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PHOTOVOLTAIC POWER SYSTEMS
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How to strip insulation from electrical wires when wiring a light switch or electrical receptacle. Here we explain how much insulation to remove and to avoid damaging the electrical wire when preparing wires for connections to receptacles or switches.
Details about how to wire up an electrical receptacle are at CONNECTION DETAILS - where to connect black, white, red, green, ground wires.
This article series describes how to choose, locate, and wire an electrical receptacle in a home. Electrical receptacles (also called electrical outlets or "plugs" or "sockets") are simple devices that are easy to install, but there are details to get right if you want to be safe.
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If the wire insulation is stripped the perfect amount then after it has been inserted into the clamp or wrapped around the screw you'll see that no wire insulation is under the connector itself, but little or no bare wire is exposed past the edges of the connector.
Above our white wire was stripped correctly - the stripped end was pushed into the clamp until it stopped, and the screw was tightened against bare copper, but just about 1/16" or less of bare copper shows above the screw (photo shown above left).
Our black wire was stripped too much (photo above-right) and some unnecessary bare copper remains exposed after the screw was tightened.
If you going to wrap the electrical wire around the terminal screw on the electrical receptacle (or a light switch terminal) you need to strip back a bit more than 1/2-inch in order to have enough copper to go around the screw leaving no insulation under the screw head when it is tightened.
Our photo (left) shows the strip gauge marked on the edge of our receptacle - those two parallel lines cast into the black plastic housing just below our stripped-back white wire.
Readers of this article should also see ELECTRICAL CODE BASICS, ELECTRICAL DEFINITIONS and also SAFETY for ELECTRICAL INSPECTORS. Our photo at page top is not an example of a proper electrical outlet installation.
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.
Nicks in Stripped Electrical Wires Make a Bad Connection & Risks Broken Wires
Don't damage electrical wires by nicking them: When installing, securing, or stripping insulation from wiring in order to make a connection, the wire and its insulation must not be nicked or damaged, as we show in the sketch at left, courtesy of Carson Dunlop Associates. Why?
Typically the ground wire is bare of plastic insulation, but it may be necessary to remove paper around the wire before connecting it. We like to remove all of the paper around the ground wire rather than leave electro-kindling inside the junction box.
In our photo, left, I've pushed the paper off of the ground wire - but have not yet torn it away from the assembly.
If there is more than one feeder wire entering the electrical junction box then all of the grounds are connected together as well as being connected to the ground screw on the receptacle itself. Special crimp-on connectors are used by professionals to join multiple ground wires in the electrical box, but it is also permitted to use a twist-on connector (which takes more space).
If the junction box is plastic, you're done.
If the junction box is metal, a ground wire is also connected to the metal box using an approved grounding screw or clamp device to tie the wire end to the box.
Most metal electrical boxes have a threaded hole intended for use as a connection point for the ground wire connecting screw, as illustrated in our photograph (left).
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
Question: When wiring an electrical receptacle, what do I do with the red wire? Can I ground it?
I have a 3 wire (Black, White, Red and ground) feeding a outlet and I want to add another receptacle to run further down the line. The line out is 14/2. What do I do with the Hot Red wire? Can i attach it to the ground. - Rick
After capping off the red wire, can I extend the line to the next plug by following the diagram above and adding the black and white wires to the respective second screw connections?
You see, the wiring has already been installed by the builders and they left the boxes without receptacles so all I have to do is connect them to the. I don't know why the extra red wire is there. It was done over a year ago. I want to finish the connections. It runs 14/3 and then 14/2. That's why I have the extra red.
Reply: how three-wire circuits or multiwire branch circuits with a common neutral (and ground) are used and wired
Rick often electricians run a 3-wire system into a building area using two hot wires and a shared neutral, to permit providing two circuits in an area while having to pull just one wire to the area. But to sort out how your wires were connected and are being used requires some expertise, visual inspection, and testing using a VOM.
Take a look at multi-wire branch circuit wiring information and hook-up details at MULTI-WIRE CIRCUITS.
Question: armor around wire through concrete?
I am running a new 15A outlet into the back of a bookcase in a 50 year old house with updated electrical. The wire runs out the back of the retrofit box and down through the concrete foundation into the crawlspace to a wire I plan to splice into. Do I need to put armor around the wire run through the foundation? It goes through open air for about 2 feet and there is no way to secure it to anything.
You need to look at the type and rating of the electrical wire to determine if it is permitted to bury it in concrete or not.
Reply: step by step tips for replacing a stripped electrical receptacle or switch box mounting screw or screw opening
If the problem is the screw itself is stripped, simply purchase a replacement screw or a hand full of them from your electrical supplier. These screws are a standard thread and length, but longer versions are available at any hardware store.
For the case you describe, if the stripped problem is the mounting hole you'll need to either enlarge and tap the hole for the next size larger screw, or purchase a clip-on adapter that slips over the stripped ear through which the original hole passed.
Taking care to move electrical wires out of the way of your drill bit, in a metal electrical box you can drill out the 6/32 screw opening to tap and accept an 8/32 screw.
For photos and step by step details on how to repair stripped electrical outlet mounting screws, see OUTLET SCREW REPAIR.
Questions & answers or comments about how to install and wire electrical outlets or receptacles in buildings.
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