Crimped electrical connections when adding or repairing electrical circuits make secure, vibration-resistant, economical and space-saving joints. When installing large devices, such as ground fault interrupter (GFI) receptacles, the space saving feature of crimped connections will save a lot of frustration.
There are instances where many wires must enter an electrical box that also contains receptacles or switches. Here also, much space can be saved by using crimped splices.
Strip the wire with a stripping tool. The stripping tool has several notches, one for each wire size. Lay the wire in the slot corresponding to the size wire being used, leaving about 3/8 inch beyond the stripper. Squeeze the handles together, rotate the stripping tool around the wire and pull 3/8 inch insulation off the wire.
Repeat the stripping procedure for all the wires being spliced.
Purchase copper crimp sleeve connectors at an electrical supply store, a good hardware store or on the Internet.
When choosing copper sleeve crimp connectors, the package will tell how many wires of each size may be crimped together. Bigger is not always better when choosing crimp sleeves. Usually it is best to select a sleeve that will accept three or four wires of the size that are to be crimped.
If in doubt, the smaller size connectors will work for #12 and #14 wire.
A good pair of electrician's crimping pliers is not inexpensive, Expect to pay in excess of £32 at an electrical supply store and £16 or more online.
These pliers are 8 inches or more in length and have a nipper at the end. Behind the nipper is a series of 2 or 3 indentations on one side and crimping projections on the other side.
For electrical circuit work, not use crimping pliers with the crimping slots in the handle behind the hinge. These pliers cannot crimp the sleeve tightly enough to make a secure splice.
A good quality crimping tool will be a lifetime investment.
Hold the crimping tool with the notches facing up and place the crimp sleeve in the notch that fits the sleeve. Some crimping pliers label the notches according to wire size.
Insert the wires that are to be crimped into the flared end of the sleeve. Being careful not to let any of the wires slip out, squeeze the handles together forcefully. Too little force applied to the crimping tool will allow the wires to come loose. Extreme force will possibly break a wire.
Tape the crimp with electrical tape. Begin taping the crimped wires over the insulation behind the splice. Pull the tape with light tension and continue wrapping the wire past the end of the splice. Fold the tape over and wrap back to the starting point behind the splice. Continue wrapping tape in this manner until at least three layers of tape cover the splice. The final wrap should not have much tension applied in order to keep the tape from unwrapping
Tuck the splice into the box and the job is done for this splice.
For house wiring, the crimping pliers with the end nippers are the type to use and the nipper is handy for cutting wires. Use only good quality pliers. The crimping tool may be used for insulated connectors, such as butt splices and end connectors, but use only uninsulated copper crimp sleeves for house wiring.
Cheap crimping pliers made for insulated connectors will not make a reliable crimp. They will only mash the crimp sleeve and the wires will come loose. Use wire strippers rather than a knife to strip wires.