I had a regular 15amp duplex outlet in my kid’s room. Because it is on the third floor, the heat doesn’t work that great and we had a small ceramic heater plugged in. She called me into her room. She unplugged the heater because there were “scorch” marks around the top part of the duplex.

Went to the hardware store and bought a new outlet. (15 amp duplex outlet with also two USB ports) Hooked it up and then tested it. The bottom half of the duplex tests “correct”, when I plug it into the top part it says open ground.

It is not controlled by a switch and I didn’t break any tabs.
What could make this happen? Is it safe to use the outlet or just the bottom of the duplex? I tested all the other outlets on that breaker and they are all fine. I also double checked my connection and the plastic box connections. Do outlets with USB ports show open grounds?

While it would be a mystery that would be good to be solved, would putting a GFI outlet in that box assure it is grounded?

Before I call someone I want to see if there is something I may be missing. Any help would be greatly appreciated.

  • Sounds like a fault in the outlet, there should not even be any tabs that break ground between the top and bottom of the outlet, only hot and neutral should have the breakoff tabs. Can you test continuity between the ground slot on the top and bottom of the outlet? If it does turn out to be a bad outlet, I'd stay away from that brand, that's a huge failure and might signal shortcuts in manufacturing.
    – Johnny
    Jan 5, 2016 at 20:17
  • 1
    A GFI outlet is not for grounding, it is more like a breaker. It checks the power flow on the hot wire and on the neutral. If they are the same or within a small margin, then the power is going how it should. If they are different, then some power is leaking off somewhere, i.e. a ground fault. A ground wire connects all conductive material back to your panel so that your breakers will flip if any of it gets energized. A GFI will save lives, but they can go bad and you should still have an adequate ground. - It's probably a bad receptacle.
    – TFK
    Jan 5, 2016 at 20:34
  • Side note, if you want a GFCI outlet and permanent USB, there are cover plates available that clip onto the terminals of the receptacle and provide an extra USB outlet below the two regular three-prongs. Snap Power is one brand I've seen used.
    – ench
    Jan 6, 2016 at 0:09
  • Ench, I've seen those before. Do they ever have "push through buttons" / "poke through holes" to test and reset the GFCI beneath? AFAIK, there isn't a standard/requirement for the location or geometry of GFCI buttons. Though there's a couple common geometries. Jan 6, 2016 at 19:22

1 Answer 1


It is not controlled by a switch and I didn’t break any tabs. What could make this happen?

  • Debris inside the socket of the ground conductor
  • A defectively manufactured outlet

Is it safe to use the outlet or just the bottom of the duplex?

Safety is a relative thing.

  • If you use the ungrounded top outlet it will be as safe as older houses that were built before grounding was a thing, and were considered safe in their time. It will also make no difference for two prong appliances.

  • If you crazyglue an outlet protector over the top outlet to prevent use of the top outlet, then it will be as safe as not using it.

  • But maybe the DC converter will short to hot and electrify the phone someone is holding up to their head.

I say take it back to the store and report the fault and get an exchange.

You got a product that is less than it should be. Safety or not, you'd return a plasma tv if it had lines down it or only received even channels. Return this outlet too.

Do outlets with USB ports show open grounds?

Only busted ones.

would putting a GFI outlet in that box assure it is grounded?

Nope. GFCIs do not create ground.

Changing the part out (with a gfci, or with any other outlet) would most likely solve the problem though. And in a kid's room, I think a GFCI is worth more than USB outlets if its a kid you want to keep.

Perhaps consider installing one GFCI in the "first" outlet box in that room, or in what ever the next closest junction before the circuit enters that room. Then USB outlets inside the room. In 60 seconds of Googling, I could not find an outlet that had GFCI and USB in one. You could also use a GFCI breaker but those are a pain in the neck.

something I may be missing

The receipt for that usb outlet, and its original packaging? With that, you should be all set. Let the clerk know it is dangerously faulty so they think longer before re-shelving it. If you get another of the same model and it has another fault, then you should tell us what model it is so it can be avoided. Good on you for testing the outlets after installing. I haven't done that on nema 5's in a while....

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