Academy Crop

Electrical Information

Electrical Basics

Calculating electrical loads is an easy math equation:

Watts = Amps x Voltage


Here are the elements explained:

Wattage (watts) is a measure of total energy used by an electrical component, in this case a light. Most of our lights are rated by wattage, and it is usually the name by which we refer to them. A 150 (pepper) consumes 150 watts, a 300, 300 watts. The 1.2K HMI consumes 1200 watts, etc. The Kinos are one of the exceptions to this rule. They draw varying amounts of power, since each of the 4 banks can be lit independently. Each of the bulbs of a Kino uses about 165W, drawing 1.4 amps (5.5A total draw for all 4 blubs).

Amperage (amps) is the draw of electricity. This is best described as the rate of flow, similar to how a river works. At any point across a river you can measure the cubic litres of water moving past you, based on the width and depth of the river at that point. Amps represent the total flow of power at a given point in a circuit.

All breakers are based on amperage, and rated as such. In practical terms amp rated breakers are a measure of the maximum amount of energy which can pass safely through that circuit. Common household breakers are usually 15 Amps. 20 Amp breakers are also normal for some higher draw plugs. Utility plugs, such as a stove or drier will often be ganged on two 30 amp breakers for a total power rating of 60 amps. This is the case of the utility plugs in the studio. Vintage breaker or fuse boxes may have lower amperage ratings. The bottom line is to always check the breaker box and confirm breaker values before setting up lights in a new location. Be sure to always map the plugs and know what amperage ratings you are working with.

LEDs help mitigate the problems traditional high amperage draw lights create, but they aren't completely immune to them!

Voltage (Volts) can be thought about as the amount of force possible in a circuit, or the amount of force needed to drive an electric device. To return to the river analogy, voltage would be equivalent to the strength of the current pushing against an object (as opposed to the amount of water present). For our purposes voltage is a constant, because standard plugs, as well as the hots in a 3 phase system carry the same amount of voltage – 120V. This is a standard throughout all of North America. Other regions may have different voltages (Europe runs on 220V). All our lights run off 120V AC, except for LEDs which require DC power and have a wall adapter (which runs off 120V), sometimes they have the option of running off battery power.

15 Amp Breaker

Calculating Loads (Mains)

Watts = Amps x Voltage

So a 120V, 15Amp (standard) circuit will be able to provide 1800 W of total power.

1800W = 15A x 120V

To figure out how many lights can plug into this one circuit (which may include more than one plug) we can add up the wattages of the
individual lights. For example, two 650s and a 150 will be:

650W + 650W + 150W = 1450 W total

This would be a safe combination on one circuit, because the total wattage is less than 1800W. We cannot plug in a 2K light to a regular
circuit, since it has a 2000W power usage. It must be fed from a stove or dryer receptacle.  As mentioned previously, a single breaker may have more than one set of plugs on its circuit, they may even be in different rooms. It is important to map out the circuits if doing an extensive lighting on location. In the studio the plugs have already been mapped for you, likewise in the studio it is easy to keep track of loads when using 3

5 Wire

Calculating Loads (3 Phase)

In the case of the distro boxes we are working with there are 6 50A breakers per box (hence the name 6x50). Remember that each hot in a Five Wire circuit can carry 100A load. The 6x50 box is split into three channels, one pair of breakers for each of the hot connections. This means each hot has two 50A breakers connected from the distro. 100A total on two breakers matches the rating of the cable, so calculating the load for each breaker is all that is required, you will not max out the cable.

Watts = Amps x Voltage
6000W = 50A x 120V

Each breaker of the 6x50 may be loaded with up to 6000W.

6000W x 6 breakers = 36,000W total system load (12000W per hot channel)
(on the 3 phase system using Five Wire)

If you were using a newer 6x60 box, then you would have to be careful not to overload the 100A Five Wire with the maximum load the 6x60 distro can handle – 120A. This might require more careful calculations, since one channel might be up to its 60A, meaning the other channel could only handle up to 40A. It is very important to double check your calculations. Running 120A total on 100A rated wire may cause the wires to overheat, potentially melting. This would be an incredibly dangerous working situation.

Likewise, if you were to T off the distro boxes and set up two 6x50s instead of just one, you are still limited to 6000W per channel, or
36000W for the whole system. You must keep track of what lights are being plugged into which channel since with two 6 x 50 distros there
is the potential to have 200A running on one of the channels of the Five Wire.

This could lead to very unsafe - potentially fatal - operating conditions!