Wall Placement of a Window Air Conditioner

What one sees of a window air conditioner from the outside is the sleeve, a metal box with ventilation louvers that houses the actual air conditioner. One sees a similar box for a wall air conditioner. Naturally, people assume they are the same. But they aren't, and this article will explain why.

The two types share some characteristics. Both span the dividing line from inside to outside, allowing all components to be housed in a single box. Therefore both utilize both inside and outside air to perform. Both are designed to condition a single room. But there are differences.

Windows are thin, and the sleeve for a window unit is designed to take advantage of this. It sits on the window sill, with the window closed onto the case to seal the top. Side panels fill the gaps on the sides. These are also very thin, so most of the sleeve is uncovered and outside. This allows for placement of ventilation louvers on the sides and top, allowing free movement of air.

This is the primary difference between the two types. The wide availability of louver space allows the unit to move a lot of air, and this means window units can be quite powerful, up to 3 tons, or 36,000 BTU! So window A/Cs can be effective for very large rooms.

In contrast, a wall air conditioner sleeve is designed for a hole through the wall. Walls vary substantially in thickness. A wall with simple sheet type siding may be only 6 inches thick, whereas a brick or stone wall can be much thicker. So wall air conditioner sleeves have ventilation louvers only in the back, to avoid louvers being covered by the wall edges. This limits the amount of ventilation space available, in turn limiting how powerful the unit can be. Wall air conditioners generally don't get much over 14,000 BTU, depending on the brand.

So are they interchangeable? This question usually arises when someone needs a lot of cooling power in a room without suitable windows for a window unit. The answer is, It depends on the wall thickness. Sleeve specifications for some window air conditioner manufacturers include the maximum wall thickness before it will cover part of the louvers.

For example, Amana's 18,000 BTU models have a max of 8.5 inches. If the wall thickness is at or below that, these models can be used in as a wall air conditioner without adversely affecting function.

So what's the problem if the wall covers a little of the louvers? Two things: 1) restriction of air movement and therefore reduced efficiency, and 2) these units pull air in very powerfully. Cut wall edges could become loose, allowing material to be sucked into the unit and potentially causing damage.

At least one manufacturer, Friedrich, has a line of models with sleeve options. For the same model, one can get a different sleeve designed for the intended use.