In outside-plant installations, conduit is usually installed underground to guard cables from damage as well as to facilitate cable placement for fast and future needs. Also you can install Conduit Fittings Wholesale inside buildings to facilitate pulling cable between two points including from your telecommunications closet (TC) to operate-area outlets, or from an equipment room into a TC. To safeguard, isolate, and identify the cables, innerduct–also referred to as subduct–may be installed inside existing larger-diameter conduit.
Conduit is defined as a rigid or flexible metal or nonmetallic raceway whereby cables might be pulled. Additionally, although conduit enables you to house various kinds of cable, the National Electrical Code (NEC) uses the word “optical fiber raceway” in Article 770 to explain conduit, or raceways, for optical-fiber cable. Several kinds of conduit are offered, including electrical metallic tubing (EMT), rigid metal conduit, PVC, fiberglass, and flexible conduit. For premises installations, how-ever, metal flexible conduit will not be recommended because of potential abrasion harm to the cable jacketing.
Metal conduit, which typically will come in 10-foot lengths, is pretty rigid and requires special tooling and accessories to sign up with it. Nonmetallic conduit can be obtained on reels in longer, continuous lengths which do not need to be joined as much.
“A possible problem with installing EMT conduit is it needs a special skill set and training, along with a great deal of practice–or you find yourself making swing sets,” explains Kevin Smith, project manager at MTS Services (Bedford, NH). “Metal conduit will come in 10-foot lengths so you must do any nonstandard bends by hand, and that`s in which the technician`s special skill is important.”
Arnco Corp. (Elyria, OH) sells innerduct towards the cable-TV, telecommunications, and electric utility markets, says Tom Stewart, electrical products sales manager. “Inside a building, several types of duct are being used–as an example, riser- and plenum-rated–but all of our products are produced from thermoplastic materials, such as polyvinylide fluoride [pvdf] and polyvinyl chloride [pvc]. The thermoplastic materials are simpler to install than metal.”
There are three different kinds (or ratings) of innerduct: outdoor, riser-rated, and plenum-rated. Robert Jensen, engineering manager at Endot Industries Inc. (Rockaway, NJ), explains: “Outdoor is usually polyethylene and it`s certainly not rated. Then there`s a riser product, rated by Underwriters Laboratories [UL], which is generally a thermoplastic material like polyethylene or PVC with fire-retardant chemicals added to it. And also the third kind of duct is UL plenum-rated, generally a pvdf product, that is fire-retardant and smoke-resistant,” says Jensen.
In accordance with Mike D`Errico, regional director of sales at Pyramid Industries (Erie, PA), most products that conduit and innerduct manufacturers make is perfect for outside plant. Some manufacturers offer prelubricated innerduct and conduit, “fairly often incorporating some type of silicon,” he says. “For premises cabling, Pyramid offers a plenum raceway (tested to UL-910) as well as a riser raceway (UL-1666) for installation in vertical shafts.” In addition, the riser item is halogen-free and it is often utilized for military, shipboard, or tunnel applications, based upon the specifications.
Of course contractors install conduit where building codes require it, but in addition where cabling system needs physical protection or defense against unauthorized access.
“We use conduit in riser and backbone systems from the building entrance to the main distribution frame,” says Karl Clawson, senior v . p . and partner, Clawson Communications (Greenwood, IN). “So we also set it up for horizontal cabling, specially in university campuses. Inside the living quarters, we install cable in conduit mainly because it affords the cable extra protection, and hopefully, keeps it all out of students` reach,” he says.
Some cabling contractors prefer to have other trades install conduit; by way of example, electricians who may have more expertise in performing this task. “Generally, the only time we use Flexible Plastic Conduit for Cables happens when we`re constructing a riser or penetrating a fire wall,” says Smith. “Typically, we will not install conduit from the wiring closet for the workstation outlet. For brief distances, just as much as 100 feet, we may install conduit between buildings according to the existing infrastructure.
Along with the traditional smooth-bore type, innerduct is offered with a ribbed inner wall to lessen friction involving the cable sheath and the innerduct wall. “A wave-rib on the inside of the duct reduces surface contact in between the cable along with the wall of your duct, thus reducing the coefficient of friction and helping you to pull cable over longer distances,” says Stewart.
Another variation will be the multicelled conduit system, which offers outerducts with pre-installed innerducts. Clawson says that, due to its cost, his company will not use conduit with pre- installed innerduct. “We keep leftover conduit in stock to use on other jobs,” he says. “But pre-installed conduit can be a special application, so overages and underages are sort of costly to deal with.”
For premises applications, Dura-line (Knoxville, TN) has created a conduit, known as Hex-line, for multiple-duct applications between buildings. “As you may pull the ducts away from the reel (two to each and every reel), they get into a collector, which Dura-line supplies free of charge,” says Ray McLeary, vice president of sales. “Each duct features a female and male part, which are snapped together, creating a multiple duct system. This saves time, space, and money, but the most significant savings is space.” He explains: “Normally, you are able to put three 1-inch innerducts right into a 4-inch conduit. With this system, you are able to fit four 11/4-inch or six 1-inch innerducts in to the conduit.”
When choosing innerduct, you also need to be worried about its tensile strength and crush resistance. “The thicker the wall material, the larger the tensile rating,” says Stewart. “If you`re planning to pull it spanning a long distance, choose a wall thickness that lets you pull the duct over that distance. The crush-resistance feature helps to ensure that the innerduct won`t be damaged throughout the placing process–or else you can`t pull inside the cable,” he explains.
As a result of limited level of tensile pull that one could exert around the cable, people seek out approaches to lessen the coefficient of friction within the conduit. “You will find products in the marketplace for example prelubricated conduit,” says Stewart. “And there`s a different technology used for placing cable, known as air-blown fiber (or ABF), the location where the fiber-optic cable is blown to the conduit. We manufacture whatever we call the `air-trak` system–a conduit system with chambers–for use in ABF installations.” [Air-blown fiber is available in the usa from Sumitomo Electric Lightwave Corp. (Research Triangle Park, NC).]
Conduit and innerduct have one thing in common: They facilitate pulling or replacing a cable for capacity inside a premises cabling system. However, every contractor is aware that for an installation grows, the amount of cables grows to fill every one of the space from the conduit. Therefore, deciding on the correct trade dimensions are important, simply because you must leave sufficient clearance involving the walls of the conduit and other cables (begin to see the eia/tia-569 standard). Typically, conduit trade sizes cover anything from 1/2 to 6 inches in diameter. Minimum conduit size suggested for backbone cables is 4 inches. Sufficient clearance must be accessible to allow pulling the cable without excessive friction or bending.
The NEC conduit-fill tables define the amount (like a percentage) of different types of cable you can utilize within a conduit. “The NEC typically covers power cables,” says Stewart. “With higher-voltage cables, you need to consider temperature and impedance, which really don`t apply in the matter of data cables in conduit. The genuine question for data cable is: Are you able to pull it into the size of duct that you`ve selected?”
“The most significant decision when installing conduit is the actual size of the conduit and clearance in the wall,” says Clawson. For external use, we use 4-inch PVC conduit, and we attempt to install all the conduit within the trenches as we can for future use.”
Cables are continually included with conduit systems which are often filled to capacity with generations of older cable. When new cables are added, friction and pulling tension can harm existing cables in the conduit. A great way to offer future changes is usually to subdivide larger conduits with innerducts, which can be smaller in diameter than conduit, generally nonmetallic, and semiflexible.
“Inside an existing structure, many installers tend not to desire to pull new cable across the cable already from the conduit,” says Stewart, “since they risk damaging the existing cable. To optimize a more substantial conduit, they`ll install several smaller innerducts within it. They`ll pull a reduced fiber cable into one of the innerducts, after which have additional ducts to be utilized for future cable placement.”
Innerducts are classified by outside diameter (OD) whereas trade-size conduits use inside diameter (ID). One-inch innerduct is usually used within buildings; however, 11/4-, 11/2-, and 2-inch innerducts are around for larger fiber cables. Although innerducts use up space within a conduit, they give additional protection and suppleness in constantly changing cabling installations.
“Generally, if you`re installing a 4-inch conduit,” says Smith, “you`ll end up investing in three 1-inch innerducts: one for fiber, one for data, and another spare. What for you to do is pull the maximum amount of dexlpky51 it is possible to at installation time.”
Typically produced from thermoplastic materials, innerduct includes a pull string already installed. It is available in ribbed-, corrugated-, and smooth-wall styles. Some types have prelubricated inside walls. These special coatings as well as the physical properties of the inner wall in the innerduct ensure less friction and tension when pulling cable.
“Corrugated innerduct is commonly used in plenum and riser products,” says D`Errico. “And, when created from high-density polyethylene, it is actually typically useful for short–1000 feet or less–installations.” Smooth wall is utilized for direct-buried, trenching, plowing, aerial, and directional boring applications. “The Metal Flexible Conduit is the fact that cable jacket is “lifted” far from and it has a smaller section of connection with the pipe, lowering the coefficient of friction. But the guideline is: the larger the hole, the simpler it`s gonna be to pull the cable,” he says.
Based on Clawson, “We use ribbed innerduct if we`re pulling one innerduct, because it`s much easier to handle. If we`re pulling by way of a directional boring machine and it`s a multiple pull, then we use smooth innerduct. It really is easier to pull smooth innerduct in addition to an easy surface, and it also doesn`t kink as easily as ribbed innerduct.”
When working with innerduct, it is important to verify be it a plenum or non-plenum area as well as install the innerduct with the appropriate support. When the innerduct is secured with tie wraps inside a plenum area, always use plenum-rated products.
Innerduct is often offered in one color–orange for your fiber-optic communications industry. Color can often be installation-specific; for example, one color for data cable, one for telephone, and the like. “You will find a movement afoot to attempt to use color designations for various applications,” says Stewart. “Orange is typically communications, red could be for electrical power, and yellow for gas.”