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Can Mini Split Line Sets Be Brazed?

Can Mini Split Line Sets Be Brazed?

Brazing is one of the most often used techniques for connecting copper. But can you braze your small split line sets, you might be wondering. Here is what we discovered after doing study on the subject.

Brazing is a legitimate option. Just make sure to perform the purge with nitro.

Learn how to braze a small split line and why nitro purging is necessary when doing so by reading on. We’ll also go through the advantages and disadvantages of brazing the lines, the best tools and materials to use, and how to check for leaks in the brazed connections.

Why Is Nitrogen Needed To Be Purged Before Brazing?

Can Mini Split Line Sets Be Brazed?

Simply brazing copper while purging nitrogen through it is nitrogen-based brazing, also referred to as brazing with nitrogen. This maintains order. Air conditioning systems must be incredibly dry and clean before adding refrigerant. You will get the effectiveness, comfort, and equipment lifetime you expect by making sure of this.

Over time, the system will be damaged if pollutants are allowed to enter the refrigerant. Even though you might not immediately notice these flaws, the best method to prevent them is to nitrogen braze your small split lines.

Brazing Mini Split Lines: A Guide

Can Mini Split Line Sets Be Brazed?

Here is a short guide that will show you how to properly braze your small split tube lines:

1. The Outside Unit Should Be Connected To The Large Suction Line

First, flare the large suction line tubing to link it to the outdoor device. The small line-set tube’s end shouldn’t be linked at this point; it should be left disconnected.

The small line set tube is known as a “low-pressure liquid tube” because, in micro split systems, the active metering device is frequently housed in the outdoor unit. As a result, when the system is in cooling mode, the metering device will lower the refrigerant’s pressure before it enters the small line set tube.

2. On The Indoor Unit, Disconnect The Flare Connections

The flare connections on the indoor unit copper stubs must be taken out, and the copper tubes must be reamed downward so that any small pieces of copper will fall out of the tube.

It is necessary to arrange the large and small line set tubes before inserting them into the indoor unit’s swaged copper stubs.

3. Connect The Nitrogen Tank To A Flow Regulator

The following step involves connecting a flow regulator to a nitrogen tank and setting the flow rate to 2-3 ft3/hr. The nitrogen hose will then be attached to the outer unit vapour service port.

The nitrogen will enter the large vapour line, proceed via the evaporator coil, the small line set tube next to the small low-pressure liquid service valve, and then exit the small line set tube.

Instead of pressurizing the tube during the brazing process, the nitrogen will drive any oxygen out of the tube. Additionally, before vacuuming, this will help to dehydrate the lines.

4. The Swage Joint Is Brazed

The swage joints should be brazed using a small brazing tip and 15% silver brazing rod. When the indoor head unit is raised to reach the underside of the unit, the swage joints can be found behind the unit, inside the building, or outside the building if the stubs pass straight through an exterior wall.

Be careful to utilize a heat shield when brazing inside a building or outside close to the siding.

5. Low-Pressure Liquid Line To Outdoor Unit: Flare

After the nitrogen has been turned off, the small, low-pressure liquid line will be flared and connected to the outdoor unit flare connector. Be sure to tighten all flaring connections to the necessary foot/lb torque value.

This is typically 12 ft/lb for copper tubes with an outer diameter of 1/4″, and 3/8″ O.D. Copper tubing typically weighs 27 ft/lb. To avoid leaks or other problems at the connections, though, always abide by the manufacturer’s instructions.

The system will thereafter be able to withstand a pressure test to check for leaks.

How Should Your Mini Split Lines Be Checked For Leaks After Brazing?

Can Mini Split Line Sets Be Brazed?

Flushing Of Nitrogen

  • Locating leaks in a system can be done using compressed nitrogen gas.
  • This test will be performed by an HVAC professional who will empty the unit of all refrigerant, swap the gas for compressed nitrogen, and listen for any noises.
  • Because nitrogen is held in the system at a higher pressure than the coolant, leaks generate an audible whooshing or hissing sound when it exits the system.

You may do a nitrogen leak test by performing the following two easy steps:

  • Perform a pressure test by injecting nitrogen gas into all of the refrigerant lines to a pressure of between 300 and 500 psi, depending on the type of air conditioning system.
  • Then wait 24 hours before checking again to see if the pressure reading has altered.

Digital Leak Detectors

  • Utilizing devices referred to as “sniffers” or electronic leak detectors, you can locate particular refrigerants.
  • These portable detectors typically provide the most economical test, but they are not always accurate.
  • Any surface that can leak needs to have electronic leak detectors installed on it to scan it, which can be challenging in small places.

Fluorescent Supplements

The additive needs to be cleaned up after a spill. Coalescent oil separators remove the additive to stop it from recirculating in the pipes and components between the oil separator discharge and compressor suction.

What Are Mini Split Lines’ Benefits And Drawbacks?

Before choosing to braze your small split lines, you should think about the following advantages and disadvantages.


  • In comparison to flaring, brazing has a number of benefits, including stronger connections, longer connection lives, and a lower danger of refrigerant leakage. No matter how skilled a flare installation is, every flare connection has minuscule gaps that let refrigerant escape.
  • Only brazing can ensure a totally sealed connection and completely eliminate the possibility of a refrigerant leak.


  • The degree of experience required to properly braze is the major disadvantage of the process. Most HVAC specialists lack the expertise required for this procedure, and even fewer installers are equipped with the right equipment.
  • A connection must be brazed rather than flared, which takes more time and needs more skill. While a brazed connection can be completed in just 15-20 minutes, a flare connection can be completed in just 5-10 minutes.
  • Due to the high temperatures used in brazing, your copper lines will oxidise after being torched. In other words, tiny flakes of charred debris and soot will gather on them anywhere they are exposed to air, or more precisely, the oxygen in the air. This could result in particulates getting into your HVAC system, which is never something you want to happen.

What Equipment Do I Need for Brazing?

Some of the supplies and tools used in brazing are listed below:

Acetylene-Oxygen Torch
Your best option is an oxygen-acetylene torch since it heats up more quickly than a MAPP gas or propane torch. Although a turbo torch should also be adequate for the majority of small-to-medium-sized projects, brazing demands higher temperatures than soldering, therefore this is crucial. Just keep in mind that MAPP gas burns hotter than propane.

Be mindful that setting up the flame on an oxy-acetylene turbo torch requires practise. You need to be aware of how much of each gas you should balance out in order to achieve the right kind of flame.

Smelting Rods
Brazing rods resemble straightened metal coat hangers and strengthen as their silver content increases, similar to solder. To join two metals, the torch burns the braze.

To connect copper lines, brazing rods made of a copper-phosphorous alloy are frequently employed. This particular type of brazing rod includes 6% silver and melts at 2174 °F.

Will A Mini Split’s Warranty Be Void If It Is Brazed?

The manufacturer of the individual equipment that is being installed should be contacted directly by technicians to confirm this.

Your HVAC system may have a number of problems over the course of its lifespan if it is not installed properly. According to warranty terms, poor installation voids the guarantee.

If you want to make sure the replacement equipment is still covered by the warranty, always consult with a trained HVAC professional who is familiar about your specific equipment.


Your tiny split air conditioner’s copper lines can be brazed. But braze your unit while attaching it to a nitrogen source to prevent any damage. This will aid in avoiding contaminants from entering your air conditioning system.

In order to prevent further leaks, only licenced and experienced personnel should do the brazing.

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Written by HVAC Contributor

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