Do mini splits have to vent outside?

Do mini splits vent outside?

No. A mini split doesn't burn fuel, so there's no exhaust to vent. What does go outside is a line set: two insulated copper refrigerant lines, a power and control cable, and a condensate drain. They pass through a hole about 3 inches across behind the indoor head and run to the outdoor unit.

So a mini split needs an outside wall or a route to one, but not a chimney or a vent pipe like a gas furnace.

What runs through the wall

Outside, those lines are covered with a line-set cover that runs down the wall to the outdoor unit.

Where the water goes

In cooling mode, the indoor coil takes moisture out of the air, and it has to drain somewhere. Most heads drain by gravity through the wall to the outside. When the head is on an inside wall or below the drain path, a small condensate pump lifts the water out.

In a Duluth winter, the drain end is placed so it can't freeze shut, and the outdoor unit sits on a raised stand or bracket. It runs defrost cycles in heating mode and drips water, which needs somewhere to go other than a snowbank.

A mini split doesn't bring in fresh air

This surprises people. A mini split heats, cools and filters the air already in the room. It doesn't pull outdoor air in. If a room feels stuffy, that's ventilation, which is a separate question (a bath fan, a window, or an air exchanger in a tight house).

Can it go on an interior wall?