Unfortunately for the time being, my whole first floor is cooled by a single portable air conditioner and "cleverly" (if that word can even be used here...) placed fans to help move the cool air around the floor space.

I don't know the specifications of the air conditioner right now but I'm sure it's not meant for the square footage of the floor.

But that aside, I'm trying to keep the air conditioner centralized in the house by keeping it in my dining room. Because the exhaust hose is short (about 4 ft), it's anchored close to my window and the AC doesn't have much wiggle room from the walls. I also have my dining room table sitting right next to it which I'm sure doesn't help.

What I'd like to know is if I can place another fan about a foot behind the AC unit to help push warmer air into the fans intake. Is this helpful? Is it dangerous? Will it even do a dang thing? Any advice is appreciated...it's hot! =(

  • Closing doors to unused rooms, so you aren't trying to cool as large a volume, is likely to make much more difference.
    – keshlam
    Commented Jun 3, 2014 at 2:02
  • Yeah, we close off all bedrooms and the basement. We even picked up a few of those under-door insulators from Menards for free (with rebate haha). Hopefully we have real central AC on the way but for now, we're stuck with this and I was hoping to stretch the capability of that portable AC in the mean time. Commented Jun 3, 2014 at 2:51
  • Understood. My solution, back when I was in an apartment, was one largeish air conditioner which could cool most of the open-plan apartment almost-adequately (obtained used from the previous occupant for USD$300), and a small window AC unit I already had which I used to cool just the bedroom overnight. My current solution is similar: a large AC to cool most of the main floor (just enough to be tolerable), a small one to cool my home office (absolutely necessary), and another small one in the bedroom. Remaining rooms get ceiling fans and/or strategic opening and closing of windows.
    – keshlam
    Commented Jun 3, 2014 at 3:28
  • Wait. Why can't you extend the exhaust pipe a bit? As long as you make sure there's a decent slope toward a window or floor drain (you don't want to push condensate upwards, specially on a longer trip), you should be OK, right?
    – alt
    Commented Jun 3, 2014 at 11:54

2 Answers 2


If your AC is seriously undersized, the compressor is probably already running 24/7 and blowing hot air into it won't make any difference. At max capacity an AC can remove a specific amount of heat from the air per hour. If you blow hotter air into the intake you will get correspondingly hotter air coming out. It's a zero-sum game.

In addition to closing off other rooms as others have suggested, here are things you might try:

  • Block as much sunlight as possible from entering the rooms
  • If you still have any old-fashioned incandescent bulbs, replace them. Ideally with LEDs, but compact fluorescents are cheaper up-front.
  • Turn off any appliances you aren't using. If you need to run a small fan to properly circulate air that's OK, but you should be aware that the fans are generating heating and in that way they work against the AC, so it's a tradeoff. Some larger fans can use 100 watts or more of electricity, which is turned into heat. 100 watts of electric consumption generates about 350 BTUs/hour of heat.

In addition to Henry's sensible comments (what a clever little boy!), I would like to add for general public consumption that the accordion duct/hose is only 3-4 ft long for a very good reason. After running the AC for a few hours, put your hand on the exhaust hose and you will feel lots of HEAT. Stringing a longer hose extension in the room would be like rigging a hot stove pipe extension...You need to place your so-called 'portable' AC as close to the venting window as possible, never more than 3 ft between unit and window including angles (which should be as minimal as possible). The less the accordion unfolds, the less heat the hose will emit on its way to the window outlet.

Calling these units 'portable' is kind of deceptive; you can't really move them around the room at will once installed without disturbing the exhaust system, especially if you put insulation around the exhaust at the window end. They should really be called just 'floor' models as opposed to 'window' models...

  • Yeah, portable is more like "it's got wheels". But I understand what you're saying. That hose isn't very well insulated by itself and I could feel the heat on it. I bet if it was long enough you'd lose almost all venting right back into the space. Thankfully though, we have central now! Crisis over! Commented May 2, 2017 at 0:42

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