If you're installing a MRCOOL mini split system with a 35ft pre-charged lineset like the DIY35-1412C, you may be tempted to skip the extras like wall sleeves and line set cover kits. After all, they’re not strictly required to get the system running, right?
That’s technically true. But speaking from experience? They're a small investment that can make a big difference in your installation's durability, efficiency, and curb appeal.
Let’s walk through why these components matter and when they become essential.
🔧 What Is a Wall Sleeve (and Why Use One)?
A wall sleeve is a small but important piece of the mini split puzzle. It’s a cylindrical pipe or tube (typically PVC or plastic) that lines the hole where your lineset passes through the wall.
The Purpose:
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Creates a clean, sealed path through siding or interior drywall
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Prevents moisture from seeping into the insulation or sheathing
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Keeps rodents and insects from nesting near the penetration
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Protects the soft foam insulation around the lineset from being compressed or torn
Why It’s Critical for 35ft Linesets:
With longer runs like the DIY35-1412C, the lineset tends to be heavier and more difficult to guide through tight wall cavities. Any sharp edge, misalignment, or over-compression can damage the foam or bend the copper. The wall sleeve acts as a guide and shield.
📎 MRCOOL's official install guide strongly recommends using sleeves for all wall penetrations.
"I skipped the sleeve at first. A week later I had ants crawling out of my drywall. I had to seal and re-install the whole line." — Mark
🎭 What Is a Line Set Cover Kit?
A cover kit is essentially a protective raceway or duct system for your lineset. It runs along your home’s exterior wall, from the point of penetration to the outdoor condenser.
What It Includes:
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Plastic or PVC channels (often in 3ft to 4ft sections)
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Mounting brackets
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Corner or elbow pieces for turns
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End caps for sealing entry and exit points
Benefits:
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Shields insulation from UV rays and weather damage
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Protects against pets, kids, and yard tools
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Makes the install look clean, finished, and professional
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Most are paintable to match siding or trim
🔗 Check options on Amazon or your local hardware store.
🏡 When Is a Wall Sleeve a Must-Have?
✅ Required For:
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Passing through brick, stucco, or cement board
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Penetrations into conditioned space or finished interior
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Routing through vinyl siding backed with foam
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Any wall that contains insulation or vapor barriers
Why?
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Keeps your building envelope intact
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Avoids trapping condensation in wall cavities
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Helps prevent interior mold or water damage
A wall sleeve only costs a few bucks. But the cost of skipping it could be a mold remediation bill, or worse.
💡 When Is a Cover Kit Essential?
📅 Recommended If:
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Your lineset runs more than 10 feet outside
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It's exposed to direct sunlight (UV damage risk)
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It runs near the ground or base of a wall (weed whackers, kids, animals)
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You want your install to look professional or meet HOA standards
The foam insulation on MRCOOL linesets is durable, but it's not indestructible. Sunlight, rain, wind, and temperature swings will degrade it over time if left unprotected.
"I didn’t use a cover kit at first. Within a year, my insulation was faded, cracking, and starting to flake. I ended up redoing the entire run with a new lineset." — Mark
❌ DIY Substitutes That Fall Short
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Spray foam around the wall hole — may crush insulation and doesn’t fully seal
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Zip-tied conduit — can pinch the lineset or rub off insulation over time
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Duct tape for UV protection — disintegrates in a few months
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Bare exposure — will shorten lineset life and potentially void warranty
These might save time short-term but often lead to rework and system inefficiency.
🔢 Choosing the Right Size Cover Kit for 35ft Linesets
What to Look For:
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Channel width of at least 3 inches to accommodate suction + liquid lines + insulation
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Total coverage length of 35 feet or more
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Includes:
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Two 90° elbows (vertical to horizontal turns)
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One wall inlet and one condenser outlet cap
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Example Kit:
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Universal 15ft kits on Amazon — buy two for full 35ft coverage
📌 Pro Tip: Buy a little extra to allow for trim, cutting errors, or custom bends.
🧑🛋 Mark’s Real-World Example
"I mounted my air handler in the attic and ran the 35ft lineset straight down the wall to the backyard condenser. Without a cover, it looked like a snake clinging to the house. I added a white 3" kit with elbows and caulked the ends. Looks way better now and hasn't needed a single repair in 2 years."
Mark also installed a wall sleeve using a 2.5" PVC pipe through the vinyl siding. He sealed it with backer rod and exterior caulk, then fed the lineset through before sealing the interior foam ring.
🪧 Installation Tips
For Wall Sleeves:
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Cut hole 1/2" larger than lineset diameter
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Insert sleeve flush with interior and exterior wall faces
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Seal with expanding foam on interior and silicone on exterior
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Use a backer rod in gaps over 1/4" before sealing
For Cover Kits:
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Mount brackets every 3-4 feet
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Dry-fit elbows and end caps before securing
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Use silicone caulk at entry/exit points to block moisture
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Paint after installation to match trim or siding
📉 Summary: When You Should Use These Accessories
| Scenario | Wall Sleeve | Cover Kit |
|---|---|---|
| Exterior run < 10ft | Optional | Optional |
| Run > 10ft with sun exposure | Recommended | ✅ Yes |
| Penetration through insulated wall | ✅ Yes | Optional |
| Through stucco, brick, or drywall | ✅ Yes | Optional |
| Ground-level lineset | Optional | ✅ Yes |
🌟 Final Thoughts: It’s a Smart Investment
Wall sleeves and line set covers might seem like accessories, but for a 35ft lineset, they’re close to essential. They protect your foam insulation, preserve system efficiency, and make your install look like it was done by a pro—even if it was just you and a Saturday afternoon.
"Skip the extras, and you’ll be reinstalling next season. Spend a little now, save a lot later." — Mark
In the next topic we will know more about: Avoid These Common DIY Mistakes When Working with MRCOOL Pre-Charged Linesets
