Electrical Wire Stripping Tips for Homeowners InspectAPedia® -
How to strip the ends of electrical wires
Types of electrical circuit wires used in homes: what are NM, NMC, UF, BX, Romex, armored cable wire types
Tools & tips for stripping electrical wires
Guide to Electrical Hazards in buildings: inspection, detection, & repair advice
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This article provides basic tips on how to strip the ends of electrical wires used in homes. Readers of this article should also see ELECTRICAL DEFINITIONS and also SAFETY FOR ELECTRICAL INSPECTORS. This website provides information about a variety of electrical hazards in buildings, with articles focused on the inspection, detection, and reporting of electrical hazards and on proper electrical repair methods for unsafe electrical conditions. Critique and content suggestions are invited. Credit is given to content editors and contributors.
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.
How to Strip the Wire Ends for Plastic-Sheathed Electrical Cable
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.
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).
Type NM electrical cable is designed for normal indoor electrical wiring such as lighting and receptacle circuits.
Type NMC electrical cable is insulated well enough to use above ground or in damp areas indoors
Type UF electrical cable can be buried outdoors. (Underground Feeder). Note that UF electrical cable intended for use underground may not be rated for above-ground outdoor use where sunlight can cause deterioration of the cable sheathing and thus may make the wiring unsafe.
How to Remove the Plastic Sheathing from Plastic-Sheathed Electrical Wire
Make certain that the electrical power has been turned off and that you've used a test tool such as a VOM or neon tester to confirm that the wires you're working on are not electrically live. Failure to take this step risks a fatal electrical shock.
Place cable on a solid flat surface.
Determine the length of insulation to be removed. The cut through the plastic wire jacket should be six to eight inches long. Some electricians spread their hand wide and use the distance between the tip of their pinkie and the tip of their thumb to choose the length of wire to be stripped.
Cut the wire cable covering in its center. Use enough pressure to penetrate the sheathing but not so much that you cut the insulation on the inner wires.
Use a utility knife to cut the sheathing along the flat side. Try to make the cut straight and as nearly as possible in the center of the sheathing.
Alternatively, use the inexpensive NMC wire stripping tool available at any electrical supply store or building supply store. This tool is a simple metal device that slips over the end of the plastic-covered electrical cable; when the two sides of the tool are pressed together a small metal tooth cuts into the center of the cable; holding the cable body in your left hand, grasp the stripping tool in your right hand, squeeze it on the wire and simply pull it towards the end of the wire and off. You'll see that this little tool makes a nice cut down the very center of the wire and that it will not damage any of the conductors.
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.
Peel back the plastic sheathing to the beginning of the cut.
Trim oft the plastic with wire cutters or large shears.
Remove and cut off the paper that is wrapped around the inner ground conductor.
If you see that you have nicked the insulation covering the hot or neutral conductors or that you have nicked the bare ground wire, simply trim off the section and try again. Here is a photo of stripped wire ends (obsolete solid conductor aluminum wire)
How to Remove the Metal Sheathing from Armored Cable ("BX") Electrical Wires
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.
Hacksaw method for stripping armored BX cable:
Make certain that the electrical power has been turned off and that you've used a test tool such as a VOM or neon tester to confirm that the wires you're working on are not electrically live. Failure to take this step risks a fatal electrical shock.
Determine the length of metal cable covering to be removed
Cut diagonally across one of the metal ribs at the desired distance from the end of the wire. Cut carefully and stop as soon as you have cut through the metal to avoid cutting into the wire insulation. If you use a hacksaw, a fine-toothed blade will work best.
Snap the armored cable: Next grasp the cable on each side of the cut and bend the cable back and forth until the armor snaps.
Slide the armor off the cable.
Unwrap the paper from the inner conductors and cut it away.
Check the inner conductors for damaged insulation. Check both at the point where you cut the armored jacket and also along the length of the conductors since in pulling off the armored jacket you could have damaged the individual conductors anywhere along their length. If the conductor insulation has been damaged you should cut off the damaged wires and begin again.
Cutting-tool method for stripping BX armored cable:
Make certain that the electrical power has been turned off and that you've used a test tool such as a VOM or neon tester to confirm that the wires you're working on are not electrically live. Failure to take this step risks a fatal electrical shock.
Bend the BX armored cable sharply until the armor buckles.
Twist the armored cable in the direction that will unwind the armor spiral. This causes a section of the armor to spring out at the point of the bend.
Slip the cutting tool through the armor where it has buckled. Trim away sharp edges. Slide off the end of the armor.
Use the shaping grip in the jaws to reform the buckled cable-end after stripping the paper from the inner conductors and trimming it off.
Trim away or bend the sharp edges of the armor at the point of the cut. Make sure no edges are in position to cut into the insulation in the inner conductors. This is important.
Check the inner conductors for damaged insulation.
Check both at the point where you cut the armored jacket and also along the length of the conductors since in pulling off the armored jacket you could have damaged the individual conductors anywhere along their length.
If the conductor insulation has been damaged you should cut off the damaged wires and begin again.
After Stripping the BX jacket from electrical wire
Protect the conductor wires (hot & neutral) from future damage from the sharp edges of the cut armored cable jacket. To eliminate the possibility of sharp edges of the armor cutting into the conductor insulation, a fiber bushing should be inserted under the armor, at the point where the conductors emerge.
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The 2008 NEC National Electrical Code (ISBN 978-0877657903) Online Access LINK (you'll need to sign in as a professional or as a visitor)
The 2008 Residential Wiring Code, a subset of the 2008 NEC, can be understood through Mastering the NEC at http://www.2008nec.com/shopping/pgm-more_information.php?id=18
Reference: Wikipedia.org on electrical wiring, September, 2008
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Recommended books on electrical inspection, electrical wiring, electrical problem diagnosis, and electrical repair can be found in the Electrical Books section of the InspectAPedia Bookstore. (courtesy of Amazon.com)
Aluminum Wiring Information Website Aluminum Electrical Wiring Hazards and Repairs: in-depth authoritative info, photos, documents including selection of proper vs. ineffective repair methods. E.g.: Ideal 65 "Twister" purple connector fails in field and lab testing with aluminum wire.
Circuit Breaker, a bad one fails to trip failure at aluminum bus-to-circuit breaker connection - field report and photographs
Electrical Panels, How to Inspect in buildings, safety for electrical inspectors, electrical panel, fusing, wiring defects, defective products. Inspection Class Presentation
Federal Pacific Electric (FPE) Stab-Lok Circuit Breaker Panel Hazards Website - Latent fire hazards, in-depth authoritative research, documents, advice on Stab-Lok electric panel and circuit breaker failures and what to do when this equipment is found in buildings.
"Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
"Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
"How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
"Electrical System Inspection Basics," Richard C. Wolcott, ASHI 8th Annual Education Conference, Boston 1985.
"Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
"How to plan and install electric wiring for homes, farms, garages, shops," Montgomery Ward Co., 83-850.
"Home Wiring Inspection," Roswell W. Ard, Rodale's New Shelter, July/August, 1985 p. 35-40.
"Evaluating Wiring in Older Minnesota Homes," Agricultural Extension Service, University of Minnesota, St. Paul, Minnesota 55108.
"Electrical Systems," A Training Manual for Home Inspectors, Alfred L. Alk, American Society of Home Inspectors (ASHI), 1987, available from ASHI. [DF NOTE: I do NOT recommend this obsolete publication, though it was cited in the original Journal article as it contains unsafe inaccuracies]
"Basic Housing Inspection," US DHEW, S352.75 U48, p.144, out of print, but is available in most state libraries.
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Electrical Wire Stripping Tips for Homeowners
