This post should describe the differences between the two types of thru-the-wall room air conditioning units.
The first type of wall unit is necessary when there is not yet an air conditioner installed. A wall unit that has a slide-out chassis should be installed. These units should already come with their own sleeve for easy installation. To install, the chassis (guts) should be slid-out of its sleeve, a hole should be cut approximately 1/4″ larger than the size of the unit’s sleeve in to the wall. The sleeve should be screwed into a stud in the wall, then the guts should be slid into the sleeve. This type of wall unit uses a sleeve for installation because if something goes wrong in the future, it can easily be removed from its sleeve for repair or maintenance.
The second type of thru-the-wall air conditioner sold (more of a specialty item) comes into play if there is already an air conditioner installed in the wall (like the first type of unit discussed above) that needs to be replaced. Although a little more expensive than the first type of wall unit on average, these air conditioners are much less expensive to install because a new hole does not need to be cut or an existing hole does not need to be altered. Most relacement thru-the-wall air conditioners are smaller than 26″ wide and 16″ tall, since the old “standard” wall unit was about that size. These thru-the-wall units are solid-sided and rear-vented so that they can slide into any existing sleeve without any trouble breathing which may result in a unit overheating. Also, since these units are typically smaller than an existing wall air conditioner (often sized 24″ wide and 14 1/2″ tall), they come with a trim-kit that slides over the front of the air conditioner to fill most gaps between the unit and the existing sleeve.
Often times, the question comes up as to why the first type of wall air conditioner can’t be installed in to an existing sleeve. Well, as discussed, these units have side-vents that allow the unit to breath, and more often than not, the side-vents in the unit will not match the side-vents in the existing sleeve and can cause the unit to overheat and damage its compressor, thereby rendering the unit inoperable, often times without any waranty coverage due to the fact that the unit being installed improperly.
Another distinguishing factor between these two types of air conditioners is that the first type of unit can usually also be installed in a double-hung window and often times comes with a side accordian sleeve (which can be removed for a wall installation).
Purchase from Feder’s Distributors (Nationwide shipping)