Thanks! "how to wire things like this" what do you mean? Doesn't it come with a usual cable and plug? "how to route things through walls" - isn't it just mounted with screws, without a back part like the common AC

What you show is called a mini split. It's like a window unit that is split into 2 halves. The part that would be hanging out the window is not in the same box but is mounted separately outside. It is still connected to the thing in your picture by hydraulic and electrical lines. These are run outside through a wall. The electric is not plugged into an outlet, it is hard-wired back to the breaker box.

@OverLordGoldDragon They come with two parts. One side that does most of the work and the small section inside(shown in your picture).

@OverLordGoldDragon there are also both electrical and mechanical building codes that govern installation of this sort of hardware in most locations. Installation of these is work that needs to follow many rules and be inspected by local building authorities.

So, one last optional thing - do all such ACs need to be piped through a wall? A big detail noone's quite explicitly mentioned...

The condenser needs to be outside, and the evaporator needs to be inside. I suppose you could run the pipes and wires through an open window, but I think you can see why that's not a good idea. The pipes connecting the two parts are quite literally what moves the heat from inside your house to outside your house, so they need to go through a wall somewhere.

@OverLordGoldDragon, All AC systems have a hot side that needs to be outside and a cold side that goes inside. In a mini-split like you show, these are separate units that need to be connected via piping. Window and in-wall units exist as an alternative. These would either be installed in a window or in a hole in the wall. The simplest DIY A/C option would probably be a window unit.

@kicken Everyone here says it, but it's simply not true - there's fully portable ACs that require water replacements, hence all my uncertainty about this AC - example. I guess this technology doesn't scale up cost-effectively though. I guess I could just force this through a net in the window... (an open window that I'd have to insulate somehow)

@OverLordGoldDragon, your water example is bad marketing. It is not an air conditioner, it's an evaporative cooler (also known as swamp cooler). Those work by having water evaporate to absorb some heat energy. These essentially turn the heat into humidity. As such, they will only work in a dry climate, and will slowly increase your humidity levels indoors.

@aquaticapetheory - at least in europe, mini-splits are commonly plugged into a wall socket like any other device. Is this an American things where you need to route it straight to breaker box because of shitty 110 volt lines?

@kicken With minimal thought, this checks out. Hmm weird, I'd think we've figured out some matter-energy conversion physics to not demand a primitive "heat-in-heat-out" exchange. Or at least energy(electricity)-energy - there's no issue portably generating heat, only ridding of it. I mean that water thing does work, but unpleasant caveat (and limited by room humidity which it drives up - then why not pipe the vapor to go elsewhere... but I digress).

re #2: you not only need expertise to install it, but highly specialised equipment as well as you have to clean the coolant tubes, fill the system with the coolant, and seal the tubes airtight.

@OverLordGoldDragon We currently think that simply removing heat, without moving it to somewhere else, violates the laws of thermodynamics.

@Davor Perhaps in your part of Europe (where?) it's like that, but I have seen lots and lots of hardwired split airco units in the Netherlands and Czechia, for example.

@Davor I don't follow why you would want to plug in something that's fixed permanently in place into a temporary connection like an outlet other than not having to run a line but then you could just wire it into the circuit that the outlet is on. I don't know for sure why the regulations are what they are but I would guess for safety reasons like not wanting a high amperage connection to go through a less reliable connection like a wall plug.

@Neinstein There are mini-split systems marketed to DIYers, that come pre-charged with refrigerant with sealed tubing that is connected then opened up upon installation. No specialized equipment required.

@OverLordGoldDragon there are two ways of piping the vapour out: recondense it and use plumbing, or replace the humid air with fresh air. The first one releases the heat which was used to evaporate it again, and the latter involves bringing in hot air from outside (which is also why single-duct portable ACs are awful).

@aquaticapetheory - a mini split is not any different than an electric stove top / oven cooker, they are both stationary, and plugged in. And due to our voltage being 230 as standard, the amperage is nothing special, they can both easily run on a standard 16 amp breaker. And the advantages should be fairly obvious.

@Davor An electric stove is an appliance that sits on the floor and can be moved. A mini-split is not only attached to the wall with fasteners but has lines running through the wall to a unit outside that is also fixed in place. It is a fixture. My boiler only needs a few amps too but that must also be directly wired. My best guess on the logic is code steers you away from wall plugs where it can.

@OverLordGoldDragon "matter-energy conversion physics" is commonly known as "nuclear power" and is not currently available as an in-home unit.

@llama Or pump it out in vapor form?

@OverLordGoldDragon How would you separate the water vapour from the rest of the air?

@JMac Dunno, how does is "naturally" happen, with high humidity air equilibrating with low? I figure just have the pipe exiting in said low humidity region, and have a pump to do the moving of high humidity output, but I have no idea - this is definitely more suited for Physics SE.

@OverLordGoldDragon The humidity would equalize inside, assuming the house is sealed. If you're moving the humid air out, you need to replace it (and that air would be warm). And as mentioned, if you try to condense the water, that releases the heat back. If you wanted to design something to get the heat from condensation out of the house instead of heating it, that would basically be an air conditioning coil, and then you're back to square one (and the evaporating cooler would be redundant, because the AC coil can take out heat anyways, and water vapor).

@JMac "If you're moving the humid air out, you need to replace it (and that air would be warm)" D'oh! Thank you for explaining. I don't quite follow the part at and after "air conditioning coil" but I'll mostly trust there's complications there too. So the simplest "air heat in air heat out" works best, go figure.