Portable air conditioning units aren't quite portable enough to carry around like a lunchbox, but they are on wheels and are small enough to easily push from room to room or office to office.
Today's portable air conditioning units generally have 1,800 to 18,000 Watts output, and some of them also have electric resistance heaters built in for winter.
There are two basic types of portable air conditioners: evaporative and refrigerative. Evaporative portable air conditioning units are also known as "swamp coolers," which is somewhat of a misnomer since they work best where relative humidity is low. These units have neither a compressor nor a condensor. Liquid water is evaporated on cooling fins, releasing vapor. The evaporating water absorbs latent heat of vaporization, cooling the air. It's similar to how sweating cools humans.
But unless the humidity is low, the amount of cooling a swamp cooler can accomplish is limited, and the air that is cooled will be extremely humid. The big advantages of these portable air conditioning units are that there's no need for hoses to vent outside the cooled area, they're inexpensive, and they use much less energy than other portable air conditioning units.
When it comes to refrigerative portable air conditioners, there are two sub-types: "split" units, and those with hoses. Both sub-types have compressors and use air to exchange heat just like any other household air conditioner. These systems dehumidify and cool the air. They collect water that condenses out from the cooled air, and they produce hot air that has to be vented somewhere outside the cooled air. The evaporation / cooling cycle of an air conditioner works as follows:
- Freon gas is compressed in the compressor unit, causing it to heat up and increase in pressure.
- The hot freon gas runs through a series of coils to dissipate the heat, and condenses into a liquid.
- The liquid Freon passes through an expansion valve. When this happens, it evaporates, becoming low-pressure, cold Freon gas.
- The cold Freon gas goes through another set of coils, allowing the gas to absorb heat, cooling down the room being air conditioned.
With hose type portable air conditioning units, there are a further two subtypes: monoblock, and air-to-air.
Monoblock portable air conditioning units collect the condensed water in a tray and automatically stops when the tray is full. Air-to-air units, on the other hand, re-evaporate the water, re-evaporate the condensed water, discharging it through a ducted hose. These can run continuously.
Though ductless split systems (often referred to as "mini-splits") are fairly new to North America, they can be used in many residential and even commercial applications. They are often chosen as retrofits for older houses or for use in houses or rooms where installing or extending ductwork is not practical. Commercially, mini-split portable air conditioning units are used in schools, and as supplemental cooling in restaurant kitchens and offices.
Like central air conditioners, mini-split portable air conditioning units have a compressor and an air handling unit that contains a fan and an evaporator. The compressor and condenser are housed together and go outdoors. The fan and evaporator unit stays indoors in the area that's to be cooled. Between the two runs a conduit containing refrigerant tubing, power cabling, suction tubing, and a condensate drain.
The main advantages of ductless mini-split portable air conditioning units is that they're easy to install, quiet, and usually don't run up against zoning difficulties. Installation requires a three-inch diameter hole in the wall for the conduit to run through, but no ductwork. The compressor unit can be placed in an inconspicuous area outdoors, or can be placed on a flat commercial rooftop if used for supplemental cooling in a commercial application. In residential settings, the energy efficiency ratings are now comparable to those of window unit air conditioners.
Compared to many other add-on or retrofit air conditioning systems, split systems tend to be more aesthetically pleasing, and the air handlers can be suspended, mounted, or floor-standing. Many come with remote controls, which is handy if you mount your air handling unit high on a wall or suspend it from the ceiling.
Air conditioning options, fortunately, have multiplied in recent times, and portable air conditioning units are more practical than ever, eliminating the need for a window unit (which can be an easy point of access to burglars), and providing cooling where zoning or the age of a building won't allow the installation of the ductwork for a central system. Many of today's portable air conditioning units are far more aesthetically pleasing than window units and also come with nice touches like remote control devices.