Is an adapter from a plug (say a NEMA 14-50) to a different socket (say a NEMA 6-20 or L14-20, or even a NEMA 6-50 for that matter) considered an extension cord by the 2014 NEC? If it isn't, then what type of device would it be, and would it matter if it was a listed assembly vs. a field-fabricated assembly?

As to the use of "extension cord" in the NEC, see 240.5(B)(3)/(4) for an example:

(3) Extension Cord Sets. Flexible cord used in listed extension cord sets shall be considered to be protected when applied within the extension cord listing requirements.

(4) Field Assembled Extension Cord Sets. Flexible cord used in extension cords made with separately listed and installed components shall be permitted to be supplied by a branch circuit in accordance with the following:

20-ampere circuits - 16 AWG and larger

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    Why are you making an adapter? You shouldn't be using a 20 ampere device, on a 50 ampere circuit. If you have a 50 ampere device with a different plug, why wouldn't you simply change out the receptacle?
    – Tester101
    Oct 9, 2015 at 12:40
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    @Tester101 -- I still have no clue why a 20A device on a 50A circuit is any different than a 1A device on a 20A circuit. Oct 9, 2015 at 22:16
  • what does a 1 amp plug look like? I don't think there's any NEMA 5-1 connectors, but I could be wrong. The difference is the size of the wiring inside the device.
    – Tester101
    Oct 9, 2015 at 22:29
  • When a device is fitted with a NEMA 5-15 plug, the device is required by UL to withstand 20 amperes. If there's a fault in the device, nobody wants the device to burst into flames.
    – Tester101
    Oct 9, 2015 at 22:32
  • @Tester101 Yeah, there are no NEMA 5-1 plugs -- a 1A device still uses a NEMA 5-15. However, for instance, the power cord for my laptop "brick" adapter (somewhere in the 0.8A range) is an 18AWGx3 SPT-2 with a NEMA 5-15P on one end and an IEC C5 coupler on the other -- the cord itself is optimistically capable of 10A, while the IEC C5 is only rated at 2.5A! Oct 9, 2015 at 22:34

1 Answer 1


I'm not sure the term "extension cord" appears in the NEC at all. There are provisions for "flexible wiring" (section 400) but those are probably not relevant for what you're talking about. (In fact, what are you talking about?)

The closest thing I can think of would be an "attachment plugs" and "cord connectors", which is discussed in section 406.7. Among other requirements are that they be listed. I would think that if you are field-assembling something out of existing plugs that as long as the plugs themselves are listed and the wiring conforms to the rest of NEC (suitable gauge, protection from damage, etc) that would be OK.


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