Article and photos by Gregory Havel
Electricians use different colors of insulation on wire to show its function and sometimes its voltage. In larger wire sizes, especially in older installations, these wires could all have black insulation, and each wire could have a band of colored tape or paint near each end. These color codes were adopted by electricians as a safe work practice, and have become part of the building and electrical codes.
We are all familiar with the cables that were used to wire our houses in the common 120-240-volt single-phase electrical system. For ordinary 120-volt circuits, each cable will have a white "neutral" wire, grounded at the service disconnect switch. Most cables will also have a bare copper or green equipment ground wire, to protect us from electrocution by faulty appliances. Each cable will have a black or "hot" wire that is connected to the circuit breaker or fuse. In addition, some cables have a red wire that is also hot. This may be part of the switching circuit for a set of three-way light switches, a separate circuit, or a 240-volt circuit when connected to a two-pole circuit breaker at one and a 240-volt appliance at the other.
The wires feeding a residential 120-240-volt single-phase electrical panel will include the white neutral wire, the green or bare copper ground wire, and two "hot" wires, which can be black and red, black and blue, or both black.
Commercial, industrial, and apartment buildings often use three-phase electrical systems for efficiency and to keep the electrical loads balanced between the wires. These systems use other color codes.
Photo 1 shows a panel fed by a 208-120 volt three-phase electrical system, using black, red, and blue for the "hot" wires, white for the "neutral," and green for the ground wire. Your local commercial, medical, and apartment buildings may use this system. 120 volts is available for use between any "hot" wire and the "neutral", for small appliances, computers, lamps, and housekeeping equipment. 208 volts single-phase is available using any two "hot" wires, as for motors, clothes dryers, and kitchen ranges, feeding from a two-pole circuit breaker. 208 volts three-phase is available using all three "hot" wires feeding from a three-pole circuit breaker, for large motors and other heavy appliances.
Photo 2 shows a panel fed by a 480-277 volt three-phase electrical system, using brown, orange, and yellow for the "hot" wires; gray for the "neutral," and green for the ground wire. Your local industrial buildings, hospital, and Wal-Mart probably use this system. 277 volts is available for use between any "hot" wire and the "neutral", and is commonly used to supply fluorescent light ballasts and high-intensity discharge (mercury vapor, sodium, metal halide) lamps. 480 volts single phase is available between any two "hot" wires; and as three-phase using all three "hot" wires, usually for large appliances, and motors for fans, pumps, and air conditioners. Since each building may have only one electrical service, this higher-voltage system with brown-orange-yellow-gray wires will supply transformers throughout the building to step the 480-277 volts down to 208-120 volts, using black-red-blue-white wires.
Please note that these color codes are not universal. They have become part of building and electrical code requirements, but these do not apply to wiring in structures built before the code requirements.
Some older buildings may have separate services for 120-240-volt single-phase and 240-volt 3-phase power. Most of these single-phase systems will use two black (or a black and a red) for the hot wires, and a white wire for the neutral. The three-phase system (with no "neutral") may be three black wires, black-red-blue, or sometimes even brown-orange-yellow.
Caution: If we are at an incident with exposed electrical wires in a building, we must respect this as a HIGH-HAZARD AREA until the wires are de-energized and locked out, no matter what their color or condition. Photo 3 shows a circuit breaker that has been properly locked out. The lock-out hasp allows additional workers to apply their own padlocks.
Warning: If the color coding is other than the black-red-white with which we may be familiar, we must respect this as an EXTRA-HIGH-HAZARD AREA until the wires are de-energized and locked out, no matter what color code is used.
Firefighters use water because it is cheap, wet, and puts out fire. Water, especially dirty water, is a good conductor, and does not mix well with electricity. Electricity is unforgiving, and frequently does not allow us to exercise the same kind of bad judgment a second time.
Any manufacturers or brand names noted above are used only as examples, and the websites only as sources of additional information. Reference to them is not an endorsement of either product or manufacturer.
|Gregory Havel is a member of the Town of Burlington (WI) Fire Department; retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II and fire officer II, an adjunct instructor in fire service programs at Gateway Technical College, and safety director for Scherrer Construction Co., Inc. He has a bachelor's degree from St. Norbert College. He has more than 30 years of experience in facilities management and building construction.|