About those air conditioners that mount in the wall, through a sleeve that’s the size of a small window: when they wear out, and need replacing, do you have to find the exact same model to fit the same sleeve? Or do you have to replace the sleeve? Does it take a carpenter to replace them every few years?
Or are there standard sleeves that fit multiple brands and models?
Unless the sleeve cut into the wall is too small for the new AC, it should work. Any excess open space around the edges could be filled in easily with foam insulation & duct tape.
I’ve got expandable edges to fit the space, but that was to fit a window (which used to be a standard mounting method) Same for the bigger wall-mounts. The smaller ones I’ve got in walls, the hole has been cut to fit exactly. But yes, the small one were more or less standard size. Because the wall studs are at standard spacing,
Apparently they’re a fairly standard size, and some manufacturers like Friedrich make units that fit other manufacturer’s sleeves. However, because they’re relatively less common and usually higher capacity (sometimes requiring 240 volts) than typical window a/c units, they can be quite expensive. You can’t really use a window a/c unit without getting creative with sheet metal and other unorthodox modifications because wall units are designed to intake and exhaust air out the back (when viewed from inside) only, whereas window units usually intake air from the sides and sometimes the top. There’s supposedly some units out there that can be converted between window and wall installations, but I haven’t really looked into the particulars.
Depending on how the exterior walls are made–thickness, basically–it’s possible to put a window unit through a wall. Optimal, no, but it can be done. I lived in a place where the prior tenants had done this in one room because there was no central AC and the windows were not double-hung. When that unit died we could have put in a proper wall-through AC unit but it was cheaper to kludge in a new window unit through the existing hole.
Funnily enough my daughter (whose room it was) hated AC and we rarely used it.
By the way, the trade name for those types of air conditioners is PTAC, for packaged terminal air conditioner. Nice to know if you need to search for them.
PTACs are different, or at least they’re a very specific variant. They’re usually much larger and mounted near or on the floor (you see them in hotels mostly, or New York City apartments/condos). Inside they look like enclosed radiator cabinets or very large a/c units. They’re almost always heat pumps with electric resistance heaters, or they’re hooked up to the building’s hot water heating loop if it has one. A through-wall a/c is maybe half the size and simpler in design and function. The one main advantage to a PTAC is that their larger size allows for bigger fans and more sound insulation, so they can run quieter.
I bought a floor mounted unit for my son’s room. It has a flexible duct that attached to an adjustable window insert. It works really well.
I’ve used these several times for computer and data rooms and they usually do the job very nicely. The only problem is that you have to consider the condensate (water) pan that most of them have. On one of my units, we had to drain the pan at least once a day, but most of them have a small pump and you simply route the drain tube to a convenient point.
They also seem a bit noisier than the in-wall units.
Those portable units are a whole other ball of wax. There was a big discussion at Portable air conditioner - one hose or two? - Factual Questions - Straight Dope Message Board regarding one hose versus two hose units, and how they should work versus how they’re actually constructed, and all the bizarre operational issues they can have. That said, I don’t recall any discussion about draining condensate. All the ones I’m familiar with sling the condensate across the condenser coil via the fan to help cooling efficiency and to evaporate the condensate and blow it outside with the hot air. It does create some splashing noise along with everything else, but it eliminates the need for a drain pan or hose.