Wiring Electrical Switches

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Wiring Electrical Switches
Updated on March 26, 2015 Dan Harmon moreDan has been a licensed, journey-level electrician for some 17 years. He has extensive experience in most areas of the electrical trade.

Contact Author Varieties of Switches to be Wired
While there are actually thousands of various styles and types of electrical switches that may be wired for thousands of various purposes, this article is devoted to the straightforward single pole, or two way, switch of the sort used to show lights on in your home.

If you’re wiring a 3 way or four way switch, please view the articles about easy methods to wire a 3 way switch and/or how to wire a four way switch. Other common switches corresponding to some simple automotive switches will behave the same electrically as a house switch although the mechanics of mounting or attaching wires may be different, and this will probably be explained in the next section of this text.

As knowledgeable electrician I have wired literally thousands of switches of varying types and styles over time. It isn’t a difficult task at all, and something any homeowner can easily understand and do themselves with just just a little work and understanding.

How Does An Electrical Switch Work?
At it is simplest, a switch is a mechanism to attach and disconnect two wires without physically removing the wires from the mechanism. It would thus require some way to attach the two wires to be connected to the switch, and all switches utilized in a house must also have a spot the attach a ground wire as well. This wire, bare of insulation or colored green, has been required throughout the US for a few years and is a very important safety feature.

The switch could have internal parts to make an electrical connection between the 2 wires and has the flexibility to either make that connection or, by flipping the switch, remove that connection. That is common to all two way switches whether or not they be for the house, in your car or the switch under the seat of your riding lawn mower that detects when you’re sitting on the seat. A switch might activate a light in your home, activate the radio within the car or provide current to run the lawn mower if there may be weight on the seat – it may do many, many different things.

In all these cases the device to be turned on (light bulb, radio, etc.) will need to have two wires to it. One wire is attached permanently (within the case of a car often using the metal body of the car as a “wire”) and the other wire goes through the switch. When the switch is turned off it leaves electric current on just one wire and the device won’t come on.

Wiring a Light Switch in the house
A lot of the wiring in your home can be of the 120 volt variety; only the range, clothes dryer, hot water tank and a handful of other high energy appliances require 240 volts. The 120 volt circuit consists of a black (“hot”) wire, a white (“neutral”) wire and a bare or green “ground” wire. The neutral wire is always attached on to the sunshine or other device, the black wire goes through the switch, and the ground wire goes to both switch and light. The wire is usually contained in a cable, all three wires bundled together in an insulating sheath with the black and white wires having their own insulation as well as the sheath enclosing all the cable. The cable originates within the panel, or fuse box, where it may be turned off by turning the right breaker off or removing the proper fuse. Always turn the ability off before doing any electrical work and preferably check that it’s dead by using a non contact voltage detector or voltmeter.

There are two common methods of physically getting the wire to the sunshine and switch in a home; which wires go to the switch is set by which method is used. The cable from the panel box will go to either the sunshine or the switch, and a second cable is always required between the switch and the sunshine.

Power to the sunshine first
In this case the cable from the panel box goes to the light box, where the sunshine is, first. The white, neutral wire is then attached to the sunshine at this point. A second cable, again containing a black, white and ground wire goes to the switch. On this case the white wire in the cable to the switch is attached to the black wire coming from the panel box with a wire nut and needs to be colored black with a magic marker or black tape to indicate that it isn’t a neutral wire. It is now a “hot” wire. The black wire from the switch is attached to the sunshine. At the switch there will now be a black and a white (colored black) wire plus the ground. All three of these will attach to the switch. It must be noted here that the 2011 National Electric Code was changed to require that every switch box have a white neutral wire in it; this means that if the facility goes to the light first the cable to the switch should have a white, black and red wire plus a ground. The white wire is attached to the white wires at the sunshine but is then capped off with a wire nut within the switch box without connecting to the switch. With both black and red wires between the light and the switch there isn’t a have to color any wires and the red wire is used rather than coloring the white wire and using it.

Power to the switch first
In this case the cable from the panel box goes to the switch first, with a second cable going from the switch to the light. There will be two cables (six wires) at the switch. The 2 white wires are spliced along with a wire nut and are to not be colored; both are still “neutral” wires. The two ground wires must be spliced along with a 3rd short piece of green or bare wire that will go to the switch. The two black wires, one from each cable, go to the switch as well.

Using a Voltage Detector
Click thumbnail to view full-sizeUsing a voltage detector shows that this wire remains to be “hot”! | SourceThis cable has the outer sheath cut back and the paper inside folded back to reveal the 3 wires inside. There’ll typically be only a small amount of sheathing visible in the box and no paper | Source Non Contact Voltage Detectors from Amazon
Fluke Voltage Detector, 1000V AC Voltage Buy Now Attaching the Wires to the Switch
There are two general methods of physically attaching the wires to the switch. Most 15 amp switches (to be used only on a 15 amp circuit with a 15 amp fuse or breaker) could have both screws on the side and small holes on the back. Wires could also be stripped of insulation for about ½ inch and bent right into a half circle, put under the screw head and the screw tightened or the insulation stripped to the proper length (there is a strip gauge on the back of the switch) and pushed into the holes where a spring will hold them. As an electrician I will not use the holes because the springs inside that hold the wire eventually weaken and make a poor connection (resulting in not only a light that will not work but a definite electrical fire hazard as well). The screws used for these two wires are typically the larger two, are a brass color and are located on the side of the switch.

A 3rd screw, typically located near or on one end, is meant for the ground wire and is usually colored green. It is normally obvious that this screw is connected to the metal framework of the switch instead of going through the plastic side. Every switch must have a ground wire attached; the only exception is for older homes that do not have ground wires within the switch box.

With the wires attached, fold the wires back into the box and push the switch in as well. Two screws hold the switch to the box; tighten firmly but not so tightly that the screw strips out the plastic of the box and will not hold any more. Attach the cover plate with a single screw in the middle.

Click thumbnail to view full-sizeA typical 15 amp home electrical switch. The dark green screw on the proper hand end is for the ground; other wires attach to the other side. | SourceA costlier, 20 amp switch. The bottom screw is at the highest left, the 2 other wires attach to the brass colored screws on the fitting. | SourceThe short groove on the left of the switch body is the “strip gauge”, showing how far to remove insulation. | SourceThe insulation has been faraway from this wire the right amount. | SourcePushing the wire into the spring loaded hole. The slot next to the hole is for removing the wire; insert a small screwdriver into the slot and the spring will release. | SourceThe ground wire has been looped clockwise around the bottom screw, ready to tighten. | Source Wiring Other Sorts of Electrical Switches
As mentioned, there are actually thousands of different types of electrical switches, from giants 6 feet tall to micro switches not meant to ever be touched by human hands. One switch may need 20 or more positions with 20 different results. Or it would operate 10 different devices, each with it is own circuit, all at the identical time. Just a only a few possibilities are shown in the photos to the best, with a quick explanation. Switches can be momentary contact, turning on (or off) only while held in position or maintained contact, remaining in the same position until manually switched on or off. Or it is perhaps timed – turn it on and it remains on for 10 minutes and turns off (a bathroom heat lamp perhaps).

The actuating force might be a human hand, a moving box on a conveyor line, a gust of wind or perhaps a light beam. It is perhaps a pressure switch, turning on a well pump or air compressor when pressure falls and turning it off when the pressure is high enough.

In every case, though, incoming current is either turned on or off and this implies that there is a line wire (a wire with constant power on it) and a load wire (a wire that’s switched on and off) to be attached. The overwhelming majority of switches do not care whether the road or the load wire goes to which terminal, although a couple of do. A lighted switch placed inside a home that lights up when the garage light is turned on as an example, would stay lit all the time if the road wire was put to the wrong terminal. Some switches light up when turned off with the intention to see them at the hours of darkness, and wire placement will matter here, too.

In such cases, try to follow the directions with the switch, particularly if the switch needs a white neutral wire to operate it’s internal light. That neutral wire must go to the proper terminal! If the road and cargo wires are inadvertently reversed, though, no damage is finished; if an internal light doesn’t work as expected simply reverse the wires and check out again.

Different types of Electrical Switches
Click thumbnail to view full-sizeA 20 amp switch, found in some homes. Note that there aren’t any holes within the back to push wire into; they should be connected to the screw terminals | SourceA small toggle switch, commonly found in automotive uses. The two nuts are used to mount it through sheet metal. | SourceThis toggle switch has 4 positions, including off; the line wire could be connected to any of 3 loads, one at a time or none in the off position. Wires must be soldered into place. | SourceThis specialty switch is operated by something moving the long 6″ rod at the highest. It operates either of two loads, thus has 2 load wire terminals and a line terminal. | SourceA circuit breaker. A switch that may turn off either manually or automatically if the present passing through it exceeds a set limit (50 amps on this case). This one controls two different circuits at the same time. | SourceA four way switch, used together with 2 three way switches to regulate lighting from multiple locations. There are four terminals to attach wires to, although none of them get a line wire. | Source Popular
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sendingmaria sial 4 years ago from united kingdom

good hub , you demonstrate all the points quite clearly

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