One of the most common calls we get goes something like this: "There are little black specks on the wall under my mini-split, and sometimes they blow across the room." If that sounds familiar, here's what's going on.
What the black flakes are
Behind the louvers of your indoor unit is a long, round fan called a blower wheel. It sits directly in the damp air coming off the cooling coil. Over months of running, dust sticks to the wet blades, and mold and bacteria grow in that layer. Eventually the buildup gets thick enough that pieces break off and get thrown out of the unit. Those are the black flakes.
Why it's common in Hampton
Mini-splits near Hampton Beach, North Beach, and the Hampton River deal with humid summer air and salt carried in off the ocean and the marsh. Many homes also run their units hard in July and August and then barely use them for weeks. That on-and-off pattern lets moisture sit inside the unit, which speeds up growth on the blower wheel.
Seasonal rentals and second homes are especially prone to it, since a unit can sit closed up and damp between visits.
Why rinsing the filter doesn't fix it
The filters sit in front of the coil. They catch a lot of dust, and you should keep rinsing them, but they don't touch the blower wheel. Once the wheel is coated, the only way to get it clean is to take the unit's covers off, protect the wall, and wash the wheel, coil, and drain pan directly.
Spray cans sold for "mini-split cleaning" usually reach the front of the coil but not the wheel, and the loosened grime has to go somewhere. Often it ends up in the drain pan or blown back into the room.
Should you be worried?
Black flakes are a sign of buildup inside a unit that's blowing air into your living space. The EPA notes that mold grows where there's moisture and recommends cleaning it up and fixing the moisture source. For a mini-split, that means a proper deep cleaning, then regular filter rinsing and a yearly cleaning to keep it from coming back.
Keeping it from coming back
- Rinse the filters every few weeks during the season.
- After a stretch of heavy cooling, run the unit in fan mode for a while to help dry it out, if your model has that option.
- Schedule a deep cleaning once a year, before summer if you can.
Common Questions
Why is my mini-split blowing black flakes?
The flakes are usually dust and mold breaking off the blower wheel inside the unit. They build up when the wheel stays damp, which is common in humid beach-area homes.
Will cleaning the filter stop the black flakes?
No. The filter doesn't touch the blower wheel. The wheel, coil, and drain pan need a full deep cleaning.
Do you clean mini-splits in Hampton Beach rentals and second homes?
Yes. We clean units in year-round homes, second homes, and rentals around Hampton Beach, North Beach, and Hampton Centre, and can schedule around guests.
Live in Hampton? See our Hampton, NH mini-split & condenser cleaning page.
We also clean mini-splits and condensers near Hampton in North Hampton, NH, Hampton Falls, NH, Rye, NH, Seabrook, NH, Exeter, NH.
Ductless Brothers serves homes from Newburyport, MA through the New Hampshire Seacoast and into Southern Maine.
