Electrical needs for the shop: Don't shortcut workplace safety

As electrical power and control devices on vehicles have changed over the years, technicians have needed to upgrade their knowledge of the automobile's electrical needs. With supplemental restraints, accident avoidance and electronic control and monitoring devices having an ever-increasing presence, technicians run into more potential electrical faults that need their attention. With this in mind, it's surprising that technicians don't pay more attention to the electrical needs of the shop.

Often shops have electrical cords running on wet floors, plugged into a circuit without a ground fault interrupter, (GFI, Fig 1). You might also see cords with unrepaired breaks, or with the ground prong removed (Fig 2); electrical machines that could draw 20 amps plugged into a 15-amp wall outlet; long cords running small welders; no electrical bonding on potentially flammable stored items; or even solvents stored next to electrical power boxes. You will even see recently built shops that don't take advantage of the cost savings and efficiency of three-phase electrical service.

Ground fault circuit interrupter (GFCI)

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 wet areas, some tools are driven by electricity, such as buffing and polishing equipment. If electrical tools must be used around wet areas, the outlet should be equipped with a ground fault circuit interrupter, (Fig 3) or GFCI, which may also be called a GFI.

This safety device will trip if it detects a ground fault of very low ampere (for Class A GFCI, 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 is designed to protect workers in those situations. In most areas, GFCIs are required by code. The one shown is 20A: notice the sideways T.

Quick disconnect

A quick-disconnect power switch, or panic button, (Fig 4) is a device to be placed throughout the shop, which, when pushed, will disconnect all electrical-driven devices, thus shutting them down in case of an 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.

Safety devices

Some of the safest shops are the ones that plan ahead and provide protective devices, such as GFCIs, panic buttons and banding, just to name a few. 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. None of us wants to see a fellow worker hurt. Additionally, from a production standpoint, a worker off on sick leave affects productivity.

Unfortunately, three of the most commonly neglected safety concerns are broken or frayed chords (Fig 5), extension cords that have the ground plug removed (Fig 6) and a too-small wire gauge on the extension cord being used for a tool (Fig 7).

During normal use in the shop, the electrical cords become frayed or damaged. Also, sometimes abuse such as driving over the cord with a car or dropping a heavy tool on the cord damages the outside insulation. Even minor damage to a cord should be repaired immediately. Either the damaged area is removed and a soldered splice with shrink-tight covering is used to repair the cord, or it is replaced with a new cord.

Cords with ground plugs removed (Fig 6) are unsafe. Although the tool will operate when plugged in with the ground plug removed, it is an extremely unsafe practice, especially when used in a body shop. Any use of electrical equipment in a wet environment, which body shops often have, whether in the paint department or during winter when wet, dripping cars are brought in, and any piece of equipment that has a ground plug removed exposes the operator to electrical shock. This is true even though the device may be plugged into other safety devices, such as a GFI.

Electrical extension cords' wire gauge should be matched to the correct amperage of both the outlet capacity and the amperage requirement of the equipment being used. If a 110 volt, 20-amp welder is being used with an extension cord with a 15-amp capacity, a dangerous situation exists. Although if the welder requires the full 20 amps during its operation, it will flow through a 15-amp extension cord. With prolonged use, that cord will heat up, possibly causing damage to the welder or a fire from the hot wires. Welders and other equipment requiring higher amperage and voltages should always have their cords matched to their proper usage.

Outlets also come equipped for both different voltage and different amperage. A 110V outlet (Fig 8), if installed correctly, can be easily identified as to its amperage rating; and a 110V 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. And 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 the 20-amp one shown in Figure 9. It, too, has a half-round ground hole, one vertical slot and a T turned on its side.

One of the questions commonly asked regarding the correct placement of an electrical outlet is whether the half-round ground hole should be placed at the bottom or the top when mounting an electrical outlet. After consulting with an electrician and my local codes, I found there was no specific regulation as to the position of the ground outlet. You should consult your local codes for recommendations, if any. Many electricians, though, commonly place outlets with the half-round ground outlet at the bottom.

The shop should be equipped with the correct circuit-load rating, and each employee should know which device can properly be 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.

Bonding

Static electricity can build in and around electrically driven equipment. This electrical charge, if discharged as a spark, can cause serious damage when flammable liquids such as thinner are ignited. To guard against this happening, a grounding system should connect all potentially flammable liquids (Fig 10).

Though most workers see the logic of this safety step, not all use the grounding straps in a shop. All potentially explosive storage containers should be grounded at all times. Then, if static electricity builds in a container, the ground will drain it off and no spark is likely to occur.

Single phase vs. three phase

Electricity in the United States is supplied to homes and small businesses as 240 volt, single-phase electricity. The supply lines 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 is sometimes seen 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 will get a 110V circuit, while by using both power wires and the neutral, 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, and 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).

Equipment should be labeled with its voltage rating, and 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 that requires 240V was wired to a 208V line, and the fan would 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 percent 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's best to have three-phase service in your business; it will cost less to operate your equipment than with the single-phase, and the equipment will last longer.

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, it's 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.

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 to weld, 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 will require higher amperage wire, including extension cords and receptacles. Though lower voltage welders do an acceptable job, they do have drawbacks, such as low-duty cycle.

For a welder and other equipment, duty cycle 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 minutes, 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 will turn off the equipment before damage is inflicted.

All of these protective devices, while very effective for preventing damage, will increase the cost of the equipment; and when coupled with the increased cost of operation, the less expensive tool may not truly cost less. When purchasing new equipment, doing a careful true cost analysis may reveal that less expensive equipment may be more costly in the long run.

A shop's electrical equipment is mainly regulated by building codes. This article is not intended to instruct how to install electrical devices in shops; this work should be done by a licensed electrical contractor. It is intended to inform or 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 is that with employees using proper precautions, such as bonding, tragedies will be avoided. Also, by understanding a little more about single-phase and three-phase electricity, shops can purchase equipment that is best suited for them and operate it at the lowest cost.