While every construction project requires a temporary power source, there is no single method to getting vital energy to the wide variety of sites and projects. In fact, there are as many different temporary power installations as there are contractors. This means that, at times, the power source may be unsafe. But when it’s done right, the temporary power—as thankless as its installation sometimes seems—helps ensure a productive and safe work environment.
There is a range of concerns common to those responsible for bringing temporary power to a site. Safe installations depend on proper equipment, securing panels and cable protection—all of which are the responsibility of those who install it. If contractors do it right, experienced personnel install the equipment and provide regular testing and maintenance to ensure adequacy of the power systems on a construction project.
One challenge is ensuring that no one accesses panels, trips over cable or creates a hazard through lack of experience with electricity. Other construction employees on a job site may not understand the proper need and use of ground-fault circuit interrupters (GFCIs), said Wesley Wheeler, safety director, NECA.
A variety of things can go wrong—someone may not understand why they shouldn’t reset a breaker that trips or know the proper loading of wiring within correct ampacity requirements. There also are exposed wiring hazards. In fact, managing the temporary power on a construction site can be a full-time job for electrical contractors and their employees. Often, larger sites have dedicated personnel who monitor and maintain temporary power infrastructure to ensure OSHA compliance and safe installations, Wheeler said.
When done right, contractors are thinking about how to ensure control over the entire temporary installation.
“They need to ensure all proper covers are in place, GFCIs are installed and functioning properly, and the correct voltage and loading requirements have been considered in the design and installation of the temporary-wiring system,” he said.
Some companies have found ways to innovate temporary power solutions to make processes safer and more efficient. For example, Anderson Electric Inc., Springfield, Ill., has created its own mobile temporary power units. These fully enclosed units roll on-site to quickly provide power and reduce the need for workers to open panels or run extra cable unnecessarily, said Wes Anderson, company president.
Traditionally, Anderson recalled, “One of the things that would give us all fits was the temporary power. With each job, the company started from scratch.”
So they decided to get smarter about it, he said. They took on a hospital project and decided to build their solution—about 15 moveable panels.
“We built them in such a way so that when you are on the job site you never have to open a panel to do anything,” such as adding a circuit or tool, Anderson said.
Each unit includes a transformer, a 480-volt panel on one side and a 120V panel on the other. They are fed from a temporary service or local panel and include eight to 10 yellow external plugs to connect equipment and services. These receptacles are mounted on steel in concrete 5-gallon buckets and spaced around the building.
“It all becomes plug-and-play. It’s a little bit homegrown,” Anderson said, adding that, “We tried to set it up for all our anticipated needs.”
Once it was installed, the process of powering equipment or lighting was just a matter of inserting a plug.
On the hospital project, workers deployed about four units on each floor. They knew what kind of power was needed for everything from dehumidification equipment for drywall to mechanical contracting equipment.
“It was designed upfront to do everything we would have to do [on a work site],” he said.
Anderson workers have rolled the units onto their projects over the past decade, and the units have been in constant use since they were built.
“Temporary power is no longer a hassle,” Anderson said.
Some larger contractors are building similar units in their prefab shops. Also, some electrical supply vendors offer their own solutions.
Clear-Vu Lighting, Central Islip, N.Y., provides LED fixtures with the flexibility to be temporarily mounted or moved as needed for each project. The Flex SLS Site Lighting System is entirely low-voltage and therefore designed to eliminate the risk of electrocution and shock hazards. In fact, the system is designed so that the electrical contractor merely connects the power supply to a 110/229V AC input source, wires the bus line along a ceiling, beam or other type of harness, and then connects the LED modules to the bus line.
Anderson said his company uses Clear-Vu Lighting for temporary job-site lighting. The company also leverages Milwaukee Tool's temporary lighting solution that claims easy setup and instant light. Milwaukee, Brookfield, Wis., offers battery-powered light sources that can be wheeled into a room and illuminated, which benefits contractors and job sites that require short-term lighting that runs on a battery.
It’s a far cry from old-school styles of temporary power and lighting systems, Anderson said. Anderson Electric’s own house-built tools make an impression.
“Our guys like it, the general contractors and owners like it. When we wheel our stuff on-site, most GCs are in awe. They’ve never seen anything like it,” he said, adding that the temporary power system is a value-added solution for the company.
Temporary power is rarely a big money maker for contractors, said Ruben Bera, corporate safety director for Commonwealth Electric Co. of the Midwest, Tucson, Ariz. Despite that, Commonwealth takes the job seriously—striving to provide a system that is secure and protected. The company offers its own temporary skids on the work site, including a 480V transformer with 208V service.
All temporary power is protected and “all of our breakers are GFCIs, labeled for that outlet. That’s not only the prudent thing to do, it’s also an OSHA requirement,” he said. Any temporary wire is then elevated and secured to prevent accidental contact.
Bera has come upon shoddy temporary power on job sites throughout his career.
“I’ve seen temporaries with no cover, panel, load center, no spacers in the breakers.” Commonwealth doesn’t work that way, he added. One thing the company does is lock the panel and label it with the company name and the project foreman’s name. The system will automatically fault if an unauthorized party goes into the panel.
It’s a far cry from the days when construction workers who lost power would go to a panel and turn breakers on and off.
“I think the industry has become very mindful. We pride ourselves in providing excellent temporary services,” Bera said. But he sees a few missed steps. “What I don’t see a lot of is marking.” In addition to name and contact information, Commonwealth marks panels with “Keep Out” and the amount of voltage as well as the foreman's phone number.
“In some cases, GCs want a key to the Panel. That’s not always the case, but it does happen,” he said.
Commonwealth also offers its own wheeled carts to make the temporary system easier to install and move.
All Bright Electric, West Nyack, N.Y., also focuses on the safe work conditions that must be sustained with temporary power. The contractor has been in operation for 45 years, providing service for commercial, industrial and residential customers in the New York metropolitan area.
Temporary power installations start with a focus on preparation, said Jim Johannemann, All Bright Electric’s president and CEO. Most projects benefit from a one-line riser sketch to determine the required size of the temporary service. For this reason, the company conducts a site visit to determine the location of the service based on the existing utility connection opportunities. The first step, then, is to contact the local utility service or customer to set up a visit to agree on a plan.
When it comes to safety, more is always better.
“We always go overboard to ensure safe working conditions. We tend to exceed NEC and OSHA requirements,” Johannemann said.
“Ground-fault protection at every level is in the forefront of our design,” he said. “Typically, we provide ground fault at the service and every branch circuit at each circuit breaker.”
The company opts in favor of occasionally experiencing nuisance-tripping as part of an effort to provide the best safety. And grounding is always done according to Code, he added.
“A solid NEC and workmanship installation is of utmost importance; a temporary service must be installed and maintained as if it were going to be permanent,” Johannemann said. “The temporary power has to survive in its best condition until it is no longer needed.”
So the system should be designed to operate safely and effectively for longer than the scheduled project timeline because projects often run longer than planned.
When it comes to changes or mobility, “Whenever the branch circuits are modified, or moved, the installation must continue to have the same integrity as the original installation,” he said.
Temporary systems maintenance, when done well, includes checking the integrity of the installation frequently and making sure all of the supporting materials from the service—down to the last temporary light bulb—continue to operate and exist in a safe condition.
All Bright Electric always has a third-party electrical inspection performed before the utility company makes a connection to the temporary service.
“We always—at the very minimum—provide lighting with proper cage protect at the foot-candle level demanded by OSHA,” Johannemann said, adding that the company tends toward providing that protection in excess of requirements.
“Pleasing the client—whether the owner or general contractor—is important. Typically, cost is an issue with the buyer. However, we will not compromise safety,” he said.