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I am looking to buy a window air conditioner. I would like the get the most powerful air conditioner my electrical system can support. I have this plug on my wall:

plug in wall

I have never seen this plug before, but based on the size and shape I think it may be a NEMA 6-30. The round outlet face is 2 and 1/8 inches and each prong opening is about 9/16ths of an inch:

enter image description here

I have not found any air conditioners with this specific plug shape and size. Would I be able to plug in an air conditioner with a different plug using some sort of adapter?

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    This is really a product usage or home wiring question, not an EE design question. Most likely that is or at least was supposed to be a dedicated circuit for a large 220v model. – Chris Stratton Jun 22 at 20:59
  • The plug has no real relation to the highest possible load. That plug may be rated for 50 amps, the wiring for 30 and the breaker for 15... – Ron Beyer Jun 22 at 21:08
  • @RonBeyer, how would I find out the correct load? – Matt Korostoff Jun 22 at 21:11
  • Guess only - look at the breaker or fuse that feeds it. That gives you an upper intended limit – Russell McMahon Jun 24 at 10:12
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That appears to be a NEMA-6 30 receptacle. According to the National Electric Code, it must be used only for a 30 amp circuit. Look for a 30 amp, 240 volt circuit breaker in you box. Unless you find another receptacle like that in the house that is connected to the same breaker, the entire 30 amps is available for use by whatever is plugged in there.

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  • Thank you. Can I safely plug in a lower amp device with an adapter? – Matt Korostoff Jun 22 at 21:19
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    @MattKorostoff you seem to be dangerously confusing voltage and current. Before anything, this is a high voltage socket, there aren't really practical adapters that would allow using a normal 120v appliance there. An air conditioner suitable for use on that circuit is either going to come with the corresponding plug, or no plug at all as it must be installed by an electrician. – Chris Stratton Jun 22 at 21:24
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    I believe that the UL, ETL or other safety listing for any product may be limited to plugging the product into the receptacle that matches the plug furnished with the product. – Charles Cowie Jun 22 at 21:26
  • You might be able to install a NEMA-6 20 amp receptacle in the box and change the circuit breaker. You could also check the product literature to see if it is allowed to be used on a 30 amp circuit. Also look for products with a NEMA-10 30 plug. – Charles Cowie Jun 22 at 21:36
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    You might want to check the circuit breaker rating for the neighbouring socket and also figure out what else is on that circuit. Otherwise you may find that you can't use your AC and TV/computer/toaster at the same time. – Chris Stratton Jun 23 at 2:55

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