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I feel like I'm missing something obvious. I know different plug styles are used based on a circuit's amperage (in the US) but is the same style of plug used for both 110V and 220V outlets of the same amperage?

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It's not clear what you mean by "connectors"? Do you mean the plugs that are used, or the wire nuts that are used to connect wires together? –  Eric Gunnerson Apr 16 '13 at 3:54
    
@EricGunnerson I'm asking about the prong configuration of plugs/outlets –  Brad Mace Apr 16 '13 at 4:22
    
Also, if you're asking if there exists a plug/receptacle that could be either 120 or 240, depending on the whim of the installer, the answer is no, any particular plug is either standardized at 120 or 240. –  Aaron Apr 16 '13 at 12:30

2 Answers 2

up vote 9 down vote accepted

No, the plugs are different for different voltages. There are many different NEMA receptacles for various combinations of voltage and current, and also a "twist-lock" receptacles. Some common ones are:

Common NEMA plugs

(From Wikipedia).

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The grid with everything oriented the same way makes it a lot easier to spot the differences, thanks. –  Brad Mace Apr 16 '13 at 13:30

An easy rule of thumb to remember is that a NEMA plug/outlet with both blades parallel is for 15A service ... if they are vertically oriented (as in normal residential), it is 120V service, if they are horizontal (in-line), it is 240V service.

20A service has the blades at right angles to one another ... 120V has the neutral blade horizontal and the hot blade vertical, while 240V has it the other way around (although there is no hot and neutral for 240V service ... both blades are hot).

Unfortunately, Aaron's other response is incorrect ... there are so-called "universal" duplex outlets that accommodate both 120/240V 15/20A configurations. Leviton has their 5825W, and there is one made by a niche supplier that is slightly different in configuration: http://www.ehydroponics.com/cap-universal-x-plug-120-240-outlet-receptacle.html

Hope this helps!

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By the by, the above answer is strictly for NEMA straight-blade outlets (i.e., NEMA 5-15, 5-20, 6-15, 6-20) ... it does not apply to the twist-lock or angled-blade varieties. Sorry for the potential confusion. –  Terry Gaus 7 hours ago

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