I have an outdoor duplex outlet which was not GFCI, nor was it protected by a GFCI outlet indoors. I tried to tone the outlet to find the specific circuit, but could not, so I shut off power at the main. After removing the existing duplex from the receptacle box, it had two pairs of wires. "No problem," I thought, "I'll see which pair is line and which is load."

I turned the power on at the circuit breaker, then tested with a multimeter. The problem is that both pairs are live. Since both are live, how do I properly wire this into a single GFCI?

  • 2
    Was the tab between the terminals broken on the old receptacle?
    – Tester101
    May 24 '16 at 17:03
  • Is there any reason you need to use both pairs? Pick one and cap the other. Howdy from St. Cloud.
    – isherwood
    May 24 '16 at 17:10
  • @isherwood Hi there, thanks for the response. I certainly could pick one pair if that's safe. Since I didn't know why it was configured that way, I wanted to understand it first. May 26 '16 at 13:19

If this truly was a split receptacle, where each receptacle was fed by a separate circuit. Then you'll have to either install two GFCI breakers/receptacles, or cap off one of the feeds.

To my knowledge, there are no multi-circuit GFCI receptacle devices available on the market.

  • Hi, thanks for responding! The non-GFCI duplex that I uninstalled was working properly but the tabs between the two outlets were connected. May 25 '16 at 22:13
  • @MinnesotaDIY I'm not sure why a receptacle would be fed by separate lines, and not be split. Are you sure both lines are supplies?
    – Tester101
    May 25 '16 at 23:02
  • I removed the old duplex, stripped the ends, separated the 3-wire pairs, then turned electrical on and tested each pair. They metered to 120V each. It could make sense if they wanted to power each outlet separately (for high loads), but like I said, the tabs are connected on the old non-GFCI duplex. Strange! May 26 '16 at 13:18
  • With the tabs in place, you could theoretically draw 30 amperes from the receptacle (40 if it were two 20 ampere breakers). Which means there's the potential to burn up the receptacle, before the breakers trip. This is quite dangerous. However, since you're installing new receptacles anyway, you can correct the problem. Install two GFCI receptacles, or cap off one of the feeds.
    – Tester101
    May 26 '16 at 13:37
  • @MinnesotaDIY I've written up a question and answer, that describes the problems that can occur from not removing the tabs.
    – Tester101
    May 26 '16 at 16:02

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