MRCOOL DIY Mini Split Installation: Step-by-Step Overview
MRCOOL DIY mini splits are specifically designed for homeowner installation, and thousands of homeowners successfully install them every month using basic tools. The pre-charged, quick-connect refrigerant line set is the feature that makes DIY installation possible. No vacuum pump, no manifold gauges, no brazing torch, and no EPA 608 refrigerant handling certification required. Here is the installation process from start to finish.
Tools and Skills Needed
You need a drill with a 3-inch hole saw for the wall penetration, a level, a stud finder, a socket set or wrenches for mounting hardware, a tape measure, and basic comfort working with hand tools. You do NOT need HVAC-specific tools, refrigerant handling certification, or brazing equipment. The one professional requirement is the dedicated 240V electrical circuit, which must be installed by a licensed electrician.
Step 1: Choose the Location
The indoor air handler mounts high on an interior wall, typically 6 to 12 inches below the ceiling. Choose a wall with direct exterior access (for the refrigerant line pass-through) and a location that allows unobstructed airflow across the room. Avoid mounting above a TV or directly above a bed where the airflow may be uncomfortable. The outdoor condenser sits on a level surface (concrete pad, composite pad, or wall brackets) outside the same wall, with adequate clearance for airflow (typically 24 inches on all sides).
Step 2: Mount the Indoor Unit Bracket
Use the included mounting plate template to mark and drill holes. Secure the mounting plate to the wall studs. Level is critical here because the indoor unit contains a condensate drain pan that relies on gravity to route water to the drain line. An unlevel installation causes water to pool and potentially leak.
Step 3: Drill the Wall Penetration
Using the 3-inch hole saw, drill through the interior wall, insulation, and exterior siding at a slight downward angle toward the outside. This angle ensures condensate drains outward rather than pooling inside the wall. A hole cover plate (included) seals and weatherproofs the penetration after the line set is routed.
Step 4: Route the Line Set
Feed the pre-charged refrigerant line set, control wire, and condensate drain line through the wall penetration. Connect the line set to the indoor unit using the quick-connect fittings. Route the line set along the exterior wall (using included clamps) to the outdoor condenser. Connect the line set to the outdoor condenser fittings. The quick-connect system is designed to seal properly when tightened by hand with a wrench. No brazing, no flaring, no vacuum required.
Step 5: Set Up the Outdoor Condenser
Place the outdoor condenser on its pad or bracket mount. Ensure it is level and has adequate clearance on all sides. Connect the line set fittings to the condenser service valves. Open the refrigerant valves (using the included valve key). The pre-charged refrigerant fills the system automatically.
Step 6: Electrical Connection (Licensed Electrician Required)
A licensed electrician installs a dedicated 240V circuit from your electrical panel to the outdoor condenser disconnect box. The specific circuit requirements depend on the model. A 12,000 BTU unit typically needs a 20-amp circuit with 12 AWG wire. An 18,000 BTU unit needs a 20-amp circuit. A 24,000 BTU unit needs a 25 to 30-amp circuit with 10 AWG wire. A 36,000 BTU unit needs a 30-amp circuit with 10 AWG wire. IB Lighting stocks all the wire gauges needed at our electrical wire collection.
Step 7: Test and Commission
Power on the system, set to cooling mode, and verify cold air output from the indoor unit within 2 to 5 minutes. Check for any refrigerant leaks at the quick-connect fittings (use soapy water to check for bubbles). Set up the WiFi connection if your model includes it. Program your preferred temperature settings.
Total Installation Time
Most homeowners complete a MRCOOL DIY mini split installation in 4 to 8 hours for a single-zone system. The electrical circuit work adds 2 to 4 hours of electrician time scheduled separately. Multi-zone systems (one outdoor unit with 2 to 4 indoor air handlers) take proportionally longer due to additional line set routing and indoor unit mounting.
Browse MRCOOL DIY systems at IB Lighting or call (800) 674-9019 for sizing recommendations. All MRCOOL systems ship free with freight insurance included.