Power Requirements
I have done a lot of production work in unusual spaces, like the rock show I did in St. John’s Cathedral. It has 7 seconds of natural reverb and a sound system that was installed in the 50’s. That meant I had to bring my own speakers, and lots of them so I could run delays. Unfortunately, they don’t have concert capable power anywhere close to where someone would want to set up speakers. We happened to find a larger power source down the hall and used larger gauge wire from that to my distro to power my gear.
I can’t tell you how many times I’ve asked clients about how much power they have and they tell me, “Oh, there’s plenty of power in there,” only to show up and find out they meant that there are plenty of outlets in the room. They don’t know if they’re all on the same circuit breaker, or even where the circuit breaker is, but there are plenty of places to plug in my equipment.
Sometimes a single 15 amp outlet–like what’s in your house–is enough power, like when we just need a couple of powered speakers or a few LED lighting fixtures. You might even get both to work at the same time without blowing circuit breakers, but plug anything else in and you’re asking for trouble.
On the other end of the spectrum, if you walk into any large performing arts venue, you’ll find not one, but multiple large power sources ranging from 200-600 amp 3-phase. The touring production companies that utilize that power have distribution systems that convert that very large power source into the smaller circuits they need for their equipment. They don’t plug into any 15 amp circuits on the wall for their concerts.
How much power do you need for your show in your venue? If you’re doing it all yourself, here are some things to consider:
Not all outlets are created equal. It has been a common building practice for a very long time now to run a bunch of outlets off of one circuit breaker, and not necessarily all in one room. Just because you have 10 outlets doesn’t mean you can plug 10 things in. If it’s a GFCI (has the “Test” and “Reset” buttons on it) then it’s likely only 15 amps and may still share one circuit breaker with lots of other outlets. Even if you don’t need a lot of power, it’s good to know how your outlets are breakered. You can purchase a tester that will tell you which circuit breaker in a panel is powering an outlet. You can also turn the breakers off one at a time to see which outlets are connected to them. Also, outlets with vertical slots are 15 amp. A 20 amp outlet will either have one of the slots horizontal or a T-shaped slot that will take either a vertical or horizontal tang on the plug.
Power strips do not multiply power. You’ve seen it in the Christmas Vacation movie and probably in real life. You can’t just keep adding power strips as you add more gear to plug in. At some point you’ll blow a circuit breaker, either in the panel or on the power strip, and hopefully that happens before you burn up the small wire that is typically associated with those strips. Check the labels to see just how much power they can handle, and remember that the first cord plugged into the wall outlet has to be able to handle the entire load attached to all the power strips plugged into it.
Wire size matters. If you’re going to run extension cords from the next room, then you need to consider the resistance of the wire. Smaller wire and/or longer distances will quickly choke out the amount of power that makes it down the full length of the cord. The short, little home extension cords can only extend a small amount of power for their entire (short) length, so don’t string them together. Instead, get large, construction grade extension cords to go longer distances, and even then, if you have to go more than 100’, consider a power distribution system, like a spider box. It uses much larger wire to get a larger power source to a box with breakers and outlets built in. The wire gauge (AWG or American Wire Gauge) will tell you how big the wire is. Unfortunately, the larger numbers mean smaller wires, so it’s not intuitive. You shouldn’t use anything less than 12 gauge, or 12/2 extension cords with a 20 amp outlet. (With AWG, the first number is the wire size followed by the number of conductors with a slash in the middle. They don’t count the ground wire)
Always use grounds! A power ground is connected by the round(ish) conductor in a common home outlet. While most equipment will work without it, it’s there for a reason and should not be tampered with or removed. It’s connected to the earth so that any stray voltage drains safely away rather than passing through your body and it tells the circuit breaker to blow when you’re about to get electrocuted. It’s also a very important component in producing clean sound with any sound system. If you are in an old building with no grounds at the outlet, use a ground adapter–common at any hardware store–that has only two prongs to plug into the wall but will accept a 3-prong cable.
Use listed equipment. There is a growing push to make sure only listed equipment is used in any commercial application. It’s already the law in the State of Washington. Listed means that it’s been tested by a laboratory, like Underwriters Laboratories (UL) or Electrical Testing Laboratories (ETL), to provide assurances that it is safe and won’t draw more current than is on the label.
Count your amperes. Electrical equipment should have a rating on it–usually near where the power cable goes into the device–that can tell you what its maximum current draw is, rated in amps or amperes. If you add up all the amperes that the devices will draw and make sure you don’t exceed the amperes your outlet can provide, you should be safe to have all those devices on that one circuit.
The same goes for generators. If you don’t have enough power in your venue for the equipment you need to use, you can bring in a generator to power the show. We do this all the time. Just make sure that you get a generator that is sized to the amount of gear you are using and you know how you plan to distribute that power from the generator to the equipment. When we do a show, I often tell people, “If it’s not on a trailer, it’s not big enough for what we need.” There are laws about grounding generators, and it’s a good idea to hire an electrician to make sure that it’s done properly.
If you’re using a reputable production company for your event, you don’t have to worry about any of those things because they’ve already done all the calculations and have the proper cabling and distribution equipment to make it happen safely. Just don’t be surprised if the power needs are greater than you expected! They’ll likely want to do a site visit to double-check your power and make sure you’re not just counting outlets.
