Power Requirements for a Lighshow or Art Installation
This page is here to help producers, promoters, event coordinators, and light artists understand the general process of calculating the size of the power source and electrical wiring needed to safely operate their lightshow or art installation. This calculator should not be used to determine your specific needs. When it comes to electrical design and electrical wiring you should always hire a licenced electrical engineer to do all electrical design and wiring. Under no circumstances should you rely upon a simple ohms law calculator like this to provide you with the answer for your specific situation. You use this calculator and all calculators on this web site at your own risk.
To help you understand the general process let's enter a fictional situation: Suppose your light show or art installation will have 4 - 575 watt projectors and 8 - 500 watt projectors, each projector has a 30 watt cooling fan. There will be 12 other small motors in the lighting rig that draw 5 watts each. Your total wattage is therefore 6600 watts. Suppose all of the equipment runs on 120 volts. To calculate the amperage you will need, enter 120 volts and 6600 watts in the calculator and press solve. You discover your light show or art installation is going to draw 55 amps.
Now look for the next larger "Ampacity" in the wire table at the bottom of this article and you will see that number 6 wire is going to handle 55 amps.
(Note: It would be rare to find a circuit in a building that provides 55 amps. So you will need to split the load. The most common electrical circuit I encounter doing lightshows in public buildings in the United States is the 20 amp commercial circuit. If I have a 55 amp load I have to distribute the load over three, separate, 20 amp circuits. Make certian that no one else is drawing power from those circuits or you will have problems.)
Knowing the amperage you will be drawing is only half the calculation. Usually the circuits needed are not close to where the lightshow will be set up so extension cords are needed. Any time you use extension cords you should consider the voltage drop caused by the extension cord.
Voltage drop is important because the higher the voltage the brighter the projector and more colorful the light it produces.
Example 2: Suppose the light show equipment is 100 feet from a 20 amp circuit and the projectors will draw 18 amps from the circuit. You have a 16 gauge 100 foot extension cord. What will the voltage be at the projectors? Should you use this extension cord? If you enter these numbers in the voltage drop calculator you will find that the voltage at the projector will only be 102.4 volts! If you use the 16 gauge extension cord you will lose 14.7 percent of your voltage! The projector's cooling fan will not run at the proper speed so the lamp will burn out quickly. The light will be dim and the color of the light will be yellowish. The electrical energy that would have gone to the projector will heat the wire in the extension cord and that might cause a fire.
Unfortunately there is always going to be some voltage drop no matter what size extension cord you use. You should try to keep voltage drop to less than five percent of the total voltage. In Example 2, if you used a 10 gauge 100 foot extension cord the voltage drop would be only 4.3 percent.
Voltage Drop Calculator
If you enter those numbers in the voltage drop calculator you will see that the 150 foot extension cord should be made of 4 gauge coper wire.
So to run a 6600 watt lightshow 150 feet from a generator you need 150 feet of 4 gauge wire. Plugs and receptacles to match. You need a power distribution panel with outlets for 12 projectors and 12 motors. The outlets should have circuit breakers rated for the amp load and each receptacle should be a GFCI type. If the show is going to be held outdoors the breakers and receptacles should be installed in a rain tight enclosure. You will also need one main breaker for the distribution box.
Will a 6600 watt gererator be large enough to run the light show all night? The rule of thumb for generators is to use a generator that provides is 1.5 times the power required. Most generators are over rated by the manufacturers and can not supply the full rated power continuously. If you multiply 6600 times 1.5 your will see that you should use a 10,000 watt generator.
All wiring should be completed by a licenced electrician. Have fun!
Wire Table for Copper Wire
Credit: The author of the "Voltage Drop Calculator" gave permission to use the code that makes the voltage calculator work.Electrician.com