Mini-split install guide
Mini-Split Rough-In Box: What It Does and What to Look For
On a ductless job, the line set, condensate drain and control wire run through the wall behind the head unit. A mini-split rough-in box gives them a defined, protected place to go before the drywall closes the bay.
Why the lines need a box in the wall
Between rough-in and trim-out, every trade works the same walls. Drywall goes up, other trades run wire, screws go in. Tubing that is left loose in the cavity has no defined path and nothing protecting it. A crushed or kinked line set means rework, and finding it after the drywall is up costs more.
A rough-in box marks the spot behind the head, holds the penetrations where you put them, and keeps everything organized for the person who sets the head unit.
What to look for
- Fits the bay. The box should sit inside a standard 2x4 stud bay without protruding past the framing.
- Mounts to wood or metal studs. Look for mounting wings with long slots, so it sits square even when the framing is not exactly on center.
- Separate knockouts. The line set, drain and control wire should each get their own opening, in sizes that match what you are running.
- Stays square. A rigid body holds its shape while every other trade works the wall.
- No loose parts. Integral wings mean nothing to assemble and nothing to drop behind the wall.
How it installs
- Position between studs. Set the box in the bay with the wings flat against the studs.
- Screw the wings. Drive screws through the long slots into wood or metal studs at 16 inch centers.
- Punch the knockouts. Open the sizes you need.
- Run your lines. Line set, condensate drain and control wire, each through its own knockout.
Folded 16 gauge galvanized steel, one piece. 18.26 x 10.02 x 3.38 in overall, 3.38 in deep for a 2x4 bay. Four knockout sizes: on each face, two large (1-1/4 or 2 in) and one small (1/2 or 3/4 in). Wood or metal studs at 16 in centers. Made in the USA.
Inside the wall vs. the outside wall
The rough-in box handles the inside: the bay behind the head. Where the line set exits the house is a different problem: weather, pests and a finish the homeowner sees every day. That is what the Lineset Box™ is for.
Questions
Where does a mini-split rough-in box go?
Inside the wall, in the stud bay directly behind where the indoor head unit will hang. It is installed at rough-in, before drywall.
Do I need one per head unit?
Yes. Each indoor head has its own line set, drain and control wire, so each gets its own box.
What about where the lines leave the house?
That is the exterior penetration. A line set box such as the Lineset Box™ gives the line set, drain and wire a clean, weathertight termination at the outside wall.