Mechanical ways to do a T branch circuit?
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    Default Mechanical ways to do a T branch circuit?

    One single phase 240VAC (Red,Black,Green 8 AWG) circuit. Want to branch two ways (Red, Black,Green 10 AWG).
    Right now I have a regular 4"x4" 2" deep box. The twist nut approach would do it but the box would be packed.
    I was thinking of screw connections but don't want to crimp on lugs.

    Could the three ground (Green) wires be terminated on the box or should they be connected and isolated from the metal box?
    Din rail mount screw terminals with shorting bars?
    Use twist connectors and just cram everything in there and forget about?
    What connector can be bought from places like DigiKey or Mouser?
    Make a custom set of three bars with screw downs?

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    I don't see where any of your proposed solutions is any more compact than just using wire nuts.

    Run your wires in a circular pattern around the inside of the box and cut the length of each wire as needed so that no wire is taking a different path. Stagger the locations of the wire nuts.

    Use a wire nut on the three ground wires and add a pigtail that goes to the box.

    The breaker size needs to be reduced to 30 amps to protect the 10 gauge wire.

    Bill

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    First take a look at the box for the cubic capacity, then check the volume per wire. You have no strap-mounted devices, so that is not an issue.

    it is 2.25 cubic inches per wire for 12 ga, I do not recall what it is for 10 ga off-hand.

    Box Fill Calculations | Electrical Construction & Maintenance (EC&M) Magazine

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    Quote Originally Posted by Bill Simmons View Post
    The breaker size ^^^ on the #8 branch being tapped ^^^ needs to be reduced to 30 amps to protect the 10 gauge wire. ^^^ unless it is so, already^^^.

    Bill
    THIS...

    ELSE ..

    The naked box you have should be swapped for one that carries one, if not two 30A fuses or breakers right at the point the subordinate branch originates.

    Common and cheap enough - seldom over $30. Big Box have those for outside unit residential Air con & such or indoors, either one:

    https://www.homedepot.com/p/GE-30-Am...0RCP/100576894

    Buy Load Centers - Free Shipping over $50 | Zoro.com


    NB: Small as my shop is, it is cheaper usually, and less confusing ALWAYS, to "home run" all circuits back to ONE large panel of Square-D "QO", single phase off the mains, plus a 3-phase "QO" off the local source for that.

    If/as/when a twist-lock outlet isn't good enough? Add inline one of the smaller unfused rotary disconnects WITH "lockout" capability that fit a common box.

    Seek and find them for under $50, sometimes half that, NOS, NIB, and even when US-Made.

    And Ron? Nary a need to "re-invent" one bit of any of this gear. It is actually both CHEAPER and FASTER to do ALL 'lectrical work "to code'.

    "By the book".

    Simple reason being that is what everyone ELSE uses, so that is where the mass-market is, all makers competing sharply on price for it, highly standardized goods keeping the price down and the ways to use them straightforward and in-your-face obvious.

    Very few industrial electricians hold Engineering degrees.

    Thankfully.

    It would be a right bitch to be without safe and reliable power whilst they were off re-inventing the wheel at every install.


    2CW

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    Quote Originally Posted by Bill Simmons View Post
    I don't see where any of your proposed solutions is any more compact than just using wire nuts.

    Run your wires in a circular pattern around the inside of the box and cut the length of each wire as needed so that no wire is taking a different path. Stagger the locations of the wire nuts.

    Use a wire nut on the three ground wires and add a pigtail that goes to the box.

    The breaker size needs to be reduced to 30 amps to protect the 10 gauge wire.

    Bill
    That's exactly what I've got. The connections would be two 10 gauge and one 8 gauge wires per twist nut.
    Compact yes. But does not look neat and clean.

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    Quote Originally Posted by rons View Post
    That's exactly what I've got. The connections would be two 10 gauge and one 8 gauge wires per twist nut.
    Compact yes. But does not look neat and clean.
    No shit? America is chock FULL of ugly stuff like that is safe and works better than it looks.

    Did you never wonder why we use solid, opaque covers on electrical boxes instead of glass or perspex?

    NOW you KNOW!

    Same reason as underwear is seldom transparent, nor mirrors common in toilet bowls.

    Lots of things do their intended tasking just fine. Even if they look strange.


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    I do not like twist nuts. Proper high pressure crimps do work well, but the appearance is shit. I prefer to use copper bus bars with threaded holes hosting properly crimped ring terminals. There are several variations of this solution including bakelite barrier strips with jumper links. However, when doing this I often use an infra-red temp gun to make certain I don't have resistive connections. It is very likely though fitting this solution in a small 4 x 4 x 2 box challenging.

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    Yes, wire nuts are ugly. As Thermite said, that is what the cover is for. This is the method that almost any electrician would use. What I find visibly offensive in a junction box is if the wires have been tortured, interwoven, folded and too short to service.

    I would almost never use them in a box with a hinged door. Maybe to lengthen a wire too short coming from out side the box and then I would still cringe.

    To look good, the solution would require a minimum 6 X 6 box (and an 8 X 8 would be better)in order to make room for a terminal block and have reasonable radius on the wires.

    What is acceptable depends on the requirements. I was NASA certified for soldering and terminal installation. If the box was wired to those standards I would want a clear cover to show it off. But you would use calibrated strippers, verify pull strength and analyze pull failure for under or over crimp on the terminals before on samples prior to crimping the terminals on the wires, verify lay of the wire strands prior to crimping, use torque wrench to tighten screws. And then initial, stamp and date all the paper work as you completed each step. Or in this case, just put wire nuts on and close the box.

    Bill

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    I used twist nuts this morning. The wire lengths are long enough so that one day I can replace the nuts with copper bus bars. For now case closed, literally.

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    1) overcurrent protection as mentioned above??????

    2) stranded or solid wire?

    If stranded, solder the connections with a large iron or gun. Insulate with tape or multiple
    covers of heat shrink.

    3) yes I know the NEC prohibits soldering. This is because you cannot trust an electrician
    with anything hot.

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    Quote Originally Posted by jim rozen View Post
    1) overcurrent protection as mentioned above??????

    2) stranded or solid wire?

    If stranded, solder the connections with a large iron or gun. Insulate with tape or multiple
    covers of heat shrink.

    3) yes I know the NEC prohibits soldering. This is because you cannot trust an electrician
    with anything hot.
    It's all stranded copper. Sometimes I solder the ends of stranded wires if the connection is a screw down. Otherwise the strands splay out to the sides. Other times I twist the strands tight before tightening the screw.

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    Quote Originally Posted by jim rozen View Post

    3) yes I know the NEC prohibits soldering. This is because you cannot trust an electrician
    with anything hot.
    No, actually, there are sounder reasons.

    If you cannot be bothered to find out WHY, just adhere to the damned Code.

    It was MEANT to be idiot-resistant, after all, and wuddn' yah know it? You have just self-identified that they were not wrong!

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    Rons,

    I have used extension rings many times to increase the
    volume and serviceability of crowded electrical boxes.
    53151-1_2.jpg

    Chuck
    Burbank, CA

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    Quote Originally Posted by Chuck Evans View Post
    Rons,

    I have used extension rings many times to increase the
    volume and serviceability of crowded electrical boxes.
    53151-1_2.jpg

    Chuck
    Burbank, CA
    Phht.. I stock enough spares, metallic and otherwise I could ship him a few and not miss 'em.

    That said? "It's our Ron". HE would insist on stripping the Zinc, TiG'ing the bits together, bondo'ing the crap out of the joint, wet-sanding the rig, and applying hand-rubbed lacquer or Acrylic and clearcoat off the back it has to LOOK NEAT, not just carry the power!

    Seriously, Ron, you do tend to get a tad anal with welding-up holes and finishing them invisible, when anyone else would pop-in a standard, CHEAP, modestly ugly, but code-compliant, nonetheless, PLUG ... and move-on.

    Same again applies, twelve-dollars all it takes for a proper mini-load center, fused or breakered, either one code-compliant and with proper terminals a bonus.

    JFDI.

    I dare yah..


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    NEC requires individual branch circuits for a reason. No where does the NEC allow 10 gauge wires to be connected to 8 gauge wires unless, as stated previously, the overcurrent device be reduced to 30 amps. Which may cause tripping of the oc device when loads on the 8 gauge portion are drawing more than 30 amps, hence NEC requires individual branch circuits for such loads. Run some 10 gauge back to the panel, on a 30 amp breaker, wire it neat or sloppy, and it will work right, and be to code.

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    Quote Originally Posted by PocoLoco View Post
    NEC requires individual branch circuits for a reason. No where does the NEC allow 10 gauge wires to be connected to 8 gauge wires unless, as stated previously, the overcurrent device be reduced to 30 amps. Which may cause tripping of the oc device when loads on the 8 gauge portion are drawing more than 30 amps, hence NEC requires individual branch circuits for such loads. Run some 10 gauge back to the panel, on a 30 amp breaker, wire it neat or sloppy, and it will work right, and be to code.
    You may have missed it, one MAY feed a subordinate load center with 8 GA, protected at the upstream for it AND NOT also locally, AND with a local "main breaker" AND with a local captive breaker serving as a main feed. See "main lug" load center guidance, various distances and safety, lockout, and basic convenience environment challenges and concerns.

    In all cases, THEN taking-off same or lesser wire WITH breakers/fuses according to its own appropriate branch circuit rating.

    Close to primary load center? Home runs make more sense UNLESS.. it hasn't the space for more breakers...

    AND/OR (my case), I want to be able to pull ALL of the "shop" power runs, entire, on move-out.

    Because it makes selling a residence easier, not harder, if it doesn't have "scary complexity" a non-craftsman would only find worrisome.

    Goods for either of fuse or breaker have been linked herein already.

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    What you are trying to do here is going to be ugly and it's not the wire nut's fault.

    If the 8 gauge circuit is already run, extend it with more 8 gauge wire.

    If it isn't already run, then run two 10 gauge branch circuits all of the way to the breaker.

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    Quote Originally Posted by Chuck Evans View Post
    Rons,

    I have used extension rings many times to increase the
    volume and serviceability of crowded electrical boxes.
    53151-1_2.jpg

    Chuck
    Burbank, CA
    That is a good suggestion, thanks.

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    Quote Originally Posted by PocoLoco View Post
    NEC requires individual branch circuits for a reason. No where does the NEC allow 10 gauge wires to be connected to 8 gauge wires unless, as stated previously, the overcurrent device be reduced to 30 amps. Which may cause tripping of the oc device when loads on the 8 gauge portion are drawing more than 30 amps, hence NEC requires individual branch circuits for such loads. Run some 10 gauge back to the panel, on a 30 amp breaker, wire it neat or sloppy, and it will work right, and be to code.
    Well the breaker is 30A and there is a long run of 8 gauge to the branch box. No regrets.


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