Most new construction and many renovation projects require the use of temporary power, which presents potential hazards, including shock, electrocution and fire. Responsibility usually falls to the electrical contractor to establish and maintain power safely. This responsibility includes coordinating with the general contractor or host on any special conditions or requirements they may have.
There are two methods of providing temporary electricity to a construction site. The first is connecting to a source supplied by a permanent utility company, such as an electrical panel. A portable generator is the other option.
A generator uses an internal combustion engine to supply electricity, so it produces carbon monoxide (CO) gas, a colorless and odorless gas that is undetectable to human senses. It is harmful because it displaces oxygen in the blood, depriving the heart, brain and other vital organs of oxygen. CO poisoning kills 150 people every year. Often, victims don’t realize they are exposed to the gas until it is too late. Never use a generator indoors, and always ensure it is properly vented.
Another potential hazard is the fuel that the combustion engine runs on. It needs to be refilled periodically, and a generator typically runs hot. As a result, a schedule of use must be established that allows the generator to be turned off and cooled down before refueling. Otherwise, the heat from the generator can mix with gas vapors and spark a fire or even an explosion. Always take the time to fuel the equipment properly, no matter what the work schedule may demand. Keep fuel containers away from generators, and remember any vapors or spilled fuel could be ignited. Spills must be cleaned up immediately.
Whether you are connecting to a portable generator or utility electrical power, a number of nuances need to be considered with temporary wiring activities. These include determining applicable codes and power requirements as well as identifying the proper materials for the installation environment. Often, electrical workers use indoor-rated cable for temporary power because it is cheaper than outdoor-rated cable. Outdoor-rated equipment must be used to protect against weather and other corrosive influences.
When working with temporary power, installation, use and maintenance need to be considered.
NECA’s Guide to Policies and Best Practices states: “Temporary wiring should be designed and installed according to OSHA, NEC and NFPA 70E requirements. Only qualified and authorized persons should design, install and maintain temporary wiring systems for any job site or location. Temporary wiring should be adequate for the load and environment it will be exposed to. All temporary wiring should be removed as soon as the need for temporary power is over.
Follow all applicable manufacturer requirements when using portable generators to provide portable/temporary power including maintenance and refueling activities.”
The same protection must be applied to temporary power as with any installation. Ground-fault protection or an assured equipment grounding conductor program must be applied to ensure the safety of temporary cords, receptacles and portable tools. Adequate lighting and individual circuits for specialty tools is crucial, too.
It also is important to install equipment in protected locations or enclosures rated for the environment. Ensure all openings are covered or closed. Panelboard, disconnect and breaker openings must be effectively closed to prevent any foreign object from getting inside.
To protect others, warning signs are needed for temporary wiring and devices. Improperly marked cables can result in serious hazards to unaware workers. Moreover, access needs to be limited to authorized personnel. When not in use, ensure doors and covers are locked. If extension cords are exposed to the elements or wet conditions, the consequences can be dire.
Prior to any temporary wiring efforts, have workers brush up on electrical lockout/tagout requirements per OSHA regulations. Finally, when conducting temporary power tasks, use the appropriate personal protective equipment.
Remember all temporary wiring should be designed and installed by qualified and authorized workers according to OSHA, the National Electrical Code and NFPA 70E requirements!