Installation Guides — DIY Mini Splits

Step 1

Sizing Your Mini Split

Getting the right BTU capacity is the most important decision. Too small and it'll run constantly without keeping up. Too large and it'll short-cycle, wasting energy and causing humidity problems.

The general rule of thumb is 20 BTU per square foot, but factors like ceiling height, insulation quality, sun exposure, and climate zone can push that number up or down.

BTU Sizing Chart

Room Size	BTU Needed	Unit Size
150–300 sq ft	6,000–9,000	9k BTU
300–550 sq ft	9,000–12,000	12k BTU
550–800 sq ft	12,000–18,000	18k BTU
800–1,100 sq ft	18,000–24,000	24k BTU
1,100–1,500 sq ft	24,000–36,000	36k BTU

Step 2

Tools & Preparation

Here's everything you'll need to have ready before install day.

For Pre-Charged Systems (Zone Air, MrCool DIY)

Drill with hole saw bit (3" for line set)

Level (torpedo or laser)

Stud finder

Adjustable wrenches (2)

Screwdriver set & socket set

Electrical wire (per manual specs)

Additional for Traditional Systems

Flaring tool kit

Vacuum pump (can rent from hardware store)

Manifold gauge set

Tube cutter & deburring tool

Torque wrenches (specific to flare fittings)

Nitrogen for pressure testing (recommended)

Step 3

Installation Walkthrough

A high-level overview of the install process. Always follow your specific unit's manual.

Mount the Indoor Unit Bracket

Use a stud finder to locate wall studs. Mount the bracket level, at least 6 inches from the ceiling and away from direct sunlight or heat sources. Mark and drill the 3" hole for the line set, angled slightly downward to the outside.

Install the Outdoor Condenser

Place the outdoor unit on a concrete pad or wall-mount bracket. Ensure at least 12" clearance on all sides for airflow. Keep it level and secure. Position it as close to the indoor unit as practical to minimize line set length.

Run the Line Set

Feed the refrigerant lines, drain hose, and communication wire through the wall hole from inside to outside. For pre-charged systems, be careful not to kink the lines. Insulate any exposed line set and seal the wall penetration.

Make the Connections

Connect the refrigerant lines to both indoor and outdoor units using the provided fittings. For pre-charged systems, simply tighten the quick-connects. For traditional systems, make flare connections and vacuum down the line set.

Wire the Electrical

Run the dedicated circuit from your breaker panel to the disconnect box near the outdoor unit. Connect the communication wire between indoor and outdoor units. Follow all local electrical codes — consider hiring an electrician for this step if needed.

Test & Commission

Power on the system and let it sit for a few minutes before starting. Run it in cooling mode first to verify airflow and temperature drop. Check all connections for leaks. Set up Wi-Fi if available, and enjoy your new climate control.

Common Questions

Frequently Asked Questions

Not for pre-charged systems like Zone Air or the MrCool DIY series — these are the only two brands currently offering true pre-charged DIY systems. Since the refrigerant is sealed in the line set and you never open the system to the atmosphere, no EPA 608 certification is required. For traditional systems (Pioneer, Senville, DELLA, Cooper & Hunter) where you vacuum and charge the system yourself, technically yes — though enforcement on homeowner installs is a gray area. Pre-charged systems sidestep this entirely.

Absolutely. All modern mini splits are heat pumps that both cool and heat. Standard units work well down to about 5°F. Cold-climate models (like Cooper & Hunter's Sophia series) can heat effectively down to -22°F. In moderate climates, a mini split can be your primary heat source. In extreme cold, it works great as a supplement to your existing system, offsetting a significant portion of your heating bill.

A single-zone DIY mini split typically costs $1,500–$3,200 for the unit itself (depending on brand and BTU). Add $100–$300 for installation materials (electrical wire, disconnect box, wall sleeve, etc.). If you need to rent a vacuum pump and buy a flaring tool for a traditional system, add another $100–$200. All in, most single-zone DIY installs land between $1,600–$3,500 — compared to $3,000–$7,000+ for a professional installation.

Start with single-zone if you're conditioning one room or area (garage, bedroom addition, etc.). Multi-zone systems use one outdoor unit to power 2–5 indoor units, which is more efficient and cost-effective than multiple single-zone systems for whole-home coverage. However, multi-zone installs are significantly more complex and may not be the best first DIY project. We recommend starting with a single-zone to build confidence.

Yes. Mini splits require a dedicated circuit from your breaker panel. Most single-zone systems (9k–18k BTU) need a 20-amp, 240V circuit. Larger units (24k–36k BTU) may need a 30-amp circuit. You'll also need a disconnect box mounted near the outdoor unit per code. If you're not comfortable with electrical work, this is the one step where hiring a licensed electrician is money well spent.

Mini split maintenance is simple: clean or replace the indoor unit filters every 2–4 weeks (most just pop out and rinse under water). Deep clean the indoor unit's evaporator coils and blower wheel 1–2 times per year with a no-rinse coil cleaner. Keep the outdoor unit clear of debris, leaves, and snow. Check the drain line periodically to make sure it's not clogged. That's it — no ductwork to clean, no furnace filters to swap.

Everything You Need to Know