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All modern receptacles have places for additional hot/neutral wires so you can add more outlets in series, but they all have a single screw or hole for the ground wire.

Why don't they have two ground holes?!? I see many receptacles wired where the installer simply twisted the wires by hand, or only used electrical tape, or used a wire nut but did not use the proper size, or did not know how to properly use a wirenut (only doing a single twist)! Sometimes the connection is good when they install it, but since there is so little space behind a GFCI for example, they had to manhandle the wires back into the box, and this caused their halfass attempt at a connection to come loose the second I pull it out of the box.

I am so tired of replacing receptacles only to find that the previous installer didn't know how to continue the ground line properly.

It would seem that adding a second hole would be preferable to the dangerous situation that arises when someone does not have/know how to use a wirenut correctly.

Is there any good reason they make them this way?

cds333
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    The goal is that ground is a safety return path for a circuit, specifically, the SINGLE outlet it is connected to in this case (not other items downstream). There is only one situation where that outlet should be supporting a return path,which is if the box or outlet or devices plugged into it) need it. Should something else in the wall or downstream the ground is tied to need to use the ground, you should not be utilizing the chassis of the outlet to complete the circuit. Your required to be wired directly to ground. The frame of the outlet is not it. This promotes safety, not them being lazy – noybman Nov 20 '19 at 02:29
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    @noybman That comment would make an excellent answer! – Tashus Nov 20 '19 at 16:52
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    This is an excellent question, and I’m glad you asked it! – Jacob Krall Nov 20 '19 at 22:21
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    You should never wire outlets in series. – Tom van der Zanden Nov 21 '19 at 08:08
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    I was unaware that the use of wire nuts was a "halfass unsafe twist connection". Can you site a section of the NEC for that? Unless, of course, you're referring to twisting the wire around the grounding screw, in which case, I am again unaware that this is considered unsafe and would love to see the NEC for that. – FreeMan Nov 21 '19 at 12:49
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    @Freeman OP did not state that wire nuts are a "halfass unsafe twist connection." The actual quote is "force people to use a wire nut or attempt some halfass unsafe twist connection" where two options are mentioned, one being a wire nut, the other being some sort of twisting connection – barbecue Nov 21 '19 at 15:22
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    Ground loops bad. electrician Hulk destroy. – Carl Witthoft Nov 21 '19 at 16:40
  • @barbecue #ReadingFail - my bad. However, I'm still curious what said "twist connection" is and why it seems to be so bad. – FreeMan Nov 21 '19 at 17:12
  • @FreeMan Based on my experience with amateur wiring, OP is referring to when somebody strips the end of two wires, holds them parallel, twist them together (sans wire nut), and then simply wraps the exposed wires in electrical tape. Generally unsafe, but not as uncommon as it should be. – Conspicuous Compiler Nov 21 '19 at 17:15
  • Would you believe, in some countries they do! – Caius Jard Nov 21 '19 at 20:11
  • @ConspicuousCompiler yes exactly! I find these very often where someone does this but they do not apply a sufficient number of twists, the result is that when they are forcing the receptacle into the box, or someone else pulls it out later, and the connection comes loose, or the wires are just barely making contact. – cds333 Nov 22 '19 at 07:43
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    @barbecue sorry, what I should have said was "force people to use a wirenut incorrectly". I edited the OP to be more clear – cds333 Nov 22 '19 at 08:05
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    @ConspicuousCompiler I would never ahem do that... nowadays. – barbecue Nov 22 '19 at 13:56

4 Answers4

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This is because removing a device isn't allowed to interrupt grounding connections

Removing a wiring device from the circuit cannot break grounding connections, or else you are violating NEC 250.148(B):

(B) Grounding Continuity. The arrangement of grounding connections shall be such that the disconnection or the removal of a receptacle, luminaire, or other device fed from the box does not interfere with or interrupt the grounding continuity.

As a result, manufacturers only put one ground screw or terminal on wiring devices, so that you're required to do the right thing and pigtail grounds using a splicing connector of some sort or another (whether it be a wirenut, a crimp, or a push-in type splicing connector).

ThreePhaseEel
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    @JimmyFix-it Do you mean a continuous ground wire which is stripped and looped around the ground screw (which is fine - you just need to disconnect the continuous ground from the receptacle to remove the latter), or do you mean two ground wires tucked under the ground screw (no, no, no, no)? – Martin Bonner supports Monica Nov 20 '19 at 11:10
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    @MartinBonnersupportsMonica, yeah you are correct. I'm not thinking straight. The bare ground wire looped under the terminal should be fine if it is unbroken... duh – Jimmy Fix-it Nov 21 '19 at 02:10
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I am glad you are finding it convenient that some devices allow themselves to also be used as splice blocks.

However, that is prohibited for certain types of wires:

  • Any and all ground wires
  • Neutral wires on multi-wire branch circuits

That is because it will cause serious problems for other (e.g. downline) loads if those connections are severed due to removal of a device.

Further, grounds are only allowed to be attached via a shepherd's hook around the terminal screw. No backstabs are allowed (they're not particularly reliable) nor should a screw-clamp connection style be used.

Devices are not obliged to provide convenient splice points. There is nothing wrong if they don't. That is when you use a pigtail, which should be part of your repertoire. You should not be attempting a half-ass anything. If you can't execute a proper pigtail, skill up.

Don't be the newbie who judges how things are done, or criticizes the previous work; it's typically more competent than you realize. (Or not, but it's hard to be sure of that when you're new). As always, we're happy to help.

Harper - Reinstate Monica
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    Unless there is but a single cable entering the box, always, that's when. – Mazura Nov 20 '19 at 19:12
  • Would this be a perfect place to provide a link to what a pigtail is and how to correctly make one? – CXJ Nov 21 '19 at 14:35
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    @CXJ Here's a link to another one of Harper's answers, which goes into a bit more detail about pigtails. https://diy.stackexchange.com/a/123816/95658 – Doug Deden Nov 22 '19 at 01:34
  • Obviously a pigtail is preferable- but when people refuse to use them, and the result is a improperly connected ground, or no ground at all (I have seen this multiple times! as if they were like "uh oh, theres no place to continue this copper wire, I guess we dont need it"), wouldn't it just be safer to have two ground screws, so newbies can still have a safely connected ground? Sure it might result in a loss of a ground sometime in the future, if someone disconnects that receptacle and leaves it disconnected, but that would be better than the alternative. – cds333 Nov 22 '19 at 08:03
  • @cds333: I would think a better approach would be to have multiple inter-connected grounding screws within a junction box, and a spring-loaded contact that touches the mounting tabs of switches, outlets, etc. – supercat Nov 22 '19 at 15:53
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    That's kinda what we do in metal boxes. @cds333 once again, the receptacle can't be a splice point, because the splice will fail if removed. I don't understand what the resistance is to doing the work to Code? How to do this is well understood and a proven technique. You seem to be fighting for the right to do electrical work without learning to do it properly. – Harper - Reinstate Monica Nov 22 '19 at 16:44
  • @Harper-ReinstateMonica I am not advocating for doing it the wrong way. I am constantly finding work done this way by other people, either the homeowner or the last handyman. They could easily go on youtube and watch a 5 minute video and learn how to do it properly- problem is they don't. Home depot and lowes are not commercial electrical supply houses, but they sell these to anyone, and with no included instructions, and the result is that people hook them up wrong. They should either include an instruction sheet and/or simply sell them with a ground lead + wirenut already attached. – cds333 Nov 24 '19 at 02:23
  • @cds ok I respect that. Selling them pre-ground-pigtailed is a good idea. You know the preamble to the Electrical Code is about 20 pages listing the individuals who sit on the various committees. You can find them and outreach them. – Harper - Reinstate Monica Nov 24 '19 at 02:33
  • On the other hand, a newbie probably doesn't need to worry about interrupting the ground because he turns the breaker off before wiring anything up. – Joshua Feb 25 '20 at 02:26
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In addition to what @ThreePhaseEel said, the purpose of having two screws on each side is not so that receptacles can be wired in series. While that is allowed, the purpose is for "split receptacle" setups, where only one outlet is controlled by a switch (or each is controlled by a separate switch). This is done by breaking the metal tab that joins the two screws.

Here's an example.

Split Receptacle

BlueRaja - Danny Pflughoeft
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    Or an outlet that is fed by two different circuit breakers -- e.g., a kitchen outlet intended to handle two high amperage loads? – bobwki Nov 21 '19 at 19:07
  • @bobwki I wonder if that would be up to code? My gut says no, but I've been wrong before. – Monica Apologists Get Out Nov 21 '19 at 20:41
  • I'm not an electrician, but every kitchen receptacle I've seen has been split, and I assumed that that was the actual reason such devices included two screw terminals (actually I was going to ask that question until seeing this answer). – canadianer Nov 22 '19 at 00:00
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    @Adonalsium: No, it's allowed. You can even have a shared neutral, as long as both circuits are opposite phase. It's called a Multiwire Branch Circuit (MWBC for short). In my experience they're not very common, but I'm not a professional electrician. – BlueRaja - Danny Pflughoeft Nov 22 '19 at 00:03
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    You'll pretty much end up with opposite poles, because two circuits serving the same yoke must be handle-tied. That's for common maintenance shutoff, so you don't plug a vacuum into one socket and trip breakers til it turns off, call it good, and get nailed by the other socket's circuit. Handle-tying pretty much forces the tied breakers onto opposite poles. – Harper - Reinstate Monica Nov 22 '19 at 01:00
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Hot and neutral wires are working wires. Ground wire is a security/reference wire. Any connection may loosen over time.

When hot wire gets loose, you'll notice it immediately - the devices behind the failure stop working properly. Same apply for the neutral wires.

On the other hand when the ground wire gets loose you want to have as few devices affected as possible. And one uninterrupted wire is the way to go. You also want to have as few hubs as possible as well - its faster to check 5 boxes than 15.

When the ground wire gets disconnected somewhere you'll lose the ground protection and you'll realize it at the time of another failure, which is too late. In the worst case You will become a grounding wire for a while. It may also result in different ground potentials over the house and some devices may malfunction because of that.

manassehkatz-Moving 2 Codidact
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Crowley
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  • Depending on what "loose" means, and depending on what you have plugged into the outlet, your first notice of a "loose," current-carrying connection could be the smell of hot insulation. – Solomon Slow Nov 22 '19 at 21:21
  • There's a point here that needs stating clearly - if the ground wire fails, the devices keep working and the user may not realise. – Criggie Jan 08 '22 at 11:43