I am getting ready to hang outdoor string lights in my back yard for which I will need an outdoor extension cord about 20’ in length to reach a GFCI outlet. The string lights have a two-pronged polarized plug which, as far as I know, tells me there is no ground. However, in the safety information for the lights, it states: “Use only two-wire outdoor extension cords that have two-prong grounding plugs and grounding receptacles that accept the appliance’s plug”.

This has me completely baffled. What does that even mean? Is there such a thing as a “two-prong grounding plug”? Aren’t all two-prong plugs by definition ungrounded? And does it even matter if I use a three prong extension cord (as pretty much all outdoor cords are) versus a two prong one? If someone can enlighten me, I would greatly appreciate it.

  • Is this extension cord at the head of the string, or between two strings of lights? Jun 15, 2020 at 23:19
  • The extension cord will be used between the outlet and the first string of lights. The box containing the bulbs has “UL Listed” on it, but the actual light strings each have a removable tag which says “ETLus Listed” and also “Conforms to UL STD. 153”.
    – Scott
    Jun 16, 2020 at 0:53
  • 1
    BTW - I live in the US and purchased these at Home Depot, so I assumed they would be somewhat mainstream. They were made in Vietnam.
    – Scott
    Jun 16, 2020 at 0:56

1 Answer 1


I'd venture it is poor wording by a low cost bottom feeder supplier in China that has no clue what they are talking about...

Assuming by your use of the term "GFCI" that you are in the US or Canada (you didn't identify), to be able to use electrical equipment with 2 wire plugs, they must be "double insulated" and the plug itself must have a tag on it or a moulding in the body of the it that displays this symbol:

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If it doesn't have that somewhere on the product, it is undoubtedly not UL listed, so what they tell you about safety is kind of pointless anyway.

All that said, if it IS double insulated and UL listed, then you can plug it into any outlet, whether the outlet is 2 prong or 3 prong, but of course any outdoor outlet must be GFCI protected now and will be 3 prong anyway.

  • I may get snipped for saying this, but let's face it. GFCI protection has functionally replaced grounding on circuits requiring GFCI protection (which is virtually everything going forward). There have been numerous mentions of situations in older homes where retrofitting some outlets with GFCI outlets without ground that are labeled "GFCI protected, no equipment ground" . I know that having both GFCI and ground is safer, so I'm OK with it. But functionally GFCI protection has largely replaced grounding. Thoughts all? Jun 15, 2020 at 23:34

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