Busway is Right for Distribution Center
Any do-it-yourselfer will tell you that it's good practice to pick the right tool for the job at hand. Sometimes, though, it seems as if any of several tools are appropriate. Past experience in similar situations usually dictates the final choice, with success the ultimate vindication. On a much larger scale, making the right choice of equipment and systems when there is more than one workable ...
Any do-it-yourselfer will tell you that it's good practice to pick the right tool for the job at hand. Sometimes, though, it seems as if any of several tools are appropriate. Past experience in similar situations usually dictates the final choice, with success the ultimate vindication.
On a much larger scale, making the right choice of equipment and systems when there is more than one workable solution is something consulting engineers face every day. In spring 2004, Charlotte, N.C-based Optima Engineering P.A., became involved in a project for Wachovia Corp., a Charlotte-based provider of banking and financial services. The fourth-largest bank in the United States based on assets, Wachovia had decided to expand its regional distribution utility center on the northern edge of the city.
To begin with, there was just one problem: The electrical room in the existing facility was in the northwest corner, but the expansion was planned for the east side of the building—a 600-ft. stretch. Thus, engineers were tasked with not only choosing between two viable methods of powering the addition, cable/conduit or busway but also the direction in which to make the connection—either trenching across the loading dock area or proceeding across the ceiling of the original facility. Both methods carried the potential disadvantage of disturbing the daily proceedings of the center, something Wachovia desperately wanted to avoid.
New function prompts expansion
The original 250,000-sq.-ft. facility was built in 1999. However, various infrastructure issues forced the company to ponder facility upgrades in early 2003, says Amy Landis, vice president, Wachovia Corporate Real Estate, and project manager for the expansion. By the end of the year, those plans were combined with a 120,000-sq.-ft. expansion that came about due to a new function Wachovia had taken on and consolidation of other functions into the expanded facility.
But determining the direction in which to expand wasn't cut and dried, Landis says.
“We could have built on either the east or west side of the building,” Landis says. “Because parking was an issue and we had land constraints, we built on the east side and made it two stories. We expanded as far as we possibly could and we provided a new employee parking lot on the west side.”
Due to the mission-critical nature of the facility, one key criterion for Wachovia was working closely with local consultant and contracting firms for the job. Enter Optima in early 2004, which previously had done work for Wachovia down the road in Winston-Salem. Once Optima was on board, Wachovia made it clear that any workflow disruptions were not desired.
“One of the things we made everybody aware of is that this is a very functional, critical site,” Landis says. “In the January time frame of the year, it's an extremely critical site. The building cannot go down at those times.”
Therein was the challenge for Brian Thompson, P.E., an electrical engineer with Optima, who also had to consider the fact that Wachovia building guidelines dictated a primary and alternate feed for the addition to provide redundancy and increased reliability.
Thompson concluded that it was impossible to dig parallel trenches for primary and secondary cable/conduit runs across the floor of the existing building.
“So the option was to trench around the back, over to the addition, which would have been across the loading dock,” Thompson says. “They have 16 docks on the existing building and we basically would have had to go across that whole area, and it would have been a logistical hurdle.”
Another complication: The electrical service area was placed toward the front of the addition. “Not only are you going around the back, but then you're making a turn and coming all the way up to the front of the addition,” he says. “You're adding a couple hundred feet of conduit, trenching and labor.”
Also meriting consideration was the segmented way that the trenching was approached; then in light of the fact that there was no way to shut down any of the loading docks, no matter how briefly. “I guess there is some way they could have been reorganized, but they would have had to work around their normal operations, going across one group of doors while they are shut down, then backfill and proceed,” Thompson says.
With that option also quashed, Thompson considered running cable/conduit overhead in the existing facility, but that, too, was problematic because of the time, and thus labor cost, of running two 5,000-amp feeds, which would be comprised of 12 4-in. conduits for each feed.
One day, while he was working on designing the switchboard setup for the expansion with Chris Morris, a consulting engineering specialist for Square D, he posed the problem to Morris, who ultimately suggested busway. But the answer wasn't cut and dried, Morris recalls.
“I can suggest anything under the sun, but he's got to make the decision,” Morris says. “I wasn't sure busway would work until I asked a number of questions. What's the layout of the facility? Do you have open space? There are a lot of questions you have to ask.”
Once busway presented itself as the likely solution, Thompson's next move was to select the correct type. Keeping in mind he needed to upsize the service feed to 5,000 amps from the 4,000-amp base requirement to meet National Electrical Code rules for voltage drop, he chose a busway meeting these specifications.
The busway proved to be an ideal choice. “You have reduced voltage drop and a lower impedance path, which is basically energy savings,” Thompson says. “The busway has a certain resistance that electricity has to overcome, and the byproduct of that is loss of energy through heat. You reduce your heat loss, and you're saving energy.”
A new electrical room had to be built in the northwest corner of the existing building, which featured a new main switchboard, new generators and a pair of 4,000-amp circuit breakers that power the entire facility, both the original building and the addition. Busways for primary and alternate power sources for the addition proceed from those breakers in separate paths across the ceiling and feed respective switchboards in the addition, which are side by side and have a tiebreaker between them.
Ease of assembly proved to be a key factor for electrical contractor W.B. Moore Co. of Charlotte Inc., which completed the busway installation in summer 2005. “Busway basically slides together and then you make the connections and tighten the bolts,” Thompson says. “When you're making a straight run, you use 10-ft. sections for the most part, so you just bolt one section to the next. If you're using conduit, you still have 10-ft. sections, but you have to put a coupling every 10 ft. Multiply that by 12 conduits, and that's 12 couplings you have to do every 10 ft.”
Todd Stevens, vice president of operations for W.B. Moore and project manager for the Wachovia job, says his team installed 1,500 ft. in the existing facility— a pair of 750-ft. runs—each of which took two weeks to install, including 100 ft. per night. Using cable/conduit, he says it would have taken six weeks to install each run. He estimates Wachovia's cost savings for both labor and material was about $400,000.
Landis said the busway allowed Optima to live up to its promise of avoiding disruptions of the day-to-day business in the existing building.
“They installed the busway basically over [workers'] heads as they worked, in some cases, and then in other cases it was done at night,” she says. “We never had to shut our warehouse function down to install the busway. We didn't have to say, 'You can't use this section of the warehouse today because we're going to install busway here.' There was no impact to that business unit whatsoever. That's the main reason we did it.”
Aesthetics also key
Wachovia began moving into the addition in December 2005, and expected to have it fully occupied by the end of February. Thus, once a consistent load is determined, the cost effectiveness of using the busway from an energy savings standpoint can be calculated, which will accrue over time.
But there is another practical benefit of using busway, from Landis' perspective.
“Maybe this is just my personal preference, but I think that it's a neater, cleaner solution,” she says. “You have your 30-ft. ceiling because it's a warehouse, and you have exposed bar joist and cross beams, but the busway just runs straight through it. I think the conduit would have been harder to install and aesthetically, the busway is just a simple, flat component that's running all the way through. You hardly notice it.”
Thompson agrees. “There are customers that like a neat appearance and busway is aesthetically pleasing,” he says. “Instead of looking up and seeing a bunch of conduit and couplers every which way, you have nice, rectangular busway going from Point A to Point B. There was actually plenty of room there, but on other jobs where there is not a lot of room, then busway is a more viable option, because it will fit into less space than conduit and wiring. That gets to be a driving issue.”