Can You Install A Mini Split On An Interior Wall?

Yes, you can install a mini-split on an interior wall. However, many people often wonder if it’s allowed, especially if, after checking the home, you determine that one of the interior walls may make a better installation location for the indoor air handler. 

Experts say you can do it – but with a few caveats. For one, it may be a tad more expensive. The installation process may also be more involving. But, if you’re prepared for the extra cost, you have the go-ahead.

Let’s find out about the caveats, costs, and considerations if you choose to install your indoor air handler on an interior wall.

NB: Interior walls are walls within a building surrounded by exterior walls. They are also known as partition walls and primarily exist to define space and provide privacy.

Why Do Most HVAC Experts Recommend Exterior Wall Installation?

Before we get to the interior wall, it may help us understand why most HVAC professionals recommend installing your heat pump on an exterior wall. The two main benefits are as follows;

Energy efficiency

One of the biggest attractions of mini split air conditioners is energy efficiency. Mini-split air conditioners are significantly more efficient than competing models such as window air conditioners, through-the-wall units, and portable units. Why? Because of the lack of ductwork.

This lack of ductwork is partly because of the short distance between the indoor air handler and the outdoor condenser – which is best achieved through exterior wall installation.  

Lower material/installation costs

Exterior wall installation significantly reduces the distance between the indoor air handler and outdoor condenser, effectively reducing the length of refrigerant lines and electrical wires needed for the installation. In addition, it simplifies the installation process by reducing or eliminating the time it takes to run wires between the outdoor and outdoor units.

Weight-bearing strength

Finally, exterior walls are also usually preferred because they are stronger. Remember that indoor air handlers aren’t always light. Some are 50 pounds or more.

Additionally, the units vibrate when running. Exterior walls are better equipped to bear the weight and withstand the vibration. If your interior walls aren’t load-bearing walls, you may not be allowed to install an AC on them at all.

When Interior Wall Installation is a More Appealing Option

Despite the apparent preferences, though, sometimes interior wall installation may appear a better option. This usually happens when;

The exterior wall is used up

Perhaps you already have the exterior wall stacked to the ceiling with items and appliances that you cannot easily relocate. For instance, perhaps the exterior wall on your kitchen already houses the main cupboard. In this case, there may not be space on the same wall for mini split installation.

The wall is compromised/weak

This is more a hypothetical scenario, given that most exterior walls are stronger than interior walls. However, if the exterior wall is notably weak, perhaps following a flood or fire, installing the air conditioner on a stronger interior wall may make more sense.

Aesthetic reasons

Aesthetics may also present a challenge, forcing you to install the air conditioner on an interior wall. A good example is when you want the exterior wall in a specific color, say yellow, while the interior walls are white. If the indoor air handler is white (most units are white, anyway), you may be more inclined to install it on the interior walls.

Personal preferences

Finally, you may also want to have the air conditioner on one of the interior walls rather than the exterior walls. For example, perhaps you’re installing the AC in the bedroom, and you want the bed to face a certain direction. If you’d prefer to have the air handler above the bed, you may be forced to install it on one of the interior walls.

Considerations and Tips

You’re allowed to install the air handler however you wish, as long as the interior walls are strong enough to support the weight. However, you must keep a few things in mind;

Materials will cost you more

How much more you’ll spend on the installation depends on several factors, including the AC model, which wall it is, and the distance from the outdoor unit.

Different mini-split systems use different refrigerant line sets. Some manufacturers will even void the product warranty if you use a non-recommended line set. Depending on the cost of the recommended line set, the extra length needed to reach the interior-wall installed indoor air handler can range from a few to several hundred. Remember that you’ll also need extra electrical wire.

The installer will charge you more

The exact cost here depends on factors such as the distance to the indoor air handler and the ease of running the line set and electrical wires. Generally, the longer the distance between the indoor and outdoor units, the higher the installation costs.

Installation costs are also typically higher if the installer has to run the line set through the wall. Creating the run lines may need masonry work that costs extra. Sometimes they also need to access the attic to run the lines. This also usually attracts a higher fee.  

The project will take more time

Running the refrigerant lines to the indoor air handler is easy when the two units, the condenser unit outside and the air handler inside, are separated by the wall. But the same can’t be said when the air handler is located perhaps on the opposite wall.

It takes more time to identify the best way to run the lines and even more time to run the lines. It also takes more time to locate and install the drain line and cover the line set. Just like that, a one-day job may become a two-day project.

Greater maintenance is needed

Finally, you should beware that a longer distance between the indoor air handler and outdoor condenser increases maintenance responsibilities. For one, a longer line set means that a larger portion of the line set is exposed to damages such as dents and cuts, which can potentially cause refrigerant leaks. Therefore, you need to be more observant.

Additionally, diagnosis becomes a little more difficult and expensive if there’s a problem with the line set. That’s because diagnosing a 2-meter line set or electrical wiring isn’t the same as diagnosing a 10-foot line set or electrical wiring.

Key Takeaway

As you can see, it’s possible to install a mini-split on an interior wall. Although many people, including HVAC experts, prefer exterior wall installations, interior wall installations can be just as effective if the conditions are right.

The only caveat is that interior wall mini-split installations are slightly more complex, thus more expensive. You need more material and are guaranteed to pay more for the installation. You must also be prepared for increased maintenance duties.

If you choose to go the interior wall route, anyway, we’d advise two things. First, consider professional installation. The higher complexity increases the risk of costly mistakes in interior wall mini-split installations. Additionally, make sure to cover every inch of the line set and electrical wires protecting them from damage and weather elements.