Ac Circuit Lab

8/13/2019 Ac Circuit Lab

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Protected Under

18 U.S.C. 707

3-Way Switch


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Concepts in brief

AC- A lternating C urrent. Alternating current means the electricalsource for feeding voltage and electrical power is alternating (orswitching polarity) over and over. This type of electrical power isin our homes, farms, businesses and industries delivered by a utilitycompany through a power plant, substations and power poles. DCelectricity is Direct Current and polarity is constant all the time as found in batteries.VAC - Volts Alternating C urrent. Common house voltages are120VAC from the typical house outlet and 240VAC sometimesrequired by air conditioning, heating equipment, ovens, and

water heaters.House wiring- The electrical wiring, and devices (such as outlets,switches, plugs, circuit breakers) found in homes, farms, and

businesses that supports electrical power from 120VAC and evenup past 480VAC.


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Concepts in brief- continued Hot- Refers to a conductor carrying voltage. The live wire that can cause injury if

not respected! Typically the black and red insulated conductor in house wiring is hot, but beware a white wire might look neutral and actually it can hot as well. The brasscolor screw on outlets, switches and loads are to be connected the hot conductor.

Neutral- Refers to a conductor returning the flow of electricity back to the sourceafter passing through an electrical load. Typically this the white insulated wire andneutrals are typically grounded back at the breaker panel. The silver screw isconnected to the neutral conductor.

Ground and grounded - Refers to conductors that are at a 0 volt state connected back at the electrical source most commonly the breaker panel in a building. Each buildinghas a rod made of copper buried deep into the earth which all ground conductors are

tied. The main purpose of grounding is safety from electrical shock or fire. If a hotwire or terminal comes into contact with metal that is properly grounded, two thingswill happen: 1) a short circuit will form between hot and the ground conductor trippinga circuit breaker and stopping the electrical flow and 2) electricity will flow to aground state much faster than entering the body preventing a shock. Ground wires arecolor coded green or bare copper. All metal electrical devices are to be grounded!


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A look at some common electrical devices used in house wiring.

Brass = Hot = Black wire

2-way switch 3-way switch

Outlet(Receptacle)

Brass = Hot = Black wire

Short slot = Hot

Silver = Neutral = White wireGreen = Ground

Plug

Ground

Long slot = Neutral


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A closer look at the 3-way switch

Common Terminal(odd color terminal)

Position Terminal

Ground

How it works: Flipping the switch up or down makes a closed circuit betweenCommon (C) to position A or Common to position B. Two 3-way switches arerequired to control an electrical load from two locations. See next page

3-way Symbol3-way Switch


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How it works: Look at the positions of switch 1 and switch 2. Electricity has a complete pathfrom the plug to the lamp and back to the plug. Rule : The common terminal a 3-way switchwill either be to the hot side of the load or hot side of the voltage source.


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How it works: Look at the positions of switch 1 and switch 2. The path of electricity is broken at switch 2, thus the light is off. What would happen if switch 1 was flipped down?The 3-way circuit allows control of the lamp from two different locations.


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So far

We have learned some terminology as it applies to house wiring.

Looked at some typical electrical devices used in house wiring.

Learned the meaning of color codes in house wiring.

Took a close look at the 3-way switch and how it functions in acircuit.

Its time to get started and wire a 3-way switch circuit.

Remember safety first! Never plug in a circuit until you havechecked your work and all terminations are done and out of theway or covered from accidental contact. Have an instructorcheck your work before you test!


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Unassembled Parts for AC Electricity Course


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Common Tools for AC electrical work


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black

bare copper(ground)

white

A look at one type of wire used in house wiring.This is often called Romex cable and in this example

the cable is a 2 conductor with a ground wire.


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copper

black

red

white

Another type of Romex cable. This cableis a 3 conductor with a ground wire.


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Start with the lab board and 5 wire restraintclamps. Clamps will be installed in the knockoutholes of the 3 metal wire boxes.

BEGIN


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Close look at wire restraint installed through knockout hole


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To tighten a wire restraint use a flat blade screw driver and forcethe locknut of the restraint tight.


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Using wire strippers and the 2 conductor wire with ground remove insulation as shown above.


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Strip outer insulation from both ends of the 2 conductor wire(with copper ground) and thread through wire restraints.


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Starting with the AC load (light) octagon box, strip and make loopson the individual conductors. See following slides for details


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Strip individual wires using strippers. Notice 14 AWGmarking on stripper is used with the 14 gauge wire.


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Making loops with needle nose pliers.


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Attach copper (grounding) wire to octagon box with green screw.


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Attach black (hot) wire to brass terminal of lamp holder. Noticethe loop of the conductor follows the direction of the screw asit is tightened, this is an important practice to follow.


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Attach white (neutral) wire on silver screw of lamp holder just like the black wire.


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Strip insulation from a piece of 3 conductor with ground cableAnd route through the switch box that has the 2 conductor cable.


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Switch box grounding. Take bare copper wire from each cableand attach to metal box using green grounding screw.


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White wires are stripped, twisted together and a wire nut istwisted over the bare wires.


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The black conductor from the lamp is attached to the

common (odd color) terminal of the 3-way switch. The red and black from the other cable are attached on the other free terminals.


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The lamp and one switch are now completely wired. Now remove theinsulation off the other end of the 3 conductor cable and loop

through wire restraint of the other switch box.


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Remove insulation from one end of power cord and route through remaining wire restraint.


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Ground the bare copper from the 3 conductor cableto metal box using green grounding screw.


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The power cord black wire attaches to the black terminal of the 3-wayswitch. The red and black wires from the 3 conductor will attach to the

remaining terminals just like the first switch. White wires are securedunder wire nut.


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Remove the insulation from the other end of the power cord

and slide cord through the plugs hood. Using the picture as aguide trim back wires for proper length.


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Remove insulation from each wire of power cord (just enoughto get under screw). Black wire goes to brass screw, white wire toto silver screw and green wire to green screw.


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Attach plug end to plug hood (tucking wires inside). Push power cord through hood and secure with hood clamp screws.


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After checking your wiring thoroughly, secure the switches, lamp holder and switch covers to metal boxes with the furnished screws.


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After securing covers place a good light bulb in lamp holder.

switch cover


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Documents

Ac Circuit Lab