Heat pump, air conditioning, refrigeration - soldering of heat exchangers, pipes, etc.

Difference between welding and soldering

From a layperson's perspective, welding and soldering may seem similar, at least in effect - they permanently join two elements. However, from a physics standpoint, there are significant differences - in welding, the original material is partially melted, to which another element is joined. This leads to a permanent connection, with the original material itself acting as the binding agent. In the case of soldering - the solder is the binding agent, and only it is melted, while the structure of the original material remains unchanged. Therefore, in air conditioning units, heat pumps, and heat exchangers for refrigerants - there is no question of welding, only soldering.

✅ Welding and soldering are not the same; they are different physical processes, although from a layperson's perspective they lead to the same outcomes.

Hard soldering and soft soldering - and what is brazing?

Of course, there are different types of soldering, brazing etc - we most commonly encounter hard soldering and soft soldering. The difference lies in the melting temperature of the solder, as naturally, solder melting is achieved by applying high heat.

✅ Hard soldering is what interests us in the context of our article - because it is usually this type of soldering that is used in air conditioning systems, refrigeration units and heat pumps. It is a process that requires a temperature higher than 450°C (840°F). On the other hand, soft soldering - is a process that occurs at temperatures lower than the aforementioned 450 degrees Celsius. It is less interesting to us, as it is less commonly used in refrigeration.

Additionally, we can also encounter the concept of high-temperature soldering - some people confuse it with hard soldering. However, it is not quite the same, as it is a process of applying solder at even higher temperatures - above 1000°C.

☑️ Hard soldering and high-temperature soldering are not the same - hard soldering occurs at temperatures > 450°C, while high-temperature soldering occurs at much higher, > 1000°C.

Sometimes we meet the term brazing... is it the same?

Capillarity - Capillary attraction - the basic property of liquid solder that determines its usefulness

Capillarity or Capillary attraction is a word characteristic of the soldering process.
✅ Capillary attraction is simply the ability of liquid solder to penetrate into the soldering gap. This occurs even against gravity. By the soldering gap, we mean the gap between elements at the soldering temperature. The smaller this gap, the easier it will be to fill the gaps with solder. (To every type of soldering there may be different types of recommandations).

☑️ In the context of the soldering gap - specifically its size and the accompanying capillary attraction - it is very important to ensure that the soldering gap, or actually the space between the different soldered elements, is suitably small. Then, capillarity will do its job and help us effectively bind the elements together. It is important to remember this during the planning stages, to ensure that individual elements such as pipes are relatively compatible in size.

What solder to use for connecting copper to aluminum, or aluminum to aluminum?

For connections between copper and aluminum, or aluminum components with each other, a zinc-aluminum or aluminum-zinc solder should be used - obviously with a flux.

Basic equipment for soldering air conditioning connections

For sporadic use, unless we are professional installers who buy equipment intended for solid exploitation, simple and compact electric soldering irons are generally used. Installers also use them - who simply buy slightly more expensive, more durable equipment. This is a compact and convenient solution, and also relatively safe - and that's what we would recommend.

✔️ Glossary of Terms Used in the Article

AC - commonly used as Air Conditioning or Air Conditioner

Brazing - solder process with temperatures over 450°C, check: hard soldering

Capillarity of solder / Capillary attraction - the ability of solder to spontaneously penetrate into the soldering gap, one might say to "glue itself" into it in an even and trouble-free manner. If a given solder has good capillarity, it will be easy to apply and will fill the soldering gap evenly, even against gravity.