Electrical – Can stranded wire be used for pigtails in a junction box

electricalwiring

I replaced a fixture today that had a piece of 12Ga stranded (probably THHN) wire used as a pigtail. The building has some wiring in conduit (other wires in this box were solid), so I'm guessing that's what the prior person had handy.

If this is a legitimate use, it seems that it may be worth keeping a bit of stranded wire handy, as the pigtails would be a little easier to work with in a tight box.

I'm in CT, USA.

Best Answer

As long as all the equipment is listed for the use, there's no problem using stranded wire. The UL White Book says that screw terminals and pressure plate terminals can be used with both solid and stranded wire.

UL White Book 2013

Receptacles(RTDV)

Receptacles for Plugs and Attachment Plugs (RTRT)

Terminals
Terminals of the wire-binding screw, setscrew, or screw-actuated backwired clamping types are suitable for use with both solid and stranded building wires.

It says switches are solid only, however, you can use terminal connectors such as fork connectors.

Switches (WFXV)

Snap Switches (WJQR)

Terminals
Terminals of the wire-binding screw, setscrew, or screw-actuated backwired clamping types are suitable for use with solid building wires unless otherwise indicated either on the device or in the installation instructions.

Terminals of a flush snap switch are permitted for use with Listed field-installed crimped-on wire connectors or an assembly, if so identified by the manufacturer.

A flush snap switch may also be provided with conductor leads with factory-installed crimped-on connectors. Such connectors may be either attached to the flush snap switch terminal or are provided with the flush snap switch in the smallest unit shipping container and are suitable for use with the terminal of the flush snap switch.

Wire connectors (including twist-on wire connectors) can be used for both solid and stranded wire sizes between 30-10 AWG, in combinations listed by the manufacturer. Unless they are clearly marked to be used with one type or the other.

Wire Connectors (ZMKQ)

Wire Connectors and Soldering Lugs (ZMVV)

Wire stranding -- Unless clearly marked "Solid," "SOL," "Stranded" or "STR" for a given wire size, wire range or wire combination, conductors in the range 30-10 AWG are both solid and stranded, and 8 AWG and larger are for stranded wire only.

Ideal Industries has a handy PDF, that lists all the allowable wire combinations that can be used with their various connectors. For example, the Ideal 74B® (their basic yellow wire-nut) can be used with 1 - 4 #14 solid or stranded conductors.

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