How to Clean and Maintain a Ductless Mini-Split

A ductless mini-split needs less upkeep than many systems, but it is not maintenance-free. The indoor units pull room air through filters and across a coil several times an hour. When those filters clog, airflow drops, the unit works harder and the room gets less comfortable. This guide covers the tasks you can safely do yourself and the ones a technician should handle.

Safety first

Before you clean anything, follow these rules:

• Turn the unit off with the remote, then shut off power at the breaker or the outdoor disconnect before you touch the outdoor unit or open more than the indoor unit's front panel.
• Do not remove fixed covers or touch wiring. The indoor and outdoor units contain electrical parts that can stay energized.
• Do not loosen line set fittings or try to add refrigerant. Federal rules under EPA Section 608 of the Clean Air Act prohibit intentionally venting refrigerant during service, and refrigerant work requires a certified technician.
• Do not spray cleaners or water into the indoor unit unless your owner's manual says it is safe for that part.

If you smell burning, see sparks or hear electrical buzzing, turn the system off at the breaker and call for service. If there is smoke or fire, leave the house and call 911.

Clean the indoor filters

This is the most important homeowner task. The Trane guide to mini-split filters says filters may need cleaning as often as every two weeks during peak heating or cooling season, and about monthly with lighter use. ENERGY STAR says to clean them when they look dirty or when the filter light comes on. Your owner's manual gives the exact schedule for your model.

1. Turn the unit off and shut off power.
2. Lift the front panel of the indoor unit until it locks in the open position.
3. Slide the mesh filters out. Note how they sit so you can reinstall them correctly.
4. Vacuum the filters with a brush attachment on low suction. Strong suction can damage the mesh.
5. If they are still dirty, rinse them with lukewarm water. Let them dry completely before you reinstall them.
6. Keep any small deodorizing or specialty filters dry. Trane notes these should not get wet.
7. Reinstall the filters, close the panel and restore power.

Clean filters in every indoor unit at the same time, including units in rooms you rarely use.

Wipe the indoor unit and check the drain

• Wipe the outside of the indoor unit and the air outlet louvers with a soft, dry or slightly damp cloth.
• Look for water drips or stains on the wall below the unit. Drips usually mean the condensate drain is clogged or the line is not sloped correctly.
• Look inside the outlet with a flashlight. Dark spots on the blower wheel or coil mean the unit needs a professional cleaning. Do not try to scrub the blower wheel or coil yourself.
• Notice any musty smell when the unit starts. That is another sign the coil or blower needs cleaning.

Care for the outdoor unit

The outdoor unit needs open airflow in summer and winter.

• Clear leaves, grass clippings and cottonwood fluff from around the unit and off the coil fins. Use your hand or a soft brush with the power off.
• Keep plants, fences and stored items back from the unit. Your installation manual lists the required clearances.
• Do not use a pressure washer on the coil. It can bend the fins.
• Check that the line set insulation is intact and not cracked or chewed.

Minnesota winter checklist

If your mini-split heats your home, the outdoor unit keeps running all winter.

• Keep snow cleared from around and on top of the unit after each snowfall so air can flow through the coil.
• Expect some frost. The unit will stop heating for a few minutes to defrost, and you may see steam. That is normal operation.
• Watch for ice on walkways. ENERGY STAR notes that outdoor units release water when they defrost, which can form icy patches.
• Do not chip ice off the coil. If the unit stays encased in ice, turn it off and call for service.
• Set the mode to Heat, not Auto. The ENERGY STAR ductless heating and cooling page recommends this so the system does not switch modes on unseasonably warm or cold days.

What professional maintenance covers

Trane recommends professional ductless maintenance at least once a year, and twice a year when the system both heats and cools. A typical visit includes:

• Cleaning the indoor coil and blower wheel
• Clearing and testing the condensate drain
• Cleaning and inspecting the outdoor coil
• Checking electrical connections and system operation in both modes
• Inspecting the line set and replacing damaged filters

When to call a professional

Book service if you see water leaking from the indoor unit, ice that does not clear on its own, weak airflow after you clean the filters, a musty smell, or a unit that runs but does not heat or cool. If it has been more than a year since the last professional cleaning, schedule one before the heating season. See our ductless mini-split services or contact us to book a visit.

Common questions

Sources

• Trane — Do Mini-Splits Have Filters?
• ENERGY STAR — Ductless Heating & Cooling
• U.S. EPA — Section 608 of the Clean Air Act