I found a junction box under my deck that has grey cable, with each individual wire wrapped in the gray sheathing. So for example, the white wire has the white insulation around the copper wire, and grey sheathing around it... and the black wire has black insulation around the copper wire and grey sheathing around it, then the copper wire (ground) is just surrounded by the grey. But each wire is individually wrapped. I used a wire tester and determined the wires are hot, but what gauge wire would I need to use to tie into this existing box in order to not have major problems?

I am wanting to add an outdoor receptacle roughly 10 feet from the junction box I found. Adding in the receptacle is no issue for me, just want to make sure I use proper gauge wire for the pigtail.

  • Are there markings on the grey jacket saying what gauge the wires in the cable are? This sounds like a UF cable, but we can't tell the wire gauge from here... – ThreePhaseEel Jul 17 '17 at 1:40
  • @ThreePhaseEel - unfortunately not, I have followed the wire as far as I can (roughly 100 feet) and I see no visible markings on the outside of the jacket. – BellHopByDayAmetuerCoderByNigh Jul 17 '17 at 1:42
  • Can you measure the diameter of the wires inside (say, with a pair of calipers)? – ThreePhaseEel Jul 17 '17 at 1:43
  • 2
    Find the overcurrent device and make sure your wire is at least large enough to match that amp rating. – Jimmy Fix-it Jul 17 '17 at 4:22
  • Yep, to re-phrase what @JimmyFix-it said, turn circuit breakers off until you identify the one that turns that wire off. As long as it's a single handle breaker if the breaker says 15 on the handle use 14 gauge wire, if the breaker says 20 use 12 gauge wire. Be sure to use UF, not NM for your extension. – Tyson Jul 17 '17 at 14:42

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