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Cable And Conduit

Loom, BX and thin-wall are the most popular types for home power circuits

Some representative conductors of electricity: 1— Two-wire armored cable, or "BX." with extra grounding wire in the center. 2—Three-wire BX. 3—A two-wire nonmetallic sheath cable, with bare ground wire. 4—Three-wire, nonmetallic sheath. 5—Single insulated wires, colored black, white or red. These are used in thin-wall conduit.

Typical utility "knock-out" box for switches, outlets, etc., so called because cable openings in back, sides or ends are made in a few seconds by hammering through partially cut holes. Boxes are  rectangular,  square  or round;  varied sizes.

Utility box at left has fitting at top for thin-wall conduit; the one at right, for BX or loom. The mounting lips on all boxes are spaced uniformly to take all outlets and other varieties of fixtures.
 
If you expect to install new power lines or renovate old ones, you should know something about cable and conduit.

The most widely used type, because it is inexpensive, flexible, easy to handle, and permitted by many local building codes, is nonmetallic sheathed cable. This is also known as "loom," because of the woven appearance of its outer covering. It consists of two or three insulated wires, with or without a bare ground wire, laid parallel to each other in a common outer jacket. For indoor applications, a combination of thermoplastic and paper insulation is employed. For tougher- service, both indoors and outdoors, a combination of thermoplastic, fiberglass and polyvinyl insulation is better.

Loom can be cut with pliers and trimmed with a knife. It can be mounted quickly by means of U-shaped nail straps, driven in with a hammer.

Some municipalities do not permit the use of loom, and require instead metal-clad wiring of some sort. The most popular is steel-armored cable, universally known as "BX" for no reason that makes sense. It contains two or three wires, and usually also has a bare bonding or ground wire running   between   them   and   the   outer cable. The latter is spiral-made of thin steel, and the whole cable is flexible enough to be pushed around corners.

BX is tough stuff. Cutting the steel jacket without nicking the wires inside is very tricky and takes quite a bit of practice.

Both loom and BX are available in rolls from 25 to 250 feet.

Thin-wall conduit is merely galvanized steel pipe in various diameters and in standard 10-foot length. It is readily assembled to standard outlet boxes and other fixtures by means of threadless, clamp-type fittings. It can be bent at a rather wide right angle with a special tool. It makes an extremely neat and fireproof job. Some local building codes specify this type of wiring.

Thin-wall is distinctly different from both loom and BX in that it does not contain its own wires. These are pulled through during or after the assembly of a whole system, usually with the assistance of a flexible steel tape called a "snake."

An advantage of conduit for many purposes is that it can be shortened, lengthened, taken apart and put together both easily and rapidly. The wires themselves, being loose inside the smooth piping, can be pulled out undamaged and reused. ,·

This is the method of bringing two-wire non-metallic sheath cable into an outlet box. Clamp at left end of the latter holds the wire securely.

U-shaped straps, equipped with built-in nails, offer an easy means of fastening a nonmetallic cable to wooden walls. Fasteners of a similar nature are available for use on masonry walls.

The BX cable is wiggly and difficult to hold by hand. Don't attempt to cut it this way; hacksaw is   almost  certain   to  slip  or  the  cable   to   twist.

Best way to cut through the outer steel jacket of BX is with aid of vise. Hold the cable close to jaws; cut lightly at angle to the spiraling. Stop when inner paper insulation appears; twist off  the  cut  section. This  leaves  wire  ends  free.

In the absence of a vise, a C-clamp and a block of wood will serve well to hold BX for cutting.

In a pinch, a large pair of pliers or a locking iaw wrench, when pressed hard against the workbench, will serve to keep the BX under control. Practice on scraps to acquire the knack of cutting  a  cable  without touching  the  wires  inside.

A special right-angle connector permits the BX to make a sharp entrance into the utility box. There are a great number of different fittings designed to ease assembly and wiring operations.

To protect wires of BX against possible chafing, push fiber bushing into cable. In photo at left, center wire is ground lead and rests against the cable. White wire in cable is always uninterrupted ground return; the white wire the "hot" side.

Thin-wall conduit is a seamless steel pipe of light weight. It can easily be cut with a hacksaw, but a much quicker and neater job is possible when done with a tubing cutter, as shown. Handwheel is turned as the tool is pulled around tubing   and  cutting   wheel  bites   into   the   latter.

After only three or four revolutions of cutter, the  sections   of   a  conduit  are   easily   separated.

Burr on inside of conduit must be removed to allow free passage of wires that will be inserted later.   Simple   reamer   is   part   of   tubing   cutter.

"Persuader" puts round, even bend into thin-wall conduit. Tremendous leverage is applied through long handle of bender tool, a useful accessory.

An uncramped bend in the thin-wall conduit is    There is no difficulty when it comes to fasten-very essential to the passage of the wires. The    ing a thin-wall conduit to a flat surface. This smooth   job   results   from   the  use   of   ¡ever   tool.         is solved by use of simple single-ended clamps.

The threadless ends of the thin-wall are readily fastened by a clamping-type connector, shown in  the  photo,   right,  attached  to   a   utility   box.

Right-angle fitting brings thin-wall close to outlet box. Hex nut on threaded shoulder tightens the internal split clamp against the conduit's end.
 
This double-ended connector, handled with use of two wrenches, makes a quick task of joining any  two  sections  of  the  thin-wall conduit  pipe.

The desired result: This finished joint of two separate pieces of conduit is now neat and tight and allows free travel of wire through passage.
 
At this point, the actual wires are both pushed and pulled through the thin-wall conduit. This is usually  the last part of  assembly  operation.

Neat, rugged and foolproof is this short installation of two duplex receptacles and thin-wall conduit on the back edge of a radio table. Outlet boxes are screwed down through their bottoms, so conduit does not require mounting straps.

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