Connecting the compressor from the refrigerator to a 220V network: diagrams, tools and safety rules

The compressor from the refrigerator is the heart of the cooling system, and even after decommissioning the equipment, it can be used for a variety of tasks: from inflating tires to creating homemade blower equipment. However connecting the compressor directly to a 220V network requires electrical knowledge and compliance with safety measures. Unlike household pumps, the refrigerator compressor does not have a built-in plug - its power is organized through a relay and a starting device, which often fail or are lost during dismantling.

In this article you will find step-by-step instructions with photographs of the key stages, connection diagrams for different types of compressors (Danfoss, Secop, Embraco etc.), as well as analysis of typical errors that lead to winding burnout or electric shock. We will not delve into the theory of operation of three-phase motors - we will focus on practicewhich will help start the compressor without extra costs.

⚠️ Warning: Working with electricity and high pressure is life-threatening. If you are unsure of your skills, contact an electrician. The article is for informational purposes only and does not replace professional advice.

1. Preparation: tools and materials

Before you start connecting, make sure you have everything you need. Most parts can be found in electrical stores or ordered online (for example, at AliExpress or Ozon). Here is the minimum set:

• 🔧 Screwdrivers (cross and flat) - for dismantling the relay and terminals.
• 🔌 Multimeter - to check the resistance of the windings and the integrity of the circuit.
• 🔗 Wires with a cross-section of 1.5–2.5 mm² - for connection compressor with a network.
• 🔄 Start relay (if the original is lost) - select according to the compressor model.
• 🔌 Plug with grounding - for safe connection to socket.
• 🛠️ Heat shrink tubing or electrical tape —to insulate connections.

If you plan to use the compressor to pump air (for example, for painting or inflating wheels), additionally you will need:

• 💨 Receiver (cylinder for compressed air) - can be made from a fire extinguisher or gas cylinder.
• 📉 Manometer - to control the pressure.
• 🔧 Check valve - so that air does not return to the compressor after shutdown.

Tip: If you do not know the compressor model, look at its case - usually there is data in the format R134a (freon type), 220V 50Hz (voltage), and serial number (for example, Danfoss NL6H18T). Using these data, you can select a compatible relay.

2. Removing the compressor from the refrigerator

The first step is to carefully remove the compressor without damaging the tubes and electrical contacts. Here's how to do it:

1. Unplug the refrigerator and let it stand for 10-15 minutes - this is necessary to relieve pressure in the system.
2. Turn the refrigerator over or provide access to the back panel. The compressor is usually located at the bottom and is mounted on spring shock absorbers.
3. Disconnect start relay (the black box with wires attached to the compressor). Usually it is mounted on latches or one bolt.
4. Cut pipesconnecting the compressor to the condenser and evaporator, using a pipe cutter. Do not use an angle grinder - sawdust may get inside the system!
5. Unscrew the compressor mounting bolts and carefully remove it.

⚠️ Attention: Freon or oil may remain in the system. Work in a ventilated area and avoid getting oil on your skin - it is toxic.

If the compressor is covered with a layer of dust or oil, clean it with a lint-free ragmoistened with a solvent (for example, White spirit). Do not use water - this may cause corrosion of the contacts.

What to do if the compressor does not disconnect from the tubes?

If the tubes are stuck or deformed, try heating the area connections using a hair dryer (not higher than 200°C). Do not knock on the compressor - this may damage internal parts.

3. Checking the compressor before connecting

Before connecting the compressor to the network, you need to make sure that it is working properly. To do this:

1. Test the windings with a multimeter:
   • Set the device in resistance measurement mode (Ω).
   • Measure the resistance between common contacts (usually they are marked as C — common, S — start, R — run).
   • Normal values for household compressors: 10–40 Ohm between C-R, 20–50 Ohm between C-S, and 30–70 Ohm between S-R.

Check the integrity housing: if the compressor has cracks or traces of oil, it cannot be used - this is a sign of internal damage.

Rotate the shaft manually: if it does not rotate or jams, the compressor is faulty.

If the winding resistance is equal to 0 Ohm (short circuit) or ∞ (break), the compressor has burned out and must be disposed of.

⚠️ Attention: If during testing you find a breakdown to the body (the multimeter shows the resistance between the contacts and the metal case), do not connect such a compressor — this may lead to electric shock.

4. Schemes for connecting the compressor to a 220V network

There are refrigerator compressors three-phase (in industrial models) and single-phase (in household ones). We will consider connecting a single-phase compressor, since it is more common. There are two main methods:

Method 1: Through starting relay (recommended)

This is the safest method, since the relay automatically turns off the starting winding after the engine starts. Connection diagram:

~220V
│
├───┬───[ Starting relay ]───┬───[ Compressor ]
│  │                       │
L───N                       C
│                          / \
PE                         S   R

Step-by-step instructions:

If the original relay is lost, buy a universal one (for example, Danfoss 103N0012 or Embraco ER35). Connect the wires according to the markings on the relay body.

Method 2: Direct connection (temporary solution)

This method is used for short-term check compressor. Not recommended for continuous operation! Scheme:

~220V
│
├───┬───[ Button ]───┬───[ Compressor ]
│  │                 │
L───N                 C
│                    / \
PE                   S   R

Algorithm:

1. Connect the phase (L) to the contact C.
2. Connect the zero (N) to the contact R.
3. Short-term (on 1-2 seconds) connect S to L via a button - this simulates a starting relay.

⚠️ Attention: When connected directly, the compressor will overheat, since the starting winding (S) will remain on. Use this method only for diagnostics!

5. Starting the compressor and checking its performance

After connecting, you need to check how the compressor behaves under load. Follow this algorithm:

1. Connect the compressor to the network via a relay or timing circuit.
2. Run it for 10-15 seconds. A working compressor should:
   • 🔊 Make a uniform hum without squeaks or knocks.
   • 🌡️ Heat evenly (not locally at one point).
   • 💨 Pump air (if connected to the receiver).

Measure the current consumption with pliers or a multimeter. Standard for household compressors: 1.5–3 A. If the current is higher, an overload is possible.

If the compressor:

• 🔥 It gets very hot —check the oil (maybe there is not enough) or ventilation.
• 🔇 Does not start —check the relay, capacitor or windings.
• 💥 The machine knocks out —possible breakdown to the case or a short circuit.

⚠️ Attention: If the compressor worked in a refrigerator with freon R12 or R22, before using it to pump air be sure to change the oil to synthetic (for example, POE). Old oil is incompatible with oxygen and can cause corrosion.

6. Typical mistakes and how to avoid them

Even experienced craftsmen sometimes make mistakes when connecting compressors. Here are the most common:

Another common problem is the compressor starts but immediately turns off. Reasons:

• 🔌 Thermal protection is triggered —let the compressor cool for 10–15 minutes.
• 🔋 Low voltage in the network —check with a multimeter (should be 210–230V).
• 🛢️ Lack of oil —add through the filling pipe.

If the compressor hums, but does not pump airpossible:

• 🔧 Piston jamming —try turning the shaft manually.
• 🔄 The check valve does not hold pressure —replace the valve.
• 💨 Leakage through the connections - check the tightness with a soap solution.

7. Modernization: how to make a full-fledged compressor

To turn a compressor from a refrigerator into a full-fledged air compressor, the system will need to be modified. Here's what you can add:

• 🛢️ Receiver — a cylinder for storing compressed air. An OU-5 fire extinguisher or a gas cylinder of 10–20 liters is suitable.
• 📉 Pressure regulator — for monitoring the output pressure (optimally: 6–8 bar).
• 💦 Moisture separator —to remove condensation from the air.
• 🔌 Automatic —pressure switch (for example, RDM-5) for automatic shutdown when maximum pressure is reached.

Example of a homemade compressor circuit:

[ Compressor ] → [ Check valve ] → [ Receiver ] → [ Moisture separator ] → [ Pressure regulator ] → [ Consumer ]

⚠️ Attention: When working with the receiver (cylinder), follow the safety rules:

• Use a cylinder designed for a pressure of at least 10 bar.
• Install safety valve on 8–10 bar.
• Do not leave the compressor unattended during pumping.

If you plan to use the compressor for painting work, add oil filter to the circuit - this will protect the equipment from oil vapors.

8. Compressor maintenance and care

To ensure your compressor lasts a long time, follow these recommendations:

• 🛢️ Check the oil level every 50–100 operating hours. Use oil for dressing POE (For R134a) or mineral (for R22).
• 🧹 Clean the compressor from dust with compressed air or a soft brush.
• 🌡️ Control the temperature —if the case heats up above 70°C, take a break.
• 🔌 Check electrical connections for oxidation or loose contacts.

If the compressor has not been used for a long time:

1. Rotate the shaft manually 5-10 times to distribute the oil.
2. Start it without load for 5-10 minutes.
3. Check the pressure and current consumption.

⚠️ Attention: If the compressor was stored in a damp room, before starting, dry it construction personnel hairdryer (not higher than 60°C) for 1-2 hours. Moisture in the windings can cause a short circuit.

FAQ: Frequently asked questions about connecting a compressor

Is it possible to connect a compressor from a refrigerator without a relay?

Technically yes, but only for short-term check. Without a relay, the starting winding will remain on, which will lead to overheating and failure of the compressor in 10–30 minutes. For continuous operation of the relay, it is necessary.

How to determine where the compressor has “zero”, “phase” and "starting winding"?

On most compressors, the contacts are marked:

• C (Common) - common contact (phase).
• S (Start) - starting winding.
• R (Run) - working winding (zero).

If there is no marking, use a multimeter: the lowest resistance will be between C-R, the average - between C-S, the highest - between S-R.

Why does the compressor hum, but does not start?

There are several reasons:

• Piston jamming (try turning the shaft by hand).
• Faulty starting relay or capacitor.
• Low voltage in the network (less than 200V).
• Break in the starting winding (check with a multimeter).

Start by checking the relay - this is the most common reason.

What kind of oil should be poured into the compressor from the refrigerator?

The type of oil depends on the freon on which the refrigerator operated:

• For R12 —mineral oil (for example, Frigcold MO 32).
• For R134a —synthetic POE (for example, Emkarate RL32H).
• For R600a (isobutane) - mineral or semi-synthetic.

Do not mix different types of oils! If you do not know what kind of freon was in the refrigerator, rinse the compressor with a solvent and fill POE.

Is it possible to use a compressor from a refrigerator for an aquarium?

Technically it is possible, but there are nuances:

• The compressor must be silent (models Danfoss SC or Secop suitable better than the old Soviet ones).
• It is necessary to install pressure regulatorso as not to pump air.
• The tubes must be sealed - check for leaks with a soap solution.

For an aquarium it is better to use a specialized aquarium compressor - it is quieter and safer.