This article provides basic tips on how to strip the ends of electrical wires used in homes.
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Sketch at page top courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].
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Watch Out: Do not attempt to work on your electrical wiring, switches, or outlets unless you are properly trained and equipped to do so. Electrical components in a building can easily cause an electrical shock, burn, or even death.
Even when a hot line switch is off, one terminal on the switch is still connected to the power source. Before doing any work on the switch, the power source must be turned off by setting a circuit breaker to OFF or removing a fuse
. See SAFETY for ELECTRICAL INSPECTORS and ELECTRICAL WIRING BOOKS & GUIDES
Different kinds of cables and electrical wire are commonly used by the homeowner or electrician when performing routine wiring tasks.
These tasks are fairly easy to do but practice with the techniques involved always helps. Before actually working with a type of wire or cable that is new to you, cut off a short piece and try stripping, joining, etc. Experiment a bit to find out which of the tools you have available are easiest for you to use and which do the best job. A little time spent in trial and error will make the job go faster.
Permanent indoor installations are made by running lengths of wire between outlets and switches along or inside walls, floors, and ceilings. An electrical circuit always needs a hot and a neutral conductor plus a ground for safety.
When these individually insulated wires (black for hot, white or gray for neutral) are held together inside plastic or metal sheathing, the unit is called an electrical cable.
The most commonly used electrical cable for indoor wiring is the flat, white plastic type plastic-covered wire, or "Romex" (a trade name). Properly plastic-covered electrical wire is called "NMC" - non-metallic-sheathed cable. .
While there are many types and grades of non-metallic cable electrical wire, there are three basic kinds of interest to homeowners for most residential applications.
Sketch courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].
The type of electrical wire and its intended use is indicated by code letters printed on or embossed into the plastic wire jacket. (Our photo shows an obsolete aluminum conductor NM wire made by Primus).
Why do we start our wire stripping procedure in the center of the wire?
When you cut the end of a NMC electrical wire you'll see how the electrical wires are arranged: you'll see an insulated black wire (the hot wire) on one side of the cable, an insulated white wire (the neutral wire) on the opposite side of the cable, and running in the center you will see a bare (or paper-wrapped) copper ground wire.
By cutting in the center of the wire to begin your wire stripping procedure, your knife tip will run alongside the bare ground wire and you'll minimize the chance of nicking or damaging the black or white insulation on the individual hot or neutral wires.
Above: photo of stripped ends of aluminum electrical wiring.
See ALUMINUM WIRING HAZARDS & REPAIRS - home
Armored cable or metallic-sheathed electrical cable has been in use since 1896 (in the U.K.) and in its most basic form contains two electrical conductors (black-hot and white-neutral) each individually insulated and both usually wrapped with a spiral of paper which is in turn enclosed in a flexible metallic sheathing such as shown in our abandoned-wire photograph below.
Below: a red-head bushing intended to protect the conductors from damage by the sharp edges of the cut metal BX sheath.
More about identifying and actual wiring methods when using flexible metal conduit / armored cable - BX is given in detail
at BX WIRING GUIDE where we illustrate using the special BX conduit cutting tool.
at ARMORED CABLE or BX WIRE IDENTIFICATION
How much insulation should be stripped off of the individual wire conductors once the wire jacket has been removed? As my friend and mentor Mark Cramer, Tampa home inspector and educator, says, "Well ... it depends." It depends on the device to which the wire is to be connected.
We want to remove enough insulation to assure good contact area between the wire and the connecting device, but not too much.
Watch out: not all devices use the same conductor insulation strip-back amount. In general you will need to remove more insulation to wrap a wire around a binding head screw connector than to push the wire into a push-in type connector. Above I've removed the jacket from 14-3 NMB electrical wire.
The ground wire is already bare but I'll need to remove insulation from the black, red, and white conductors before they can be connected to a device or to a splice.
Excerpting from HOW to CONNECT WIRES to a RECEPTACLE or SWITCH
Above I'm showing the wire strip-back gauge area marked on the back of a 15A electrical receptacle. This gauge shows the amount of insulation that should be removed presumably for either of the types of connectors provided on this particular device.
For the device shown above we are to remove from 1/2" to 5/8" of insulation, or about 16mm.
Below is a rather shorter wire stripping gauge telling us that for the device where this gauge appears - in this case a screw-clamp type wire connector, somewhat less insulation is to be removed. For the device shown below we are to remove 9mm of insulation - about 0.35" - quite a bit less insulation than for the device above.
Watch out: don't strip off too little insulation or the wire will not make a safe, reliable electrical connection: either the wire won't push far enough into the screw-clamp connector or the insulation may prevent the binding head screw from pinching the wire - it'll pinch onto the insulation instead, making a loose, poor electrical contact.
And don't strip off too much wire insulation or the extra length of bare wire may cause a short circuit when you push the device back into its electrical box. That's more than embarrassing, it's dangerous. Trust me.
Most light switches and receptacles include this indicator that tells you how much insulation the manufacturer recommends stripping off when wiring this device.
Typically we're removing from 1/2" to about 5/8" of insulation, taking care not to damage or notch the wire. It makes sense, then, to actually look at these instructions given by the manufacturer, as not all strip gauges show the same strip-back quantity.
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