The Pre-Wire Process

The Pre-Wire Process

The process of pre-wiring a house consists of the following major activities:

1. Determine the locations of the distribution panel, outlets and devices.

2. Create wire chart (see Table 3-1).

3. Place outlet boxes or mud rings at each location.

4. Pull the appropriate type and number of cable runs to each outlet and device location.

5. Label all cables at distribution panel.

6. Terminate or protect the cables at the outlets with the appropriate connecters or bagging .

7. Test all cable runs and connections.

   Table 3-1: A Home System Wire Chart. Used with permission from Heneveld Dynamic Consulting, Inc.

   Pulled	Tested	Run #	Type	Source	Destination	Device	Length	Special Instructions
   		1	Cat 5	House feed	Control center (CC)	Phone feed		Phone feed
   		2	Cat 5	House feed	CC	Future		Future
   		3	RG-6	House feed	CC	Future		Cable feed—Future
   		4	RG-6	Attic	CC	Future TV antenna		Loop extra cable
   		5	RG-6	Attic	CC	Future FM antenna		Loop extra cable
   		6	RG-6	Roof	CC	DSS feed		Satellite TV
   		7	RG-6	Roof	CC	DSS feed		Future satellite service
   		8	Cat 5	CC	Studio A	Phone jack
   		9	Cat 5	CC	Studio A	Data jack
   		10	RG-6	CC	Studio A	TV jack
   		11	Cat 5	CC	Studio B	Phone jack
   		12	Cat 5	CC	Studio B	Data Jack
   		13	RG-6	CC	Studio B	TV jack
   		14	Cat 5	CC	Living room Ent.	Phone jack
   		15	Cat 5	CC	Living room Ent.	Data jack
   		16	RG-6	CC	Living room Ent.	TV jack
   		17	Cat 5	CC	Up bedroom	Phone jack
   		18	Cat 5	CC	Up bedroom	Data jack
   		19	RG-6	CC	Up bedroom	TV jack
   		20	Cat 5	CC	Living room	Phone jack
   		21	Cat 5	CC	Living room	Data jack
   		22	Cat 5	CC	Up hallway	Phone jack
   		23	Cat 5	CC	Up hallway	Data jack
   		24	Cat 5	CC	Master bedroom	Phone jack
   		25	Cat 5	CC	Master bedroom	Data jack
   		26	Cat 5	CC	Up bedroom	Phone jack
   		27	Cat 5	CC	Up bedroom	Data jack
   		28	Cat 5	CC	Kitchen	Wall phone jack		Mount jack high on wall
   		29	Cat 5	CC	Front door	Future doorbell/intercom		Pre-wire for doorbell
   		30	16-4	Living room Entertainment	Living room Stairway wall	Speakers		Pre-wire for speakers—located on stairway wall, either side of opening

Pre-Wiring Tools

Before beginning the pre-wire phase of your project, ensure that you have the tools you’ll need to drill holes, pull, strip, terminate, and test the installed cabling. The types of wiring and cabling to be installed should dictate the specific tools in your kit, but at minimum, you should have:

• Cordless hand drill and drill bits slightly larger than the diameter of the cables   To drill cable path holes through studs, floors, and ceilings, as required

• Wire cutter /stripper   For cutting the cable to length and stripping its outer jacket during termination

• Needle-nose pliers   For use when terminating all cable types

• Screwdrivers   For the most part, you need both slotted head and crosshead recessed (Phillips) screw drivers

• Volt meter/continuity tester   For testing each cable run before termination and trim out

Wire Chart

Table 3-1 shows an example of a wire chart that should be created during the planning phase of a structured wiring project and used as a guide for the pre-wiring, rough in, and trim out of the structured wiring of a home. The format shown in Table 3-1 is only an example and you may want to include additional columns for other information, but the columns shown represent the minimum information needed during the complete wiring project.

A wire chart, like the one in Table 3-1, should be created during the planning phase of a structured wiring project and used to track the installation of the wiring throughout the remaining phases of the project. The information in the wire chart is taken directly from the project design and planning documents. If abbreviations are used on the wire chart, a legend should be created to ensure that everyone associated with the project understands their meaning.

The columns included in this wire chart example are

• Pulled   After each cable run is installed (pulled) from the source indicated in the “Source” column to the location listed in the “Destination” column, this column can be checked off and initialed by both the installer and whomever inspects his or her work. A double-check of the work is highly recommended to prevent oversight, errors, and omissions.

• Tested   During trim out and after each cable run is terminated and tested, the corresponding box in this column for the cable run can be checked off and initialed by the tester and the person verifying the test. A double-check of the work is highly recommended to prevent oversight, errors, and omissions.

• Run #   This column is used to create a unique identity and reference number for each cable run. The number or code assigned in this column can later be used in cable documentation and when labeling each cable. Cable number labeling systems provide self- adhesive numbered labels that can be affixed to each cable run at the distribution panel or control center (CC) end.

• Type   The type of cable to be used is entered into this column for each cable run.

• Source   The location from where the cable run is to begin is entered into this column. The Source and Destination columns provide the starting point and the ending point of the cable run.

• Destination   The location to where the cable run is to be pulled is entered into this column. The Source and Destination columns provide the starting point and the ending point of the cable run.

• Device   The source, distribution, control, or outlet device to which the cable run is to be connected or will support is identified in this column. When a cable run is being installed for future-proofing (see Chapter 5) purposes, this information should be recorded as well.

• Length   This is an optional column but can be helpful when comparing wire usage estimates to the actual installation. After guess-timating or length testing is completed on each cable run record the length in this column. Wire types used can be totaled up and compared to total usage wire estimates for the project. The information in the Length column may come in handy later when you are troubleshooting a cable for possible attenuation problems.

• Special Instructions   Because it is common for one technician to design and plan a structured wiring job and another technician to install its cable, this column can prove valuable in noting any issues or instructions the installer should know before beginning his or her work such as device height. Any problems encountered by the installer should also be recorded should yet another technician perform the cable testing. This column can also be used to record any other information relating to a particular cable run that may be valuable for future reference.

Wall Outlets

The system plan that was developed earlier in the project (and discussed earlier in this chapter) reflects where you and the homeowners have decided the connections, speakers, and controls for home’s integrated system should be placed. However, it’s one thing to mark it on a floor plan and quite another to religiously follow the plan exactly. Sometimes the wall studs, pipes, vents, or another room feature may not support the original placement of a system device. In these cases, you should coordinate with the homeowner to decide on a new location for the device.

Locate Outlets

The first step in the pre-wiring process is to install the outlet boxes and mud rings or plaster rings. In each location, an outlet box or mud ring should be nailed to a wall stud at the same height from the floor as the electrical outlets placed by the rough-in electricians and should be 12-inches or 300 millimeters above the floor. The boxes should also be from 12- to 16-inches from any nearby electrical outlets. A standard recommendation is locate low voltage outlets at least one wall-stud cavity away from an electrical outlet.

The outlet box (see Figure 3-2), backless outlet box, or mud ring should be of appropriate size to accommodate the size and amount of cabling that is to terminate or pass through that location, as well as the number of connectors and jacks to be installed. Outlet boxes should be placed so that when the drywall is installed they are flush with the front edge of the drywall. A mud ring will be stuck to the back of the drywall by joint compound.

Figure 3-2: A standard electrical outlet box can be used to mount connectors and faceplates for structured wiring.

Photo courtesy of Lamson & Sessions.

Sidecar Brackets

Several manufacturers make specialized low-voltage boxes and brackets that are able to service both AC electrical power lines and low-voltage structured wiring lines. The double-gang box shown in Figure 3-3 includes a separator panel in the center that meets the requirements of the NEC and EIA/TIA standards 568 and 570 for the separation of these lines.

Figure 3-3: A double-gang box that uses a separator panel to segregate AC power lines and structured wiring lines

Photo courtesy of Lamson & Sessions.

Another box type attaches to the side of an electrical service outlet box to create a tandem box that will appear, after the drywall is installed, to be a two-gang box. Add-on or sidecar brackets (see Figure 3-4) allows the outlet box to be paired with an electrical outlet, creating the finished look of a two-gang box rather than two separate outlets a short distance from each other on the same wall.

Figure 3-4: An add-on bracket can be attached to the side of an electrical box for structure wiring that creates the appearance of a two-gang box.

Photo courtesy of Lamson & Sessions.

When using sidecar brackets be sure to wire the low-voltage wire as far away as possible from the electrical wires. For example, the electrical wiring comes down the stud that the electrical box is mounted on, so wire the low-voltage wire down the opposite stud of that stud opening, wiring into the two-gang box at a right angle to the electrical wiring.

Cable

A variety of composite cable systems, like the one shown in Figure 3-5, are available that combine coaxial cable and Cat 5e cables into a single bundle, called a “2 + 2” bundled cable. Some manufacturers also offer what amounts to a “2 + 2 + 2” that includes two runs of fiber optic cable as well.

Figure 3-5: An example of a composite cable with 2 RG-6 and 2 Cat 5 runs

Photo courtesy of Smarthome, Inc.

Cable Schemes

Table 3-2 lists the recommended cables that should be installed for a variety of structured wiring applications. Remember that this is only a recommendation, but it does adhere closely to most of the recognized standards.

Cable Installation

After the outlet boxes and mud rings have been installed, the next step in the pre-wire process is to install the cabling. In a new construction pre-wire situation, the structured cable runs through holes drilled in the wall studs and runs parallel to the electrical wiring that should already be in place.

As a general rule, the path through the wall studs used for the structured cable should not be placed too close to the electrical power lines to avoid the possibility of electrical interference on the structured cabling. The general guidelines for how far a structured cable should be placed from an electrical line vary from 6- to 24-inches (with 6-inches the absolute minimum distance). However, the generally accepted standard and convention is that 12-inches is the minimum that should be used, unless for some reason the structure doesn’t permit it. If the electrical cable in question is a high-voltage line, such as a 240V line, the minimum distance moves out to 24-inches. If an electrical cable must be crossed, the structured cabling should do so at a 90-degree angle.

Nearly all structured wiring cable products are designed for installation in residential settings, so by and large, the bend radii required to pull a cable down between two wall studs is well within its specifications. However, sharp bends or kinks should be completely avoided.

The primary concern for pulling cable into an existing structure is to spread the runs of the various cable types over as wide a space as possible. If it is absolutely necessary to cross cabling, there are standards and guidelines for the installation of low-voltage cabling that covers overlap, separation, and crossing angles.

In general, structured wiring cable should be installed using the following guidelines:

• Use no more than 25 pounds of pull on the cable.

• Use at least 12-inches of separation between 120 volt power and structured wiring cables, and at least 24-inches of separation for 240 volt lines.

• If a low-voltage cable crosses a power cable, it must do so at a 90-degree angle.

• The low-voltage cable should avoid fluorescent light fixtures, and if you must run a cable by a fluorescent fixture, treat it like a 240 volt electrical line.

• Cable sheathing should not be stripped more than 1.25-inches from the connection end of the cable and 1-inch is better.

• UTP wire pairs should not be untwisted more than 0.5-inch and 0.375-inch is even better.

• The bend radius of a cable should be at least 1-inch, but some cable types are more sensitive than others.

• Between a transmitting source and a terminating (receiving device), a UTP cable segment should not be longer than 100 meters or a bit more than 300 feet.

  Note

  In North America, UTP is the most commonly used cable for low voltage (LV) data networking installations. However, outside of North America, shielded twisted-pair (STP) and screened twisted-pair (ScTP) wiring are commonly used.

Cable Path

In a structured cabling environment, one or more separate cable runs are strung between the outlet location and the central distribution panel so that each outlet has its own home-run of cable back to the panel.

When routing the structured cable through a wall stud, you should use a 5/8-inch auger drill bit to drill a hole in the horizontal center of the stud. This provides both a hole big enough for most cable bundles and composite cabling, but also enough wood is left in the stud on each side (at least 1-inch) of the hole to retain the strength of the stud. If you are concerned that the dry wall installers may penetrate your cable when they screw on the dry wall, place a nail plate on the front edge of the stud even with the cable hole. Minimize the number of holes drilled through a wall stud to maintain the integrity of the stud.

Another cable path that can be used is to pass the cable through a hole drilled in the header of the wall (the boards to which the studs are fastened) and run the cable through the attic or crawl space above or below the house. Using this path, the cable can be placed on J-hooks (see Figure 3-6) or tie wraps that hold the cable in place without the threat of damage from nails , staples , or other fasteners used to secure the cable to wall studs.

Figure 3-6: A J-hook can be used to suspend cable in open spaces.

Service Loops

At the outlet end of the structured cable pulled through the walls, leave at least 2 feet of cable length to work with during the trim-out phase of the cabling project. At the distribution panel have at least 2 feet of cable after the panel location, or better yet, have all cables reach the floor. Having ample cable in a service loop provides some flexibility when you are terminating the cable at an outlet or the distribution panel.

Tuck the service loop into the outlet opening of the wall in such a way that it can later be pulled out through the outlet or mud ring after the wallboard is installed.

It is beneficial to protect the distribution panel cable by putting a large piece of cardboard to fit in the panel opening to cover all the cables.

Cable Handling

Cat 5 and RG-6 are high-frequency cables and must not be damaged during installation. This means that staples or any other type of cable fastener that dents, pierces, or crimps the cable in any way shouldn’t be used. Also avoid bending these cable types too sharply when entering or exiting a wall stud cavity. The minimum bend radius for Cat5 is 1-inch, or 25.4 millimeters (mm), and for RG-6 is 2.5-inches, or 63.5-mm, (see Figure 3-7).

Figure 3-7: The bend radii of Cat 5 and RG-6 cables

Another important part of cable handling is to label or tag each run of cable per the wire chart. Each cable should be numbered per the wire chart and the number recorded on its labeling. This identification links the cable back to the cable plan created during the design and planning phases.

Cable Trays, Conduits , and Chases and Other Cable Supports

Most often, residential cables are routed through stud walls. However, if the cable has to be routed through an attic, basement , or another open space, the cables must be supported and organized, so typically they are routed through cable (J) hooks (see Figure 3-8) or tie-wraps nailed to the rafters (Figure 3-8).

Figure 3-8: Cable ties nailed to the overhead beams can be used suspend and support a cable run through an open space.

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