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It is essential that low-voltage contractors know how to efficiently fish cables into internal and external wall cavities in retrofit applications. Unlike pulling wires through half-inch EMT conduit, fishing requires skill, experience and the right equipment.
Installers know all too well the difficulties involved with installing multiple-conductor, 18-AWG cables into external walls packed with insulation.
No more than a decade ago, this task required two men—one up and one down—to bring a difficult retrofit job within budget. Advances in retrofit installation techniques over the last decade, however, have made the job of retrofitting less troublesome.
Armed with a myriad of ingenious tools designed to assist the installer fish low-voltage cables, a single installer now can perform the task easier and faster than ever before.
Self-made fishing tools
One reason why low-voltage installers experience anxiety when they have to fish an external wall involves the time it takes to negotiate the insulation therein. It’s not easy to insert, locate and pull a wire from atop a wall into a basement location. A single wire can take from 10 minutes to more than an hour. Fishing wires under a carpet or above a suspended ceiling also can take considerable time.
Ten or 20 years ago, there were only so many factory-made tools available for fishing walls, carpets and ceilings. Installers often fashioned their own tools from household items or objects found in an office, workshop or service van.
The ordinary coat hanger is probably one of the most common self-made fishing tools. Using a pair of large diagonal cutters, the hook is removed and the hanger straightened. A small hook is then formed at one end and a small handle at the other.
A cable is first inserted into the wall using some means of weighting it, such as a string or chain with a weight attached, (see sidebar on right) so gravity carries it as deep into the wall cavity as possible. The hook is inserted into the wall, usually through a hole placed where the wire is intended to exit.
The easiest wire to fish with this contraption is one that involves a single- or two-gang box where you can put your hand into the wall to find the string. By adding a slight double bend to the hook end of the coat hanger, it is possible to rotate the hanger assembly until the hook catches the wire or the attached string or chain.
Today’s modern marvels
When I searched for prefabricated fishing tools on the Internet, I was surprised at just how far these modern marvels have come. Some of the available resources on the Web include videos you can watch, such as on the Magnepull Web site (www.magnepull.com).
The Magnepull consists of a strong, hand-held magnet and a metal sinker-type object that the technician fastens to the wire when he drops it into the wall. The sinker is located by moving a magnetic roller back and forth on the surface of the wall. Once found, the technician works the Magnepull back and forth as he moves toward the exit hole.
The same magnetic-based tool can be used to retrieve magnetic tools and drill bits trapped in a wall cavity. According to the manufacturer, this method of retrieval may not be viable where it involves metal studs.
When you watch the Magnepull videos, you’ll note that the demonstrator drills the entry hole close to the edge of the top plate. In the real world, extreme care must be exercised when doing this because of the possibility of breaking through the drywall into the room.
Additional wire-fishing aides
There are other interesting modern marvels on the market, all designed to make the job of fishing easier and faster. One is a fiber optic scope with a built-in infrared (IR) illuminator.
Labor Saving Devices’ model VS48 (www.lsdinc.com/content/product_details/32) allows the installer to actually peer into a wall to see where the pull string, chain or long flexible drill bit is (see sidebar on flexible drill bits, below). This particular model comes with two settings on the IR illuminator portion.
Fishing also can be a challenge in horizontal spaces, such as ceilings. Here, installers can use an expandable fiberglass pole assembly equipped with a hook designed to snag a cable. These poles can be expanded 12 to 18 feet, depending on the model.
Fiberglass rods can be connected together, which allows installers to run a wire the entire length of a ceiling or under a continuous floor space for relatively long distances without interruption.
When using any of the above cable fishing tools, always use caution. For instance, when the job involves suspended ceiling spaces and code is a consideration, cable hangers usually are necessary.
Safety is the installer’s first priority, because accidents can be costly to both an injured installer as well as the company that employs him.
COLOMBO is a 32-year veteran in the security and life-safety markets. He currently is director with FireNetOnline.com and a nationally recognized trade journalist located in East Canton, Ohio.