Article 110 of the NEC (National Electric Code), Requirements for Electrical Installations, should be studied carefully by every DIY electrician because a project passing or failing inspection depends on compliance with the requirements of this section. Section 110.12 cover the mechanical execution of the work. Simply put the work must be executed in a workman like manner. If the work is sloppy and appears amateurish the inspector will be far more critical than he or she would be if the work appears to have been done by a professional even though they know it was done by a DIYer. Mechanical execution involves everything from the way the wiring is ran through framing members to the way splices are made in device boxes and J-Boxes (Junction Boxes). Making good, solid splices isn’t only essential for passing the rough-in inspection, they are essential for the safe and reliable operation of the electrical wiring system.
Making good, solid solderless electrical splices begins with selecting the right size connectors for the splice. What size connectors you will need depends on the size of the conductors being spliced together and the number of conductors in the splice. I’m not one for reinventing the wheel and the Ideal™ Corporation, a manufacturer of Ideal Wire-Nut® wire connector has made available a connector selection chart that’s approved by the Underwriters Laboratory for UL Listed Wire Combinations. Every DIY electrician needs to download and printout this pdf file for future reference. This is a good time for you to start building your reference library. Like professional electricians you should start a MSDS (Material Safety Data Sheet) reference file at this time too. The MSDS in pdf file format can be downloaded and printed out here.
The most common size splices made by the DIY electrician involve a combination of AWG (American Wire Gage) sizes 14, 12 and 10 copper conductors and Ideal 92® (green), 451® (yellow), 452® (red) and 454® (blue). These numbers are strictly applicable to the Ideal line of wire-nuts but the colors apply to all brands of screw-on wire connectors. The “Greenie” or grounding wire-nut is especially designed to make grounding pigtail splices easier with a hole in the end of the cap. All other wire nuts have a solid cap.
Wire-nuts makes making good solid splices so easy that anyone can learn to do it after a few minutes practice and that’s the objective of this how-to, to teach you how to make professional looking splices using wire-nut. For the practice session you will need the following tools and supplies
· Diagonal pliers (“Dikes”) (Wire cutters)
· AWG 12 solid cu White wire
· AWG 12 solid cu Black wire
· AWG 12 solid cu Green wire
Making practice splices
For this training exercise the color of the insulation doesn’t matter, our objective here is to simply learn how to make physical and electrical sound splices that will pass inspection with flying colors.
Exercise #1 connect two 12” lengths of AWG 12 Cu wire using a yellow wire nut.
· Begin by stripping 1” of insulation from one end of each conductor. When stripping the insulation from the wire be careful to not nick or score the copper conductor because nicking or scoring will weaken the conductor physically and also increase its electrical resistance, neither of which is a good thing
· Hold the bare conductors side-by-side
· Grasping the very ends of each conductor with the Linemen’s Pliers twist them together making sure that both conductors turn. Do not allow one of the conductors to turn around the other conductor. Although it’s not necessary to twist the conductors together when using modern wire nut with threaded inserts, good practice dictates that you twist the ends together first because every good electrical connection begins with a solid mechanical connection.
· Once you have twisted the bare copper conductors together in candy cane fashion, trim the ends so that they don’t end in sharp points
· Screw the wire nut firm in place on the splice and check to see that there is no bare copper showing
· If there is any bare copper visible, remove the wire nut and trim the end of the splice back far enough so no copper is visible when you replace the wire nut.
· Grasping the wire-nut firmly in one hand pull on each wire separately to make sure it’s firmly secure in the wire-nut.
Exercises #2 and #3
Exercises #2 and #3 follow the same steps except you will be splicing 3 and 6 conductors together respectfully using the required size wire nuts. Refer to the pdf file that you downloaded or to the chart that comes with the wire-nuts to make your selection.
When twisting 3 or more wires together the thing you have to guard against is the problem of one or more wires remaining straight while the others twist around them. The best way to prevent this is to bend each wire so they are at a 45 degree angle to one another. Once the first twist is made they will then be firmly locked together and will be pulled tighter together with each new twist of the Lineman’s pliers.
Be especially vigilant when checking splices containing three or more conductors because it takes little force to pull one or more of the conductors free if the splice was made incorrectly. A poorly formed splice that works loose later on can cause you all kinds of headaches.
It’s not required by the NEC or by any local code that I know of but I like to wrap my finished splices with plastic electrical tape as an added measure of protection against accidental shorts and as an extra means of assuring a tight and permanent splice. Don’t tape the splices until after the rough-in inspection because the electrical inspector is going to want to see the wire-nutted connection. They’ll be looking for exposed copper beyond the lip of the wire-nut.
