Prefabricated Components

By Jeff Griffin | Jan 15, 2005
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Using prefabricated and preassembled electrical components often can bring substantial cost savings, especially on large projects such as hotels and hospitals that have a large number of identical layouts.

Some contractors have used preassembled products for years, others are trying them for the first time, while there are some who have yet to do so.

And while labor issues that once restrained the practice of assembling electrical parts off the job site are less an issue today, some contractors say many electricians in the field are not happy when prefabricated assemblies are used, feeling that they devalue their skills and experience and ultimately could threaten jobs.

“Prefab stuff?” snorted one union electrician. “They don't need us for that. A monkey can do that work.”

Even so, suppliers of prefabricated components and the contractors who install them say that their use is growing steadily and that the trend will continue.

The selection of prefabricated electrical components is increasing as electricians recognize the cost savings that can be achieved by using them, said Randy Petak, vice president of PW Wiring Systems.

“Panelboards were among the first, then breakers mounted on panelboards, and then modular wiring for overhead fixtures,” he said. “Then drops down walls and branch-circuit wiring were introduced. The use of prefab components is increasing day by day, and if contractors are not purchasing products from suppliers like our company, they are making their own prefabricated systems in-house. Savings on a job can amount to as much as 70 percent.”

PW's prefabricated power product line includes brackets, boxes, plaster ring device covers and harnesses attached to devices. The company also offers engineering services to create a complete design using prefabricated wiring components.

St. Louis' Sachs Electric Co. has broad experience in the use of prefabricated components on a wide range of projects.

And Sachs Electric uses the technology in every variation-buying prefabricated components from various suppliers, assembling components in a 3,000-square-foot prefab shop, and establishing a prefab area on job sites.

Among the most-used prefab components are quick pulls, boxes with devices, precut conduit and precut MC, said Robert Moeller, Sachs Electric vice president of technology.

Other prefabricated components frequently used by Sachs Electric include light fixture brackets, rough-in electrical systems, power and data communications box assemblies, conduit and large pipe bends, customized nipples for rigid pipe, component assemblies, and box supports for concrete pours.

“The benefits are labor savings and schedule savings as well as emergency benefits to field personnel when standard ordering and delivery of supplies and tools would delay an installation,” Moeller added. “They also help a job progress when there are unanticipated schedule changes.”

“During the estimate process,” said Moeller, “we evaluate if there is an opportunity to use prefabricated components. When there is, we generally incorporate these and other methods into the project to render cost and time savings.”

ACS/Uni-Fab (ACS) has manufactured prefabricated modular high-bay and fluorescent lighting since 1983.

“In the early 1990s, we expanded our product line to include an 'intelligent' floor system that delivers general purpose and isolated ground power to work stations in raised-floor environments,” said ACS' Mike Medeiros. “The lighting side of our business has been growing incrementally over the years and modular wiring for lighting is still the greatest percentage of our total company sales, but the greatest leaps have been in the intelligent floor area. The use of the raised-floor technology to deliver power, HVAC, voice and data has really begun to catch on.”

Chad Reynolds, senior product manager for Thomas & Betts, said prefabricated components usually fall into three general categories:

_Components purchased by contractors who build assemblies, including devices and whips, in company prefab shops; the products usually are the same used in traditional construction, and the most popular are prefab brackets that can be used in a variety of assemblies

_Box and bracket assemblies used by contractors who want to take advantage of prefabrication to reduce costs, but are not equipped to do a complete take-off on the job and build assemblies to the device and whip level

_Complete assemblies, including devices and whips, purchased by contractors who want to benefit from total cost savings offered by prefabrication, but do not want to establish a prefab shop.

“With labor accounting for 60-plus percent of the job, prefabricated components offer an effective way to reduce the total cost of construction,” Reynolds said. “Also, increasing material costs of steel products is encouraging many contractors take a second look at prefab. And when a contractor in a local market adopts this concept and begins winning jobs, others soon follow.”

Currently Thomas & Betts offers a variety of box and bracket assemblies using its most popular boxes, brackets and covers.

Prewired raceways also are popular prefab products

“For many years, all perimeter raceway had to be cut and assembled on-site prior to installation,” said Kevin Baker, Wiremold Co. product manager. “Prewired raceway, manufactured to customer specifications, is delivered ready to install, and can be installed in as little as one-third the time required for field-assembled perimeter raceways.

“Unlike field-wired raceway, which requires that the wires be pulled before the devices can be wired, electricians simply mount raceway lengths and connect the feeds. This enables contractors to get off the job faster, so they can take on more work with the same labor. Because these units are fully assembled, installation and supervisory time are sharply reduced,” Baker said.

Sachs Electric was the electrical contractor for the $50 million Lindbergh Tunnel, which carries traffic beneath a new runway at Lambert-St. Louis International Airport. The tunnel, which opened last fall, has two quarter-mile-long, 46-foot-wide cells and is constructed to accommodate the force of a 1.25-million pound aircraft touching down directly on top of it.

In the tunnel's utility corridor, Sachs Electric's work included the installation of more than 300 polymer concrete preformed boxes placed in concrete walls to provide access to equipment and cabinets. The corridor and ancillary building houses electrical, electronic and mechanical systems.

“Use of prefabricated components definitely is a national trend,” said Moeller. “They can be used most anywhere, and we see them being used more often in the future.”

Oklahoma Electrical Supply Co. (OESCO) has frequently used modular lighting, but used prefabricated wiring components for the first time on a recent new hotel project.

“We used prefabricated wiring for all outlets in guest rooms, for switches, cabling to fixtures and fixture-hard connections,” said Tim Sardis, manager of construction for OESCO's Oklahoma City office.

The project was a learning experience for OESCO, Sardis said. Prefabricated components did save time on the job, but planning required a lot of up-front time and follow-up reviewing of plans to make certain everything met the project's specifications.

“Once we got everything right, work proceeded smoothly,” said Sardis. “Prefabricated components included kick plates, four-square boxes, and plaster rings and devices. We just plugged components in, pushed in quick connectors and the installation was done. With precut lengths of MC cabling, everything was already done with all connections in boxes, we just had to take the prefabricated MC cable from point to point.”

Sardis said that using the components speeded up the electrical work, but complicated the drywallers' job of cutting holes in Sheetrock, resulting in political issues with the general contractor and drywall contractor.

“The typical drywall contractor today uses a router to cut the device hole in the Sheetrock,” Sardis said. “The prefabricated components have the device already installed with a protective flat cover over the device. This cover makes it difficult for a drywaller to cut the hole for the device. It really comes down to the relationships that have been developed and the ability of the electrical contractor to sell the general contractor on the benefits of using the system.”

Prefabricated components did save labor costs on the project, Sardis said.

Another benefit can come during the trim-out phase of a job.

“Schedules,” he said, “often fall behind, and it's necessary to make up time at the end of the job, and prefabricated components can help make up lost days by helping alleviate inevitable labor stacking problems. Already having a large portion of the trim-out complete makes a significant difference at the finish stage.”

Sardis said that OESCO will use prefabricated components in the future, but that company personnel likely will put them together, rather than purchasing them from suppliers. OESCO has set aside warehouse space for a prefab department to assemble components for future projects.

“We can take the drawings, layout the project, put it on CAD and have our people put the components together,” he said. “We believe that will be more efficient.”

For example, Sardis said, all components for each room on a hotel project can be packaged together and sent to the job from the OESCO warehouse. When several jobs are underway at the same time, the in-house prefab department could do two or three products at once and get everything needed to each project. Sardis said use of prefabricated components clearly is a trend that will continue.

“A lot of contractors have used them extensively, but we are just starting out with it,” he said, “and it takes a different way of thinking to make it work. There is no question that prefabricated components can save on labor costs, but it can be a problem to get your people to buy into the process because it takes away the skill level required on the job.

“With prefabricated components, you're paying two to three times more for materials, so you have to cut labor costs substantially, or it won't work,” Sardis said.

Many contractors today want to find ways to control costs, particularly in highly competitive markets, Sardis said.

“One way to do that is to apply manufacturing techniques to construction where it is possible to do so,” he said. “Using prefabricated components is one way that this can be accomplished.” EC

GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at 405.748.5256 or [email protected].


About The Author

GRIFFIN, a construction journalist from Oklahoma City, can be reached at [email protected].





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