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Six steps to good electrical wiring splices & connections at electrical boxes or devices:
This article shows how to joint electrical wires using twist-on connectors at an electrical box.
This article series answers most questions about how splices (connections between two or more electrical wires) are made to connect & secure electrical wires together in residential or commercial building electrical wiring systems. We also discuss the use of electrical splices or wiring connectors outside of electrical boxes.
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Six Easy Tips for Successful Installation of A Twist On Connector Make a Good Electrical Wire Splice
In making copper wire splices using a twist-on connector you should watch all of the six details we describe and illustrate below.
Cut away damaged or nicked wire ends that might break off, causing a splice failure and a dead circuit or fixture that can be difficult to diagnose later. Sketch provided courtesy of Carson Dunlop Associates, a Toronto home inspection & education & report writing tool company.
Strip back insulation 3/8" to 7/8" - depending on wire size and connector size
An Ideal Wingnut 451 requires stripping 3/8"
An Ideal Wingnut 452 strips to 1/2"
An Ideal Wingnut 454 Strips off 7/8" of insulation
Watch out: If you don't strip enough insulation the insulation that is up under the twist-on connector cap may prevent a tight electrical connection between the wires even though the connector itself feels "tight" - you'll have a loose connection and flickering lights or overheating or even a fire.
Watch out: if you strip away too much wire insulation you'll see bare wire extending out below the bottom of the twist-on connector - inviting a shock or short circuit.
Be sure the wire ends are straight and un-damaged and of equal length (photo below)
If one of the wires is a multi-stranded wire such as for a light fixture, let that end extend about 1/8" past the solid wires.
In my photo below I've extended the light-fixture's multi-strand ground wire about 1/8" past the end of the solid copper ground wire before installing the twist-on connector.
Hold the wires closely together. In my photo below I don't have the white neutral wires fully touching and close together but I'm working on it. Also I need to extend that white multi-strand lamp wire about 1/8" out past the solid copper wires before I start installing the twist on connector.
If the wires are not straight I will use my pliers to make them as straight as I can before inserting them into the twist on connector.
Twist on the twist-on connector (clockwise) until tight. Some electricians (and I) twist firmly until the wires themselves begin to twist together below the connector.
My photo below shows all three sets of wires connected using orange twist-on connectors: white netural, black or hot wires connected using the twist-on connector, and the light fixture's ground wire connected to my circuit ground.
At ELECTRICAL BOX GROUND WIRING we point out that if this had been a metal electrical box I'd also have had to bond the ground wire to the box itself.
Some electricians, to make a particularly secure connection, perhaps where they feel there is extra risk, also wrap the assembly in electrical tape - a step not discussed in any of the manufacturer's instructions or catalogs we reviewed. I do this too, particularly when working with old house wiring installations.
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In addition to any citations in the article above, a full list is available on request.
Timothy Hemm, Yucala, CA, contributed various photographs of electrical equipment installed in California buildings. Mr. Hemm can be contacted at TimHemm@yahoo.com
NFPA - the National Fire Protection Association can be found online at www.nfpa.org
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
"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.
"Simplified Electrical Wiring," Sears, Roebuck and Co., 15705 (F5428) Rev. 4-77 1977 [Lots of sketches of older-type service panels.]
"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.
In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Carson Dunlop Associates provides extensive home inspection education and report writing material. In gratitude we provide links to tsome Carson Dunlop Associates products and services.