How and how to properly solder a refrigerator evaporator: solders, fluxes and equipment safety

The evaporator is a key element of the refrigeration unit, responsible for heat exchange and chamber cooling. If it is damaged (corrosion, mechanical holes, cracks), the system ceases to function effectively, and the compressor wears out. Soldering an evaporator is a task that requires not only skills, but also the right choice of materials. An error in choosing solder or flux can lead to repeated leakage of freon, oxidation of the seam, or even failure of the entire system.

In this article we will look at which solders and fluxes are suitable for repairing different types of evaporators (aluminum, copper, steel), which tools is needed, and how to avoid common mistakes. We will pay special attention to safety issues - working with refrigerant and high temperatures requires strict adherence to the rules. If you have never soldered refrigeration equipment, we recommend that you first practice on unnecessary parts or contact a specialist.

Types of evaporators and their features when soldering

Before choosing solder and flux It is necessary to determine what material the evaporator of your refrigerator is made of. The soldering technology, the melting temperature of the solder and even the type of burner depend on this.

The most common types of evaporators:

• 🔹 Copper —most common in older models (Atlant, Biryusa, Stinol). They are easily soldered, but require protection from oxidation.
• 🔹 Aluminum —used in modern refrigerators (LG, Samsung, Indesit). Difficult to solder due to the oxide film, they require special fluxes.
• 🔹 Steel (galvanized) - found in industrial and some household models. Soldering them is more difficult due to the risk of damage to the zinc coating.
• 🔹 Combined (copper + aluminum) - used in inverter systems. They require solders with high adhesion to both metals.

Aluminum evaporators are the most capricious. Their surface is instantly covered with an oxide film, which prevents solder adhesion. To work with them you will need active fluxes (for example, Castolin Aluflux or F-SW21) and high temperature (350–400°C). Copper evaporators are easier to solder, but it is important not to overheat the thin tubes - this can lead to their deformation.

Choice of solder for soldering the evaporator

Solder is an alloy that melts when heated and connects metal parts. Not all types of solders are suitable for refrigeration systems. The main selection criteria:

• 🔥 Melting temperature - must be below the melting temperature of the evaporator metal, but high enough for a reliable seam.
• 🛡️ Refrigerant compatibility - solder should not react with freon (especially important for systems on R600a or R134a).
• 🔧 Strength and tightness —the seam must withstand the pressure in the system (usually 2–10 atm).

Below is a table with recommended solders for different types evaporators:

Critical: for systems with When using refrigerant R600a (isobutane), you cannot use solders containing zinc or cadmium - they can cause a chemical reaction and damage the compressor. Also avoid lead solders in refrigerators with food compartments (for example, Liebeherr or Bosch) if you plan to use them for food storage.

Fluxes: which one. choose and how to use

Flux is a substance that removes oxides from the metal surface, improves the spreadability of solder and prevents oxidation during soldering. Without the right flux, even the highest quality solder will not provide a sealed seam.

The following types of fluxes are suitable for soldering refrigerator evaporators:

• 🧪 Active (acid) — F-34A, F-64. Suitable for copper and steel, but require careful washing after soldering (residues can corrode the metal).
• 🧴 Neutral (rosin) — FKSp, FIM. Used for copper, do not require rinsing, but are less effective against oxides.
• 🔬 Special for aluminum — Castolin Aluflux, F-SW21Contains active components to destroy the oxide film.
• 🌿 Acid-free — Interflux 2005. Suitable for food refrigerators, do not require washing.

For aluminum evaporators, flux is applied immediately before soldering —an oxide film is formed almost instantly. For copper and steel, flux can be applied in advance, but not earlier than 10–15 minutes before heating. After soldering, the remaining active flux must be removed with a solvent (for example, isopropyl. alcohol), otherwise they can cause corrosion.

⚠️ Attention: Never use soldering acid (for example, HC or TsO-12) for refrigerator icers! Its residues may react with freon and compressor oil, which will lead to system failure.

Required tools and equipment

For high-quality soldering of the evaporator, one soldering iron is not enough. You will need a specialized tool that will ensure uniform soldering. heating and control over the process. Here is the minimum set:

• 🔥 Burner or soldering station — for aluminum, a propane torch with adjustable flame is suitable (Rothenberger Super Fire), for copper - a butane gas torch (Dremel 22001).
• 🛠️ Soldering iron with a power of 100–150 W — for small work (for example ERSA 60/150 or Quick 961BW).
• 🧲 Fixation devices - clamps, vices or magnetic holders so that the parts do not move during soldering.
• 🔍 Magnifying glass or endoscope — for monitoring the quality of the seam in hard-to-reach places.
• 🧴 Solvent and brushes —for applying flux and cleaning (acetone, isopropyl alcohol).
• 🛡️ Protective means —heat-resistant gloves, goggles, respirator (when working with active fluxes).

For aluminum soldering, you may additionally need ultrasonic soldering iron (for example, Weller WUP 200), which destroys the oxide film by vibration. Also useful temperature indicator (thermocouple or infrared thermometer) to avoid overheating thin-walled tubes.

Determine the evaporator material|Select solder and flux according to the table|Check the burner for gas leaks|Clean the soldering area from dirt and oil|Prepare protective equipment (gloves, glasses)|Check for ventilation in the room-->

Step-by-step instructions for soldering the evaporator

The process of soldering the evaporator can be divided into several key stages. It is important to follow the sequence and not skip steps, especially if you are working with aluminum.

1. Surface preparation

Clean the soldering area from dirt, oil and old solder (if this is a repeated repair). For copper, use sandpaper (grain size 200–400), for aluminum - wire brush or a special scraper. Then degrease the surface acetone or isopropyl alcohol.

2. Applying flux

For copper and steel, apply flux with a brush in a thin layer. For aluminum, use active flux and immediately start heating - an oxide film forms in seconds. Do not skimp on flux: its deficiency will lead to poor solder adhesion.

3. Heating and soldering

Heat the soldering area evenly with a torch. For copper, a temperature of 250–300°C is sufficient, for aluminum – 350–400°C. As soon as the flux starts to bubble, apply solder. It should spread on its own under the action of capillary forces. Do not overheat the part - this may lead to deformation or burning of thin tubes.

4. Cooling and monitoring the seam

Allow the seam to cool naturally (do not cool with water!). Inspect it for cracks or pores. To check the tightness, use soap solution (apply to the seam and apply nitrogen to the system under a pressure of 2-3 atm - bubbles will indicate a leak).

5. Cleaning and testing

Remove flux residues with a solvent. Connect the system, evacuate it (the pressure should drop to 0.5 torr) and charge the refrigerant. After refueling, check the operation of the compressor and the temperature in the chamber.

What to do if the solder does not stick?

If the solder rolls off or does not spread, the reasons may be as follows:

1. Insufficient heating - increase the burner temperature.

2. Oxide film (especially on aluminum) - use a more active flux or mechanically clean the surface.

3. Contamination - degrease the soldering area again.

4. Unsuitable solder - check compatibility with the metal of the evaporator.

Typical mistakes and how to avoid them

Even experienced craftsmen sometimes make mistakes when soldering evaporators. Here are the most common of them and ways to prevent them:

• 🔥 Overheating of the tube — leads to its deformation or burnout. Solution: use a burner with flame control and control the temperature with a thermocouple.
• 🧴 Lack of flux —the seam turns out to be porous and unreliable. Solution: apply flux liberally, especially on aluminum.
• 🔧 Using the wrong solder —may cause corrosion or reaction with freon. Solution: always check the compatibility of the solder with the metal and refrigerant.
• 🚫 Soldering under pressure —if freon remains in the system, it may ignite. Solution: Before soldering, bleed off the refrigerant and purge the system with nitrogen.
• 🧼 Unremoved flux residues —lead to corrosion. Solution: rinse the seam with solvent after cooling.

Another common mistake is soldering without evacuation of the system. If you do not remove moisture and air before charging freon, the compressor will quickly fail due to water hammer. Evacuation should last at least 15–20 minutes at a pressure of 0.5 torr.

⚠️ Attention: If you are soldering a refrigerator evaporator with a system No Frost (for example, Samsung RB37J5240 or LG GA-B489YDQL), please note that it may have several contours. Damage to one of them will lead to defrosting only part of the chamber. Before soldering, be sure to study the diagram of a specific model!

Safety when soldering the evaporator

Working with refrigeration equipment is associated with several dangerous factors:

• 🔥 High temperatures - risk of burns and fire.
• 💨 Refrigerant —some freons (for example, R22) are toxic, and R600a (isobutane) is explosive.
• 🧪 Active fluxes —can cause chemical burns if in contact with skin.
• ⚡ Electricity —when checking the system under voltage.

Basic safety rules:

1. Work in well ventilated area or with the hood on.
2. Use heat resistant gloves and safety glasses.
3. Before soldering bleed off freon in accordance with environmental standards (do not release it into the atmosphere!).
4. Do not smoke or use open fire near refrigerator - the remaining refrigerant may ignite.
5. After charging the system, check it for leaks soap solutionand not with an open flame.

If you are working with R600a (isobutane), remember: it is heavier than air and can accumulate in the lower parts of the room. Use gas analyzer to control concentration or work outside.

FAQ: Frequently asked questions about soldering the evaporator

Is it possible to solder an aluminum evaporator with a regular soldering iron?

No, a regular soldering iron is not suitable for aluminum due to the high melting point solder (350–400°C). You need a powerful soldering iron (150–200 W) or a gas torch. You will also need a special flux for aluminum, for example Castolin Aluflux.

Which solder is better for a copper evaporator in a refrigerator Atlant?

For copper evaporators of refrigerators Atlant (models MXM-170, MX-280 i etc.) optimally use POS-61 or Sil-Fos 5%. These solders provide good weld fluidity and strength. If the refrigerator operates on R600a, avoid solders with zinc.

What to do if the seam drips after soldering?

If the seam drips, this means that:

1. Insufficient heating - repeat soldering at a higher temperature.
2. Poor surface cleaning - remove old solder, clean the metal and apply new flux.
3. Inappropriate solder - check compatibility with the metal of the evaporator.

After re-soldering, be sure to check the seam for tightness with a soap solution.

Is it necessary to vacuum the system after soldering?

Yes, vacuuming is mandatory! It removes moisture and air from the system, which prevents:

• Compressor water hammer (due to condensation).
• Oxidation of oil in the system.
• Reduced cooling efficiency.

Vacuum the system for 15–20 minutes until pressure 0.5 torr.

Is it possible to solder the refrigerator evaporator No Frost on your own?

Soldering the evaporator in systems No Frost (for example, Samsung RL38 or Indesit DF 4180) is possible, but more difficult due to:

• The presence of several circuits (risk of damage to adjacent tubes).
• Thin-walled aluminum tubes that are easy to burn.
• The need for precise refueling freon (excess or deficiency will lead to malfunction).

If you do not have experience, it is better to contact a service center.