The central AC in our apartment is not working effectively in the summer; we are running the AC continuously for 14 hours a day to keep the temperature below 80 degrees. As you can imagine, our electric bill has become a huge problem.

(Edit: Please note the maintenance staff are incompetent and management doesn't care about our problem at all -"getting the central AC fixed" is not an option, if it's even fixable)

I bought a used portable AC unit (around 11,000 BTU, rated at 12 amps) and plugged it into an arbitrary outlet near a window, because I was always able to do so with a similar AC at my parent's house. The portable unit worked great for a couple of minutes and then tripped the circuit breaker, which also shut off my computer.

After a lot of testing I have determined that all of the outlets in the two bedrooms and in the living room run off a single 15-amp circuit (which was 'helpfully' labeled "lighting" in the circuit box). This rules out every outlet that is within reach of a window. There are two circuits labeled "plugs" in the circuit breaker, but AFAICT they aren't connected to anything (unless they're for the outlets in the kitchen).

Obviously because it's an apartment I can't do anything with the wiring, and I can't use an extension cord on an 11,000 BTU AC... Am I screwed here? Is this typical for an apartment with central AC?

The full set of circuits is (as they are labeled):

  • Central AC: 2x30A
  • Central Heat: 2x30A
  • Bathrooms: 2x15A
  • Plugs: 2x20A
  • Lights: 1x15A (again, this actually covers outlet in 3 rooms, there is no overhead lighting)
  • Garbage Disposal: 15A (nowhere near a window)
  • Dishwasher: 15A (nowhere near a window)
  • Electic Range: 2 x 40A (oven/stove)
  • 2
    Have you contacted your landlord about maintaining the central AC? It could be something as simple as a clogged filter.
    – friedo
    Jul 1, 2015 at 2:45
  • 1
    If you mean a portable A/C with a hose that blows the hot air out a window, Consumer Reports found that they are very inefficient and barely cooled their test rooms. A smaller window unit may cool better and use less current, like this 10,000 btu Kenmore rated at 8.8 amps.
    – Johnny
    Jul 1, 2015 at 3:11
  • 1
    My point is that if you're satisfied with the cooling from a 12 amp 11,000 BTU portable unit (12 amps is about the max you can continuously draw from a 15A circuit at 80% load, so that gives you no spare capacity for your computer or lighting), then you can probably get the same cooling from a smaller 10,000 or even 8000 BTU window unit. Since a window unit requires no permanent installation or modifications, it's not clear why you can't use one in an apartment if you have a suitable window (unless you're in a high-rise that prohibits them for safety reasons).
    – Johnny
    Jul 1, 2015 at 5:12
  • 1
    I've lived in about a dozen different apartments, and the only one that had window restrictions was the 40 floor high rise. As long as the opening is 14" wide or so, there are window units made for it. In any case, sounds like a window unit won't work for you, but you have few options. You can try a smaller portable unit that consumes less current, you can live with the poorly operating A/C, or you can seek legal advice to try to get your landlord to fix the central A/C that he's leasing to you (or terminate the lease, or reduce your rent)
    – Johnny
    Jul 1, 2015 at 5:36
  • 3
    Since you're in an apartment where you can't do any work yourself, I'd say this question is off topic here. You may want to contact a lawyer, to see if there's any legal action you can take against the landlord (even if it's just to get out of the lease, so you can move).
    – Tester101
    Jul 1, 2015 at 12:31

3 Answers 3


We resolved the problem with the portable AC by purchasing a heavy-duty, 15-amp, 12-gauge extension cord and running it from the bathroom to the AC by the window. Since the bathroom is on its own circuit, the AC does not trip the breaker. A big thank you to those who suggested this in the comments.

Ironically, management has decided to replace our central air conditioner after I discovered mold in the unit, and their subsequent inspection also revealed it to have a serious Freon leak.

  • 1
    Glad your landlord is taking care of things. Some of them really do care about their property - I swear. :)
    – friedo
    Jul 20, 2015 at 19:43
  • Even more ironically, they have since discovered toxic mold in the unit next to ours. At least the central AC system got replaced and they only had to repair the new AC system once after installing it...
    – user45623
    Oct 2, 2015 at 22:28

If you test each outlet, and find a drop in voltage on any of them, you might be able to claim that the wiring does not meet code, and force the landlord to make some changes that way.

(NEC 210-19 FPN No. 4) in the National Electrical Code states that a voltage drop of 5% at the furthest receptacle in a branch wiring circuit is acceptable for normal efficiency. In a 120 volt 15 ampere circuit, this means that there should be no more than a 6 volt drop (114 volts) at the furthest outlet when the circuit is fully loaded. It also means that the circuit has a resistance that does not exceed 0.4 ohms.

  • Very clever. I would love to try this out, but our lease is up pretty soon and we've had it with this place.
    – user45623
    Oct 21, 2015 at 20:27

Plug it into the stove it is 240

  • 1
    Hello, and welcome to Stack Exchange. The original poster's A/C was a 120VAC unit, not 240; things don't run faster/better when you double the voltage. Jul 5, 2018 at 21:48

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