After the electricians and plumbers complete their work installing the electrical lines and plumbing in the open walls of a new home, a structured wiring project can proceed with the installation of the cabling, and placement of the distribution panel and outlet boxes. This phase of the project is commonly referred to as the rough-in phase because after this work is completed, the dry wall installers come in and put the wallboard up. Following this step, the next phase of the structured wiring project – trim-out (see Chapter 8) – can be performed.
This chapter focuses on the steps performed during the rough-in phase of a structured wiring project, which is primarily include locating the distribution panel, locating the outlet boxes or mud rings, and pulling cable through the wall studs, headers, joists, and floors.
Using the information developed in the planning phase of the project (see Chapter 6), you should have a very good estimate of the amount of cabling and outlets required for the project. You should also be able to determine the best type and size of distribution panel for the home.
The National Electric Code (NEC) requires all residential wiring be inside an electrical box (see Figure 7-1) whenever it connects to a receptacle, switch, fixture, or another wire. This practice is also good for low-voltage connections, such as Cat 5, coaxial, and twisted pair cabling.
Figure 7-1: An electrical outlet box.
Photo courtesy of Lamson & Sessions.
Structured Wiring Outlet Boxes
The best place to begin the rough-in process is by mounting either outlet boxes or mud rings around the house in their designated locations. Deep or backless low-voltage brackets, such as those shown in Figure 7-2, are sometimes referred to as mud rings and are a good choice for use with communications and structured wiring.
Figure 7-2: An assortment of low voltage brackets.
Photo courtesy of Lampson & Sessions.
As shown in Figure 7-3, double-gang boxes are also available that can be used to combine electrical (110 volt) and structured wiring (low voltage) at the same location. The box features a center divider, which is required by the NEC for dual-purpose boxes, and prevents crosstalk and electrical interference from reaching the low-voltage (structured wiring) side of the box.
Figure 7-3: A double-gang box used to mount both electrical and structured wiring in a single location.
Photo courtesy of Lampson & Sessions.
There are also “sidecar” brackets (see Figure 7-4) that allow a low voltage outlet to be attached to an electrical outlet. Sidecar brackets go around and over a standard electrical box. After the faceplate is installed, the two boxes give the appearance that the electrical and low voltage outlets are in a common two-gang box.
Figure 7-4: A sidecar bracket allows a low voltage box to be attached to the side of an electrical outlet box.
Photo courtesy of Lampson & Sessions.
It is common practice to use blue outlet boxes for AC or high-voltage connections and orange boxes for structured wiring and low-voltage connections.
Installing Outlet Boxes and Brackets
Outlet boxes are secured to a wall stud by either nailing them to the inside edge of a stud (as shown in Figure 7-5) or by screwing them to the face of a stud. If the building is using steel studs, the wall box will have to be fastened with screws.
Figure 7-5: An outlet box nailed to a wall stud.
Photo courtesy of Lampson & Sessions.
The front edge of the outlet box or bracket should extend beyond the stud so that it will be flush with the front surface of the drywall when it’s installed. Most outlet boxes have a raised line or mark for where the front of the stud should be. Once the drywall is in place, you can cut out only a portion of the wall to access the outlet box or bracket, so be sure of your measurements before you nail or screw the box in place.
Outlet boxes that are to support data or video connectors should be placed so that the bottom of the box or bracket is at the same height from the floor as the electrical boxes on the same wall and should be in the range of 12 to 16-inches from the floor.
Outlet boxes or brackets that will support volume controls, wall telephones, or other types of local units should be placed at the same height as any light switch boxes on the same wall and should be between 46 to 48-inches above the floor.
If the job requires the use of floor-mounted boxes, be sure you use outlet boxes specifically manufactured for that purpose to overcome any bend radius issues inside the floor joists.
Don’t take the term rough-in too literally. Take the time to line up the outlet boxes or brackets so that they are straight. A box or bracket that is not aligned will result in a faceplate that isn’t straight on the wall.
Some ceiling mounted devices (and wall mounted speakers) either come with a rough-in kit or have one available. This kit contains either a mud ring or a mounting ring, like the one shown in Figure 7-6 provides a template for the drywall to be cut for the speaker. The speaker is then attached during trim out. Be sure to leave enough wire to allow for easy installation of the device at trim-out.
Figure 7-6: A rough-in mounting bracket for a speaker.
Photo courtesy of Crutchfield New Media, LLC.
During the pre-wire or when locating speakers during trim-out that didn’t have speaker brackets, the cabling or wire should be installed using a zigzag pattern between the wall studs, as illustrated in Figure 7-7. The cable should be stapled loosely to the studs so that the staples can be easily removed during trim-out by lightly tugging on the cable.
Figure 7-7: Zigzag wiring between wall studs during pre-wire.
It’s a good idea to photograph the placement of the cabling during pre-wire to show a reference point, such as a door or window corner, to aid in locating the cable behind the drywall during trim-out.
The distribution panel in a structured wiring system, like the empty one shown in Figure 7-8, interconnects all of the external communications lines, such as television, telephone, and Internet, with the interior structured wiring running throughout a home. Inside the distribution panel, each incoming signal is divided and, in most cases, amplified before being sent out on the structured wiring throughout the home.
Figure 7-8: An open design distribution panel into which the control units for a home’s systems can be mounted.
Photo courtesy of Smarthome, Inc.
If the distribution panel for the structured wiring system is housed in an in-wall or flush-mounted box, the mounting box (without components) should be installed during rough-in. They are made to fit easily between standard stud dimensions on 16-inch centers. Otherwise, the installation of the panel can be delayed until the trim-out phase when the panel will be surface mounted. Locate the panel at about eye-height, similar to the height of the electrical panel. If multiple panels are installed, they should be side-by-side on the same level with conduit between them inside the wall for interconnectivity.
During rough-in, the location of the distribution panel must be decided and set permanently so that the structured cable runs have a starting point. There are two methods that can be used to install the cable during rough in:
Be sure and label each wire as you begin pulling so that when you reach the distribution panel or destination room you know where each wire goes. Leave at least a 2-foot length of extra cable at the outlet and at least 3 feet at the distribution panel (or better yet, let it hang and touch the floor) to enable termination of the cable during trim out.
The details of connecting structured wiring into the distribution panel are covered in Chapters 7 and 8.
The process used to install cable is very different in a new construction situation than it is in a remodel or retrofit situation:
In either case, the guidelines for installing, handling, and routing the structured wiring cable remains the same. These guidelines are specific to each type of structured wiring cable and are discussed in the following sections.
See Chapters 1 and 2 for more information on individual cables and their installation requirements.
Several manufacturers offer pre-bundled structured wiring cable that can be installed as a single set. Like the bundle shown in Figure 7-9, these cable bundles come in a variety of individual cables to satisfy the cable requirements of virtually every structured wiring requirements. At minimum, commercial structured cabling bundles include two runs each of Cat 5e (or better) and RG-6 coaxial cable. However, higher-end bundles may also include fiber optic cabling (included for future-proofing a home).
Figure 7-9: A commercially available structured wiring bundle.
Photo courtesy of Belden Inc.
Structured wiring bundles are typically wrapped with a twist wrap, with an attachment method called “banana peel,” such as the one shown in Figure 7-9, or a with a flexible outer jacket to improve their pull-ability. At the point where the outer wrapping needs to be removed to route individual wires to outlets or controls, the binding is easily removed by cutting or a pull-string.
“Bonded” bundled cable is also available and makes individual cable preparation easy. In a bonded cable, the outer sheathing is attached to the shielding layer, which is attached to the insulation around the inner conductors. The benefit of bonded cable is that it is highly waterproof and is a more rugged cable.
Audio cable is typically made up of two or four stranded wires of 16-gauge or larger wire. There are no standard color-coding schemes for audio wiring, but in most cases, one wire can be distinguished from the other by its jacket color, markings, ridges or other jacket features. In some cables, one conductor wire may be copper-colored and the other silver-colored. The ability to tell one conductor from another in the audio cable is important because this allows you to ensure the polarity of its connections.
During rough-in, audio cabling home runs can be pulled starting at the control amplifier or equipment and toward the speakers and controls in each room or zone. Multiple cables can be pulled together to an area of the house and then branch off separately to their designated room locations. Cables can also be pulled from the room locations, and merged together as they leave an area of the house and head back to the equipment. Remember to label all wiring per the wire chart.
Cable should also be pulled to all volume control, keypad, and speaker locations with a service loop of extra cable length (about 2 feet) provided at the volume control/keypad location. One way to reduce the task of pulling speaker wiring during rough-in is to install a multiple conductor cable to service more than one speaker. Each speaker requires two conductors and if a 4-conductor cable is pulled into a room, two conductors can be routed to each speaker location. This allows a single pull of cable to service the two speakers instead of pulling two 2-conductor cables by just pulling the cable to the first speaker and then looping it on to the second speaker.
Some controversy exists as to which type of coaxial cabling is best for video distribution. Some prefer the more rigid and less flexible RG-6 while others prefer the flexible and more easily installed RG-59. RG-6 has become the preferred coaxial cable of residential system installers because of its ability to handle a wider range of RF channels. In either case, coaxial cabling should be chosen to match the application in use, per the system manufacturer’s specifications. Remember that different sized coaxial cable, single-braid coaxial cable and quad-shield types of coaxial cable require different types of terminators and connectors.
See Chapter 1 for guidelines on installing coaxial cable.
Coaxial cabling, of either specification, is easily pulled through walls, open or closed. However, you should avoid tight bends or kinks in the cabling because they can change the impedance of the cable and this can lead to signal loss.
The current standards for data networking cabling in business (EIA/TIA 568) and homes (EIA/TIA 570) call for Category (Cat) 5 or Cat 5e cabling, respectively. This four-pair twisted-pair cable is available as shielded (STP), screened (ScTP), or unshielded (UTP) cable. The most commonly used cabling for residential installations is UTP cable.
UTP cabling is also the cable type most often included in structured wiring bundles. For areas where this cabling must be installed nearer to potential interference sources, such as fluorescent lighting fixtures or electrical motors, ScTP or STP would be a better choice than UTP.
The handling guidelines for installing category cabling are:
The orderly arrangement of all cabling in a residential installation is not only for aesthetic reasons, but it can simplify maintenance, troubleshooting, and later additions to the system.
Cable management begins in the placement of the cabling. The standards permit running cable over ceiling joists, but in longer open spaces, it may be better for the safety of the cable and its performance to use some form of cable management.
Here are a few guidelines for the use of cable management devices.
Figure 7-10: Cable ties are used to bundle cables together.
Figure 7-11: A ladder style cable tray can be used to bridge large amounts of cable across open spaces.
Figure 7-12: Flexible residential structured wiring conduit.
Photo courtesy of Lampson & Sessions.
Figure 7-13: A J-hook cable management device with a built-in Velcro cable tie.
In some situations, especially when not enough time is available to pull the cabling in the walls of a new construction project or should the cable not be available when this step must be performed, installing a pull-cord instead of the actual cable is a faster way to go. A pull-cord is a stiff cord that can be placed through the cable path and later used to pull the structured wiring cable into place. Although a pull-cord can be used to install structured wiring, whenever possible, it’s always best to pull the actual cable.
However, there are a few downsides to using pull-cords:
The cable guidelines that apply to new construction situations (in addition to those listed previously) are:
Several obstacles exist for installing structured cabling in an existing home, including outside walls filled with insulation, horizontal cross-members in walls, and the lack of pre-existing pathways through wall studs.
One solution is to install the cabling in the attic, placing the cabling in J-hooks or attached to the rafters with cable ties. Another is to pull the cabling underneath the house in a basement with an open ceiling or in the crawlspace under the house. On some homes, the only choice may be to run the cabling on the exterior of the home. Other solutions include using commercially available cable raceways – some styles can be used in front of or to replace wall baseboards.
The NEC requires that all residential electrical wiring be inside an electrical box wherever it connects to a receptacle, switch, fixture, or another wire and this is considered to be a good practice for low voltage structured wiring as well.
To begin the rough-in process, mount the low-voltage outlet boxes or brackets throughout the home. Outlet boxes or brackets are secured to a wall stud by either nailing them to the inside edge of a stud or by screwing them to the face of a stud. If the building is using steel studs, the wall box will have to be fastened with screws. The front edge of the outlet box or bracket should extend beyond the stud so that it will be flush with the front surface of the drywall when it’s installed. Most ceiling and wall-mounted devices have rough-in kits available that contain a rough-in mounting bracket.
The distribution panel interconnects external communications lines to interior structured wiring. Inside the distribution panel, incoming signals are divided and distributed to the structured wiring. If the distribution panel for the structured wiring system is housed in an in-wall or flush-mounted box, the mounting box should be installed during rough-in. Otherwise, the installation of the panel will be surface mounted and can be delayed until the trim-out phase. During rough-in, the location of the distribution panel must be decided and set permanently.
Several manufacturers offer pre-bundled structured wiring cable that can be installed as a single cable pull. These cable bundles usually include two runs each of Cat 5e and RG-6 coaxial cable. Higher-end bundles may include an additional two runs of fiber optic cabling.
During rough-in, audio cabling home runs should be pulled starting at the control amplifier and toward the speakers and controls in each room or zone. A service loop of cable should be placed at each end of the cable. Coaxial cabling is easily pulled through walls, but tight bends or kinks in the cabling should be avoided. All cabling should be labeled during rough-in per the wire chart. The EIA/TIA and NEC standards require certain handling rules for installing Cat 5e cabling.
Cable management is important for more than aesthetic reasons. It can simplify maintenance, troubleshooting and later additions to the system. Options available for mounting cable include special cable staples, cable ties, cable trays, conduit, and J-hooks.