In this video, This Old House plumbing and heating expert Richard Trethewey explains how the pros retrofit a compact cooling unit.
How to Install a Mini-Split Air Conditioner
- Turn off the electricity to the circuit.
- Hold mounting bracket to the wall, level it, then mark the screw hole locations and where to bore a hole for the refrigeration lines, condensate discharge line and electrical cable.
- From inside, bore hole into the block wall with rotary hammer and 3-inch-diameter masonry coring bit. Once the bit's pilot penetrates the wall, finish boring the hole from the outside.
- Screw the mounting bracket to the wall, making sure it's level.
- Install the air-conditioning unit to the wall-mounted bracket. Pass the refrigeration lines and condensate discharge line through the hole in the wall.
- Attach a vertical chase directly below the hole in the exterior wall; the chase will house the refrigeration lines, condensate discharge line and electrical cable.
- Extend the condensate discharge line down to within a few inches of the ground by attaching a length of PVC pipe. Secure the discharge line to the pipe with duct tape. Fasten the lower portion of the pipe to the chase by screwing on a metal C-clamp.
- Carefully bend the copper refrigeration lines down into the chase. Use two adjustable wrenches to remove the compression fittings from the ends of the copper lines.
- Slide a brass nut onto a new length of copper tubing, then use flaring tool to flare the end of the copper tubing.
- Hold the tubing's flared end against the end of the refrigeration line coming from the air conditioner. Hand-tighten the nut to hold the copper tubing to the refrigeration line. Repeat to attach the remaining refrigerant line.
- Set the outdoor condensing unit onto a level pad adjacent to the chase.
- Use two adjustable wrenches to tighten the compression fittings on the refrigerant lines. Then wrap pipe insulation around each line.
- Run weather-tight conduit from an outdoor electrical box to the condenser unit. Feed electrical wires through the conduit.
- Run a length of nonmetallic electrical cable from the condenser unit through the hole in the wall to the indoor air conditioning unit.
- Snap the cover onto the chase to conceal and protect the lines and cable.
- Make all electrical connections at condenser and at air conditioner, then pressure test the system with nitrogen to 300 pounds per square inch.
- Vacuum out the nitrogen, then open valves to release refrigerant into the system.
- Turn on the electricity and test the air conditioner.