What you don't know about your shop's electrical specs might stun you
Often shops have electrical cords running on wet floors, plugged into a circuit without a GFI (Ground Fault Interrupter). Shops also frequently sport cords with un-repaired breaks or with the ground prong removed or electric machines that could draw 20 amps plugged into a 15-amp wall outlet. Shops also sometimes run long cords into small welders, employ no electrical bonding on potentially flammable stored items or store solvents next to electrical power boxes. Some newly built shops don't take advantage of the cost savings and efficiency of three-phase electrical service.
Don't make these mistakes. Get your shop up to proper electrical specs with the following steps.
Step 1: Learn the difference between single-phase vs. three-phase power
Electricity in the United States is supplied to homes and small businesses as 240V, single-phase electricity. The supply lines (see graphic) that enter the circuit box are divided into two 120V electrical circuits or one 240V circuit. AC, or alternating current, as its name implies reverses cyclically as opposed to DC (direct current) whose direction remains constant.This means that machinery using a single-phase 110V circuit potentially cycles as well. This sometimes presents itself as a flicker in incandescent and more notably, fluorescent lights. In most cases this does not produce noticeable problems until larger loads such as the paint booth or welder are used. By using the neutral and either of the other two wires, you get a 110V circuit. Using both power wires and the neutral means the circuit will be 220V. In a home or small business, these two applications will be sufficient. Small loads of 15 to 20 amps work well on 110V, while heavier power needs such as dryers, water heaters, and ranges require larger voltages and amperages.
Three-phase supply lines entering a business have three circuits of electrical power at (in the U.S.) 60 Hz. These three phases of electricity are supplied so that, as each reverses cycle, there is always one that is at peak. This enables motors and welders to run longer and more efficiently. In most cases, three-phase power is less expensive to the consumer as well. Though three-phase electrical supplies can supply commonly used 110V, what is often confusing is the difference between 220V and 208V power supply, and the fact that they cannot operate without the aid of a converter (buck-boost transformer).Many body shops choose a smaller 110V MIG welder because of its supposed lower electrical needs. And that assumption is correct. It only requires 110V. But all welders convert AC electricity to DC, and though smaller welders may have a smaller voltage requirement, that welder will require higher amounts of amperage to operate it properly. That higher amperage draw requires higher amperage wire, including extension cords and receptacles. Though lower voltage welders can do an acceptable job, they have drawbacks such as low duty cycle (which is the amount of time a machine can be operated expressed in percentage. If a machine has a duty cycle of 30 percent, that means it can be operated for 3 minutes in each 10-minute period or 30 percent of the time.
Using the equipment longer may result in damage (burn-out). Some electrical equipment may have a built in current interrupter. When the item is used beyond its recommended duty cycle, this interrupter turns off the equipment before damage can occur. All of these protective devices, while very effective for preventing damage, increase the cost of the equipment. When coupled with the increased cost of operation, less expensive tools may not truly cost less. When purchasing new equipment, performing a careful true cost analysis may reveal that less expensive equipment is be more costly in the long run.Step 2: Identify outlets
Outlets also come equipped for both different voltage and different amperage. A 110V outlet, if installed correctly, can be easily identified as to its amperage rating. A110V welder that requires 20A should not be plugged into a 15-amp outlet. An outlet with two vertical slots and a half round ground hole is a 15-amp outlet. Though a welder that requires 20 amps peak can be plugged into this receptacle, that 20-amp draw will trip the 15-amp fuse. The correct receptacle is this 20 amp one. It has a half round ground hole, one vertical slot, and a T turned on its side.
Shops should be equipped with the correct circuit load rating, and each employee should know which device can be properly plugged into which receptacle. If a fuse blows, the cause of that interruption should be found and eliminated. If the problem is ignored, the alternative result could be tragic.Step 3: Grounding your problems
Body shops are notorious for having wet floors, particularly in the paint department. And though the majority of the tools are driven by air and do not pose a risk when operated in those wet areas, some tools are driven by electricity, namely buffing and polishing equipment. If electrical tools must be used around wet areas, the outlet should be equipped with a ground fault circuit interrupter or GFCI (which may also be called a GFI). This safety device trips if it detects a ground fault of very low amperes (for a class A GFCI, this is a ground fault of 0.004 to 0.006 ampere). This protects workers from dangerous shocks. Though electrical equipment should not be used in wet areas, a GFCI will protect workers in those situations. In most areas, GFCIs are required by code. (The one shown is 20A. Notice the sideways T.)
Step 4: Quick disconnect
A quick-disconnect power switch, or panic button, is a device placed throughout the shop that when pushed will disconnect all electrical driven devices, thus shutting them down in case of accident. Some systems cut off all power throughout the building, while others leave on just essentials such as lighting, so that an injured party can be cared for. The one pictured is a large red button about 2.5 inches in diameter. These are easily seen, generally placed at chest level through the shop. This one cannot be turned back on without a key, so that the responsible party can make sure the potential problem that caused the "panic button" to be pushed has been resolved before the power is restored.Step 5: Bonding
Static electricity can build in and around electrically driven equipment. If discharged as a spark, this electrical charge can cause serious damage, especially when flammable liquids such as thinner are ignited. To guard against this happening, a grounding system should connect all potentially flammable liquids. Though most workers see the logic of this safety step, many often don't make use of all of the grounding straps in a shop. All potentially explosive storage containers should be grounded at all times. If static electricity builds on a container, the ground will drain it off and no spark is likely to occur.
Final word: A note of caution
A shop's electrical equipment is mainly regulated by building codes. This article is intended to inform and remind owners and workers about some of the requirements and safety devices that are available to them. It is easy to plug a 20-amp welder into a 15-amp outlet and then be surprised when it blows a fuse. It is also easy to trip a GFCI, go to the fuse box, and not see a fuse that needs resetting, thus wasting time. The hope here is that with employees using proper precautions, such as bonding, no explosion will cause a tragedy. Lastly, by understanding a little more about single-phase and three-phase electricity, shops can purchase equipment that is best suited for them and operate as efficiently and cost effectively as possible.
Finding the facts
So how would a business know if it has three-phase electrical service in the area? For standard U.S. supply to homes, there are two hot wires (180 degrees out of phase to each other) to a transformer on a pole. That transformer (depending on its capacity) will supply two 110V lines with a neutral (ground) lead to the house, if above ground. If in your area there are only two large power wires on it, it is likely that you have only single-phase power available. If, though, you see three large power wires, it is probable that you have three-phase power. You should call the electrical supplier for the most accurate information. If three-phase electricity is available to your area, and your business is adding larger equipment such as a new screw compressor or paint booth, they could be operated more efficiently with three-phase power.
The right volt
Equipment should be labeled with its voltage rating. If the incoming voltage is not within that range, either degraded operation or damage may occur. As an example, a large misting fan in a commercial shop, which requires 240V, is wired to a 208V line. The fan does not start. In this case the fan had degraded performance. It tried to start, but because of the low voltage, it would not. A buck-boost transformer could be used to increase the voltage to the needed amount, but it would draw a significantly larger amount of energy than if it was wired to the power source it requires.
For larger adjustments of voltage (15 to 20 percent), a two-winding transformer is used. Industrial equipment such as paint booths and larger welders may require 440V. If high voltages are connected to equipment with lower voltage requirements, the equipment may burn out quickly. Though there are ways to convert 240V single-phase electricity to 308V three-phase equipment, they increase the cost of both operation and installation. It is best to have three-phase service in your business. It costs less to operate your equipment than with the single-phase, and the equipment lasts longer.
Safety devices
Some of the safest shops are the ones that plan ahead and provide protective devices such as ground fault circuit interrupters, panic buttons, and banding. These are as important as safety glasses and respirators in a collision shop. All of us need to realize that the most valuable tool in a shop is the worker. No one wants to see a fellow worker hurt, and from a production standpoint, no shop wants to lose a worker, even for a short time.
