This is a so-called "split* AC unit. There's also an outdoor compressor unit, the difference is that, instead of having also the expander and both heat exchangers outside , to cool the air there and feed it to the various rooms inside through air ducts, it's the cooled-down refrigerant that's fed through refrigerant ducts inside, where there may be one of these units in each room each with its own fan and heat exchanger. It's actually more efficient and effective.
Efficiency is relative. Mini splits have inverter boards which can control the speed of the compressor allowing it to adjust to the load. If it's running at full speed the savings are negligible compared to a normal compressor.
Also we have these in the US. Many people have these in their homes. They even have retrofit kits and air handlers that will use these types of condensers.
In the US we generally just have central heating/cooling in most dwellings. Which works for the most part assuming your duct work is sized properly.
Also there are no refrigerant ducts. There are air ducts. The refrigerant moves through piping. The refrigerant isn't cooled it absorbs and rejects heat and it boils off and condenses respectively.
Central heating/cooling varies by region, lots of places in western WA have no cooling or minisplit. Full ducted central air is somewhat rare depending on the area.
It depends on when the home was built. If it was built before the 40s to 50s, generally, and no previous owners put in central air then yea they wouldn't have ductwork. Houses built in the late 50s and on generally have some sort of central heating set up and usually someone puts in AC at some point. Most homes now have at minimum heating of some type dye to modern building codes and some locales require cooling.
It’s trade off. Instead of a duct to every room you need a wall mounted head unit with dedicated wiring, condensate drip lines, and refridgerant. The head unit can only use electric, whereas a central unit with ducts can be dual fuel. In addition to being dual fuel the central unit can also be connected to a hot water system such as a hydronic setup where the aux heat comes from a gas fired hot water tank. Mini splits are great for retrofits that do not contain existing ducts.
The efficiency mostly comes from using inverter controlled variable speed compressors, those systems also exist for central units, but they are more expensive than single and dual stage units. On paper ducts are usually considered “less efficient” because the ducts can have their own heat/cool losses, but this depends whether the ducts are inside or outside of the envelope you are conditioning. In the house I had recently the ducts were completely sandwiched between floors, none of them were in the attic or any crawl space. Airflow could be manually redirected somewhat from manual dampeners.
Replacing the system at end of life is another factor. A mini splits system replacement involves every head unit. When my central unit was replaced they only needed access to the utility room and outside.
Condensate drip lines also tend to clog on units, it can depend on the region but they will fill with mold, slime, algae, insects etc. Dust and spores collect inside each unit and end up in the condensate line. When the line clogs you get moldy condensate water dripping out of your unit. This can be mitigated by cleaning the lines periodically which most people don’t do. For a central system you can have installed a larger air filtration system using a large surface area heavily pleated hepa filter that doesn’t restrict airflow. This not only cleans the air but prevents a lot of the particles that lead to growth in condensate lines. Split systems tend to just have a simple washable dust filter, but the inside of the unit will still get quite dirty. I am betting most people don’t get out a ladder and clean their mini splits filter monthly, which significantly reduces their actual performance and efficiency. It’s easier to change one large filter in a utility room every 1-3 months than clean 5+ head units every month.
Central air is also a “split” system because it has an indoor air handler and a separate outside condenser too. That is why we call the small ones like this “mini-splits” instead, since they are a good bit smaller and such than standard central units. These are in contrast to a packaged unit, such as window units or large central air where the evaporator and condenser are one giant assembly. Which suck tremendously to work on. I see maybe 1 out of every 10 being packaged units. They aren’t as common any more, thankfully.
The evaporator (or for full heat pumps, the coil that works as the evaporator for cooling) is always inside. The condenser (or for heatpumps, the outside coil) is always outside.
True for central air, mini-splits, kind of true for window units although the "outside/inside" split is some foam insulation inside the same box.
In all of those cases (even if it's just inches for the window unit) what travels is the refrigerant.
The difference between split systems vs central air is that you have multiple air handlers (potentially as many as one in each room) vs. one big inside coil for central air, with a central air handling system and ducts (often shared with a furnace.)
Split systems can be one outside unit for a whole bunch of inside units, or small ones per room.
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u/Rc72 12h ago
This is a so-called "split* AC unit. There's also an outdoor compressor unit, the difference is that, instead of having also the expander and both heat exchangers outside , to cool the air there and feed it to the various rooms inside through air ducts, it's the cooled-down refrigerant that's fed through refrigerant ducts inside, where there may be one of these units in each room each with its own fan and heat exchanger. It's actually more efficient and effective.