Basics of A/V Electricity
Electrical competence is a must have for AV technicians. This article will give you a quick rundown on the basics of electricity. It is critical that you understand how electricity works and flows so you can be safe and effective on the job site.
Electrical Safety
First things first: safety. Make sure electrical equipment is properly connected, grounded and in good working order.
Ensure that you are using the right power sources for the right devices. Ensure that you are not overloading the circuit as this can result in a loss of power or cause an electrical fire.
Ensure there are no exposed wires touching each other as this can cause a short-circuit. If you notice a cord is damaged, set it aside and mark it for repair back at the shop.
Ensure you aren't running electrical cords into standing water and if it's raining, tape any exposed connections with electrical tape to ensure water does not get into the connection. Wet environments can increase the risk of electrical shock.
Working with electrical equipment necessitates that you are aware and cognizant at all times. Safety is the priority.
Electrical Flow
Now that we've covered safety, let's start with the basics of electrical operation.
To help keep things familiar and simple, I'll be using a regular wall outlet and string lights to help explain. Power comes from the outlet flowing down the hot line into each bulb until it reaches the end of the line. The power then comes back down the neutral line back into the outlet. Once there, it is grounded. So, it comes out hot and then returns neutral to the outlet. The hot line is the black wire, the neutral line is white, and the ground wire will be green. Sometimes, at least for the older cables, the green wire will be absent, and the ground will exist only at the outlet. You can tell which cables have the ground by whether they are 2-prong or 3-prong. 2-prong doesn't have the ground included.
To recap, power flows out and then back on a closed circuit. If that closed circuit is broken at any place, the electrical flow will be interrupted resulting in a loss of power.
Amperage and Watts
Now that you understand the flow of electricity, let's talk about amperage and why it's important.
Amps refers to the measure of how much electrical energy is being supplied through an electrical line. For our example, a regular wall outlet is 15 amps. This means that there are 15 amperes of energy available through this outlet. The reason this is important is because light fixtures require a certain amount of power to function. When we talk about fixtures, we don't use amps. Instead, we use watts. A phrase we like to use that's easy to remember is "100 watts = 1 amp". Now this isn't the exact conversion, but it's what we like to use in the field. The actual math is about 100 watts = .89 amps, but we like to round up just to give us a little extra buffer of safety in the field. So, an average power outlet is 15 amps which gives us about 1,500 watts. Using this, we can determine how many fixtures we can run off one power outlet. For example, the string lights use 11 watts per bulb. So, this means that one 15-amp outlet can potentially supply power to about 136 individual string lights.
What this means in the field is that we can use 1 100-footer or 2 50-footers on one single outlet.
(Learning Check: Let's go ahead and test your knowledge. If 1 Parcan takes 500 watts, how many Parcans can we put on 1 15amp outlet?)
A key thing to keep in mind is that when calculating amperage, always round up just to keep things safe. Also, just because an outlet can support 3 Parcans in theory does not mean we should. We make a habit of not maxing out outlets to err on the side of safety. If an outlet is maxed out, it will become hot, and this can lead to electrical fires or a malfunction of some sort. Remember, watts are the individual consumption of the unit, and the amps is what the outlet puts out.
One thing we haven't talked about is voltage. Voltage essentially means the strength of the electricity. Wall outlets output 120 volts and a big power distro-box used to run concerts outputs a lot more. Voltage is the strength of the power, amps is the amount of power available, and watts is the amount used by each individual fixture. We won't go too much in depth on voltage. Instead, we want you to focus on amps and watts for now.
Field Applications for Amperage and wattage
Understanding amperage and watts is important for all our techs to understand. Typically, all these calculations for power are done by the lead techs in the shop during the planning phase. However, we want all our techs to be capable of calculating power usage.
For example, let's say you just setup lights at a wedding. You have power and everything is working. Then, the wedding vendors start showing up. They begin hooking up their coffee makers and hot pots. Next thing you know, they overload the circuit, and it kills your lights. Now it's become your problem because your lights aren't working anymore. Knowing how many watts we are going to be pulling out of an outlet will help us determine where we need to go for power. This way, we can preemptively assess how much power is going to be drawn from an outlet by us and the vendors.
Therefore, it's important to understand amps and watts so that when a problem arises, you can know how to fix it. We need to be aware of power and how it gets affected by vendors and caterers so that our lighting operations are not compromised.
Wire gauge
Now, let's go over wire gauge and why it matters. We need to know what the gauge of the wire is because this determines the number of watts and amperage that can flow along that wire. Think of the wire as a pipeline and the different gauges carry different amounts of power. In the AV world, the gauges you'll typically see are 16, 14, and 12. This goes off the American Wire Gauge system, or AWG for short. You can look on the cable jacket to find the gauge number. The number of the gauge denotes its size with 16 being smaller than 14 and 14 being smaller than 12. The bigger the gauge, the more power it can carry. For reference, most triple taps will be 16 gauge.
Now, how do we apply this knowledge to real-world scenarios? Let's go back to our 15-amp outlet again. Using 16-gauge wire on a 15-amp outlet might work for one or two lights, but more than that might overload the wire. If we have 1 100-footer string lights, we will use a 12-gauge wire triple tap to supply power. Be aware that when you start adding more lights and daisy chaining them, you need to be cognizant of how much power is being drawn. Proper procedure would be to use a 12-gauge wire at the outlet, and then reducing the gauge the farther out from the outlet it goes. Always start with the fattest gauge at the outlet to be safest.
GFI's
Part of understanding the basics of electricity involves GFIs. GFI is short for Ground Fault Interrupter and these outlets precisely monitor the power going through them. These outlets have the Test and Reset buttons on the front with a small light indicator. If they sense anything amiss, they will trip, resulting in a loss of power. This affects what machines we can put on these outlets when out in the field. For example, a snow blower machine will sometimes put power on the ground, which would result in the GFI tripping. This can be a pain in the ass so be aware of this feature they have and plug your devices in accordingly.
Conclusion
To recap, we covered electrical safety, power flow, amperage and watts, wire gauge, and GFIs.
This article provides the loose foundation for the beginnings of electrical AV competence. Be sure to tune in to our YouTube as we will begin releasing a series of training videos meant to help train and inform new techs.