Mitsubishi Electric helped pioneer the mini-split (or ductless) technology as a means of providing Japan’s growing population with a highly efficient way to cool and heat their homes and businesses. They designed the Mr. Slim system to fit into spaces that could not otherwise have been effectively heated or cooled due to the close proximity of Japan’s buildings, plus they needed a system that was extremely quiet. See more history below…

The term ductless means simply that no ductwork is involved. The system is comprised of two units: a slim-line outdoor condenser, and an indoor air handler. The condenser supplies coolant to the air handler through refrigerant lines that run through a small opening in the wall or ceiling and into the back of the unit. The air handler takes in supply air from the room through the front grill and dispenses the newly-cooled air back into the room. For certain models special filters are available that promote added humidity control and filtration.

Mr. Slim models are perfect for spaces where ductwork cannot fit or window a/c units are not practical. As a general rule, 1 ton of a/c (or 12,000 BTU/h) can satisfy about 400 square feet of space. For a better recommendation, please use our online BTU/h calculator.

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History of Mr. Slim in Japan

Air conditioning was a recently-added comfort for Japan. Americans introduced window and central air conditioning to Japan at the end of World War II in the forms of ducted systems and window units. These types were not suitable for Japan because of the limited interior spacing and close proximity of its buildings. And with the high density of population Japan required a more compact and noiseless air conditioning system. Additionally, energy costs were very high for the Japanese people, as much as five times higher than that of the United States.

Japan’s answer to these constraints, and consequently, their gift to the world was a split-type ductless system that was quiet, yet powerful, and space conscious as well. This form of air conditioning also provided a more energy efficient way to cool a home, room by room. Mitsubishi Electric’s factories began producing its own room air conditioners in 1954. Then in 1968, after much engineering and marketing research and development, Mitsubishi Electric introduced its wall mount split-type ductless design then known as “Kirigame”, or “Smoky Mountain”, now known as Mr. Slim®.