Is preparing for an air conditioner worth it?

Thanks in advance for your answers! So far, I have understood that you need:
- probably two pipes per indoor unit (one supply and one return?)
- power on the roof (or at the outdoor unit)
- power at the indoor unit
(a bus system is not an option for us)

The condensate forms at the indoor unit (I assume), which means I have to run some kind of hose to a drain pipe, right? That alone probably wouldn’t be the problem, more likely potential odors from the sewage system if no precautions are taken here.

As for the refrigerant line. Where could the sticking point be here? Sounds like rather small metal pipes, does the pipe diameter vary from manufacturer to manufacturer?
In principle, one would think that laying these pipes in a timber house not yet planned from a manufacturing perspective shouldn’t be a huge problem, or is it?

I hadn’t considered the weight, what load can such a roof bear per m²? And how much does an average outdoor unit weigh?

The preparation is actually just a 10cm thick empty conduit and an outlet near the indoor unit. I consider 1300.-- to be too much for that. I wouldn’t lay refrigerant lines in now either, they just get dirty, seals become porous, and if a new refrigerant comes in a few years, it won’t fit. The condensate can be drained anywhere, onto the roof, dripping down, or even into a tray that you empty yourself. With the "simple" units, only one indoor unit can be connected, so it is often cheaper to have 3 indoor/outdoor units than 1 outdoor and 3 indoor units.

Thanks already for your answers! So far, I’ve gathered that you need:
- probably two pipes per indoor unit (one supply and one return?)
- power on the roof (or at the outdoor unit)
- power at the indoor unit
(a bus system is not going to be used in our case)

The condensate forms at the indoor unit (I assume), so I have to run some kind of hose to a wastewater pipe, right? That alone probably isn’t the problem, rather possible odors from the sewage system if no precautions are taken.

Regarding the refrigerant line: where could the tricky point be? Sounds like rather small metal pipes, does the pipe diameter vary from manufacturer to manufacturer? In principle, you would think that installing these pipes in a timber house that isn’t yet planned in terms of manufacturing shouldn’t be a huge problem, or is it?

I hadn’t considered the weight; what can such a roof carry per m²? And what does an average outdoor unit weigh?

- By BUS system I don’t mean KNX or similar, but that some manufacturers require an additional cable as a bus connection to the outdoor unit.
- A cable on the roof would be useful ;)
- Indoor units usually don’t need an additional power supply since they are powered by the outdoor unit
- Just google "refrigerant line insulated" (it’s a ring)
- If you want to connect the condensate to the wastewater pipe, you have to install a siphon in between
- The most common refrigerant line is 1/4 x 3/8 and usually sufficient for normal systems. Anyone can really install this themselves, you just have to make sure there is a continuous refrigerant line between the indoor and outdoor unit (otherwise you might have to open the wall in case of leaks because there could be a solder joint). Also, the maximum length specified by the manufacturer should not be exceeded

- If you want to connect the condensate to the drain pipe, you have to put a siphon in between

My air conditioning technician also said that there must be a free fall section for the condensate so that no bacteria from the wastewater can get into the air conditioning.

- Power at the indoor unit

The supply line for the indoor unit regularly comes from the outdoor unit. You can simply run the cable through the empty conduit or already lay a cable from the outdoor unit location to the indoor unit.

- The indoor units usually don’t need an extra supply line since they are powered by the outdoor unit

Correct!

The condensate can be drained anywhere, onto the roof, drip down, or even into a tray that you empty yourself.

I wouldn’t do that in new construction. Water already accumulates there. I would always lay or prepare a wastewater line at the locations of the indoor units.

Man, there's really a lot of action here! I'm definitely not alone when it comes to how I perceive heat :D.

The thing with the empty conduits somehow makes sense, but I can only imagine that it's easier to lay these two "tubes" directly along with a power cable; somehow you can probably always fit that in. But those are just assumptions...

It doesn't sound like that much at all! Adding a wastewater pipe now, in my opinion, shouldn't be a problem at this point.

I think I'll just bring it up directly with the house provider. Your writing is hopeful.

I looked up the weight of the outdoor unit, it's under 50kg; isn't that a load that should be easily supported by a roof?

What I couldn't find was the maximum length of the pipes. Does anyone here maybe have a ballpark figure? That would make it easier to estimate where I could alternatively place the outdoor unit instead of the roof...