All About Portable Air Conditioners

How is a portable air conditioner different from central air or a window unit?

Air conditioners generally fall into four categories:

• Portable air conditioners use a unit that is not permanently attached or mounted, so it can be moved from room to room.
• Window air conditioners are installed into the window of a single room in order to cool the air in that room.
• Through-the-wall air conditioners that are mounted into a wall and cool a room by exchanging inside air with outside air.
• Central or commercial air conditioning units are designed to cool your entire house or a building.

Is a portable air conditioner different from an air cooler?

Yes. An air cooler (or swamp cooler) cools air by absorbing heat through pads that are continually soaked with water. Air conditioners cool air by removing heat and sending it out of the room to some place else. Air coolers cool less effectively, affect a smaller area and add humidity to the room as the water evaporates.

Can a portable AC unit cool more than one room?

If the rooms are adjacent and there is good air flow between the two, perhaps. But they are basically designed to cool a single room.

What does a portable AC unit require?

Portable air conditioners generally require three things:

• the space for the unit;
• an electric outlet rated at 15 amps or higher (some larger units require 20 amps and a special type of plug);
• an external window or wall exhaust vent for the hot air exhaust;

A few units also have a "boost" setting that only produces its rated cooling output when you add water to an internal tank that is used to help make the unit produce cooler air.

Can I rent a portable air conditioner instead of buy?

Rental of residential portable air units is not available. However, for large temporary installations (such as an enclosed tent or other large space) some companies do offer "portable" air conditioner rentals.

Read about commercial A/C rental and see the list of commercial models here.

What's the vent hose?

The vent hose is essentially an exhaust hose through which hot air is removed from the room being cooled. The hose runs from the unit to some place where the warm air can be released, such as a window, another room or a drop ceiling. Keep this in mind when you’re shopping. The vent hose is typically about 5 feet long. A exhaust hose kit designed to allow you to vent the hose through a window comes with most portable air conditioners. Portable air conditioners have either a single hose or dual hose system.

Read more about vent kits here.

What's the difference between a single-hose unit and a dual hose unit?

• A single-hose system takes in the air from the room, cools it and puts it back into the room. A single-hose unit creates a slight negative pressure in the room it cools because it does not return all of the air it takes in from the room. A small amount is used to cool the unit and is expelled through the exhaust system. Unconditioned air from adjacent rooms is often drawn into the cooled room to compensate, and this creates a slight inefficiency in the system. A single-hose system usually cools a room down faster than a dual-hose system.
• A dual-hose system takes in air from the outside with one hose, cools it for the room, then expels the hot air out the other hose. Because a dual-hose system takes in air from the outside, it avoids the negative pressure problem. When the outside air is cooler than the room, the dual system can cool down a room faster. However, when the outside air is warmer and more humid than the air in the room, it is less efficient than a single-hose system. A dual hose system also usually has two fans, which means that energy usage is higher, but it may cool the room faster.
• (A mini-split air conditioner is less common than the other two but is sometimes considered portable. These units separate the compressor and condenser coil from the fan and evaporator coil. The compressor is located outside of the home and air handler is located inside the home. Some models come with multiple air handlers that use one compressor. Usually, each air handler cools one room. These units work more like a central air conditioner, but are less expensive. They generally require professional installation.)

Where do I place the vent hose?

Many portable conditioners come with kits that can help you secure the hose in a window or ceiling area. But the kit may not work for the type of window you have. Sliding glass doors may not work with some units, for example. And crank windows are not usually suitable for vent hoses. A window screen should not interfere with the exhaust hose, as most hoses don't run outside the window, so you can usually leave the screen in place.

Read the box or check with the seller to see if you can properly vent the unit in the way you want, or if you can buy accessories that will enable you to vent it properly.

It is also a good idea to insulate the hose with insulating material because it tends to get very hot, which lets heat back into the room and reduces the effectiveness of the air conditioner.

What if the hose isn’t long enough to reach the window or ceiling?

Make sure it is before you buy because it’s not a good idea to lengthen the hose. It could damage the unit and it could void your warranty. The vent hose is typically about 5 feet long.

Is a portable air conditioner also a dehumidifier?

Yes, because all portable AC units take water from the air. Manufacturers usually specify how many pints (or liters) the unit can remove from the air in a 24-hour period. The higher the amount, the more the unit can dehumidify and even cool the room, but it could mean that you'll need to empty the water collection tank or drain the unit more often, unless the unit does a good job of expelling it out the exhaust hose.

Where does the water go?

Good question, and another important factor to consider before you buy. There are units that:

• require you empty the unit by hand (usually less expensive units). These have either a removable water tank which must be emptied, or have an internal tank and a drain, where you have to empty the water into your own pan. Sometimes the drain is on the bottom of the unit, making it hard to find a pan that will fit under the unit to drain it.
• discharge most of the water through the exhaust hose (usually more expensive units). This is called "Auto-evaporation" or "Self-evaporating" feature.

Most units are made so that they can be drained with a gravity hose that flows to a drain inside or outside your house. But the water must drain down. If the drain is higher than the unit, you may need a condensation pump to move the water upward. A few units do include a pump to send the water a short distance through the drain pipe.

Can I use a portable AC unit to keep my servers cool in an enclosed room?

You can, but you must have some place for the exhaust hose to release the warm air. Because most rooms housing servers do not have windows, you will want to expel the air into the ceiling, another room, or outside the building. Make sure the unit you buy comes with a kit to do this, or that you can purchase a kit that will work with the unit you’re are purchasing. Also, because server rooms generate more heat than an average room in your home, you can't use the room size estimates the same way. You should buy a portable air conditioner rated for at least double the size room as you normally would.

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