How to choose the right capillary tube for refrigerator: technical nuances and calculations

Why do you need a capillary tube and what will happen if you make a mistake in the choice

The capillary tube is a refrigeration circuit assembly that regulates the supply of refrigerant to the evaporator. Its correct selection determines the cooling efficiency, energy consumption and durability of the compressor. If the diameter or length of the tube does not correspond to the system parameters, the refrigerator will either not freeze, or the compressor will wear out, which will lead to breakdown in 1–2 years.

Typical consequences of the wrong choice: overheating of the compressor due to insufficient refrigerant flow (too narrow/long tube), the formation of ice plugs in the evaporator (due to excess flow), or complete stoppage of circulation due to blockage. For example, in models Atlant and Indesit with refrigerant R600a an error in diameter of 0.1 mm can cause a temperature difference of up to 5–7°C.

B In this article we will look at how to calculate the parameters of a capillary tube for a specific refrigerator model, what materials to use, and how to avoid typical mistakes when replacing. The information is relevant for household refrigerators manufactured in 2010–2026 with compressors Danfoss, Embraco, Secop and other popular brands.

Basic parameters of a capillary tube: what to consider when choosing

When selecting a capillary tube, four parameters are critically important:

• 🔹 Internal diameter (measured in mm or inches; standard values: 0.6–1.2 mm for household refrigerators).
• 📏 Length (depends on the compressor power and the type of refrigerant; usually 1.5–3.5 meters).
• 🛢️ Refrigerant type (R134a, R600a, R290 —require different diameters).
• 🔧 Material (grade copper M1 or M2; aluminum is not used due to corrosion).

For example, for refrigerators Samsung with a refrigerant R600a and a compressor Embraco EG80HLE a standard capillary tube has a diameter 0.76 mm and a length 2.4 meters. If you replace it with a 0.6 mm tube, the compressor will overheat due to increased resistance, and if it is replaced with a 0.9 mm tube, the evaporator will not be completely filled with refrigerant, which will lead to insufficient cooling.

Important: diameter and length are interrelated. Increasing the length of the tube by 30% allows you to use a larger diameter (for example, instead of 0.7 mm, take 0.8 mm when extending from 2 to 2.6 m). This rule only works within ±15% of the factory parameters.

⚠️ Attention: In refrigerators with a No Frost system, the capillary tube is often integrated into the heat exchanger. Replacing only the tube without taking into account its resistance will lead to unbalancing of the system.

How to determine the diameter of the capillary tube for your model

The exact diameter is indicated in the technical documentation compressor or on the refrigerator nameplate (look for type inscriptions Capillary Tube or Ø0.76). If the documentation is lost, the diameter can be:

1. Measure with a caliper on an old tube (measure internal diameter, not external!).
2. Calculate according to the formula, if the compressor power and the type of refrigerant are known (see table below).
3. Select by analogy with popular models (data for Atlant, LG, Beko are given in the next section).

Formula for approximate calculation:

D = (Q / (L × ΔP))^0.5, where:

• D —diameter in mm;
• Q —thermal power of the evaporator (W);
• L —tube length (m);
• ΔP —pressure drop (usually 1.5–2.5 bar for household refrigerators).

To simplify, use the correspondence table:

⚠️ Attention: Refrigerant R290 (propane) requires a tube with a wall thickness of at least 0.8 mm due to the increased pressure. Using a standard 0.6 mm tube can lead to rupture!

Measured the internal diameter of the old tube

Checked the type of refrigerant (on the nameplate or in the documentation)

Checked the compatibility of the material (only copper M1/M2)

I combined the parameters with a table for my compressor power

I bought a tube with a margin of length (+20 cm for installation)-->

The length of the capillary tube: how to calculate and what happens if there is an error

The length of the tube affects on resistance to refrigerant flow. A tube that is too short will lead to excess flow, which will cause:

• 🧊 Freezing of the evaporator and the formation of ice plugs.
• 🔥 Overload of the compressor due to frequent inclusions.
• 🌡️ Unstable temperature in the chambers (fluctuations ±3–5°C).

A tube that is too long, on the contrary, will create excess resistance, which will manifest itself:

• 🐢 Slow cooling (the compressor operates without stops).
• ❄️ Warming in the freezer by 2-4°C.
• 💥 Risk of water hammer when starting the compressor.

To calculate the length, use a rule of thumb:

L = (P × 10) / D, where:

• L — length in meters;
• P — compressor power in kW (for example, 0.15 kW for Atlant MXM-1708);
• D — internal diameter in mm.

Example: For a 180 W compressor (0.18 kW) and a 0.76 mm tube:

L = (0.18 × 10) / 0.76 ≈ 2.37 m.

Round the result to standard values (2.4 m in this case).

What to do if there is no data on the compressor power?

If the compressor power is unknown, it can be approximately determined by the volume of the refrigerator:

- Up to 150 l → 80–120 W

- 150–250 l → 120–180 W

- 250–350 l → 180–250 W

For accuracy, check the energy consumption table on the nameplate (for example, 1.2 kWh/day ≈ compressor 150–180 W).

Tube material and quality: copper vs alternatives

99% of household refrigerators use copper tubes brands M1 or M2 according to GOST 859–2014. Alternatives (aluminum, stainless steel) are not suitable for the following reasons:

• 🔧 Aluminum: corrodes upon contact with compressor oil, breaks when more flexible.
• ⚡ Stainless steel: too high resistance, difficult to solder.
• 🧲 Plastic: does not withstand refrigerant pressure (especially R290).

When purchasing, check:

1. Marking on the tube (should be M1 or M2).
2. Wall thickness: not less 0.6 mm for R600a and 0.8 mm for R290.
3. No dents and oxidation (especially on the cut).
4. Certificate of conformity (for domestically produced tubes - GOST, for imported ones - ASTM B280).

Critical error: using recycled copper tubes (remelted cables). Such copper contains impurities that clog the capillary and cause the compressor to fail in 3–6 months.

Step-by-step instructions for replacing the capillary tube

Replacing the tube requires complete depressurization of the system and vacuuming. It is impossible to carry out the work without special equipment (vacuum pump, pressure manifold). If you do not have experience, it is better to contact a specialist. Below are instructions for those who are ready to take the risk.

Necessary tools:

• 🔧 Gas wrench (for disconnecting the tubes).
• 🔥 Blowtorch or gas torch (power 500–800 W).
• 🧲 Vacuum pump (at least 2-stage, with a check valve).
• 📏 Pipe cutter (not a grinder! it leaves burrs).
• 🛠️ Solder POS-40 and flux for copper.

Work order:

1. Turn off the refrigerator, drain the oil from the compressor (through the service port).
2. Have a snack use a pipe cutter to remove the old tube 2–3 cm from the filter drier.
3. Place the new tube onto the filter, measure the length with a margin of 10–15 cm.
4. Solder the connection, avoiding overheating (maximum 30 seconds per place).
5. Connect the vacuum pump, evacuate the system to pressure -0.9 bar (at least 30 minutes).
6. Charge the refrigerant (the weight is indicated on the compressor nameplate).
7. Check sealing with soapy water (there should be no bubbles!).

⚠️ Attention: When soldering, do not point the flame at the compressor or plastic parts. Temperatures above 120°C destroy the insulation of the compressor windings.

Typical mistakes and how to avoid them

Even experienced craftsmen make mistakes when working with capillary tubes. Here are the most critical ones:

1. Using a tube from another refrigerator (even if the diameter is the same, the length and material may differ). For example, a tube from Samsung RL-34 is not suitable for LG GA-B409 due to different condensation pressures.
2. Soldering without flux —leads to microcracks and leaks after 1–2 years.
3. Bending the tube at an acute angle (bending radius must be at least 3× tube diameter).
4. Incorrect charging of the refrigerant (excess is as harmful as underfilling).
5. Ignoring the replacement of the filter drier (be sure to change it every time you open the system!).

To check the correct installation, turn on the refrigerator and observe:

• ✅ The compressor should turn off 10-15 minutes after starting.
• ✅ The temperature in the freezer should drop to -18°C in 2-3 hours.
• ✅ The condenser (grid at the back) should be warm, but not hot.

If the compressor runs non-stop and the freezer does not cool below -10°C, the tube is too long or narrow. If, on the contrary, the compressor turns off too often, and the evaporator freezes, the tube is short or wide.

FAQ: Frequently asked questions about capillary tubes

Is it possible to clean a clogged capillary tube instead of replacing it?

Theoretically, you can wash the tube solvent (for example R141b) or flush with nitrogen, but in practice this is a temporary solution. Metal particles and oxides remain on the walls and will clog the system again in 3-6 months. Replacement is more reliable.

Which solder is best to use for soldering?

The optimal choice is POS-40 (tin-lead solder with 40% lead). It melts at 183–235°C, which is sufficient for a reliable connection without overheating the copper. Do not use acid fluxes - only FIM or F-38N.

What if I can’t find a tube of the required diameter?

The deviation is ±0.05 mm. For example, instead of 0.76 mm you can take 0.78 mm, but then the length of the tube needs to be increased by 10–15%. If the difference is greater, look for the tube from official dealers Danfoss or Embraco - they supply components for most refrigerators.

Is it possible to shorten the capillary tube if it is too long?

You can shorten it, but no more than 20% of the original length. After trimming, be sure to check the patency (purge the tube with nitrogen). If the flow resistance has increased, the compressor will overheat.

How to check that the tube is clogged?

Signs of a clogged tube:

• The compressor runs non-stop, but does not freeze.
• The condenser is cold (refrigerant does not circulate).
• When the power is turned off, a gurgling sound is heard (liquid refrigerant does not pass through).

For accurate diagnosis, you need to check the pressure with a pressure gauge. If there is pressure, but there is no suction, the tube is clogged.