Terminating Stranded Wire On Receptacles -VS- Switches

[jusme123]

This is the reply of a question submitted for clarification ;



Q: I want to secure #12 AWG THHN stranded conductors to the screw terminal of wiring devices, duplex receptacles and/or toggle switches, even though the stranded conductor spreads and does not make full contact with the screw terminal and remains undamaged throughout the maneuver. Can I just wrap the stranded conductor around the screw terminal and tighten using a torque screwdriver or must I use a T & B Sta-Kon crimp terminal to prevent the strands from spreading? There is another method that comes to mind, strip a small portion of insulation and allow it to cover the tip of the strands, thereby minimizing the amount of spread at the conductor end. If I must use a crimp terminal or some other method, please explain why since there is no mention of this in Section 110.4 or anywhere else in the Code.

I understand some contractors have received a violation on this matter using section 110.14 of the Code.

A. UL Listed receptacles are evaluated for use with solid and stranded conductors. Also, 2012 UL White Book permits terminals of a receptacle are permitted for use with certified field-installed crimped-on wire connectors or an assembly, if so identified by the manufacturer. (Refer to UL product category RTRT).
General use switches are Listed for use with only solid conductors unless otherwise indicated in their installation instructions. 2012 UL White Book doesn’t include permitting language to use certified crimped-on wire connectors or an assembly. (Refer to UL product category WMUZ).

 

[infinity]

You need to follow the listing of the device, if they permit stranded conductors you can use stranded conductors without a fork style terminal. If you use a fork style or other crimp terminal technically you must use the crimper that is part of the listing of the terminal not the crimper in the back of your lineman's pliers.

 

[winnie]

I find that if I twist the strands in the 'backwards' direction prior to forming a hook and putting the wire under the screw terminal, then when the screw is tightened the strands get pulled together rather than pushed apart.

-Jon

 

[ActionDave]

I don't know why recpts are ok for stranded but switches are not. Are the factories using different screws? I don't think so.

 

[templdl]

You need to follow the listing of the device, if they permit stranded conductors you can use stranded conductors without a fork style terminal. If you use a fork style or other crimp terminal technically you must use the crimper that is part of the listing of the terminal not the crimper in the back of your lineman's pliers.

The way that I see it is that ir goes back to NEC art 110-3(B) installation and use.
Listed or labeled equipment SHALL BE INSTALLED and used in accordance with any instructions in the listing and labeling.

As such what do the instruction say and/or how is it labeled. In stranded wire allowed.

 

[tom baker]

I use non insulated crimp on spade lugs

 

[Dennis Alwon]

Crimps are good but if you strip the stranded wire but leave the insulation on at the tip about 1/4" then the wire won't unravel. Of course you still need to go by the listing of the device.

 

[JFletcher]

Interesting. I wouldnt have thought either would be listed for stranded, and have pigtailed solid from stranded to screw terminals on both.

 

[Smart $]

Why bother wrapping or using crimp-on spade terminals....


Just use pressure-plate, back-wire devices.

 

[Smart $]

...Just use pressure-plate, back-wire devices.

PS: I've yet to see a switch with pressure-plate, back-wire terminals. Are there any out there?

 

[user 100]

PS: I've yet to see a switch with pressure-plate, back-wire terminals. Are there any out there?

I think some of Levitons industrial/commercial sp switches have the plates/are rated for stranded.

 

[ActionDave]

Cooper used to make some. I'll bet Hubbell does.

 

[JFletcher]

PS: I've yet to see a switch with pressure-plate, back-wire terminals. Are there any out there?

Decora switches have pressure plates.

 

[kwired]

PS: I've yet to see a switch with pressure-plate, back-wire terminals. Are there any out there?

P&S have them, catalog numbers start with CSB...

A CS20AC1-I would be standard 20 amp screw terminal, CSB20AC1-I would have pressure plate terminals. Believe it or not my supply house doesn't ordinarily have them but the big box store does:roll:

 

[Strathead]

P&S have them, catalog numbers start with CSB...

A CS20AC1-I would be standard 20 amp screw terminal, CSB20AC1-I would have pressure plate terminals. Believe it or not my supply house doesn't ordinarily have them but the big box store does:roll:

Same thing with Leviton. I don't think resi grade has back wire, but why would you be using stranded wire in a residential installation. The back wire devices are more expensive but worth it as far as I am concerned. I have my field guys just using the back wired ones and not worrying about the issue.

 

[MasterTheNEC]

This is the reply of a question submitted for clarification ;



Q: I want to secure #12 AWG THHN stranded conductors to the screw terminal of wiring devices, duplex receptacles and/or toggle switches, even though the stranded conductor spreads and does not make full contact with the screw terminal and remains undamaged throughout the maneuver. Can I just wrap the stranded conductor around the screw terminal and tighten using a torque screwdriver or must I use a T & B Sta-Kon crimp terminal to prevent the strands from spreading? There is another method that comes to mind, strip a small portion of insulation and allow it to cover the tip of the strands, thereby minimizing the amount of spread at the conductor end. If I must use a crimp terminal or some other method, please explain why since there is no mention of this in Section 110.4 or anywhere else in the Code.

I understand some contractors have received a violation on this matter using section 110.14 of the Code.

A. UL Listed receptacles are evaluated for use with solid and stranded conductors. Also, 2012 UL White Book permits terminals of a receptacle are permitted for use with certified field-installed crimped-on wire connectors or an assembly, if so identified by the manufacturer. (Refer to UL product category RTRT).
General use switches are Listed for use with only solid conductors unless otherwise indicated in their installation instructions. 2012 UL White Book doesn’t include permitting language to use certified crimped-on wire connectors or an assembly. (Refer to UL product category WMUZ).

I will assume (bad more here) that you are talking simply about snap switches. If that is the case then UL Guide WJQR is fairly straight forward.

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.


Screwless terminal connectors of the conductor push-in type (also
known as ‘‘push-in terminals’’) are restricted to 15 A branch circuits and
are intended for connection with 14 AWG solid copper wire only. They are
not intended for use with aluminum or copper-clad aluminum wire, 14
AWG stranded copper wire, or 12 AWG solid or stranded copper wire.
Terminals of switches rated 30 A and above not marked ‘‘AL-CU’’ are
intended for use with copper conductors only. Terminals of switches rated
30 A and above marked ‘‘AL-CU’’ are for use with aluminum, copper and
copper-clad aluminum conductors.

Guess I should also add Receptacles ( UL Guide RTRT)

TERMINALS


Terminals of 15 and 20 A receptacles not marked ‘‘CO/ALR’’ are for use
with copper and copper-clad aluminum conductors only. Terminals
marked ‘‘CO/ALR’’ are for use with aluminum, copper and copper-clad
aluminum conductors.


Terminals of receptacles rated 30 A and above not marked ‘‘AL-CU’’ are
for use with copper conductors only. Terminals of receptacles rated 30 A
and above marked ‘‘AL-CU’’ are for use with aluminum, copper and
copper-clad aluminum conductors.


Terminals marked ‘‘75 C’’ may be wired using the ampacities for conductors
rated 75°C as well as conductors rated 60°C in Table 310.16 of the
NEC.


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


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


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


Screwless terminal connectors of the conductor push-in type (also
known as ‘‘push-in-terminals’’) are restricted to 15 A branch circuits and
are for connection with 14 AWG solid copper wire only. They are not
intended for use with aluminum or copper-clad aluminum wire, 14 AWG
stranded copper wire, or 12 AWG solid or stranded copper wire.


Single and duplex receptacles rated 15 and 20 A that are provided with
more than one set of terminals for the connection of line and neutral conductors
have been investigated to feed branch-circuit conductors connec.
ted to other outlets on a multi-outlet branch circuit, as follows:

• Back-wire (screw-actuated clamp type) terminations with multiple

wire-access holes used concurrently to terminate more than one conductor.

• Side-wire (binding screw) terminals used concurrently with their

respective push-in (screwless) terminations to terminate more than one
conductor

 

[augie47]

..............................................


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.

........................................................


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

Is it commonplace or rare for receptacles and/or switches to be identified by the mfg for use with crimp on wire connectors ?

 

[MasterTheNEC]

Is it commonplace or rare for receptacles and/or switches to be identified by the mfg for use with crimp on wire connectors ?

Now that my friend would be a great question to present to Mr. Holland to bring to NEMA since I honestly do not know the answer to that one. It is not something I have given much thought to over the years. I would tend to think that Hubbell is a great resource to ask on that so maybe I will call up a few of my old friends...if I do I post what they say here.

Clearly we know they can...just not sure how often they do.

 

[augie47]

I dropped him an IM asking for his input. Thanks,

 

[cleatus_sask]

Twist your stranded wire left-hand or backwards of what it usually is- pulls the stands in as it tightens!