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I'm trying to figure out if I can split a single branch circuit into two runs. Basically, I want to add an outlet to a circuit, but it's not in a convenient place to put it in line with a single run. The wiring would look something like:

 -----------
 | Panel   |        --------
 |         | 12/2   | Jct  |  12/2
 |     20A |--------| Box  |---------Outlet-------Outlet----...
 |         |        |      |
 -----------        --------
                       |
                       \ 12/2
                        -------Outlet

Will NEC allow this? Thanks!

Logan Bowers
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1 Answers1

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Yes, that's fine, you can "tee" circuits. I just did one that looks like a tree... starting with a 3-way split right in the service panel. And two branches themselves have splits downstream.

Now let's talk about splicing. USA receptacles provide two screws or backstabs per side. That has several uses, but the most common use is an easy way to do a 3-way splice: one for the power source, one for the downstream feed to the next outlet, and of course the receptacle itself. Here's the thing: people get hung up on this, and forget this is only one of several ways to do a splice. You can use any listed method.

So with both screws full, how do you add a third wire?

  • you cannot use both screws and backstabs. You must use one system or the other only, and don't use backstabs anyway becuase they fail a lot.
  • You can use a short pigtail to come off one screw, and then any of a variety of splices to join the pigtail and two of the wires. One remains on the other screw (or not; you can just join all the wires at the splice, I do that when the receptacle is in a really awkward location.)
  • you can use special receptacles called screw-and-clamp which can accommodate four wires (plus the receptacle itself obviously). You have to hunt these down, but they cost about $3 - not unbearable.

What kind of splices would you use? Any listed splice. Some examples are wire nuts -- Alumiconns (they work fine on all copper wire) -- Euro type terminal blocks -- push-in (unreliable) -- snap-down splice connectors. I use wire nuts myself.

Harper - Reinstate Monica
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  • "you cannot use both screws and backstabs." <-- This is a claim I have seen repeated without citation to either UL or NEC paragraph. I believe the claim is incorrect. NEC is not online, unfortunately, but found using "fair use" searches and this exact, quoted search: "terminals used concurrently with their respective push-in.

    Example: https://www.mecknc.gov/LUESA/CodeEnforcement/Tools/CodeInterpretations/CodeInterpretations/APRIL%202011%20QTR.pdf THAT SAID, I agree backstabs are substandard connections and should not be used to feed downstream outlets (and I'm just a lazy homeowner).

     – Scott Prive Mar 17 '19 at 16:33
  • @Crossfit_and_Beer I can quote it for you from memory. NEC 110.3 "Equipment must be used in accordance with its labeling and instructions". – Harper - Reinstate Monica Mar 17 '19 at 16:38
  • I am quoting it from a the ACTUAL UL doc: http://productspec.ul.com/document.php?id=RTRT.GuideInfo

    ... " The UL Whitebook states as follows: ... Side wire (binding screw) terminals used concurrently with their respective push-in (screwless) terminations to terminate more than one conductor". Please consider, your quote is not incompatible with mine. :-)

     – Scott Prive Mar 17 '19 at 16:40
  • @Crossfit_and_Beer Interesting. So you're saying UL requires that all receptacles pass that test? Or only those whose instructions authorize concurrent stab and screw connections? – Harper - Reinstate Monica Mar 17 '19 at 16:49
  • According to the UL link above, the ONLY qualification I see is "restricted to 15 A branch circuits and are for connection with 14 AWG solid copper wire only.". If they say it is allowable, wouldn't you agree it "is" (and therefore covered by their tests) UNLESS followed by explicit caveats? – Scott Prive Mar 17 '19 at 17:08
  • Shorter: Using both screws and backstabs - concurrently - are a "listed method" – Scott Prive Mar 17 '19 at 17:17
  • The question in my mind relates to applicability of the document. Does UL require concurrent support for every receptacle it lists? Or is the manufacturer allowed to state in instructions whether it is supported? Also, when did this become so, as many receptacles people deal with in the field are old. – Harper - Reinstate Monica Mar 17 '19 at 17:34
  • Great questions. I'm not an electrician. Perhaps it became allowed or perhaps it always was allowed but some original wording was unclear and left the method open to another interpretation. – Scott Prive Mar 18 '19 at 00:35
  • To be clear, I was not advocating I was pointing out interesting UL text on this. That said... just because something is permissible, doesn't mean it is a good idea. :) I remove every backstab I find and use pigtails when necessary. – Scott Prive Mar 18 '19 at 00:41
  • The link in the answer text under screw and clamp is giving a 404 error. The Internet Archive found a bunch of versions of it with a 403 error. Not finding anything that looks right with Google. Is there another term for this that can be used to find the item? Or an updated link? – Mike Eng Aug 20 '20 at 01:59