Official MRCOOL DIY Installation Resources
Please refer to the resources below on how to install a mini split yourself.
STEP 01
Mounting Plate (Indoor) 
Mount the interior bracket to studs. It must be perfectly level to prevent water leaks.
⚠️ PRO TIP FROM THE MANUAL: Always use a level! If the indoor air handler's wall bracket is not perfectly level, the condensation drain pan won't work properly, and water will leak down your inside drywall.
STEP 02
The Wall Sleeve 
Drill your hole at a downward angle. Use the sleeve to protect lines and improve soundproofing.
⚠️ PRO TIP FROM THE MANUAL: Drill your 3.5-inch wall hole at a slight downward angle (about 5 degrees) toward the outside. This ensures gravity pulls the condensation water outside, rather than draining back into your house.
STEP 03
Outdoor Placement
Set the outdoor unit on a level pad. Ensure adequate clearance for airflow on all sides.
⚠️ PRO TIP FROM THE MANUAL: Keep the condenser elevated on a pad or wall bracket to avoid standing water or yard debris. Ensure you have at least 12 inches of clearance in the back and 24 inches in the front so the compressor doesn't overheat.
STEP 04
Line Set Connection 
Connect Quick-Connect® lines. Start by hand, then use a torque wrench to specifications.
⚠️ PRO TIP FROM THE MANUAL: Unroll the line set carefully and flat on the ground. DO NOT unspool it vertically like a garden hose, or you risk kinking the copper lines. Leave protective caps on until the exact second you connect them. Always use TWO open-ended wrenches to tighten connections.
STEP 05
Drain Pipe Routing 
The drain pipe must remain at the bottom of the bundle with a steady downward slope.
⚠️ PRO TIP FROM THE MANUAL: Avoid any "U" shapes or dips in the drain line to prevent water backups into the indoor air handler.
STEP 06
Leak Check & Release 
Perform a soap-bubble test. If secure, use the hex key to release the pre-charged refrigerant.
⚠️ PRO TIP FROM THE MANUAL: When opening the King Valves with your hex wrench to release the refrigerant, turn them counter-clockwise until they completely stop. Do not force them past the stopping point, and ensure both top and bottom valves are fully open before powering on.
STEP 07
Communication Cable
Connect the signal cable between units. Ensure the color-coded wires match exactly at both ends.
⚠️ PRO TIP FROM THE MANUAL: Tighten wire terminals firmly. Loose communication wires are the #1 cause of the dreaded "E1" error code on the indoor display.
STEP 08
Electrical Finish
Final high-voltage power connection must be completed by a licensed electrician.
⚠️ PRO TIP FROM THE MANUAL: Installing a dedicated HVAC surge protector at your outdoor disconnect box is highly recommended to protect your unit's sensitive inverter board. Always coordinate with your licensed electrician to install this during the final power connection.
