There are two basic aspects of working with electricity. One is to move enough electrical power from point A to point B to adequately energize the equipment that requires it. The other is to do it safely. Sometimes, these two factors will be in conflict with each other, usually because of budgetary restraints Large wire and cables are needed to move a lot of power, and they are expensive to purchase and install properly, but small, cheap gangs of “extension cords” may seem to get the job done, until a plug or receptacle burns out, or a cable catches on fire. And therein lies the potentiality for serious problems.
What is Power?
Before discussing specific practices, like why you don't want to run 500 feet of 18 gauge wire to power a 20,000 watt lighting system, it's a good idea to understand the basics of EMF, Electromotive Force.
Electricity is a form of energy that's characterized by voltage (V) and amperage (A or I for current), which when multiplied together, produce a value known as wattage, which is identical to power. V x A = W (or P). In the simplest possible terms, power is the ability to get work done. A horse demonstrates power when pulling a plow, hence the use of the term ‘horsepower.' Water, wind and all forms of engines generate power. It's just a matter of what you choose to do with them that dictates their usefulness for a given situation.
Voltage is the unit of measure of the intensity of electrical energy. There are many situations in which the voltage can be high, but the power level is quite low. The ignition system in your car is a prime example. The 100,00 volts (or more) that make your spark plugs spark, do not contain enough power to harm you. It might make your finger sting, but that's the usually the extent of it. The electrical impulse does what it's supposed to do, it makes a spark that creates combustion in the engine. But it does not provide the motive force that drives the engine. That comes from the fuel which might be gasoline, diesel, propane, or another form of combustible material. The spark plug just gets the process started.
In classic terms Voltage is most easily related to water pressure. You could have a very small garden hose but if it's connected to a high pressure source, a lot of water would ‘seem' to come out. It might shoot across the parking lot, but in reality that same hose might take two or three days to fill a moderate sized swimming pool.
Amperage is almost the opposite of Voltage. It is the unit of measure of the volume of electricity. Again, using the water analogy, a storm drain could move many millions of cubic feet of water per hour, but the pressure might be low enough that you could float a small boat on the upper water level of the drain and have a great ride. Not recommended, but you get the picture.
Now, when you combine a lot of amperage with a lot of voltage, you get a lot of power. It may be enough to light a city, melt vast amounts of steel in a steel mill, or run a large church production. And then it's time to become highly respectful of the potential life-threatening consequences. No, your ignition system isn't going to kill you. Nor is the 12V battery in your car going to shock you – though it might have enough power to melt your jumper cables, or cause a dropped battery wrench to vaporize, both of which could cause burns or other forms of harm. But lethal? Highly unlikely. Not so with higher voltages and amperages. They can be lethal upon contact.
The Great Balancing Game
Electricity has the property of being easy to manipulate. Understanding the relationship between amperage, voltage, and power is not automatically intuitive, but the water analogy helps a lot.
Unlike water however, an enormous amount of power can be transferred through relatively small cables, the kind that we see by the roadside every day. This is because the voltage has been intentionally raised to a very high level, as much as 100,00 volts or more, which proportionally decreases the amperage needed for a given amount of power transfer. In fact, it's far better to use high voltage and small cables, than low voltage, high amperage, and large cables. Think about the size of a good pair of jumper cables. They are thick and expensive. Imagine running 12VDC all the way from the Hoover Dam to Los Angeles! The size of the required cables would fill many lanes in a freeway and cost billions in coper.
Resistance is the third governing element. If there were no resistance, electricity would be flying everywhere (well it already is, in the form of RF), but could not be channeled into a working system.
Resistance is what your amplifier encounters when it drives a speaker. Or you lighting dimmer powering the lights. Or the motor that runs your ventilation system. Without resistance, no work gets done. That's why the power outlets in a room aren't shooting out energy – that is until a resistive load is plugged in. That could be you console, your phone charger, your desk lamp, or a bank of amplifiers. Or anything else that is compatible with the voltage source.
The great benefit of electricity is that it can be manipulated through voltage and amperage trade-offs to accomplish almost anything that the system designer wants to achieve. And therein lies the potential danger. You can't see electricity, except as a representation on a meter, or until it manifests as sparks, fire, or explosions, and then it's probably too late.
Getting Practical
Now that you have an understanding if the basics, let's talk practicality. While there is no way to replace the full text of the National Electric Code in an article, nor would you want to, the very expensive – and hard to understand- book covers many things that are far out of the realm of the average church tech's need for electrical knowledge. So while it's recommended to borrow one from the local library and become familiar with it, it's not a ‘must-read' for a weekend church technician. Almost any edition of the past five years will do; electrical code changes slowly and deliberately. A 2009 NEC Book will tell you just about as much as you need to know for your daily work, as a shiny new 2015 version... and at a lot less money.
The Church Tech Punch List
Some of the questions we've been asked to address are included below. And we'll be glad to continue this series to discuss additional needs, if requested. The “Punch List,” if you will is a short compilation of questions that are often asked, and answers about how to deal with the issues. Let's start by taking about compliance with the building codes. Fines and shutdowns can occur if violations are detected. Here are a few classic violations that are rarely even realized.
Power strips. Often called Waber Strips the same way refrigerators are called Frigidaire and Kleenix is called Kleenix, they are a means of providing additional outlets for specific purposes, virtually always for temporary usage.
While power strips are permitted for temporary usage, such as in offices for desk lamps, they are not permitted for use in amplifier rooms, machine rooms, or other permanent installations. They are never allowed to be ganged in series, though at a temporary show this will usually be overlooked. They are never to be used in ceilings, under stages, or other difficult to access locations. The theory is simple: unlike a junction box or terminal strip, they are not designed to provide a long term connection. Over time the connections can oxidize and cause resistance, which results in heat that can cause a fire. Also, in this day and age of ultra-cheap products from overseas, the internal electrical integrity may be of very poor quality. A power strip should always carry a UL (Underwriter Laboratories) listing mark, or an ETL mark. Both are of equal value. However, both marks and labels are often forged on cheap electrical products.
The NEC (National Electric Code) is not quite as specific when referring to power strips as they are other wiring practices, because of the inherent portability of the devices, but this pretty much sums it up:
“Relocatable power taps are not intended to be permanently secured to
building structures, tables, work benches or similar structures, nor are they
intended to be used as a substitute for fixed wiring. The cords of relocatable
power taps are not intended to be routed through walls, windows, ceilings,
floors or similar openings. They are not intended to be used outdoors, nor on construction sites.”
Author's note: as convenient (and inexpensive) as power strips have become, I recommend that when you need them, purchase high quality designs that are made in the US. Better yet, if you're so inclined, build a power distribution system of quad boxes using high-grade duplex outlets (think $20 each, not .89 cents ea) and use tough portable cordage that's rated for construction site usage, such as 12/3 or 14/3 SJO. Use excellent quality AC plugs and make sure all terminations have been carefully made. After making connections, go back and re-tighten the pressure screws because copper will ‘flow.' After a half hour or so under pressure, the connections will be loose again. Loose connections create high resistance which causes heat across the resistance that can lead to an incendiary condition. The infamous three pin ‘stage plug' that has been used for decades for theatrical lighting is an example of a poorly designed mating system that is almost guaranteed to cause overheating sooner or later. Does the potential incendiary condition occur before or after the last act? Do you really want to test that?
Readers, If there's enough interest, I'll be glad to sketch out some stage and FOH power distro systems than can be built by anyone inclined to visit the hardware store, take care with wire terminations, purchase quality components, and utilize good assembly practices. This is much preferred over spending money on power strips and extension cords.
Several specific questions were asked by readers, and here are the answers:
1.Extension cords of the variety that hardware stores sell, are never rated, nor acceptable, for running through ceilings, walls, under stages, etc. All such wiring must be permanent, but it may not have to be in costly conduit. Depending on your state, county, and city requirements, you may be able to use Romex, instead of THHN in conduits, which will save a lot of money. But this needs to be checked for your specific application. Romex is permitted in residential and some industrial solutions, but must be checked with local ordinances. They vary quite a bit, and are application specific. For example, you probably can't power your 70,000 BTU chiller and 400 amp icemaker with Romex, but you probably can power your 15,000 BTU A/C unit with it.
2.There are such things called cable trays that can eliminate the need for conduits, but their permitted usage falls under local electrical codes. When allowed, they make for easy additions to the wiring plan and are idea for congregations that are growing rapidly, or may wish to add video or lighting in the future. One thing though, it is never a good idea to run audio cables alongside (or on top of) power cables in a cable tray. The EMF from the power cables is likely to cause hum and noise on the audio cables, and probably the video signal cables as well.
3.When conduit is absolutely required, there are multiple types that may be permissible. It's possible to get a county building inspector to visit you, or to at least have a phone call, to explain what is permissible and what is not. You don't have to be a licensed electrician to make contact with an inspector.
Conduit types range from rigid, which is heavy and very expensive to install, to EMT (Electro Metalized Tubing) and IMT (Intermediate Metalized Tubing). Conduits also include plastic (PVC), plastic coated metal of several compositions (steel, stainless steel, Aluminum) and more. There are basic rules of thumb: rigid is usually reserved for high voltage, high current because of the cost. EMT and IMT are permissible in some applications, but not in all states and counties. Plastic (PVC) or plastic coated steel conduit should always be used for direct burial. Steel conduit in the ground won't last long due to corrosion.
4.There are cables made for direct burial without conduit, but they are usually not the best solution for long term service, though that depends on the soil and on whether or not the region has insects and other critters who like to munch on cable.
5.Medium and high voltage (600 volts up, and specially the higher voltages like 5,000 volts (which is actually called ‘medium voltage'). Such power runs should always be in conduit and if in an outdoor environment, the conduit is normally encased in concrete marked by a red dye and buried at least 24” deep, though there are exceptions.
6.The NEC books provides exceptions to almost every rule, based on the type of equipment being used and other factors. It's a long, hard read which almost no one can recite verbatim.
On the other hand, if you're moving hundreds of amps around for large lighting and sound systems, rigid metal conduit is the safest way to go for indoor work, and concrete encased duct banks are the safest system for UG (Under Ground work). UG involves backhoes, concrete trucks, and many other aspects of construction that may apply to a new, large campus project, but have little meaning to the small worship center that wants to run a simple video feed to a nearby building.
In most cases, simply owning a good quality, modular power distribution system, with proper circuit breakers and perineum quality wiring devices (the fancy name for connectors), should suffice for your portable needs.
Following basic building codes for permanent, or semi-permanent AC power installation work, should allow you to get the job done without needing to farm it out to an electrical service. Nonetheless, it's highly recommended that you discuss your intentions with a licensed electrical contractor, obtain a bid or two, and then look at what you can do to reduce costs while following ‘to the letter' the prescribed work. If you develop a good relationship with a local EC (Electrical Contracture), and especially if he or she is a member of the church, you can save the ministry some money without compromising the quality of the work. As your EC to come in and do an inspection before the work is fully completed and subject to the county building inspector's review.
As you can see, there is no simple answer to what is actually a rather large question, but there are quite a few things to avoid. Extension cords, power strips, and other temporary wiring devices are simply not OK for permanent installations.
Let's finish up with answers to some of the specific questions we've been asked by readers:
Q: Can you do an article on using extension cords and power strips safely? There's enough electricity on the stage to power everything, but in seasons when 20 lamp fixtures in one cluster are needed (for example) not all of our outlets are in one place on the stage.
A: As stated above, power strips are not intended for anything more than temporary usage, and should not be daisy chained, so while they are permissible for short-term productions, that's the extent of what they're designed for. Do not thread the cables through any structures, walls, props, or other physical objects. They should be 100% visible from end to end when the Fire Marshall comes to inspect. Fire Marshalls are adept at stopping shows in their tacks for violations, and confiscating the offending hardware.
Extension cords can be used on stage in the same manner as power strips, but are not recommended. Most are not fused or protected by circuit breakers, whereas power strips normally do carry some form of protection, often including surge protectors and sometimes RF filters as well.
Extension cables are usually poorly constructed, intended for low power requirements and short-term usage in mind, such as plugging in an extra reading lamp for a visit with friends. That said, there are some expensive and well-made power cords that might be considered extension cords on steroids. I have owned many of these when a last minute requirement had an assistant running to the nearest hardware store to pay double what the cable and connectors are actually worth.
That said, even the largest, fattest, most expensive ‘big bright yellow' extension cord I've ever owned (at about $250, thank you), burned out its molded plug and receptacle after just a few days of being connected to a 20 amp source. And it was actually rated at being able to handle 20 amps.
Compare this to 40 years of building power distribution systems from premium components such as Hubel wiring devices, normal J-boxes, and good quality 14/3 or 12/3 SJ or SJO cable, and I've never seen a wiring device fail, nor a cable melt down, except when improperly wired to begin with.
Q: Is it safe to roll equipment over cords?
A: That depends on the weight of the equipment, the size and type of wheels, and the quality of the construction of the power cord(s). No. I would not roll a 2,000 lb cart of line array modules that have metal wheels over a household-grade 18/3 extension cord. But rolling a small equipment dolly with pneumatic tires, like a kid's toy wagon, over a heavy duty 10/3 power cord won't do any immediate damage. We all do it. The key here is to use common sense. 100 trips over the cordage will do more damage than one or two. If you have a situation in which this is going to happen often, there are many versions of cable ramps that protect the cables and allow even heavy equipment (i.e. forklifts) to safe cross the cable ramps, as often as they need to. Very common on large shows with active and complex load-ins and load-outs.
Q: How do I avoid getting a buzz from the lights coming through my sound system due to something plugged in an outlet?
A: Buzzes and hums are usually the result of ground reference problems, though they could also be induced by EMF (Electro Motive Force) that's transferred magnetically from one device, like a dimmer pack, to another device, like an audio mixing console...or just a placement of audio cable that's too close for comfort to the dimmer pack, or its power feeder.
So the answer is to do some isolation-type of trouble shooting. Try moving items around to see if they are affected by close physical proximity. Try isolating the audio feeds by using
Jensen Iso-Max transformer isolators, Lundahl isolation transformers, IL-9's or other brands. We're talking about signal level transformers, not big, expensive, and heavy power transformers. Usually, and in almost all cases, an audio isolation transformer will do the trick. They are also available from companies like Jensen and others to eliminate the black hum bars that are seen on video screens, also the result of ground loops.
Worst case, use a power isolator transformer, such as a Topaz (which can often be obtained surplus for a fraction of the original price). It can separate the audio and lighting power so that one is transformer isolated and the other is not, or both are isolated on separate transformers. Employing a Topaz (or equiv) will almost always eliminate hum, buzz, and noise (though an Iso-Max or other audio transformer might be needed in the audio path as well).
There are numerous other troubleshooting techniques that go beyond the scope of this article, but hopefully, this will get you headed down the safety corridor.
Q; Not only do I not want to be shocked, but I don't want to start a fire or trip a circuit mid-service either. …And that buzz! Not good stuff.
A: Without knowing your specific issues, such as what's causing the hum and buzz, our advice can only remain general. The buzz you're experiencing is just one symptom of poor power distribution and probably poor ground references. Again, a good grade of audio transformer can usually solve the problem in an instant. Alternately, the potential for a fire, or one-or-more tripped breakers is quite a different aspect. This implies that too much power is being demanded from an inadequate power source, or inadequate wiring (such as cheap and thin extension cords). Take a look at your whole PD scheme (that's Power Distribution for the uninitiated), and look to find any weaknesses. Sometimes, the building itself is not properly grounded. This can be ‘fixed' by adding on or more ground rods and re-doing the ground reference wiring, but it's a topic that will require a full article on the difference between CTG (Clean Technical Ground) and the ‘normal' way of doing it for typical residential and industrial buildings. There are many ways to beat the system, as it were, especially if your ministry is operating a video broadcast studio or other high-tech requirement.
With that in mind, the author will take specific questions for the next few weeks, and do his best to provide a personal answer to each reader. No promises for immediate response...but I'll try! Please try to frame any questions you have as clearly as possible.
