A line set is a set of copper pipes that link the indoor and outdoor units of an air conditioner or heat pump. When connected, these copper pipes are part of the sealed system under pressure in an air conditioner and move refrigerant (Freon) throughout the system.
Most residential line sets these days are soft-drawn copper. They can be bent around some corners and formed by hand to go through attics and crawl spaces. An installer sometimes welds a fitting onto the pipe to make sharp bends or connections.
I always plan my installations to have no welded joint in attics or crawl spaces where it becomes almost impossible to locate a leak. One weld at each end of the pipe is ideal but not always possible. There are times when hard-drawn copper is used because it’s very straight and looks much neater in exposed areas.
Soft copper in rolls will tend not to roll out very straight. Hard-drawn copper is used more in industrial applications. That doesn’t mean it can’t be used in a residential application. It also requires more welded joins because the sticks are only 20 feet long. Rolls of soft copper come in lengths up to 50 feet.
Why Are Line Sets Insulated?
Line sets are insulated for the same reason you insulate your home. To hold the temperature created by the compressor and not have the pipe containing the refrigerant exposed to the ambient weather. Also, pipe insulation helps prevent condensation from dripping into unwanted places, which can cause mold and damage ceilings and walls.
If you are thinking about repairing some old insulation that the sun has beat to death, I prefer to use a product made by K-Flex (ad) that comes already slit with adhesive that allows for easy installation. Be sure you know the outside diameter of your pipe if you order any of this insulation.
Pipe insulation is rated by an R-value, like windows or wall insulation. Most of what I’m seeing available is with 1/2-inch walls. That should be very adequate for most climates.
Do I Need A Line Set Cover?
Line set covers are mainly used when a line set has to be installed over exterior siding. It helps clean up the detraction that an ugly line set can create when exposed. Most covers you will see are associated with mini-split installations.
You’ll notice that both lines are insulated in the mini split above. Full-house heat pumps and air conditioners only insulate the larger line of the two pipes. That’s an article for another day. It’s primarily to conserve energy.
Line set covers can be painted to blend in and be less conspicuous. These covers come in various widths and depths for larger line sets.
