Ductless mini-split installation in Seattle, WA

As with any HVAC system, a mini-split can develop various issues that affect how well it works and potentially lead to it using more energy than it should. In this article, we’ll look at the most common problems that can cause a mini-split system to struggle and what you can do to solve the issue.

Coils Are Dirty

Ductless mini-split systems are a type of heat pump that, like central air conditioners, rely on evaporator and condenser coils to facilitate the heat transfer process essential for cooling and heating. They can both heat and cool a space by reversing the flow of refrigerant. In cooling mode, the system absorbs heat from inside the home and releases it outside. In heating mode, it absorbs heat from the outside air and transfers it inside.

However, when either the outside or inside coils become dirty and covered in dust, the system’s efficiency drops significantly. Dust acts as an insulator, reducing the coil’s ability to transfer heat effectively. When in cooling mode, a dirty evaporator coil cannot absorb enough heat, and a dirty condenser coil cannot release heat properly. As a result, the air blown out of the indoor air handler is not as cool as it should be, and the mini-split system struggles to maintain your desired temperature.

Keeping the evaporator and condenser coils clean is crucial to ensure your mini-split system operates efficiently. Having an HVAC professional clean the coils during annual maintenance can help prevent your ductless mini-split system from failing to cool your home adequately.

During their visit, the technician will use a soft brush or compressed air to remove loose dust and debris from the coil’s surfaces. For caked-on gunk, they may use a no-rinse coil cleaner. It dissolves grime without needing to be rinsed off, which is especially useful for hard-to-reach areas.

Air Filter Needs to Be Cleaned

The primary purpose of the air filters in your indoor air handlers is to prevent dust and debris from entering the system and damaging internal components. They also play a vital role in maintaining indoor air quality by capturing airborne contaminants that would otherwise recirculate through your living spaces. However, when they become clogged, they will reduce airflow through the system and reduce your mini-splits ability to cool your home.

For your mini-split to work effectively, you need to clean the air filter in each indoor unit at least every two to three months. To clean the filter, you first need to shut off the air handler and then open the cover on the front. The filters usually have several clips that hold them in place, and you want to be careful when prying the filter out to avoid breaking any of them. Once you have the filter out, the easiest way to clean it is to use either a garden hose or the sprayer on your kitchen faucet. If you can’t wash away all of the debris just by spraying the filter, use warm, soapy water and a soft-bristle brush. After cleaning the filter, let it dry completely before putting it back in place to prevent mold and mildew growth.

Outdoor Unit Doesn’t Have Sufficient Airflow

One important part of keeping your mini-split properly maintained is to regularly clean up any leaves and debris from around the outside unit. You also want to make sure there is no vegetation growing within two or three feet of the unit. In some cases, you may need to shut the system off and remove leaves that are stuck to the vents on the front and back of the unit as well.

All of these things are necessary to ensure that the unit’s fan can continually draw in sufficient air. The air flowing through the unit is what allows the outdoor coil to release the heat it captures from inside when the system is in cooling mode. If the unit doesn’t have proper airflow, the system won’t be able to cool nearly as effectively since the refrigerant will retain heat when it flows back inside. Another more serious issue that can occur is that the outdoor unit can end up overheating and potentially being damaged. However, the mini-split’s safety features will usually shut down the system in this scenario, preventing the need for costly repairs.

System Doesn’t Have the Correct Refrigerant Charge

If your mini-split air handlers are blowing lukewarm air into your home, it may indicate that the refrigerant level is low. Since modern mini-splits are closed systems, they will only lose refrigerant if there is a leak.

A mini-split system must have a specific refrigerant level to work correctly. If the charge is low, the system’s pressure drops. This low pressure can cause the indoor coils to freeze up, as the lower the pressure is, the colder the refrigerant becomes. When the air handler coils freeze, the unit will blow hot air instead of cooling your home effectively.

Alternatively, there is a slight chance that the refrigerant level could be too high due to improper maintenance or installation. If the charge is too high, the refrigerant won’t be able to get as cold as it needs to for the system to cool correctly. This can also result in the system blowing lukewarm air and not cooling your home as it should.

If you suspect a refrigerant issue, contact an HVAC technician. If the system is overcharged, they know how to remove refrigerant from the mini-split safely. They also have the tools and experience to repair leaks and recharge the system as needed.

System Isn’t Properly Sized

One last possibility is that your mini-split system is simply too small or too large for the area you’re trying to cool. Sizing a mini-split system is more difficult than sizing a central HVAC system. That’s because you need to make sure that the outdoor unit is sufficiently sized to cool every room that has an air handler. You also need to make sure that each air handler is the correct size for the room or part of the home that it’s in. The size of the outdoor and indoor units also depends on the number of people living in your household and how well your home is sealed and insulated.

An undersized system will struggle to meet your cooling needs and run constantly. Alternatively, an over-sized system will short-cycle. Short cycling in a mini-split system occurs when the unit turns on and off frequently in short intervals rather than running in longer more efficient cycles. These issues can prevent the system from adequately cooling your home and increase wear and tear on the components.

Contact the Pros

At Black Lion Heating & Air Conditioning, we have served Kirkland, WA residents for over 20 years. We install, maintain, and repair heating and cooling systems. In addition, we provide indoor air quality, duct cleaning, and electrical services. Contact us today to schedule an appointment with one of our experienced team members if you are having any issues with your mini-split system.