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As the title states, are there any code restrictions in general on using crimped spade and ring terminal connectors when wiring household electrical circuits?

I've actually been doing this for a while, using 600V rated spade connectors from Home Depot, and Wago's Wall-Nuts, and I've inspected some of my work that has been installed for over a year and saw nothing worrisome but I thought it might be good to ensure I'm not totally violating code here.

An example of something done recently: enter image description here

EDIT: I predict a lot of "you don't need to do that" or "that's overkill" replies: Yes, that's totally obvious, but I like to over-engineer things.

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  • can't answer specifically to code, but your installation seems unusual. I presume that wire is stranded? If you are using solid wire, it would be better if you just wrapped the wire around the outlet's screw and tightened it.
    – Edwin
    Mar 19, 2015 at 5:51
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    Yes it's all stranded. I prefer stranded, as #12 solid copper is quite difficult to move when pushing the device back into the box. Stranded costs more, but it's much easier to work with, and I feel it gives a better end-result which is why I've been doing it this way.
    – William S.
    Mar 19, 2015 at 5:54
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    Since you're working with stranded wire, it's actually probably a good idea that you're using these connectors. I doubt there's a code issue here. If the terminals are not designed for such connectors, it could be a violation because you'd not be following the manufacturers installation instructions. Make sure you're using the proper sized connectors, and you shouldn't have a problem.
    – Tester101
    Mar 19, 2015 at 12:40
  • The primary issue with crimp terminals is using a GOOD crimper with the proper size dies for the connector and wire size/number - otherwise you can get crummy connections that fall apart.
    – Ecnerwal
    Mar 19, 2015 at 13:32
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    Note: Please use imgur to host images you're adding to posts, or use the 'Image' feature of the site. Nobody likes crap downloading automatically to their computers.
    – Tester101
    Mar 19, 2015 at 15:05

5 Answers 5

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After further review, it appears that receptacles and switches are listed for use with crimp terminals. So this installation would not be a violation of NEC 110.3 (B).

National Electrical Code 2014

Chapter 1 General

Article 110 Requirements for Electrical Installations

110.3 Examination, Identification, Installation, and Use of Equipment.

(B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

2013 UL White Book

Receptacles (RTDV)

Receptacles for Plugs and Attachment Plugs (RTRT)

Terminals
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.

Switches (WFXV)

Snap Switches (WJQR)

Terminals
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.

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  • Apparently, not all outlets are identified for use with crimped-on ring or spade terminals, even if they are listed under UL486A. It makes me wonder if the verbiage from the White Book you quoted was intended to apply to proprietary "modular wiring device" connection systems (Arrow-Lock, Lev-Lock, PlugTail)...
    – ThreePhaseEel
    Mar 24, 2015 at 22:29
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First point: your terminals need to be listed under UL 486A in order to be usable in household wiring; many are, but some aren't, so check the package for the solderless terminals you are using!

Second: provided the terminals are listed for the application, NEC 110.14(A) also applies here:

Terminals. Connection of conductors to terminal parts shall ensure a thoroughly good connection without damaging the conductors and shall be made by means of pressure connectors (including set-screw type), solder lugs, or splices to flexible leads. Connection by means of wire-binding screws or studs and nuts that have upturned lugs or the equivalent shall be permitted for 10 AWG or smaller conductors.

Terminals for more than one conductor and terminals used to connect aluminum shall be so identified.

Obviously, the device itself needs to be identified for use with ring or spade terminals as well, as per Tester's UL White Book quote above. (P.S. typical spec- or builder-grade wiring devices may not be identified for use with ring or spade terminals -- I called Leviton's tech support and asked, and got a "no" back.)

Also: have you considered any of the single-connector wiring device lines available? (Cooper Wiring Devices, Leviton, and Legrand all have different versions of this, but it's the same basic idea -- you install a specialized, three-terminal connector onto the wire-ends in the box, and then the outlet or switch simply snaps onto said three-terminal connector.)

Finally, I would highly recommend that you obtain and use a ratchet-type crimping tool if you do not already own one -- even an inexpensive ratchet-type crimp tool will get the job done reliably, where as crimp-pliers (or heaven help, regular pliers!) can yield loose crimps.

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Pardon my wordiness below – I just wanted to be as clear as possible, and hope some of it will be useful. I have not searched the NEC re. crimp/solderless connectors so I will not address that question. As someone who also has a strong preference for stranded wire, however, I will offer some suggestions that might alleviate some compliance concerns – based on what I have been doing for years.

My first choice is to install devices, when available (they can be difficult to find at some big-box stores like Home Depot and Lowe’s), that are equipped with 'clamp' side screw terminals. These terminals operate similarly to the screw terminals on many GFCI receptacles, as well as the load-side lugs on many circuit breakers (the devices I refer to are often called ‘spec grade,’ which is not necessarily a correct designation). The clamp side screw terminals on these devices can be used in the conventional sense (looping a solid conductor around the screw then securing it by tightening the screw), but using the clamp allows a straight (not looped) length of bare (solid or stranded) conductor to be inserted into the clamp area and firmly secured using the same screw. The clamp termination provides an equally solid and reliable termination for both solid and stranded wire, and eliminates the need for ‘tinning’ stranded conductors (tinning allows a loop to be formed without fraying loose copper strands). The devices with clamp side screw terminals typically cost more than the more basic devices (usually about double that of general use devices – albeit NOT the typical, and much cheaper, $.70 ‘builder grade’ device), however, in addition to having clamp side screw terminations, they are noticeably higher in overall quality. I have never experienced any problems with the clamp terminations on these devices – either during installation or later.

Another method I have used (albeit much less often) is to utilize solderless terminals. If using solderless terminals, I first try to utilize a ring type (to maintain the connection even if a screw comes loose), but with most terminal screws being ‘captive’ the screw cannot be removed on most devices I am often unable to use a ring terminal. I then opt for either a hook or a flanged spade style solderless terminal –either of which is much less likely to completely detach from a loose screw terminal than a straight spade (“fork”) terminal. Whichever terminal I use, I always solder the terminal to the conductor after it is securely crimped to the conductor – especially important when a terminal is crimped to a solid conductor. Soldering the terminal often destroys any insulator attached to the terminal, so I then add one or two layers of shrink-tubing to replace the original insulator (if I have reason to believe there will be significant bending of the conductor where it exits the terminal, I apply two layers of shrink-tubing – making certain that the outer layer extends over the conductor insulation sufficiently to serve as a strain-relief. [NOTE: I NEVER rely on solder alone to secure a terminal to a conductor . . . if the circuit heats sufficiently for any reason, the solder can flow and allow the conductor and terminal to separate]

Regardless of what termination method I use, once completed, I always wrap two layers of electrical tape around the side screws and finish by placing a small wire tie over the electrical tape (electrical tape, esp. in the Deep South heat where I live, WILL come loose over time – the wire tie holds the tape in place). Once installed in a wall box, it is nearly impossible for anyone to contact a side screw terminal on the device with a screwdriver or other tool inserted into the box. Is this overkill – probably to many, but I have never had a problem with a termination on any device I have installed (over more than twenty years) . . . but I HAVE witnessed the outcome of fires resulting from loosened or poorly tightened device terminations.

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    I can attest to this great advice. These devices (receptacles/switches) are available at big box stores and labeled 'pro' grade (Leviton at HD). The wire clamps are effective and code compliant for both stranded and regular solid core. Simply strip, stab in and tighten. They're NOT to be confused with the vastly inferior spring-loaded back-stab holes found on the back of residential grade receptacles.
    – pscl
    Jul 21, 2017 at 8:00
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NEC may allow it, but the UL Question Corner column in the November-December 2008 IAEI NEWS states: "UL Listed receptacles are evaluated for use with solid and stranded conductors; however, they are not Listed for use with spade terminals."

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No code problems as long as they are sized to maintain an acceptable cross/surface area. Which translates into use the right size and you are good to go.

Yellow are 10-12 gauge -- only one wire per connector -- the hole or opening in the crimp is a match for the screw or bolt -- use the correct tool -- and crimp into the split in the wire cup

They do come with the seam brazed, they are a big step up in quality and finish.

There are also little copper barrels, like a wire nut without the plastic part, and crimp instead of spring. These are the correct part to use when trying to get a stranded wire under something like a load center neutral screw bar.

  • Trivia note - NASA uses terminal lugs instead of soldering, whenever possible.

Completely personal opinion, on wire terminals and associated parts.

I do not use the generic wire terminals with the plastic 'strain relief' covering, like those shown. They rely on the crushing of the plastic to insure proper wire contact. The plastic in these things is not engineered to crush,'just right.'

If I wind up in a situation where they are all I have, I pull the plastic off of them and use them without. This also allows me to see if the wire insulation jacket really meets the edge of the connector, to make sure all of the wire strands made it inside the barrel of the connector, and to check and see if or how much the seam opened.

Heat shrink after, if it will help with strain relief, or just look nice, is the way I finish them.

The right tool, the 12 in 1 tools sold right next to the terminals, are just not good (except for the screw cutter in the Greenlee brand one, thing works great, I carry one for just that reason.)

The Klein 1006 is the best generic terminal crimp tool of its kind. It 'feels right', it has good weight, it is not stamped sheet steel, the crimp forming nests are supported and sized well, and under $30 on the home depot web page.

If you must use insulated terminals, and there are valid situations for it. The Klein 1005 is made to crimp both insulated and non-insulated connectors.

Wire Strippers, I know real men use linesman's pliers for almost everything, but sometimes, they are just not the right tool. Klein 11049 are designed for Stranded Wire 8 to 16 gauge. You have no idea how wonderful the difference vs. using strippers for solid wires. They have 4 pair in this series big and small in both stranded and solid.

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  • The plastic covering is there for insulation purposes, not strain relief. The plastic has nothing to do with the crimp, the wire is held by the metal barrel inside, not the plastic.
    – Tester101
    Mar 19, 2015 at 14:57
  • Thanks, I've thought about using heat shrink on some connections but the heat shrink itself is expensive unless you buy large rolls of it, and I have been leery of investing heavily if I ended up not using it. I use the insulated connectors vs the non-insulated because it makes the junction box a little safer to work in if it's live.
    – William S.
    Mar 19, 2015 at 17:23
  • Understood completely cathode, I was raised in an unusual industry, with odd thoughts of what was right. :P
    – Some Guy
    Mar 19, 2015 at 21:20
  • Tester, I realize we see things from a different perspective often, and that is why places like this are good. I have no problem being wrong. The plastic is for both insulation and strain relief, which is part of the reason that I put strain relief in quotes in my answer. We see the plastic differently, again no problem. When I crimp terminals like that, I actually squeeze the plastic, which then presses on the barrel. So all the energy required to crimp the metal barrel around the wire is a direct result of the plastic. Your tool works only on the metal and not the plastic. Then I am wrong.
    – Some Guy
    Mar 19, 2015 at 21:34
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    For what it's worth, I ordered this from Amazon.com today: amazon.com/gp/product/B0045CUMLQ/… And I'm looking forward to turning out some more professional looking crimps than what I've been able to achieve with the plier-type crimpers.
    – William S.
    Mar 21, 2015 at 23:02

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