Ductless mini-split heating and air-conditioning units bring climate-controlled air to spaces where traditional ducted systems aren’t feasible. A do-it-yourselfer can usually handle the regular maintenance. Here’s what you need to know.
Ductless mini-split monthly maintenance
Your mini-split unit inside the house has a return air intake with two filters shielding thin evaporator coils from airborne dust. The intake is on the top of the wall unit. Below the evaporator coils is a long, cylindrical fan that blows the treated air out the front of the unit.
Each month you must open the front cabinet panel, remove the filters and clean them. Be gentle in both removing and returning the panel. Forcing the plastic snaps could break one.
Slide the filters out and suck the dust off with a vacuum cleaner hose, then rinse with water. The filters are quite thin and will dry quickly. Return them to the unit and close it back up.
Once or twice a year
Even with faithful filter cleaning, dust will accumulate on the evaporator coils. You’ll need to clean them once or twice yearly. Here’s how.
- Gather a Phillips screwdriver, a soft-bristled one-inch paintbrush, and a foam cleaner can, available online or at a home improvement store for the evaporator coils. You’ll also need a spray bottle of clean water and a shop vacuum with an attachment reducing the end to three-quarters of an inch. You can order an apron to attach to the unit to catch all fluids and dust.
- You’ll be spraying liquids inside the mini-split, so begin cleaning by shutting off power to the unit at the breaker box.
- Remove the cover panel and filters, cleaning them as usual. Next, remove the whole cabinet housing by locating and removing two or three screws along the bottom edge of the front blower vent. Plastic tabs along the top edge snap and hold the housing in place at the top. Gently push down on those tabs and gently ease the housing off. Set it aside.
- To clean the evaporator coil fins and cylindrical fan, cover the right end of the unit with a small towel to shield the electronics from moisture. Spray the cleaning foam between the evaporator fins at a downward angle. Let it sit for 20 minutes.
- You can access the fan by unscrewing the left side of the evaporator coils and swinging them out. You can also leave the coils in place and see the fan by looking upward through a tight space underneath them. In either case, slowly spin the fan with your finger while using the one-inch brush to remove dust along its length and the entire circumference.
- Take the shop vacuum outside and connect it to the end of the condensation line, then turn it on.
- Return inside and gently mist water over the coils to rinse the foam and dust from them. The dirty rinse water will drip into the drain pan, and the vacuum will suck it out of the drain tube. Let the vacuum run for about five minutes, then put everything back together. Wait half an hour, then turn the unit on. If water drips from the bottom of the cabinet, the drip pan inside is overflowing. Rerun the vacuum on the end of the line until the drip stops.
If you’d like a visual cleaning lesson, you can watch a YouTube tutorial.