I intend to use 14 AWG copper pigtails for the receptacles in the 15-A circuits because #14 folds into the boxes so much easier than #12. The AlumiConn connectors take up more room than the Scotchlok red wire nuts, and the boxes are not generously sized.

I have on hand some solid copper wire (not romex but separate wires in white and black insulation) labeled "GCC P 14 AWG TYPE THHN OR THWN 600 VOLTS GAS AND OIL RESISTANT VW-1 OR AWM" which I used to pigtail switches and light fixtures on #12 AL. Is it OK to use that to pigtail receptacles in 15-A circuits in #12 AL? Or would it be better for some reason unknown to me to buy new Romex, cut the sheath off, and use the wires for pigtails?

The original 20-A circuits are in #10 AL and I will have to use #12 CU to pigtail those, but half of the 20-A circuits are dedicated and so have only one receptacle on them and so one cable in the box. Some receptacles I changed to CO/ALR and I won't pigtail those, at least not now.

When I pig-tailed the aluminum wiring in my house 35 years ago I used #14 pigtails on the light switches and the ceramic light fixtures and #12 pigtails on all receptacles, even in the 15-A circuits, because I thought three equal diameter wires (2 AL and 1 CU) would make a better connection in the Scotchlok 20058 red twist-on spring connectors I was using. The AlumiConn connectors have each wire in a separate hole.

  • Have you tried the two port AlumiConns? They're almost as small as a standard wire nut. AFAIK you can only order them online tho.
    – Machavity
    Nov 27, 2016 at 0:36
  • I have some 2-port AlumiConns. They would be used for switches and terminal receptacles. There are a few connections with 4 (or 5?) wires which I made 35-years ago with grey Scotchlok twist on spring connectors. Those will just have to be remade with the same type connectors but with Penetrox A joint compound. I originally used NoAlOx which is no longer recommended. Nov 27, 2016 at 11:03
  • you want stranded THHN wire for your pigtails. It is 100 times easier to cram in a box. Just make sure your splices and receptacles are listed for use with stranded wire. If you only buy one color, buy white, it can be taped to be a hot, or stripped bare to be a ground. Nov 28, 2016 at 0:43

1 Answer 1


THHN should be more than fine for a pigtail job; in fact, the wires in Romex aren't intended to be used by themselves i.e. outside of the cable jacket as they have no UL listing for that use -- the cable as a whole is the only thing that carries the listing.

(THHN/THWN is what's used inside metal-clad cables and when wiring conduits -- it's the "standard" wire as far as individual wires go for building-wiring use.)

  • What wire would be used for the ground pigtails? Is bare copper wire in #14 available to use as the ground pigtail? What would it be called? Or is solid copper with green insulation available? I understand that in the UK green/yellow stripe tubing is slipped over the bare copper ground in the junction boxes. Presumably this is not available in the US and just not used. Nov 27, 2016 at 3:03
  • @JimStewart -- green THHN is a thing, but you can also get bare copper wire in #14. Nov 27, 2016 at 3:07
  • by USA Code, any bare copper wire is ground, it doesn't need to be tagged further. Nov 28, 2016 at 0:49
  • @Harper -- just saying he can use green THHN if he can't find bare 14AWG :) Nov 28, 2016 at 1:15

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