My junction box

This my first attempt at a junction box . I am kind of worried the wires are too short. They are all in the push connectors. Is this safe?enter image description here

  • 4
    You should probably say what country you're in. Different countries have different definitions of 'safe'.
    – Dan W
    Commented Feb 11, 2019 at 18:19
  • 5
    looks way too short ..... you should be able to pull the ends of the wires out of the box and work on them comfortably
    – jsotola
    Commented Feb 11, 2019 at 18:56
  • 6
    Those wires are so short that you are actually at risk of a wire or junction break -- especially if that space is subject to freezing temperatures. Commented Feb 11, 2019 at 23:25
  • 3
    Going to guess that the second picture is your re-do? Much, much better.
    – JPhi1618
    Commented Feb 12, 2019 at 15:45
  • 1
    I'll add, since I haven't seen it below, that in the places I've done home wiring (Ontario and Nova Scotia, Canada), the excess external insulation is a problem. Shouldn't be more than a cm or so from the cable clamp (I don't have my simplified code with me to get the exact amount.
    – Auspex
    Commented Feb 12, 2019 at 15:56

4 Answers 4


I'm no electrician, but at first glance I would say two things:

  1. Ground the box itself. That ensures that there's no chance the box itself can become energized, because if a hot wire ever touched the box, it would trip the breaker. Unlikely situation, but I always do that when I'm working with metal boxes just to have some peace of mind. You should be able to do this with a common ground screw.

  2. Plug those open holes unless there are more wires going in there. You can buy little knockout plugs for less than $.50 at most home improvement stores. Open holes into a live electrical box are never a good idea.

In the future, I'd leave a little bit more extra wire in there, but it should function just fine assuming you've used the correct gauge wire for your current rating.

  • 19
    It's worth noting all of these, including the wire length, are required by code. Metal boxes must be grounded, unused knockouts must be covered, and the wire must be able to extend at least 3 inches from the opening (6 inches of extension if all dimensions of the box are at least 8 inches; 6 inches is a general rule is typical).
    – GManNickG
    Commented Feb 11, 2019 at 5:31
  • 1
    Also, use screw terminals, they're a lot safer and more reliable.
    – Dan W
    Commented Feb 11, 2019 at 18:22
  • @K4KFH If I use a plastic box with a metal top cover, should I ground the top cover somehow?
    – Roy Tinker
    Commented Feb 11, 2019 at 20:25
  • 4
    @DanW actually push connectors are safer than screw terminals, because people often over or undertighten them, the copper can wander and screws can work themselves loose over time if there is vibration. Push-connectors like wago always have the correct pressure, and they can take much more current than the wires are rated at. See Big Clive talk about them here: youtube.com/watch?v=zWc_awaQFPg
    – Lenne
    Commented Feb 11, 2019 at 23:58
  • 2
    @danw as big Clive is a professional electrician and electronic guru, who lives on Isle of Man, but also works in mainland UK, I believe him to judge wago as safe, legal and good. Seen the video? I also trust German chain Bauhaus not to sell dodgy stuff.
    – Lenne
    Commented Feb 12, 2019 at 9:19

The work is solid with a few exceptions.

Yes, that's too short. You should be leaving 9-12 inches. The legal minimum is 6" past the clamp, or able to reach 3" beyond the finished wall surface. It can seem cluttery, but cluttery is good.

Are you using a book on electrical? The book would tell you this. People learning electrical work best when they have a general overview of all aspects - a primer if you will. Google can't substitute because Google only answers questions, and without a well rounded set of concepts, it's hard to know all the questions you should be asking.

You will need to replace all three legs, and you will be better off doing it now, rather than waiting until the drywall is up, you are doing any kind of maintenance, and you are forced to improvise. Remove the old cables carefully and you can reuse them - maybe even for each other.

These push connectors are particularly problematic with short wires, because it is annoying/difficult to wrest the wires out of the push connectors, so people usually just snip them. You'll want even more length for that.

Some people get snipper-happy and go out of their way to cut wires as short as they can. Perhaps they think there are brownie points for that... Code does mention "neat and workmanlike", but functionality and maintainability come before neatness. Another trouble spot is the panel - it's in vogue to go snip-snip*, but for maintainability, you should give every circuit enough length so both hot and neutral can reach every breaker position in the box.

You need to ground the box also. Most boxes have a threaded 10-32 hole in the back for a ground screw. Some are on dimples so they work flush against a surface, look for that feature in boxes. They sell special green #10-32 ground screws. But any will do. Do not use a deck screw or sheetmetal screw unless it is cut -32 thread or finer.

Rather than spend a big budget on connectors, I would recommend using wire nuts instead. Not least because you can take apart wire nuts and reassemble them. But even more, because wire nuts produce reliable connections, and push connectors - like any backstab - are notorious for series arcing and failure. At least you are in a metal box, which will contain all but the worst series arcing.

I also see where you have knocked out two additional knockouts. You need to fill those with knockout plugs. Those are trivial cost, about a buck for five. Alternately, if you are expecting more cables to come in, you are painted into a corner with those push connectors.

Assuming you'll have 5 cables, it's time to start talking about box fill. If the box is getting too crowded, you can get either box extensions or "mud rings" which provide some additional cubic inches. On the Web there are "official" tables and calcs for box fill, but if you are leaving yourself 9-12" of wire, you'll know when boxes are getting crowded. The takeaway is that extensions (and larger boxes) are available.

My signature box when I have >5 cables converging is the 4-11/16 square x 2-1/8 (120 x 55mm) which I buy at electrical supply houses, where they are much cheaper.

* check out this disaster of a box. Looks purdy, but now add a generator interlock and a whole house surge suppressor: those need to go on top, so every breaker must move down 2 spaces. That expensive subpanel cable definitely will not reach, ouch! And then, when they add GFCI or AFCI to some breakers, none of the neutrals can reach. But he leaves lots of slack for the short service line (why?) Also, the panel is completely full, so it was a poor choice.

  • 3
    Harper referenced "additional cubic inches", but to further explain, there are calculations in the electric code that tell you how many wires, connections, and receptacles can be used in a certain sized box. So, if you ever say, "man this seems like too many wires for this box!", you can use the calculations to determine what size box code requires.
    – JPhi1618
    Commented Feb 11, 2019 at 15:46
  • Re "disaster of a box": Of course you can add a surge suppressor or two, just run the subpanel cable straight down and with a nice sharp turn right into the breaker and it'll reach (maybe after some tugging first). Or grab a couple of serious wire nuts and splice a short extension in. Sure, it'll be the mother of all code violations and an instant fire hazard as well, but who cares about that when you can post a great-looking photo? :)
    – TooTea
    Commented Feb 12, 2019 at 11:22

In addition to everything else everyone's said, if you don't have any spare length in the wires, it limits your ability to make changes to your wiring later.

You would struggle for example to bring in a 4th wire, and you've no spare length to correctly wire the earth wires to the metal box.

You may also need a little slack if you later adjust another fitting, or split a wire to make another spur off the ring.

  • Concur - OP or some other future person is gonna be grumpy if they need just a little slack somewhere in a wire.
    – Criggie
    Commented Feb 11, 2019 at 23:04
  • Yeah, I’ve done that to myself, had to re-run the wire because I’d not left a couple of inches slack.
    – Dan W
    Commented Feb 11, 2019 at 23:07

Looks ok I think it will work just needs a little sprucing up .

Providing your cable runs are long enough you may want to insert additional cable into the metal box, if you do. Strip back the cable sheathing within the metal box at least 6inches then connect them to the push in connectors ,also ground the box itself either by adding an additional bare wire to your connector if it is a 4slot type connector if not then loop an existing ground wire clockwise to the ground /bonding screw sometimes they are green .

Also reverse all of your clamps have the screw portion of the clamps on the outside of the metal box and then use knock out plates to cover the two spaces on the left side of the box.

  • 1
    Thanks for the tips. I added more slack along with wire nuts. I added a ground screw and wrapped the main line ground around it before splicing. I got the wrong size knock plugs so I will put those in tomorrow. Commented Feb 12, 2019 at 1:16

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