For popular brands of refrigerators, suitable relays:

• Atlant, Minsk: RTK-HKL, RTK-HKL-1 (Russian analogues).
• Indesit, Ariston: ASCO RSE-1 or Danfoss 103N0210.
• Samsung, LG (inverter models): an original relay with a control board is required.

⚠️ Attention: Cheap universal relays (for example, Chinese ones without markings) often do not provide correct protection. For compressors with a higher power 150 W use a relay with thermal protection (thermal protector).

Common mistakes and how to avoid them

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

1. Confused. terminals S i R:

   If you connect the starting winding S as a working one, the compressor will not start or will hum, but not rotate. Check the resistance with a multimeter!

2. Using a fixed button:

   The button should not be latched (instant action). If it remains pressed, the starting winding will overheat in a few minutes.

3. Incorrect capacitor capacitance:

   Capacitor on 100 µF instead 30 µF will cause overload of the starting winding. Use only calculated values!

4. No grounding:

   The compressor housing must be grounded - in the event of an insulation breakdown, this will protect you from electric shock.

5. Long-term operation without a relay:

   Even if the compressor has started, do not operate it like this for more than a day, the risk of breakdown increases every minute.

If after connecting the compressor:

• 🔊 It buzzes, but does not start — check the capacitor or button, perhaps there is not enough starting current.
• ⚡ The machine knocks out —short circuit in the windings or incorrect connection.
• 🔥 It gets very hot —immediately turn off the power and check the resistance of the windings.

FAQ: Answers to. frequently asked questions

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

No. The starting relay not only starts the compressor, but also protects it from overheating. Without a relay, the service life of the compressor is reduced by 5-10 times. Maximum - 1-2 days as a temporary measure.

What capacitor is needed for a compressor with a power of 140 W?

For compressors with a capacity of 120–160 W a capacitor with a capacity of 25–35 µF with an operating voltage of at least 400Vis suitable. For example, CL21-35-400 or similar.

What to do if the compressor starts and immediately turns off?

There are several reasons:

• Faulty starting relay (if you connect through it).
• Tripped thermal protection due to overheating.
• Low voltage in the network (less than 200V).
• Lack of refrigerant (refill required).

Check each of these conditions in order. Is it possible to start an inverter compressor without a relay? data-i="257">Where to buy a new relay for a refrigerator?

Is it possible to start an inverter compressor without a relay?

No. Inverter compressors (LG Linear Compressor, Samsung Digital Inverter) are controlled by an electronic board. A direct connection to a 220V network will damage them. In this case, diagnostics of the control board is required.

Where to buy a new relay for a refrigerator?

Original relays are sold in manufacturer service centers (Atlant, Indesit etc.), as well as in spare parts markets (for example, AliExpress, eBay - but be careful with fakes. For older models, universal relays are suitable. RTK-HKL or Danfoss 103N.