Joining two seemingly unrelated products to make an even better product is an American tradition. Ice cream and bananas were eaten separately for centuries until 1904, when a young man in Boston served the first Banana Split. The result was a tasty treat that is a favorite everywhere. Last year, over 25 million banana splits were served by one fast food franchise alone.
Such is the case for MC cable and wire mesh cable tray. Both have existed for years and have become invaluable in their respective uses. MC cable saves many hours of labor costs when used to install power cables in exposed and complex installations. Wire mesh cable tray is lightweight and easy to install, yet sturdy enough to support the heaviest of loads. It can be installed with simple hand tools on the job site, saving time and labor. Used together, MC cable and wire mesh tray have an even greater cost advantage over traditional conduit and pulled wire. With material and labor costs rising, owners and contractors who are looking for new ways to keep costs in line, are taking notice. 
MC Cable Saves Install Time
Electrical contractors have used smaller MC cable for branch circuits for years. These cables offer the same protection as most forms of rigid conduit, but are much simpler to install, which reduces labor costs. Many electrical contractors are now lowering installation costs by focusing on MC cable for much larger feeder lines in commercial construction, in some cases replacing up to 90 percent of the rigid conduit with MC cables.
“Installations that include conduit as their primary wiring method are being converted to MC cable at an increasing rate,” says Dave Mercier, technical director of the electrical division of Southwire. “The primary reason for this change is an average of 50% labor savings in installation costs.” Mercier’s observations are supported by recent industry studies that show a rapid growth in the use of MC cable, while conduits sales continue to decline.
A recent trend in construction features open interior spaces, which exposes a building’s infrastructure, including electrical cable. Examples of this type of construction are large “warehouse” stores, stadiums, and even commercial offices. MC cable can be installed to a neat and orderly appearance, but for this to be accomplished, the electrical contractor must pay attention to aesthetics when planning and installing the electrical system.
Because NEC code requires that MC cable be supported every six feet, instead of every 10 feet for rigid conduit, the support method for these open interiors needs to be inexpensive and good looking. The choices for mounting MC cable are primarily the same methods used to install rigid conduit, including channel framing and threaded rod. Basket or wire mesh tray is another method that is acceptable to both inspectors and owners.
The advantage of wire mesh tray becomes obvious after the first installation. Installation labor needed to fasten MC cable is dramatically reduced, since multiple MC cables can be pulled at the same time. In addition, MC cables pull quickly and easily due to the round wire construction and the 2”x4” grid.
Wire Mesh Cable Tray Comes of Age in the U.S.
Historically, conduit has been the cable pathway of choice in the U.S. When this country made the conversion from gas lamps to electrified lighting, it seemed natural to run wires into the existing gas pathways made from pipe. Over the years, building codes were based on this conversion and are still in place today. Countries outside the U.S. and Canada do not share this history, and as a result, did not embrace conduit in the same way. Today, laborsaving cable tray is used extensively throughout Europe, South America and Asia.
Introduced to the U.S. market roughly 10 years ago, wire mesh cable tray has shown remarkable growth in recent years. “Our studies show that the U.S. wire mesh cable tray market grew by 25 percent in 2005,” says Tim Place, president of Cablofil. “and we expect that growth to increase in the coming years.” Other independent studies have supported this trend.
The major reason for this growth in wire mesh cable tray is a reduction in overall installation costs when compared to steel conduit. A recent study completed by Hargis Engineering for a “big box” store chain compared labor and material costs for an installation using rigid steel conduit versus wire mesh cable tray. A 30 percent cost reduction was projected when using MC cable supported by wire mesh cable tray. (See Chart 1)
Wire mesh cable tray compares favorably to other forms of cable management. In 2004, NECA published a labor rate index that listed a 30 percent labor savings when installing wire mesh cable tray over ladder tray.
Data cabling professionals have been the early adopters of wire mesh tray in the U.S. Their experience shows that wire mesh cable tray is simple and inexpensive to install. Its versatility in making moves, adds and changes is also an important advantage.
A recent example of success in data cable management is Enterprise Leasing’s 100,000-square-foot data center completed in Weldon Spring, Missouri. Guarantee Electric selected wire mesh cable tray plus MC cable for the building’s under-floor installation and was so pleased with the results, they committed to extending the system into the second phase of construction.
“We chose wire cable tray because it was easy to use and took up less space,” says project manager Dipak Kapadia. “The system is very flexible and it costs much less to install than conduit.” Kapadia had used wire mesh tray very successfully for data installations and had been so impressed with the system that choosing wire tray for power cable installation was an obvious solution.
Wire Mesh Tray – Raceway or Support System?
A major hurdle to widespread acceptance by U.S. electrical contractors is the misunderstanding of wire cable tray function—is it a raceway or an open support system? Article 100 of the NEC code defines raceway as: “an enclosed channel of metal or non metallic materials…” While Article 100 includes most cable pathways that are in use today, wire mesh cable tray is not included under Article 100 because it is not considered a “raceway”– it is an open support system that does not enclose the cables.
Also, under Article 392, the code states that MC cable must be secured every six feet in open installations. However, wire mesh cable tray is considered a “containment vessel.” So when MC cable is installed in a wire mesh cable tray per NEC Article 392, securing every six feet is no longer required.
In vertical installations, MC cable must be supported at regular intervals and meet the same requirements for supporting conductors in vertical raceways detailed in NEC table 300.
The Synergy of MC Cable and Wire Mesh Cable Tray
MC cable in wire mesh tray is a new idea that makes for a neat and orderly installation. It saves installation time, which in turn, reduces installation costs.
Detractors argue that the cost of MC cable alone is comparable to conduit plus wire, and they question how the additional cost of wire mesh cable tray can be added while still reducing overall installation cost. The answer is simple: reduced labor costs. MC cable supported by wire mesh cable tray is so quick and easy to install that the additional material costs are more than offset by lower costs of labor.
This trend toward laborsaving components is becoming increasingly popular. Pre-wired outlets and power screwdrivers are just a few of the innovative ways contractors have found to reduce labor.
As the economics of the cabling industry change, so will the products that are offered by suppliers and used by the installers. Also changing is the mindset of the average electrical contractor. They are increasingly motivated to use new products that finish the job faster, because they know this will help them win new projects.
A Simple Guide to Planning an Installation with MC Cable Supported by Wire Mesh Cable Tray
1. Discuss the concept of MC cable supported by wire mesh tray with the engineering firm in the initial stages of planning the electrical system. Most manufacturers have a wealth of case studies online that can show you how others have planned similar projects and can supply engineering expertise.
2. Use manufacturer-supplied cost studies to illustrate the potential cost savings to the end user. Win new contracts on the basis of forward thinking, not just price.
3. Be familiar with the products. Seek proper training to make sure the system is installed correctly and meets all local codes. Many manufacturers will provide on-site training free of charge.
4. Keep an open mind. New ideas—like the banana split—are an important part of the American tradition.
Bob Crain is a Technical Sales Manager for Cablofil, a U.S. manufacturer of wire mesh cable tray.
