I have two rooms both has the area of 100 sq.ft and together 200 sq.ft.

According to AC tonnage calculation , 1.5 TON AC is enough upto 90 to 250 sq.ft area.

Sine I have 1.5 Ton AC , I'm thinking to drill the wall and connect the rooms using duct.

So the room with AC will exhaust fan.

In laymen terms , it seems to be a great idea to me. Since I don't have to buy one more AC for the other room.

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But as I dig deeper in the subject ,it raises concern of leaving the AC room bit warmer as the warm air from the non-ac room will get displaced back to AC room and it'd be hotter and it might put a strain on the AC and increase the electricity bill and it might reduce the lifespan of AC itself.

But is there any technique that will prevent the shortcomings of this and still use one AC for two rooms.


  • So here is my AC name: Whirlpool 1.5 Ton 5 Star Split Inverter AC - White (1.5T Magicool Pro 5S COPR INV, Copper Condenser)

  • I will have to run this duct for 10 feet through a low roof.


  1. https://www.youtube.com/watch?v=JHL2mMWzK1U

  2. https://www.youtube.com/watch?v=Bpv0BE8ma80

  • 1
    You may want to try if for a while, if you haven't already done so. I find that my unconditioned room, surrounded on four sides by conditioned space and not getting a lot of sun load, doesn't seem to need powered hear exchange. But yes, if I needed that I have considered thru-the-wall ducting with a couple of low-power fans as a way to combine it with the adjacent room, probably through the shared wall of the room's closets.
    – keshlam
    Jun 1, 2023 at 22:36
  • 1
    Moving air between the 'warm' room and the AC room isn't going to put any more strain on the AC than if it were just installed in a larger room.
    – brhans
    Jun 2, 2023 at 0:49
  • 1
    the ac-having room won't stay hotter, as long as the thermostat is in it. You also need two ducts, not one: one in, one out, otherwise there will be no flow. Also keep in mind you just need another wall unit, you can use the existing compressor/condenser to drive both units, so it might not be as expensive as you think to add another unit.
    – dandavis
    Jun 2, 2023 at 3:55
  • 1
    Should still work. May or may not work well depending on the duct size/type)position, the fan(s) chosen, the size of the room's vs the capacity of the unit... But it isn't a wholly unreasonable idea to try to treat the two linked spaces as a single room.
    – keshlam
    Jun 2, 2023 at 12:24
  • 1
    that's right. you would just possibly need a small hole in the outside wall to run the additional coolant line. There's might be enough room in the existing hole, but even if not, adding one is no big deal. Since the liquid is about 1000X more effective than air at moving heat, the holes can be 1000X smaller.
    – dandavis
    Jun 2, 2023 at 17:52


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