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Consider the following statement: By taking the time to test low-voltage cabling in residential construction an installer can increase profitability. Testing takes time, and requires people and equipment. Since there is no requirement in the electrical code to test low-voltage cabling, why do it?
Until recently, it made sense to "wire and walk." The equipment available to test the wiring for telephones, TVs, entertainment systems, security and home computer networks was designed for commercial projects. Today, low-voltage wiring in residential contracting is more complex. A standard designed for residential installation (TIA-570-B) specifies test procedures appropriate for this market. A new generation of tools designed for the residential installer make testing faster, simpler and more profitable.
Twenty years ago, low-voltage wiring in a house probably addressed telephone lines, a coax run for a TV and maybe wiring for speakers in multiple rooms. Today's house has far more complicated requirements. The home network probably starts with a run of unshielded twisted pair (UTP) cable, properly terminated in virtually every room, sometimes with multiple locations in a single room. This UTP installation is probably rated at CAT 5e or CAT 6, allowing data transmissions as fast as 1 gigabit per second.
This UTP network may serve all the low-voltage needs: telephone, television, music, video games, security and computer traffic. There may be separate runs involving coax and bell wire for individual tasks. Whatever the design, complexity has grown, as well as the chances of an installation defect. The cost of a callback to fix such a defect is well above $200. So the practice of "wire and walk" can save money up front, but is offset by the cost of expensive repairs. This is where an installation standard designed specifically for the residential market can help by describing the right steps to minimize defects, and the most efficient means to test and repair defects that do occur.
TIA-570-B Standard
Residential installers received new guidance three years ago with the adoption of the TIA-570-B Residential Installation Standard. This standard is voluntary, and currently not part of the NEC or most electrical inspections. It does, however, describe best practices for testing a residential project. The standard cites three stages for the testing process: visual inspection, verification and final test.
Visual inspection. The visual inspection detects obvious problems such as checking for kinks and knots, and making sure the correct separations are kept from electrical wiring and other communications cabling as interference is unfavorable with electronic systems.
Verification. Either during or after visual inspection, the installer should use a verification test tool to ensure the cables are connected correctly. Verification test tools are often the first line of defense for cable troubleshooting. These tools allow you to see if the cable is properly connected. Verification test tools perform basic continuity functions (such as wiremap and toning). These verification test tools sometimes include additional features such as a Time Domain Reflectometer (TDR) for determining length to the end of a cable or distance to a trouble spot. They may detect if a switch is connected to the cable under test or check coaxial connections.
Verification testing confirms that a cable meets established national or international standards of conductor configuration and passes basic continuity testing. Verification may be performed on two-conductor, or multi-conductor twisted-air cabling.
If the wiring is faulty, an advanced verification tool's wiremap will identify the problem and faulty pair. Tools such as the MicroScanner Pro's unique TDR length function measure the full length of a cable, pinpoint reversed or crossed pairs and identify split pairs. These tools display individual pair lengths and whether the cable is connected to a hub. The length measurement is useful for billing and inventory purposes. If a fault is detected, time is often wasted with visual inspection. An advanced verification tool's toner function allows continuity verification and tracing cable.
