I'm trying to decide where to install my ductless split Air-Conditioner.

For the indoor unit, is it okay to install it above a window? Will placing the indoor unit at the corner of the wall reduce the efficiency of the cooling (instead of installing it at the center).

For the outdoor unit, I want to place it in a place where I can get the minimum level of noise as possible. So I have two options, either install it on the front house wall, or just put it on the roof. So which option is better?

Finally, is putting the outdoor unit above/below the indoor unit has any affect?


1 Answer 1


In order of questions asked:

  1. It is best to install the indoor unit near the area of maximum heat loss and gain. Above a window is a fine place, provided you have space to run the refrigerant piping and condensate line.

  2. Near a corner is okay, but a less central location means there will be a longer time required to circulate air around the room.

  3. As a licensed refrigeration person I can say that outdoor installations near the ground are usually more pleasant to service than those that are on a roof. Most modern mini splits are very quiet. As long as the outdoor unit is not directly next to a window, you probably will not be bothered by the noise.

  4. Outdoor unit installed above or below the indoor unit does not matter as long as the total lift and length of piping is within the manufacturer specifications.

  • Thank you for your response, I've installed the outdoor unit on the roof of my room, but I've noticed that the outdoor unit doesn't have any legs or something to sit on, so the HVAC person just put it down and installed it. for the first week it was working fine, but now I can hear noise other than the fan noise coming out of the outdoor unit, is this normal ?
    – donald
    Jul 17, 2015 at 5:14
  • On a flat roof, the condenser would normally be secured to a stand or at least some 4x4 boards to keep it out of a pond of water when it rains. The only noise from most mini-split condensers is the fan and a soft purring or rumble from the compressor. Sometimes technicians accidentally leave the exterior panels on the housing loose and they may rattle in that case.
    – user39367
    Jul 18, 2015 at 1:38
  • take a look at this video [ vid.me/zdCd ] of my outdoor unit, it is making some noise that is still audible inside my room. is this normal ?
    – donald
    Aug 3, 2015 at 20:10
  • I hear 2 noises that could be normal. It is hard to tell through a camera microphone and my laptop speakers. One noise is the purring of the compressor. The second noise is the hissing of the refrigerant through the metering device. To be honest, the compressor sounds a little loud and this could indicate a problem such as refrigerant overcharge, but some units are noisier than others. I notice there appears to be no insulation on your copper refrigerant lines. Unless the insulation starts just out of view of the camera, that would be substandard.
    – user39367
    Aug 5, 2015 at 0:42
  • Another problem that can cause a compressor to labor hard is air in the system. Air settles in the outdoor coil, taking up space and causing very high head pressures. A tech is required to fix this, however if you are able to use an AC induction amp meter you can test if this is likely. With the unit running on a warm day, measure the amperage being consumed by the unit and compare it to the total on the UL label. If the amperage is at or above the labeled amount, there is likely air in the system or some other installation problem.
    – user39367
    Aug 5, 2015 at 5:26

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