In outside-plant installations, conduit is generally installed underground to protect cables from damage and also to facilitate cable placement for fast and future needs. You may also install Conduit Fittings Wholesale inside buildings to facilitate pulling cable between two points for example through the telecommunications closet (TC) to be effective-area outlets, or from an equipment room to some TC. To shield, isolate, and identify the cables, innerduct–also called subduct–could be installed inside existing larger-diameter conduit.
Conduit is defined as a rigid or flexible metal or nonmetallic raceway through which cables can be pulled. Additionally, although conduit enables you to house various types of cable, the National Electrical Code (NEC) uses the word “optical fiber raceway” in Article 770 to illustrate conduit, or raceways, for optical-fiber cable. Various kinds of conduit are offered, such as electrical metallic tubing (EMT), rigid metal conduit, PVC, fiberglass, and versatile conduit. For premises installations, how-ever, metal flexible conduit is not really recommended due to potential abrasion problems for the cable jacketing.
Metal conduit, which typically comes in 10-foot lengths, is pretty rigid and needs special tooling and accessories to sign up for it. Nonmetallic conduit is offered on reels in longer, continuous lengths which do not really need to be joined as frequently.
“The only issue with installing EMT conduit is it requires a special skill set and training, in addition to plenty of practice–or you end up 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 the location where the technician`s special skill is necessary.”
Arnco Corp. (Elyria, OH) sells innerduct towards the cable-TV, telecommunications, and electric utility markets, says Tom Stewart, electrical products sales manager. “In a building, various kinds of duct are being used–for instance, riser- and plenum-rated–but all of our products are produced from thermoplastic materials, including polyvinylide fluoride [pvdf] and polyvinyl chloride [pvc]. The thermoplastic materials are simpler to install than metal.”
You will find three various sorts (or ratings) of innerduct: outdoor, riser-rated, and plenum-rated. Robert Jensen, engineering manager at Endot Industries Inc. (Rockaway, NJ), explains: “Outdoor is generally polyethylene and it`s not necessarily rated. Then there`s a riser product, rated by Underwriters Laboratories [UL], which happens to be generally a thermoplastic material such as polyethylene or PVC with fire-retardant chemicals included with it. And also the third sort of duct is UL plenum-rated, generally a pvdf product, which can be fire-retardant and smoke-resistant,” says Jensen.
According to Mike D`Errico, regional director of sales at Pyramid Industries (Erie, PA), most products that conduit and innerduct manufacturers make is made for outside plant. Some manufacturers offer prelubricated innerduct and conduit, “frequently incorporating some type of silicon,” he says. “For premises cabling, Pyramid supplies a plenum raceway (tested to UL-910) along with a riser raceway (UL-1666) for installation in vertical shafts.” In addition, the riser item is halogen-free and it is often useful for military, shipboard, or tunnel applications, depending on the specifications.
Naturally contractors install conduit where building codes require it, but in addition the location where the cabling system needs physical protection or defense against unauthorized access.
“We use conduit in riser and backbone systems from the building entrance for the main distribution frame,” says Karl Clawson, senior v . p . and partner, Clawson Communications (Greenwood, IN). “And that we also install it for horizontal cabling, specially in university campuses. Within the living quarters, we install cable in conduit as it provides the cable extra protection, and hopefully, keeps it of students` reach,” he says.
Some cabling contractors would rather have other trades install conduit; for example, electricians who definitely have more expertise in performing this. “Generally, the only time we use Flexible Plastic Conduit for Cables takes place when we`re creating a riser or penetrating a fire wall,” says Smith. “Typically, we may not install conduit from your wiring closet towards the workstation outlet. In short distances, just as much as 100 feet, we would install conduit between buildings based on the existing infrastructure.
As well as the traditional smooth-bore type, innerduct is offered having a ribbed inner wall to reduce friction in between the cable sheath and the innerduct wall. “A wave-rib on the inside of the duct reduces surface contact involving the cable and also the wall of your duct, thus decreasing the coefficient of friction and letting you pull cable over longer distances,” says Stewart.
Another variation is definitely the multicelled conduit system, that provides outerducts with pre-installed innerducts. Clawson states that, due to the cost, his company does not use conduit with pre- installed innerduct. “We keep leftover conduit in stock to utilize on other jobs,” he says. “But pre-installed conduit can be a special application, so overages and underages are form of costly to manage.”
For premises applications, Dura-line (Knoxville, TN) has created a conduit, referred to as Hex-line, for multiple-duct applications between buildings. “While you pull the ducts off the reel (two to each and every reel), they get into a collector, which Dura-line supplies totally free,” says Ray McLeary, v . p . of sales. “Each duct carries a female and male part, that happen to be snapped together, making 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. Using this type of system, you can fit four 11/4-inch or six 1-inch innerducts into the conduit.”
When choosing innerduct, you must also be worried about its tensile strength and crush resistance. “The thicker the wall material, the higher the tensile rating,” says Stewart. “If you`re planning to pull it over a long-distance, choose a wall thickness that permits you to pull the duct over that distance. The crush-resistance feature helps to ensure that the innerduct won`t be damaged through the placing process–or maybe you can`t pull from the cable,” he explains.
Due to limited quantity of tensile pull you could exert in the cable, people try to find methods to decrease the coefficient of friction within the conduit. “There are products on the market including prelubricated conduit,” says Stewart. “And there`s a different technology being utilized for placing cable, known as air-blown fiber (or ABF), where fiber-optic cable is blown to the conduit. We manufacture what we call the `air-trak` system–a conduit system with chambers–to use in ABF installations.” [Air-blown fiber can be obtained in the states 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 more capacity within a premises cabling system. However, every contractor is aware that for an installation grows, the amount of cables grows to fill all of the space from the conduit. Therefore, choosing the correct trade size is important, simply because you must leave sufficient clearance between the walls in the conduit along with other cables (begin to see the eia/tia-569 standard). Typically, conduit trade sizes range from 1/2 to 6 inches in diameter. Minimum conduit size suggested for backbone cables is 4 inches. Sufficient clearance must be offered to allow pulling the cable without excessive friction or bending.
The NEC conduit-fill tables define the amount (being a percentage) of different types of cable you may use inside a conduit. “The NEC typically covers power cables,” says Stewart. “With higher-voltage cables, you will need to consider temperature and impedance, which really don`t apply with regards to data cables in conduit. The true question for data cable is: Are you able to pull it into the size of duct that you`ve selected?”
“The most crucial decision when installing conduit is the actual size of the conduit and clearance through the wall,” says Clawson. For external use, we use 4-inch PVC conduit, and we attempt to install just as much conduit inside the trenches since we can for future use.”
Cables are continually put into conduit systems that happen to be often filled to capacity with generations of older cable. When new cables are added, friction and pulling tension may damage existing cables inside the conduit. A great way to offer future changes is always 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 would like to pull new cable over the cable already from the conduit,” says Stewart, “because they risk damaging the current cable. To optimize a larger conduit, they`ll install several smaller innerducts inside it. They`ll pull a lesser 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 often used within buildings; however, 11/4-, 11/2-, and 2-inch innerducts are for sale to larger fiber cables. Although innerducts consume space in a conduit, they give additional protection and flexibility 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 you wish to do is pull just as much dexlpky51 you may at installation time.”
Typically created from thermoplastic materials, innerduct comes with a pull string already installed. It is available in ribbed-, corrugated-, and smooth-wall styles. Some types have prelubricated inside walls. These special coatings and the physical properties of your inner wall of your 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 typically employed for short–1000 feet or less–installations.” Smooth wall is commonly used for direct-buried, trenching, plowing, aerial, and directional boring applications. “The Metal Flexible Conduit is the fact that cable jacket is “lifted” clear of and possesses a reduced region of experience of the pipe, lowering the coefficient of friction. Although the general guideline is: the larger the hole, the simpler it`s likely to be to pull the cable,” he says.
In accordance with Clawson, “We use ribbed innerduct if we`re pulling one innerduct, because it`s much easier to handle. If we`re pulling using a directional boring machine and it`s a multiple pull, then we use smooth innerduct. It can be easier to pull smooth innerduct on top of an effortless surface, plus it doesn`t kink as easily as ribbed innerduct.”
When utilizing innerduct, you should verify whether it is a plenum or non-plenum area and also to install the innerduct using the appropriate support. In case the innerduct is secured with tie wraps inside a plenum area, always use plenum-rated products.
Innerduct is normally offered in one color–orange to the fiber-optic communications industry. Color can occasionally be installation-specific; for instance, one color for data cable, one for telephone, etc. “There exists a movement afoot to try to use color designations for various applications,” says Stewart. “Orange is typically communications, red could be for electric power, and yellow for gas.”