When summer strikes with a vengeance, a portable air conditioner can be just the thing you need to make it through the hottest days. A portable unit can cool a single room without the expense of adding ductwork for a new central air system in older homes that don’t have A/C. Portable air conditioning is also a good way to boost the cooling power of an aging system or add a shot of cold air in rooms where a window unit isn’t practical.

Portable A/C is a bit more complicated than an evaporative cooler of the same size, however. In addition to being plugged into a power source, they should also be vented for optimal efficiency. The requires a bit of forethought about the installation to make sure you get the most out of your new appliances.

But first, it’s helpful to understand exactly how air conditioning works in the first place.

How Your Portable Air Conditioner Works: A Quick Guide

Though specific models vary, all air conditioning units — from an old window air conditioner to the bright white mini-split air conditioners that also function as heaters — function in the same basic way. They use a chemical refrigerant that can turn from a gas into a liquid and back again.

This chemical flows through the air conditioning system via a series of metal coils. When the chemical is in the evaporator and is in touch with the hot air in your house, it absorbs that heat. Your house gets cooler, but the chemical gets hotter — hot enough to make it transform from a liquid into a gas.

The hot gas then flows through the system to the condenser, where it’s pressurized and made even hotter. From there, it moves to the condenser, which squeezes the gas back down into a liquid chemical again. In doing so, it forces the refrigerant to release all the heat that it sucked up from your house back into the air. The cool liquid chemical is now ready to flow back to the evaporator to absorb more heat from your room.

Did you catch the part where heat is released back into the air in the condenser? In a window or wall air conditioner, this process happens outside the house. It’s why you’ll feel a blast of hot air if you ever walk by a bunch of condensers on a commercial building on a warm day. This is easy to visualize in a window unit: The evaporator is on the inside of the house, absorbing heat; the condenser is on the outside, releasing that heat into the atmosphere.

For a portable air conditioner to be effective, the warm air from the condenser needs to be removed from your room somehow. Otherwise, it’s just filling up your room and making your unit work harder. That’s why venting is the most important part of installing any portable air conditioner.

How to Vent Your Portable Room Air Conditioner

Most portable air conditioners come with an exhaust hose, but if yours did not — or if it is cracked or missing — you’ll need to purchase one at a hardware store. This is most easily done by purchasing a window kit that comes with a vent hose and several sizes and shapes of plastic flanges to attach the hose to a window opening. If you can’t find a dedicated venting kit, you can build your own with a piece of plywood, a dryer hose and some duct tape.Follow these steps to install your portable A/C through most windows and sliding doors:

1. Choose Your Location

The closer your unit is to a window, the easier it will be to vent. Scout your room for a spot on an exterior wall that is near a suitable electrical outlet and window. Measure the distances to make sure the cord will reach and that you have sufficient hose length to reach the window.

2. Measure Your Window

Any window or door that slides along a track will work well. This includes standard and double-hung sashes and many sliding doors. If you’re using a kit, you typically only need to measure the window’s width, because the piece of plastic that will sit in the window is already cut to height. Measure the window and cut the plastic to width. This piece will fit in your window snugly. Place it on top of the sill and close the sash over the plastic to hold it in place. There should be no gaps on the sides if you did a good job measuring.

If you aren’t using a kit, you’ll need to measure both the width of the window and the diameter of the exhaust hose. Add a few inches to the hose measurement and use this for the height of your crosspiece, which will be held in place the same way.

If you’re installing your exhaust system through a sliding door, installation works the same way, but you’ll place the hose on the side of the door instead of on the bottom of the window. Just imagine your door is a big, sideways window, and you’ll be able to follow window directions with similar results.

3. Attach the Hose

Follow the directions on your air conditioning unit to attach one end of the exhaust hose to the machine. This is typically at the back near the bottom. You may need to use duct tape to secure it, or there could be special screws or adjustable nuts to hold it in position.

Next, attach the other end of the hose to the plastic window adaptor If you’re using a kit, this piece looks like a vacuum cleaner attachment. One end is large and round like the hose; the other is smaller and designed to clip to the plastic window piece you’ve already measured and cut. Use duct tape as required to attach this adaptor to the hose, then snap the adaptor to the window piece.

If you’ve made your own window piece out of wood, cut a circular hole the same size as the hose and thread the hose through the wood. You’ll need duct tape to secure it before you put the window piece in place and close the sash over the window opening.

Adapting Your Portable Air Conditioner for Special Circumstances

If you don’t have traditional windows or a sliding door for venting your unit, don’t despair. There are other ways to make sure that you can enjoy cool, crisp air flow all summer long.

Use Your Casement Windows

Windows that swing outward with a crank handle can still be used for venting an air conditioner, but you’ll need to install a temporary Plexiglass shield. Have one cut to the size of your window opening, and ask for a hole the size of the hose while you’re at it. Open the casement window for air and cover the inside of the opening with your clear shield. Retainer clips can help hold it in place, and weatherstripping is a good idea to create a seal to keep out water and air leaks. Once this is in place, attach the hose and seal any gaps between it and the Plexiglas.

Use Your Chimney

If you have a corner fireplace, hearth or wall mounted fireplace that has a chimney or other vent to the outside, you may be able to use this existing escape hatch to vent your portable air conditioner. You’ll need to run the hose as far into the chimney as you can.

Use the Ceiling

Offices with a drop ceiling offer easy access to existing ductwork that could offer a great way to vent hot air away from your portable air conditioner. Likewise, you may be able to vent your unit into an unused attic space if you don’t have any other options in your home.

Use the Wall

If you’re thinking about a more permanent installation and don’t live in an area with very cold winters, you might consider cutting a small hole in an inconspicuous corner of an exterior wall. A contractor can frame small wooden opening that will hold a hose. This will ultimately work like the wood piece that is temporarily placed in the window but will be a permanent feature of your building. This isn’t usually a great option for a formal living room, but a wall vent could be just the thing for a windowless garage or outdoor workshop where looks aren’t as important as comfort.

Portable air conditioners are an affordable alternative to central air conditioning, especially when you only need it for a short time each summer or want to focus on cooling a particular room of your house. A window kit makes it easy to install this cooling unit in the vast majority of homes, but even houses with unique windows and layouts can enjoy cool air with a little ingenuity and a trip to the hardware store. Once your A/C is vented, you’re ready to turn it on and enjoy cool, refreshing air wherever you need it most.


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