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Installation Guide: What to Know Before You Cut a Hole in the Wall

Intro: Planning Beats Patching

Installing a through-the-wall air conditioner sounds intimidating. I get it — “cut a hole in your wall” doesn’t exactly sound homeowner-friendly. But with the right prep, the process is straightforward and clean.

Over my years in HVAC, I’ve seen two kinds of installs: the ones that look factory-built and the ones that scream DIY gone wrong. The difference isn’t skill — it’s planning.

Before you touch a saw, here’s everything you need to know to make your installation solid, safe, and efficient for years to come.

1. Understand What a Wall Unit Really Needs

A through-the-wall AC isn’t like a window unit you pop in and out every season. It’s permanent. Once installed, it becomes part of your home’s envelope — meaning air sealing, framing, and drainage all matter.

Every wall system has three main parts:

The AC unit itself
A metal wall sleeve (holds and supports the unit)
Exterior grill (protects the outdoor vent side)

That wall sleeve is the unsung hero here. It keeps the system stable, aligned, and sealed from rain, air leaks, and pests. Think of it as the holster your AC slides into.

If your system doesn’t include one, get a matching model — like the Amana WS900 Wall Sleeve — before you start cutting.

2. Pick the Perfect Spot

Placement can make or break both comfort and performance.

Here’s Jake’s checklist before picking up tools:

✅ Exterior Access:
The wall must face outside (not into a garage or attic).

✅ Clear of Obstructions:
Avoid studs, plumbing, wiring, or vents. Use a stud finder and cutout template.

✅ Centered on the Wall:
Place the unit at about 12–18 inches above the floor for best air distribution.

✅ Shade Helps:
If possible, choose a wall with limited direct sunlight. Shaded walls reduce heat load and improve efficiency.

✅ Accessibility:
Ensure there’s space inside for the unit’s airflow and outside for drainage and maintenance.

Jake’s Tip: “If you can, avoid putting it right above furniture — you want open airflow, not an AC blowing straight at your couch.”

3. Measure Twice, Cut Once (Seriously)

Each AC model lists its sleeve dimensions — width, height, and depth.
Example: A typical 12,000 BTU unit may need a 26" x 15.5" opening and about 16" of wall depth.

Use the provided paper template or make your own out of cardboard. Tape it to the wall and double-check:

It’s level
It clears all studs
It’s centered properly

Once you’re confident, outline your cut with a pencil.

4. Gather Your Tools

You don’t need a contractor’s truckload of gear — just these essentials:

Inside Work:

Stud finder
Level
Drill and drill bits
Reciprocating saw or oscillating tool
Utility knife
Measuring tape
Caulk and gun

Outside Work:

Exterior-grade screws
Flashing tape
Weatherproof caulk
Paint or exterior trim (optional for clean finish)

If your wall is brick or stucco, rent a masonry saw or hire a pro. For wood framing, most homeowners can DIY comfortably.

5. Cut the Opening Safely

Now, the part everyone worries about — cutting into the wall. Take it slow.

Drill pilot holes in each corner of your outline.
Use your saw to connect the dots, cutting clean lines.
Remove insulation and debris carefully.
Frame the opening with 2x4s to support the sleeve.

You’re essentially creating a mini window opening. It needs to be square, secure, and ready to hold 60–100 pounds of weight.

Jake’s Take: “Most homeowners mess up not by cutting wrong — but by skipping the framing. Don’t trust drywall to support that unit.”

6. Install the Wall Sleeve

Slide the metal sleeve into the opening from inside.
It should extend slightly beyond the exterior wall — about ½ inch — to let water drain outward.

Secure it to the framing with screws through the sleeve’s mounting flanges.
Check that it’s:

Level side-to-side
Tilted slightly downward toward the outside (¼ inch drop) for drainage

Seal around the sleeve with expanding foam or weather stripping. From outside, use silicone caulk to close gaps.

Then attach the grill or rear cover on the outdoor side.

7. Slide in the AC Unit

Once the sleeve’s ready and sealed, it’s time for the easy part: sliding in your AC.

Remove any packing materials.
Check your electrical cord length (you’ll need a dedicated outlet nearby).
Carefully insert the unit straight into the sleeve.
Secure it with the manufacturer’s screws or side brackets.

Plug it in and test the controls. You should feel steady airflow right away.

8. Electrical & Power Requirements

Most through-the-wall air conditioners come in two voltage types:

Voltage	Use Case	Example Size
115V	Standard outlets	6,000–10,000 BTUs
208/230V	Dedicated circuit	10,000–18,000 BTUs or heat models

Always check your breaker panel before buying.

9. Weatherproofing & Sealing

Once installed, it’s time to lock out the elements.
Good sealing prevents leaks, drafts, and mold issues.

Jake’s checklist:

Apply silicone caulk around the sleeve perimeter (inside and out).
Use foam gasket strips around the unit’s edges.
Check the drain hole at the bottom of the sleeve is clear and angled outward.
Touch up paint or trim for a finished look.

A proper seal not only keeps weather out — it improves efficiency by stopping air loss around the unit.

10. Final Safety and Function Checks

Before you call it done, test everything:

✅ Turn it on and check for vibration or rattling.
✅ Make sure the drain is clear (no backflow or dripping indoors).
✅ Verify cool air is steady and consistent.
✅ Confirm the circuit isn’t overloaded when the unit runs.

If you hear odd noises, recheck your sleeve alignment — even a slight tilt or loose bracket can cause vibration.

11. When to Call a Pro Instead

DIY is doable for many homeowners, but there are times when calling an HVAC or general contractor saves headaches:

Your wall is brick, stucco, or concrete.
You’re unsure about electrical connections.
You need multiple units installed (like for an apartment or rental).
You find hidden pipes or wires behind the drywall.

Professionals handle the messy stuff quickly — typically charging $300–$800 for installation, depending on wall type.

Jake’s advice: “If cutting through the wall makes your stomach drop, that’s your gut telling you to hire it out.”

12. Post-Install Care

Once installed, through-the-wall systems are low-maintenance.
Follow this simple routine:

Clean the air filter monthly during cooling season.
Vacuum coils twice a year.
Check seals around the sleeve every spring.
Inspect drain hole before heavy rain.

That little bit of maintenance adds years to your system’s life and keeps efficiency high.

13. Final Thoughts: Cut Smart, Cool Smarter

Installing a through-the-wall air conditioner isn’t hard — it just rewards precision.
Measure carefully, frame securely, seal tightly, and your system will look professional and perform beautifully for years.

Let’s recap: