Mini-Split Installation: What Drives the Job

What a mini-split or ductless heat pump installation involves

ENERGY STAR describes the indoor unit, called a head unit, as mounted on an interior wall or ceiling, with an accompanying unit outside. The refrigerant pipes between them are called a line set. GE's manual has the installer bundle the refrigerant piping, the drain piping and the wiring, then route the bundle through one hole in the wall.

In the manuals read for this page, the installer chooses the indoor and outdoor locations, mounts a plate on the wall, drills the hole and hangs the indoor unit. The outdoor unit is set next. Then the pipes and wiring are connected, the pipes are pressure-tested with dry nitrogen, the system is pulled into a vacuum, and the factory refrigerant is released into the lines. A final check ends the job, and it includes whether the condensate drains.

In our reading, the parts that matter most are the ones nobody sees after the crew leaves: the leak test, the vacuum and the charge. What a correct AC installation involves covers those readings and what to ask for, so this page does not repeat them.

Single-zone or multi-zone: how many indoor units

A zone is one indoor unit and the area it serves. A single-zone system has one indoor unit. A multi-zone system connects several indoor units to one outdoor unit, and each indoor unit has its own line set. In our reading, each added indoor unit means another wall hole, drain route and pipe run.

GE's multi-zone manual shows how the limits stack up. For each model its table gives the pipe length the factory charge covers and a rule for adding refrigerant beyond it. The table also gives a maximum length for each branch, which in our reading is the run to one indoor unit, a maximum for the whole system and a minimum length. For most models the minimum is 6 feet per indoor unit and 20 feet per system. In our reading, a third room is therefore not a small add-on, because it changes the pipe plan and the charge.

Sizing is part of the same decision. ENERGY STAR says your contractor should verify the proper size using a calculation called Manual J, which estimates how much heating and cooling a home needs. It also says a system that is too large or too small for its space will struggle to meet comfort needs. For why sizing matters even more in humid Florida, see what size AC you need.

Pipe length and height: the limits a manual sets

A manual sets a maximum pipe length, and some also set a maximum height difference between the indoor and outdoor units. The numbers differ by manufacturer and model, so a general rule cannot replace the manual. Daikin's manual for its R32 split series lists a maximum pipe length of 65-5/8 feet for some models and 98-1/2 feet for others. It also lists a separate maximum height difference and a suggested minimum of 10 feet, to avoid noise and vibration from the outdoor unit.

The refrigerant charge follows the pipe run. The outdoor unit comes with refrigerant for a standard pipe length, and the installer adds more by weight for a longer run. GE's single-zone manual treats 25 feet as the standard length. When the run is a different length, it says to adjust the charge by adding 0.2 ounce per foot of 1/4-inch liquid line, the thinner of the two copper pipes. Daikin adds 0.18 ounce per foot beyond 32-13/16 feet (10 meters) and warns that failing to add the proper amount may result in reduced performance.

Both manuals have the installer record the charge on a label, with one box for the factory charge, one for the refrigerant added in the field and one for the total. Ask to see it filled in.

For R-32 equipment the pipe run has a second effect. EPA lists R-32 as acceptable with use conditions and describes it as a refrigerant with lower flammability. Daikin's R-32 instructions say a minimum floor area of the room may be required. The area is worked out from the total charge, which is the factory charge plus any refrigerant added in the field. In our reading, a long pipe run adds charge and so can raise the minimum room size. Check the manual for the model, and see R-454B vs R-32 for the two refrigerants.

The indoor unit and the wall hole

The indoor unit needs a wall that can carry its weight, clear space around it and a route for the drain. GE's manual has the installer find the wall studs, leave more than 4 inches at each side, keep at least 4 inches below the ceiling and avoid a spot near a doorway.

The pipes, drain hose and wiring leave through one hole. In GE's manual it is cut with a 2 1/4-inch hole saw and tilted so the outside end is at least 1/4 inch lower than the inside end, which lets condensate drain.

In our reading, an indoor unit on an exterior wall near the outdoor unit makes a short, simple run. By the same reading, an interior wall or a second floor means a longer pipe run and more wall work.

Where the condensate goes

In both manuals read for this page, the condensate leaves the building by gravity. GE's multi-zone manual says the condensate pipe must slope down at least 1/4 inch for every foot. Its single-zone manual says the line needs a constant downward pitch, with no kinks or rises that could trap water. Daikin says the drain hose should incline downward, that no trap is permitted and that the end of the hose must not sit in water.

A heat pump's outdoor unit sheds water too. GE says to keep moisture-sensitive items out of its drain path, and Daikin says the water draining from the bottom of the unit should cause no trouble. In our reading, if the water cannot run downhill to a safe end point, the indoor location or the drain plan has to change.

The electrical supply

A mini-split needs its own electrical supply. GE's multi-zone manual says power should come from a dedicated circuit that meets branch circuit ampacity requirements. A branch circuit is the wiring from the panel to the unit, and ampacity is the current it can carry safely. Daikin says to use a dedicated power supply circuit only, never one shared with another appliance, and to protect it with a circuit breaker that follows local and national codes. GE's single-zone manual says the right fuse or breaker size is printed on the unit's nameplate.

GE says all electrical work must be done by a qualified electrician and meet local and national building codes. In our reading, the electrical panel must have room and capacity for the new circuit, so an older or full panel can add electrical work to the job. Ask who will do that work and who will pull the permit. HVAC permits in Florida explains what a permit and inspection cover.

The outdoor unit (condenser): mounting, salt air, wind and flood zones

The outdoor unit sits on a level pad or on wall brackets. GE's manual says to bolt it to a mounting pad or brackets, and to follow local code when mounting it on a wall or roof or in an area with strong winds. It also asks for clear air space and a spot where noise and hot air will not bother neighbors. Daikin adds that the unit should not be directly exposed to rain, strong winds or direct sunlight, or to salt, which may shorten the unit's life.

Salt air is a Tampa Bay factor. GE's single-zone manual says the outdoor unit should be at least half a mile from salt water, including seacoasts and inland waterways. For a site between half a mile and five miles away, it says to protect the unit from sea breeze, for example by placing it near buildings. In our reading, an address near Tampa Bay, the Gulf of Mexico or a tidal canal may fall inside that range. How the coil itself resists corrosion is covered in coastal coil protection.

Flood zones add another rule. In a flood hazard area, section R322.1.6 of the 2023 Florida Building Code, Residential, says heating, ventilating and air conditioning equipment shall be located at or above the elevation the code requires. It also says equipment shall not be mounted on or pass through walls built to break away in a flood. The same section has an exception for equipment designed and installed to keep floodwater out of its parts. Whether the rule or the exception applies to your job is a question for the local building department. In our reading, the answer can decide between a ground pad, a raised stand and a wall bracket.

Who may do which part

Federal rules cover refrigerant handling. EPA's Section 608 rules require technicians who maintain, service, repair or dispose of equipment that could release refrigerant to be certified. GE's single-zone manual goes further for its own units: it says a licensed certified technician and a qualified electrician are required for installation and service. Daikin tells the owner to ask a dealer or qualified person to do the installation and not to attempt it.

In Florida, the Department of Business and Professional Regulation (DBPR) says each construction business must be qualified by a properly licensed individual contractor. DBPR also explains how to check a license with the license number, the contractor's name or the business name.

This page gives no steps for refrigerant or electrical work, and it has not read the instructions of any owner-install kit. EPA 608 certification and the refrigerant rules explains what the federal rules cover.

What drives mini split installation cost: a written checklist

A dollar figure for a mini-split installation would depend on the items in this guide, which is why this page gives none. Ask each bidder to put the following in writing, then compare the bids item by item.

1. How many indoor units, which room each one serves, and how the system was sized (Manual J or another method).
2. The pipe length for each indoor unit, the height difference, the model's maximum for both, and the refrigerant added for the run, shown on the filled-in charge label.
3. Where each drain ends and how it falls.
4. The electrical work: the new circuit, the breaker size from the nameplate, who does it and who pulls the permit.
5. How the outdoor unit is mounted, how far the address is from salt water, and whether the lot is in a flood hazard area.
6. The vacuum (evacuation) and charge readings described in what a correct AC installation involves.
7. The model and serial numbers, the installation manual followed, the permit number and the inspection result.
8. What is not included, such as patching and finishing the wall.

In our reading, a longer pipe run, a new drain route, a panel that needs work or a flood-zone mounting each adds scope, so two bids for the same rooms can differ. Manuals for other brands may differ, and the page reports no measurement from a Blume job.