Installing 2 Aircon Units in Two Different Rooms

Hey guys, for the upcoming summer my brother and I are looking at buying an air con unit each for our room but we heard we could cut down on installation costs if we hooked it up to the same outdoor unit(?)

Both our rooms are on the second storey and quite close to each other but far enough that we'd need a separate unit as we're on opposite sides of the hallway.

We're happy to throw down a $1000 each for our own unit and was told by a relative that during installation, we can ask the installer to hook it up to one unit to save on costs.

If anyone has experience, could you explain how it works?



  • If they're on opposite sides of the hallway, it would probably cost a lot more to do a single compressor to 2 head units compared to doing 2 separate installs.
    Pipework would need to run either around the entire house to the compressor, or up through the roof using a condensate pump. You could potentially just run the cabling and pipework through the roof and the drain out through another wall to prevent the condensate pump, but running all the pipework through the ceiling would still cost a lot of money.

    Furthermore, for you to use a single compressor to 2 head units, the compressor needs to be large enough to support both head units on at the same time, so you can't just buy 1 complete unit and add a new head unit to it.

    • It's not that hard to mount the compressor to the side of the building (if there's a suitable spot) up high so less pipework is required for the 2 heads.

      • It's not about the position of the compressor in relation to the wall, it's in relation to 2 rooms on opposite sides of a building. The pipework needs to reach the compressor from both sides, and the only way to do that are the methods I posted above. Suppose you have the compressor on one side of the house, and you have to run one from the other side, the minimum extra pipework through the ceiling, assuming a very small room of 3 meters, plus a hallway of 1 meter, would be 4 meters of pipework through the ceiling to reach the compressor from the second head unit.
        If you did it this way, it would absolutely require a condensate pump, which are hundreds of dollars by themselves, and prone to failure far quicker than the compressors.

        If you did it with the second head unit against the opposing external wall, you would then need a minimum 3 + 1 + 3 meters of pipework through the ceiling, with the drain pipe running through the opposite external wall and no condensate pump required. 7 meters of pipework through a ceiling, even if you assumed a very cheap price of about $60-70 per meter, would be over $400 just for the extra pipework (and that excludes up and down runs as well).

        No matter how you look at it, the economics of running 2 units to a single compressor on opposite ends of a house is never going to work out.

  • heard we could cut down on installation costs if we hooked it up to the same outdoor unit(?)

    You're talking multi head units, and at the end of the day there really isn't a saving but a more just shifting the figures around. Cheaper hardware costs are normally offset by the extra labour.

    Downsides of multi head units, total costs are about the same as installing single units. Can only run in the same mode ie cooling or heating. You can't have one inside head cooling and one heating. If the outside unit dies you lose all the inside heads attached.

    Upsides, smaller outside space needed.

  • You need a twin or triple head unit. You will have to ask the installer if your house layout is suitable.

    My neigbour has a triple head unit but it was for 3 rooms on top of each other so the pipework goes straight up the wall. It looks good.

  • As said, you're after a multi head and it's not even close to worth it, especially for two.
    You're also looking at more than $1000 each for unit plus install id say.

  • Didn't know this was possible to do - thank you!

  • Might as well just go fully ducted.

  • You're better purchasing two separate units.
    Multi head units rarely turn out to be cheaper, just usually more pleasing to the eye.
    Installing two units at then same time might get you a small discount if you go if the same installer.

  • Thanks for the answers everyone, looks like we'll just install the two units separately