Can You Run Mini Split Refrigerant Lines in Walls?


Not everyone like to have a chunk of refrigerant lines visible in their house. Hence, many people are asking if they can run mini split refrigerant lines in walls. Since I've been doing it for many years, I should be able to provide some helps.

Mini split refrigerant lines can be run in walls. It is a common practice to hide the refrigerant pipes of mini splits in dry walls for aesthetic purposes. Apart from being more difficult to repair, concealing the refrigerant lines in walls have no impact on the performance of the mini splits.

Running mini split lines in walls can be risky because it is difficult to repair later. However, when done properly, it improves the interior and exterior of the house dramatically.

How to Run Mini Split Lines in Dry Walls?

There are four types of walls needed to be discussed regarding the conceal of mini split lines; a) dry wall, b) stud wall, c) partition wall and d) RC wall.

Dry wall is the most common type of wall found in homes and commercial buildings. In countries like the United States and Canada, homes are mostly insulated. Hence, there is a layer of stud wall complete with insulation on the dry wall.

Partition wall is more common in office towers and low cost homes. It is a simple thin board without insulation. Meanwhile, RC wall or reinforced concrete wall is getting popular nowadays to eliminate columns in buildings.

Most people want to conceal mini split lines in dry walls. Although mini split lines can be run on the surface of dry walls and cover them with a line-set cover or PVC trunking, some people don't like the look of it as it indeed affects the aesthetics of the house.

Built-In Mini Split Lines

In construction projects, high-rise residential buildings are often built with the refrigerant lines, condensate drain line and wires of mini split air conditioners concealed in dry walls. As a result, new homeowners only need to install the mini split indoor and outdoor units.

There are 4 components involved in the conceal of mini split lines in walls as follow:

  • Insulated Copper Tubes – A pair of copper tubes are used to transfer the refrigerant from the mini split indoor unit to its outdoor unit. Refrigerant pipes must be insulated as usual or else, condensation will occur.
  • Non-Insulated PVC Pipe – A class E PVC pipe, which is a thicker type, is used to discharge the condensate water of the mini split indoor unit. Insulation is not required because the wall acts as an insulation and the condensate water temperature is not as low as the refrigerant. Hence, condensation will not occur.
  • PVC Cable – PVC cables are used to transmit power and signal to the mini split indoor unit. The quantity of the cable varies depending on the mini split system. However, they must be protected with a PVC conduit.
  • PVC Conduit – PVC conduits are used to house and protect PVC cables. Without them, PVC cables can get damaged and safety is a concern.

Usually, PVC conduits and PVC pipe (class E) are not included in the mini split package. Hence, you need to purchase them separately. Once you are ready, it's time to conceal the lines.

Procedure to Conceal Mini Split Lines in Walls

Following is a step-by-step procedure on what we normally do to conceal the refrigerant lines, drain line and wires of wall-mounted mini splits:

DIY Underground Bunker Plans
DIY Underground Bunker Plans

Mark the Mini Split Position and Lines Route

  • Mini split should be around 7-8 ft above the floor and 8″ from the ceiling. Side clearance should be around 4″ and 8″ clearance below the unit.
  • Drain line should be running down vertically. Running horizontally even with slope is not recommended.
  • Refrigerant lines and wires should run horizontally without any slope or vertically upward if the room has a ceiling.

Measure the Length of Mini Split Lines

  • Measure the length of the refrigerant pipes, drain pipe and wires from the mini split indoor unit to its outdoor unit.
  • Cut the pipes and wires and check again the entire route from the mini split indoor unit to its outdoor unit.

Cut the Wall to Fit the Mini Split Drain Line

  • Use a hand grinding machine to cut the wall to fit the mini split drain line.
  • Paste a few points of cement plaster along the drain line to temporary hold it in place.

Cut and Run the Mini Split Drain Line in the Floor

  • Use a hacking machine to cut a path for the mini split drain line to run in the floor.
  • Conduct a flow test. Pour water at the inlet of the drain pipe to test check for any leakages and the smoothness of the water flow.
  • Concealing a drain line in the floor is difficult on existing houses. Hence, you can put the mini split indoor unit on a toilet wall. Then, drill a hole through the wall and run the short length of drain line exposed in the toilet.

Additional resources:

Cut the Wall to Fit the Mini Split Refrigerant Lines and Wires

  • Further cut the wall to fit the mini split refrigerant lines and wires.
  • Bundle the refrigerant lines and wires together with the drain line using black tapes to hold them firmly in place.

Patch Back the Wall with Cement Plaster and Touch Up

  • Check if all the lines are correct and appropriate.
  • Measure the length of the mini split lines protrude from the wall to confirm if it are sufficient.
  • Patch back the wall with cement plaster and touch up with paint afterward.
  • See resources on wall plastering to ensure that it won't crack when it's done.

Run the Refrigerant Lines and Wires to the Mini Split Outdoor Unit

  • Run the refrigerant lines and cables to the mini split outdoor unit.
  • Repeat the wall cutting process to conceal the refrigerant lines and wires at the outdoor unit.

Conduct a Pressure and Megger Test Before Connecting the Mini Split

  • Conduct a pressure test for the refrigerant lines and a megger test for the wires.
  • Check everything again and connect the lines to the mini split indoor and outdoor unit.
  • Power up the mini split and test accordingly.

Additional resources:

Tools and Material Needed for Mini Split Lines in Walls

Following are the tools mentioned and needed for the above procedure. These are affiliate links to Amazon for your convenience.

Other Ways to Hide Mini Split Lines

If concealing mini split lines in dry walls seems too difficult or costly for you, there are other ways to hide mini split lines.

Concealed in Between Wall Studs

Pipes Running Through Wall Studs

Houses with insulation have a layer of wall studs where mini split lines can run in between. In fact, it is very common for pipes to run around wall studs in insulated houses. Such an installation method is easier than concealing in dry walls. However, it is only applicable to certain houses.

Concealed Above the Ceiling

Many mini splits have their refrigerant lines, drain line and wires installed above the ceiling. However, if the mini split indoor unit is a wall-mounted unit, the lines are still visible below the ceiling unless you conceal them in the wall.

Hence, you may want to consider changing the mini split indoor unit to a ceiling cassette unit or a ceiling ducted unit so that the lines can be perfectly concealed above the ceiling.

As you can see, both units are having their lines running at a high level. Once the ceiling is installed, the lines are hidden above the ceiling.

Relevant post: Ducted Mini Split Guide: Basics, Comparison & Installation.

Should You Run Mini Split Lines in Walls?

I normally don't recommend people to run mini split lines in walls if they are installing in an existing house because it is too complicated, costly and risky to do. However, if you are dedicated and follow proper procedure, I wouldn't stop you from doing it since it really improves the aesthetics of the house.

The major concern about running mini split lines in walls is repairability. If the refrigerant lines or drain line is leaking, it is almost impossible to repair because we don't know exactly where is the leaking point. Usually, we just run a new set of lines instead of trying to repair the concealed ones.

In Malaysia and Singapore where mini splits can be found in almost all buildings, the drain line is mostly concealed on the floor. Most of the time, we conceal the drain line before the tiles are placed.

Meanwhile, the refrigerant lines are concealed in the wall from the mini split indoor unit to the ceiling above it. Then, the refrigerant lines run above the ceiling to the outdoor unit where they run exposed but covered with metal trunking. Concealed lines at the outdoor unit are less common.

So, if you are not going to do a major renovation for your house, I would suggest you try not to cut and conceal mini split lines. However, if you are ready for a big project, go ahead and hide those eye-soaring lines.


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