Chapter 4

 Lighting Cable and Electrical Distribution

If it were not for electricity, we would not have light.  We have to provide this electricity to our lighting units for them to project any amount of luminance.  This is actually a little more straightforward then most people think.  The electric company gets the electrons to the building.  The initial builder and electrician will get the electricity to a variety of circuit breaker/fuse boxes in the building.  When your dimmers are installed, a licensed electrician will then get the electricity to the dimmer packs.  At that point, you are responsible to get it to the lights.  Of course, there are a number of different ways for this to happen, and we will discuss some of them. The most simple is an extension cord.  If a light has a plug cord on it that is 30 inches long, but the source of your power, whether it is a dimmer or a wall outlet, is ten feet away, you have a problem.  Fix it by using a ten-foot extension cord to connect the two.  In choosing this extension cord there are a couple of things to keep in mind.  The first is that you are using the same type of plug that the light and the electrical source are using.  The second is that the extension cord (cable) can handle the electric amps that you will be using. 

We generally use what a three-conductor cable.  Inside one outer jacketing are three individual stranded copper cables.  The white one is the neutral, the black one is the hot and the green one is the ground.  Electricity works in a loop.  The electrons must flow from the source, through the light bulb and then back to the source.  Any full interruption of this loop will result in the light bulb not turning on.  We generally call that a switch.  Any partial interruption of the electricity will dim the light bulb.   We generally call that a dimmer.  It is a series of switches and dimmers that help us achieve all of the wonderful artistic ideas that we have. 

The black wire brings the electrons to the light bulb and the white one returns it to the source.  The green (ground) wire is a safety device.  Electricity desires to return to the earth.  The ground wire connects to the outside of the metal housing of the lighting unit and a rod then brings it to the earth.  This way if there is a short in the wire (break allowing the electrons to electrify the outside of the lighting unit); the electricity will sooner go through that ground wire instead of you.  Do not believe for a second that you will not feel or receive a shock from a lighting unit that has a short, but the majority of the electricity will by pass you.  If you ever see, feel, witness or suspect a lighting unit with a short, immediately cut all electricity from it and have it repaired.  These conductors inside the cable may have a different amount of copper wire in them allowing them to handle different amounts of electricity.  We use three common Gauges, 12, 14 and 16 Gauge.  I recommend 12 Gauge for up to 2250 Watts, 14 Gauge for up to 1600 watts and 16 Gauge for up to 1000 watts. Always look to the side of caution.  Use a heavier Gauge cable then necessary.

For the most part, theatres should be equipped with 12 Gauge cable straight across the board.  Some folks will bring some 14 Gauge cable in to save money (less copper).  I do not think it is the best idea because someone will inevitably not realize that it is 14 Gauge and put to much power through it.  When I spec out individual cables I usually use 12   Gauge cables.  Please also be aware that you must always consider whatever the weakest part of the cable is. a regular Edison cable, the connector is often a 15-amp connector.  Therefore, even if the cable is 12 Gauge and can handle 2400 watts, you really should not put more then 1800 on it because of the connector.

Extension cords, typically known as cables, are a simple means of getting the electricity from the source to the unit is one of the most common uses. In some, more established theatrical buildings, there are units called raceways.  They are a more permanent extension cord.  Using electrical conduit and rectangular boxes are a common way to distribute circuits throughout the theatre.  They can either come wired directly from the dimmer and then distributed to a circuit in the theatre or pass through a patch panel (much like an old phone operator station).