How DIY systems differ
A standard mini-split arrives with empty refrigerant lines. An HVAC technician connects them, pulls a vacuum and releases refrigerant, which requires EPA certification. DIY systems, led by MRCOOL’s DIY line, ship the refrigerant sealed in pre-charged line sets with quick-connect fittings. The current 5th generation uses R-454B.
What a homeowner typically does
- Mount the indoor unit’s wall bracket and drill the 3-inch hole through the wall.
- Set the outdoor unit on a pad or wall bracket.
- Run and connect the pre-charged line set and the drain line.
What needs a licensed electrician
- A dedicated circuit for the outdoor unit, often 240 V for larger sizes, and the outdoor disconnect switch.
- Any panel work.
Many towns require a permit for both the electrical and mechanical work. Some manufacturers’ warranties also require professional electrical installation; read the warranty before you start.
Sizing
Mini-splits are sized in BTU: 9,000 to 12,000 BTU covers a typical bedroom or living room. Multi-zone outdoor units serve two to five indoor heads. For a whole-house system, pay for a Manual J load calculation instead of guessing.