Mini Split Wall Sleeve - Line Set Pass-Through
Print Profile(6)
Description
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If this sleeve saved you from a flimsy OEM replacement or a trip to the hardware store, please consider hitting Boost, it costs you nothing and helps other DIY mini-split installers find the design. This one took 4 prototype revisions to nail the telescoping fit, the half-collar AC clearance, and the 9–14" wall range. Every boost lets me justify the time to publish more HVAC parts. Thanks for printing, drop a photo of your install if you can, I love seeing them in the wild!
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Mini Split Wall Sleeve — Line Set Pass-Through (MrCool DIY)
A heavy-duty 3D-printed Mini Split Wall Sleeve for the line-set pass-through on MrCool DIY 3rd / 4th / 5th Gen and other ductless mini-split installations. Telescoping two-piece design fits thick walls from 9" to 14" (229–356 mm), with optional screw flanges and a half-collar variant that clears the indoor head unit when it mounts close to the pass-through.
What it is
When a ductless mini-split is installed, a 3-1/2" hole is drilled through the exterior wall to pass the refrigerant line set, condensate drain line, and low-voltage control wire. The flimsy plastic sleeve that ships with most units sags, cracks in UV, and never quite seals against pests or air infiltration.
This is a sturdier 3D-printed replacement designed specifically for the MrCool DIY 3rd Gen line-set bundle, but compatible with any mini-split using a 3-1/2" hole saw — Mitsubishi MSZ, Pioneer Diamante, Senville Leto, Daikin, LG, and others.
What's Included — 6 Print Profiles
The set is a two-piece sleeve: one exterior wall piece + one interior wall piece. Profiles are provided both as individual pieces (mix and match) and as two pre-bundled kits:
Pre-bundled kits (both pieces on a single plate)
Half Collar – Mount Holes (MrCool kit)
Interior half-collar (clears the AC head unit) + exterior with mount holes.
Full Collar – No Mount Holes (universal kit)
Interior full collar + exterior with smooth flange (no fasteners).
Individual pieces
Outside Wall – With Mount Holes
Exterior collar, Ø135 mm flange with pre-drilled holes for #8 × 1" stainless screws.
Outside Wall – No Mount Holes
Exterior collar, clean flange face for adhesive / silicone install.
Inside Wall – Full Collar
Interior sleeve, Ø111 mm full circular flange. Universal use when the indoor head unit is mounted well away from the pass-through.
Inside Wall – Half Collar (MrCool)
Interior sleeve with a section of the flange cut away so the indoor head unit body can sit flush against the wall directly over or beside the pass-through. Required for tight MrCool DIY installs where the unit sits close to the sleeve.
Fitment
| Spec | Metric | Imperial |
|---|---|---|
| Wall hole (drill / hole saw) | 89.3 mm | 3.516" (≈ 3-1/2") |
| Exterior collar OD | 135 mm | 5.315" |
| Exterior tube length | 187 mm | 7.362" |
| Interior sleeve OD | 111 mm | 4.370" |
| Interior tube length | 229 mm | 9.016" |
| Min wall thickness | 229 mm | 9.0" |
| Max wall thickness | 356 mm | 14.0" |
| Required tube overlap | ≥ 60 mm | ≥ 2-3/8" |
| Mount-hole screws | #8 × 25 mm | #8 × 1" stainless |
Wall Thickness Compatibility
Designed for thick-wall constructions: ICF, double-stud, deep exterior-foam retrofits, brick veneer + interior framing, and masonry/CMU walls.
| Wall thickness | Compatibility |
|---|---|
| Under 9" / under 229 mm | Not compatible — interior sleeve too long |
| 9" – 14" / 229 – 356 mm | ✓ Fits |
| Over 14" / over 356 mm | Not compatible — insufficient tube overlap |
Measure your finished wall thickness (exterior siding face → interior drywall face) before printing.
Install Steps
- Drill a Ø89.3 mm (3-1/2") hole through the exterior wall per your mini-split's install manual.
- From outside, push the Exterior Collar tube into the wall hole until the flange seats flat against the siding.
- From inside, slide the Interior Sleeve over the exterior collar's tube — they telescope together to fit your wall thickness. Confirm at least 60 mm of tube overlap.
- (Mount-hole variant) Drive four #8 × 1" stainless pan-head screws through the exterior flange into siding.
- Run the line set, condensate drain, and control wire through the sleeve. For MrCool DIY: orient the half-collar cutout so it aligns with the AC head unit's mounting position.
- Pack the inside of the sleeve around the line set with foam or non-hardening putty per the mini-split manual.
- Apply an exterior silicone bead around the outer flange to weather-seal the siding penetration.
Why Printed Beats OEM Plastic
The thin sleeves that ship with most mini-splits are made for shipping, not service life. This print is:
- UV-stable when printed in ASA — won't crack or chalk after a season of sun
- Stiff enough that fasteners don't deform the flange
- Thicker walled for a better thermal break and less condensation inside the wall cavity
- Replaceable if your line set ever changes
Material Recommendation
- ASA — best choice. UV-stable, weatherproof, stable across full outdoor temperature range.
- PETG — acceptable for shaded or protected installs.
- Avoid PLA on the exterior collar, it will soften and sag in direct summer sun.
Print profiles attached, open in Bambu Studio for one-tap printing. See each profile's description for slicer settings.
License
You may create derivative works based on this object, provided that all such derivative works are published exclusively on the MakerWorld platform and include proper attribution to the original creator. You may not share, upload, host, distribute, or publish this object—or any derivative work of this object—on any other digital platform, marketplace, or distribution channel. Commercial use of this object and any derivative works is strictly prohibited. This includes, but is not limited to, selling, renting, sublicensing, or using the object in any context in which you receive monetary compensation or other financial benefits.
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